• 10 high-level NEET PG questions, mixed subjects
• I'll post one question at a time with 4 options (A-D)
• Reply with your answer, and I'll give you the explanation + move to the next question
• Score tracked throughout

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🩺 NEET PG High-Level Quiz

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Q1 of 10 — Pharmacology

• Warfarin - hepatically metabolized, no renal dose adjustment needed
• Rivaroxaban - ~33% renal excretion, use with caution but not as restricted
• Apixaban - only ~27% renal excretion, actually the safest NOAC in CKD

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Q2 of 10 — Pathology

• Pelger-Huet - bilobed "pince-nez" neutrophils, seen in MDS or inherited
• Dyskeratosis - abnormal keratinization, seen in epithelial disorders
• Ringed sideroblasts - iron-laden mitochondria around nucleus, seen in sideroblastic anemia

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Q3 of 10 — Physiology

• ↑ RBC mass - EPO-driven erythropoiesis kicks in after ~48-72 hours; by 3 weeks, RBC mass is significantly elevated
• ↑ 2,3-BPG - hypoxia stimulates glycolysis, increasing 2,3-bisphosphoglycerate production in RBCs
• Right shift of ODC - 2,3-BPG binds to deoxyhemoglobin and stabilizes the T (tense/deoxy) state, reducing O₂ affinity → facilitates O₂ unloading to tissues
• ↑ EPO - initially very high (peaks at ~24-48 hrs), then comes down but remains elevated during acclimatization

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Q4 of 10 — Anatomy

• In posterior dislocation, the femoral head is driven posteriorly and superiorly, directly into the path of the sciatic nerve as it exits the greater sciatic foramen below the piriformis
• The peroneal division of the sciatic nerve is more vulnerable than the tibial division (peroneal fibers are more lateral and tethered)
• Clinically: foot drop, loss of dorsiflexion, sensory loss over dorsum of foot

• Superior gluteal nerve - injured in anterior dislocation or iatrogenically during posterior hip surgery (THA); causes Trendelenburg gait (gluteus medius paralysis)
• Femoral nerve - injured in anterior hip dislocation
• Obturator nerve - can be injured in obturator/anterior dislocation, not posterior

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Q5 of 10 — Biochemistry

• Jaundice + hemolytic anemia - accumulation of Gal-1-phosphate is toxic to RBCs and liver
• Cataracts - galactose is converted to galactitol (by aldose reductase) which accumulates in the lens
• Urine reducing substances positive - galactose is a reducing sugar, detected by Benedict's/Clinitest
• Glucose oxidase negative - confirms it is NOT glucose (glucose oxidase is specific for glucose)

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Q6 of 10 — Medicine

• Phenoxybenzamine (non-selective, irreversible alpha-blocker) is the drug of choice - started 1-2 weeks preop
• Once adequate alpha-blockade is achieved, beta-blocker (propranolol) is added if tachycardia persists

• Alpha-blockade causes volume expansion (due to vasodilation) → patients also need high salt diet + IV fluids preop to prevent post-resection hypotension
• During surgery, phentolamine (IV alpha-blocker) is used for hypertensive crises
• Nitroprusside is used intraoperatively as backup
• Rule of 10s: 10% malignant, 10% bilateral, 10% extra-adrenal, 10% familial, 10% in children

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Q7 of 10 — Microbiology

• Chocolate agar - used for Neisseria gonorrhoeae and H. influenzae, not treponemes
• Gram-positive spore-former - T. pallidum is a spirochete, too thin to be seen on Gram stain (0.1-0.2 μm wide)
• Ziehl-Neelsen - used for acid-fast organisms (Mycobacterium, Nocardia); treponemes are visualized by dark-field microscopy or silver staining (Warthin-Starry)

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Q8 of 10 — Surgery

• NPO (bowel rest)
• Octreotide (reduces pancreatic secretion)
• Total parenteral nutrition (TPN) or enteral nutrition
• Keep drain in place, monitor output

• Delayed gastric emptying - presents with nausea, vomiting, inability to tolerate oral feeds; drain amylase is normal
• Bile leak - drain bilirubin elevated, not amylase
• Chyle leak - milky white drain fluid, high triglycerides

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Q9 of 10 — Medicine (Nephrology)

1. Haematuria (persistent microscopic, episodic gross)
2. Sensorineural hearing loss (cochlear involvement)
3. Ocular abnormalities (anterior lenticonus - pathognomonic, macular flecks)

• X-linked dominant (85%) - mutation in COL4A5 gene (X chromosome)
• Males are more severely affected (progress to ESRD by 20-30 years)
• Females are carriers - may have mild disease
• Autosomal recessive (15%) - COL4A3 or COL4A4 mutation
• Autosomal dominant - rare

• Alport: Irregular thickening with splitting/lamellation - "basket-weave" or "moth-eaten" GBM
• Thin BM disease: Diffuse thinning only (< 150 nm), NO splitting - benign, good prognosis

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Q10 of 10 — Pharmacology (Final Question!)

• PLP is a cofactor for over 100 enzymatic reactions
• Critical for neurotransmitter synthesis: GABA, serotonin, dopamine
• Deficiency → impaired myelin synthesis → peripheral neuropathy (sensory > motor)

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🏁 QUIZ COMPLETE!

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📊 Final Scorecard

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🎯 Final Score: 8/10 (80%)

• Q4 - Posterior hip dislocation injures the Sciatic nerve, not superior gluteal
• Q8 - Elevated drain amylase post-Whipple = Pancreatic fistula, not delayed gastric emptying

Honest Assessment: Your NEET PG Prep

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💪 Strengths (what you got right)

• Pharmacology - Strong. You nailed both Pharm questions (NOACs in CKD + INH neuropathy). These are conceptual, not just memory - good sign.
• Core clinical medicine - Pheochromocytoma preop prep, Alport syndrome, Galactosemia - all correct. You're thinking in mechanisms, not just memorizing.
• Microbiology + Pathology - Clean answers, no hesitation-type errors.
• Physiology - High-altitude acclimatization is a multi-step reasoning question. Getting that right shows strong integration.

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⚠️ Areas to Tighten

1. Surgery (Operative complications) - The Whipple's question was a classic trap. Post-op complications after major surgeries (POPF, DGE, bile leak) are heavily tested in NEET PG. Spend more time on surgical complication criteria and their management algorithms.
2. Anatomy (Nerve injuries) - You mixed up posterior vs anterior hip dislocation nerve injuries. Orthopedic anatomy nerve injury patterns are a regular NEET PG topic - worth a focused revision session.

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📈 Realistic Verdict

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🔧 What to do now

1. Do subject-wise timed mocks - especially Surgery and Anatomy
2. Focus on post-op complications - they appear every year
3. Don't neglect Forensic Medicine and PSM - high-yield easy marks that many ignore
4. Revise nerve injury patterns systematically - brachial plexus, hip, knee, wrist

• "What gap areas" - want me to list your weak topics in detail?
• "Let's go again" - want another quiz round?
• Something else entirely?

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⚡ PRE-GT RAPID REVISION

NEET PG | 1 Hour Plan

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🕐 BLOCK 1 - PHARMACOLOGY (10 min)

• Dabigatran = 80% renal → most restricted in CKD (CI if GFR <30)
• Rivaroxaban = 33% renal
• Apixaban = 27% renal → safest in CKD
• Warfarin = hepatic → no renal adjustment

• INH → Peripheral neuropathy (B6 depletion), hepatitis, drug-induced lupus, seizures
• Rifampicin → Orange discolouration, hepatitis, enzyme inducer, flu-like syndrome
• Pyrazinamide → Hyperuricaemia (gout), hepatotoxicity
• Ethambutol → Retrobulbar neuritis (red-green colour blindness), loss of visual acuity
• Streptomycin → Ototoxicity (vestibular > cochlear), nephrotoxicity

• ACE inhibitors → renal agenesis (2nd/3rd trimester)
• Tetracycline → teeth/bone discolouration
• Warfarin → fetal warfarin syndrome (1st trimester), bleeding (3rd)
• Methotrexate → abortifacient, teratogen
• Thalidomide → phocomelia
• Fluoroquinolones → cartilage damage
• Aminoglycosides → ototoxicity in fetus

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🕐 BLOCK 2 - MEDICINE (10 min)

• Nephrotic + "spike and dome" on EM → Membranous nephropathy (anti-PLA2R Ab)
• Nephrotic + "foot process effacement" only → Minimal Change Disease (responds to steroids)
• Nephrotic + "wire loop" lesions → Lupus nephritis (Class IV)
• Nephritic + "tram-track" GBM → MPGN
• Nephritic + "RBC casts" → all proliferative GN
• Nephritic + "subepithelial humps" on EM → Post-streptococcal GN
• Haematuria + hearing loss + basket-weave GBM → Alport syndrome (X-linked, COL4A5)

• Digoxin toxicity → ECG: Scooped ST (reverse tick), AV blocks, ventricular ectopics; treat with anti-digoxin Fab
• Amiodarone side effects: Pulmonary fibrosis, thyroid (hypo + hyper), corneal deposits, photosensitivity, hepatotoxicity, peripheral neuropathy
• Most common cause of drug-induced lupus: Procainamide > Hydralazine > Isoniazid

• Phaeochromocytoma Rule of 10s: 10% malignant, 10% bilateral, 10% extra-adrenal, 10% familial, 10% in children
• Cushing's: Best screening test = 24hr urinary free cortisol or overnight dexamethasone suppression test
• Addison's: Best confirmatory test = Short ACTH (Synacthen) stimulation test

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🕐 BLOCK 3 - SURGERY (10 min)

• Obstruction: Colicky pain, tinkling bowel sounds, ladder pattern on X-ray
• Ileus: Silent abdomen, generalised distension, "ground glass" appearance

• Most common position: Retrocaecal (65%)
• Rovsing's sign: RIF pain on palpating LIF
• Psoas sign: Pain on right hip extension (retrocaecal appendix)
• Obturator sign: Pain on internal rotation of right hip (pelvic appendix)
• Alvarado score: ≥7 = operate; 5-6 = observe; <5 = unlikely appendicitis

• Recurrent laryngeal nerve injury → hoarseness (unilateral), aphonia (bilateral)
• Superior laryngeal nerve (external branch) → loss of high-pitched voice (singer's nerve)
• Hypoparathyroidism → hypocalcaemia → Chvostek's + Trousseau's sign

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🕐 BLOCK 4 - ANATOMY (10 min)

• Posterior dislocation → Sciatic nerve (peroneal division most vulnerable) → foot drop
• Anterior dislocation → Femoral nerve OR Obturator nerve
• Posterior hip surgery (THA) → Superior gluteal nerve → Trendelenburg gait (gluteus medius paralysis)
• Intramuscular injection (upper outer quadrant safe zone) → Sciatic nerve if given wrong quadrant

• Common peroneal (fibular) nerve → lateral neck of fibula fracture → foot drop + inversion
• Femoral nerve → inguinal ligament → loss of knee extension (quadriceps)
• Obturator nerve → obturator foramen → loss of hip adduction

• Foramen rotundum → V2 (maxillary)
• Foramen ovale → V3 (mandibular)
• Foramen spinosum → Middle meningeal artery
• Jugular foramen → IX, X, XI
• Hypoglossal canal → XII

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🕐 BLOCK 5 - PATHOLOGY + MICROBIOLOGY (10 min)

• AFP → Hepatocellular carcinoma, testicular (non-seminoma), neural tube defects (amniotic fluid)
• CEA → Colorectal carcinoma (not diagnostic, used for monitoring)
• CA 125 → Ovarian cancer (serous)
• CA 19-9 → Pancreatic carcinoma
• PSA → Prostate cancer
• β-hCG → Gestational trophoblastic disease, testicular (choriocarcinoma)
• Calcitonin → Medullary thyroid carcinoma
• Chromogranin A → Carcinoid/neuroendocrine tumours
• S-100 → Melanoma, neural tumours, Langerhans cell histiocytosis

• AL amyloid → Multiple myeloma (most common systemic)
• AA amyloid → Chronic inflammatory conditions (TB, RA, Crohn's)
• Aβ amyloid → Alzheimer's disease
• ATTR → Senile cardiac amyloid (transthyretin)
• β2-microglobulin → Long-term dialysis patients

• Can NOT be cultured in vitro: Treponema pallidum, Mycobacterium leprae
• Obligate intracellular: Chlamydia, Rickettsia, Coxiella, viruses
• Capsulated organisms (SHiNE SKiS): S. pneumoniae, H. influenzae, N. meningitidis, E. coli, Salmonella, Klebsiella, S. agalactiae
• Chocolate agar organisms: Neisseria, H. influenzae (need Factor V + X)
• CAMP test positive: Streptococcus agalactiae (Group B Strep)
• Quellung reaction: Capsular swelling with specific antisera (S. pneumoniae)

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🕐 BLOCK 6 - PHYSIOLOGY + BIOCHEMISTRY (10 min)

1. Immediate: ↑ ventilation (hypoxic ventilatory response)
2. Hours: Respiratory alkalosis, ↑ 2,3-BPG
3. Days-weeks: ↑ EPO → ↑ RBC mass, right shift of ODC
4. Long-term: ↑ mitochondrial density, ↑ capillary density

• Obstructive (asthma, COPD): ↓ FEV1, ↓ FVC, FEV1/FVC <70%, ↑ RV, ↑ TLC
• Restrictive (fibrosis, sarcoidosis): ↓ FEV1, ↓ FVC, FEV1/FVC normal or ↑, ↓ TLC

• Megaloblastic: Macro-ovalocytes, hypersegmented neutrophils, ↑ MCV, nuclear-cytoplasmic asynchrony
• Iron deficiency: Microcytic hypochromic, pencil cells, ↓ ferritin (earliest), ↑ TIBC

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🎯 LAST 5 MINUTES - RAPID FIRE ONE-LINERS

• Most common cause of Cushing's overall → Iatrogenic (exogenous steroids)
• Most common cause of Cushing's syndrome (endogenous) → Pituitary adenoma (Cushing's disease)
• Virchow's triad → Stasis + Hypercoagulability + Endothelial injury
• Beck's triad (cardiac tamponade) → Hypotension + Raised JVP + Muffled heart sounds
• Charcot's triad (cholangitis) → RUQ pain + Fever + Jaundice
• Reynolds pentad (severe cholangitis) → Charcot's triad + Hypotension + Altered consciousness
• Most common type of Hodgkin's lymphoma → Nodular sclerosis
• Best prognosis Hodgkin's → Lymphocyte predominant
• Worst prognosis Hodgkin's → Lymphocyte depleted
• Reed-Sternberg cell → CD15+, CD30+, background of reactive cells
• Owl-eye nucleus → Reed-Sternberg cells in Hodgkin's
• Drug of choice for Pneumocystis jirovecii → Co-trimoxazole (TMP-SMX)
• Drug of choice for Cryptococcal meningitis → Amphotericin B + Flucytosine (induction)
• Waterhouse-Friderichsen syndrome → N. meningitidis, bilateral adrenal haemorrhage
• Lucid interval → Extradural haemorrhage (middle meningeal artery tear)
• Talk and die syndrome → Extradural haemorrhage

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✅ You're Ready!

1. Read every question twice - NEET PG is famous for "EXCEPT" and "NOT" traps
2. Your Pharmacology and Medicine are strong - those will be your scoring subjects
3. In Surgery questions, think "what's the drain output telling me?"
4. In Anatomy, always think "what structure is closest anatomically?"
5. Trust your first instinct - don't overthink

🦠 Microbiology: All Toxins

Complete NEET PG Master Guide

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PART 1 - CONCEPT FIRST

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PART 2 - EXOTOXINS (THE BIG LIST)

🔴 A-B TYPE TOXINS

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1. CHOLERA TOXIN

• B subunit binds GM1 ganglioside on intestinal epithelium
• A subunit ADP-ribosylates Gs protein → permanently activates adenylyl cyclase
• ↑↑ cAMP → massive Cl⁻ secretion → water follows → rice-water diarrhoea
• No mucosal invasion - purely secretory toxin

• Stool: Rice-water, fishy odour, no blood, no pus
• Massive isotonic fluid loss (up to 20 L/day)
• Treatment: ORS + Doxycycline

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2. E. COLI HEAT-LABILE TOXIN (LT)

• ADP-ribosylates Gs → ↑ cAMP → secretory diarrhoea
• "Traveller's diarrhoea"
• Plasmid encoded

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3. E. COLI HEAT-STABLE TOXIN (ST)

• Activates guanylyl cyclase → ↑ cGMP → inhibits NaCl absorption → diarrhoea
• NOT an A-B toxin
• Plasmid encoded, heat stable (survives boiling)

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4. PERTUSSIS TOXIN

• ADP-ribosylates Gi protein → inactivates Gi → adenylyl cyclase remains active → ↑ cAMP
• Also causes lymphocytosis by inhibiting lymphocyte migration into lymph nodes
• Results in: whooping cough, lymphocytosis

• Adenylate cyclase toxin (invasive AC) - directly increases cAMP in host cells
• Tracheal cytotoxin - kills ciliated epithelium
• Filamentous haemagglutinin - adhesin

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5. DIPHTHERIA TOXIN

• A subunit: ADP-ribosylates EF-2 (Elongation Factor 2) → blocks protein synthesis → cell death
• Affects heart (myocarditis), nerves (neuropathy), kidneys

• Toxin gene carried by lysogenic bacteriophage (β-corynephage)
• Bull-neck appearance (cervical lymphadenopathy)
• Pseudomembrane on tonsils/pharynx (bleeds on removal)
• Schick test: intradermal diphtheria toxin - wheal = susceptible (no immunity)

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6. PSEUDOMONAS EXOTOXIN A

• Same mechanism as diphtheria toxin - ADP-ribosylates EF-2 → blocks protein synthesis
• Different receptor binding (uses LRP/α2-macroglobulin receptor vs diphtheria uses HBEGF)

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7. ANTHRAX TOXIN

• PA (Protective Antigen) - binding component (like B subunit) - basis of vaccine
• EF (Edema Factor) - adenylate cyclase → ↑ cAMP → oedema
• LF (Lethal Factor) - metalloprotease → cleaves MAP kinase → cell death, cytokine storm

• PA + EF = Oedema toxin
• PA + LF = Lethal toxin

• Toxin encoded on plasmid pXO1; capsule on pXO2
• Spores survive in soil for decades
• Woolsorter's disease = inhalational anthrax

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8. SHIGA TOXIN

• NOT an A-B toxin in classic sense but has A+B subunits
• B subunit binds Gb3 (globotriaosylceramide) receptor on endothelial cells
• A subunit is an N-glycosidase → cleaves 28S rRNA → blocks protein synthesis → cell death
• Targets endothelial cells of kidney and gut → HUS

• Bloody dysentery
• Haemolytic Uraemic Syndrome (HUS) = microangiopathic haemolytic anaemia + thrombocytopenia + acute renal failure
• Gb3 receptor is abundant in kidney (especially children) → HUS more common in children

• Shiga toxin = from Shigella
• Shiga-like toxin (Verotoxin) = from E. coli O157:H7 (STEC/EHEC)
• Same mechanism, slightly different receptor affinity

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PART 3 - NEUROTOXINS

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9. TETANUS TOXIN (TETANOSPASMIN)

• Toxin produced at wound site → travels retrograde up motor neurones
• Reaches spinal cord (Renshaw cells) and brainstem
• Cleaves SNARE proteins (synaptobrevin/VAMP) → blocks release of GABA and glycine (inhibitory neurotransmitters)
• Loss of inhibition → spastic paralysis, tetany, trismus (lockjaw)

• Trismus (lockjaw) - first symptom
• Risus sardonicus (sardonic smile)
• Opisthotonus (arched back)
• Autonomic instability

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10. BOTULINUM TOXIN

• Toxin ingested (preformed) or produced in gut/wound
• Travels anterograde to neuromuscular junction
• Cleaves SNARE proteins → blocks ACh release at NMJ
• Results in flaccid paralysis (opposite to tetanus!)

• Descending flaccid paralysis (starts with cranial nerves - diplopia, dysphagia)
• Dry mouth (blocked ACh at salivary glands)
• NO fever
• Constipation (autonomic)
• Pupils dilated and fixed (blocked pupillary constriction)

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🔑 TETANUS vs BOTULINUM - THE MOST TESTED COMPARISON

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PART 4 - CYTOTOXINS / MEMBRANE-DISRUPTING TOXINS

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11. STAPHYLOCOCCAL TOXINS

• Forms pores in cell membranes → cell lysis
• Haemolysis, tissue necrosis

• Sphingomyelinase → cleaves sphingomyelin → cell lysis
• "Hot-cold haemolysin"

• Superantigen - binds MHC class II + TCR outside antigen-binding groove
• Activates up to 20% of all T cells at once (normal antigen activates 0.01%)
• Massive cytokine release → toxic shock syndrome
• Fever, hypotension, rash (diffuse erythroderma), multi-organ failure, desquamation

• Serine protease - cleaves desmoglein-1 in the stratum granulosum
• Splits epidermis → Staphylococcal Scalded Skin Syndrome (SSSS)
• Bullae, Nikolsky sign positive
• Nikolsky sign = superficial skin shearing with gentle pressure

• Bi-component pore-forming toxin
• Destroys leukocytes
• Associated with CA-MRSA (community-acquired MRSA)
• Causes necrotising pneumonia, skin and soft tissue infections

• Superantigens → food poisoning
• Pre-formed toxin in food, heat stable
• Vomiting within 1-6 hours (very short incubation)
• No fever (toxin-mediated, not invasive)

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12. STREPTOCOCCAL TOXINS

• Oxygen-labile haemolysin
• Binds cholesterol in membranes → pore formation → haemolysis
• Antigenic → ASO titre used to diagnose past streptococcal infection
• Not produced by S. aureus

• Oxygen-stable haemolysin
• Responsible for beta-haemolysis seen on blood agar (surface colonies)
• Non-antigenic (no ASO rise)

• Superantigens - same mechanism as TSST-1
• Cause Streptococcal Toxic Shock Syndrome (STSS)
• SPE A = Scarlet fever erythrogenic toxin (also called Dick toxin)
• Encoded by lysogenic bacteriophage (like diphtheria toxin)

• Converts plasminogen → plasmin → dissolves fibrin clots
• Helps spread of infection
• Used therapeutically as thrombolytic

• Breaks down hyaluronic acid in connective tissue
• Spreads infection through tissues

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PART 5 - SUPERANTIGENS (GROUP TOGETHER)

• Normal antigen: processed, presented in MHC groove, activates 0.001-0.01% T cells
• Superantigen: binds OUTSIDE the groove (MHC class II β-chain + TCR Vβ region)
• Activates 5-25% of all T cells
• Massive IL-2, TNF, IFN-γ release → cytokine storm → fever, hypotension, shock

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PART 6 - GAS GANGRENE & CLOSTRIDIAL TOXINS

• Lecithinase (phospholipase C) - cleaves lecithin (phosphatidylcholine) in cell membranes
• Causes haemolysis, tissue necrosis, gas production
• Nagler reaction: Opalescence on egg-yolk agar (lecithinase activity)
• Stormy clot reaction: Rapid gas production in litmus milk medium

• Toxin A (enterotoxin): Glucosylates Rho GTPases → disrupts cytoskeleton → fluid secretion
• Toxin B (cytotoxin): Same mechanism but 1000x more potent → mucosal damage
• Cause: Pseudomembranous colitis (antibiotic-associated)
• Diagnosis: Stool PCR for toxin genes / EIA for toxins A+B
• Treatment: Oral Vancomycin or Fidaxomicin (first line); Metronidazole (second line)

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PART 7 - ENDOTOXIN (LPS)

• Lipid A (toxic component) + Core polysaccharide + O-antigen (outermost, variable, serotyping)

• Released from dying Gram-negative bacteria
• Binds LPS-binding protein (LBP) → complex binds CD14 on monocytes/macrophages
• Signals through TLR4 (Toll-Like Receptor 4) + MD-2
• Activates NF-κB → massive cytokine release (TNF-α, IL-1, IL-6, IL-12)
• → Septic shock

• Fever (pyrogenic - via IL-1, IL-6, TNF-α → PGE2)
• Hypotension (NO-mediated vasodilation)
• DIC (activates coagulation cascade)
• Complement activation
• Neutrophilia → neutropenia (in severe sepsis)

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PART 8 - RAPID FIRE TOXIN TABLE (NEET PG Favourite Questions)

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PART 9 - PHAGE-ENCODED TOXINS (COMMONLY TESTED)

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PART 10 - CLINICAL SCENARIO APPROACH

• "Rice-water diarrhoea" → Cholera toxin → ↑ cAMP
• "Watery diarrhoea in traveller" → ETEC → LT (↑ cAMP) or ST (↑ cGMP)
• "Bloody diarrhoea + HUS in child" → Shiga toxin / STEC O157:H7
• "Pseudomembrane on throat, myocarditis" → Diphtheria toxin → blocks EF-2
• "Whooping cough + lymphocytosis" → Pertussis toxin → blocks Gi
• "Lockjaw, opisthotonus, spastic" → Tetanus toxin → blocks GABA
• "Descending flaccid paralysis, diplopia, no fever" → Botulinum toxin → blocks ACh
• "Infant with honey exposure, floppy baby" → Infant botulism
• "Scalded skin, bullae, Nikolsky positive in child" → Exfoliative toxin → desmoglein-1
• "Sudden vomiting 1-6 hours after food" → S. aureus enterotoxin (preformed)
• "Fever, hypotension, rash, multi-organ failure" → Superantigen (TSST-1 or SPE)
• "Gas gangrene, Nagler reaction positive" → C. perfringens alpha toxin
• "Pseudomembranous colitis after antibiotics" → C. difficile toxin A+B
• "Woolsorter's disease, oedema" → Anthrax EF toxin

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🎯 TOP 5 MOST REPEATED NEET PG TOXIN QUESTIONS

1. Cholera toxin mechanism - ADP-ribosylates Gs → ↑ cAMP (asked every year)
2. Tetanus vs Botulinum - spastic vs flaccid, retrograde vs anterograde
3. Diphtheria toxin - phage-encoded, blocks EF-2
4. Superantigen mechanism - TSST-1, massive T cell activation
5. Shiga toxin - HUS, cleaves 28S rRNA, N-glycosidase

🦠 Complete Microbiology

NEET PG Master Guide — All Topics

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SECTION 1: BACTERIOLOGY BASICS

Gram Staining — The First Step

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Cell Wall Structures

• NAM (N-acetylmuramic acid) + NAG (N-acetylglucosamine) linked by β-1,4 bonds
• Cross-linked by peptide bridges
• Target of: Penicillin (inhibits transpeptidase/PBP), Vancomycin (binds D-Ala-D-Ala)
• Lysozyme cleaves β-1,4 bond between NAM and NAG

• Lipoteichoic acid (LTA) - anchored to membrane
• Wall teichoic acid - anchored to peptidoglycan
• Important virulence factors, activate complement

• Lipid A (toxic) + Core + O-antigen
• Endotoxin activity via TLR4/MD-2/CD14

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Special Staining Techniques

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Culture Media

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Bacterial Growth & Kinetics

1. Lag phase - adaptation, no division
2. Log (exponential) phase - rapid doubling, most sensitive to antibiotics
3. Stationary phase - growth = death, nutrients depleted
4. Decline/Death phase - cells die

• Most heat-resistant biological structure
• Autoclave (121°C, 15 psi, 15 min) required for sterilisation

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SECTION 2: GRAM-POSITIVE COCCI

Staphylococcus

Staphylococcus aureus

• Coagulase positive (slide + tube)
• Beta-haemolytic on blood agar
• Golden yellow colonies (carotenoid pigment)
• Catalase positive
• Protein A - binds Fc region of IgG → evades opsonisation
• MRSA - mecA gene → altered PBP2a (low affinity for beta-lactams)

• Skin: Folliculitis, furuncle, carbuncle, impetigo, cellulitis
• SSSS (Scalded Skin Syndrome) - exfoliative toxin, desmoglein-1
• Food poisoning (1-6 hrs, preformed toxin, vomiting dominant)
• TSS (TSST-1, superantigen)
• Pneumonia (post-influenza), bacteraemia, endocarditis
• Osteomyelitis (most common cause in all ages)

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Coagulase-Negative Staphylococci (CoNS)

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Streptococcus

1. By haemolysis: Alpha (partial, green), Beta (complete, clear), Gamma (none)
2. By Lancefield grouping: A, B, C, D, F, G (based on cell wall carbohydrate)

S. pyogenes (Group A Streptococcus)

• Beta-haemolytic, Lancefield A
• Bacitracin sensitive (A disc)
• M protein - major virulence factor, antiphagocytic, basis of serotyping

• Pharyngitis, tonsillitis
• Impetigo (school sores)
• Scarlet fever (SPE erythrogenic toxin, phage-encoded)
• Necrotising fasciitis
• Streptococcal TSS (SPE superantigen)
• Post-streptococcal: Rheumatic fever, Post-streptococcal GN (PSGN)

• Carditis, Polyarthritis (migratory), Sydenham's chorea, Erythema marginatum, Subcutaneous nodules
• CATCHES = Carditis, Arthritis, Chorea, Erythema marginatum, Subcutaneous nodules

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S. agalactiae (Group B Streptococcus)

• Beta-haemolytic, Lancefield B
• CAMP test positive (arrowhead haemolysis with S. aureus beta-lysin)
• Hippurate hydrolysis positive
• Normal vaginal flora in 20-30% women

• Neonatal meningitis + sepsis (most common cause)
• Neonatal pneumonia
• UTI in pregnant women
• Diabetic foot infections

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S. pneumoniae

• Alpha-haemolytic (green on blood agar)
• Lancet-shaped diplococci
• Bile solubility test positive (autolysis in bile/deoxycholate)
• Optochin sensitive
• Inulin fermentation positive
• Quellung reaction (capsular swelling) - for serotyping

• Capsule - most important (prevents phagocytosis)
• IgA protease, pneumolysin, surface proteins

• Lobar pneumonia (most common cause in adults)
• Meningitis (most common in adults + elderly)
• Otitis media (most common in children)
• Sinusitis
• Most common cause of CAP at all ages

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Viridans Streptococci

• Alpha-haemolytic (partially), bile insoluble, optochin resistant
• Normal oral flora
• Most common cause of Subacute Bacterial Endocarditis (SBE) - S. sanguis, S. mutans, S. mitis
• S. bovis (now S. gallolyticus) - associated with colorectal carcinoma (always colonoscopy!)
• S. mutans - dental caries

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Enterococcus (Group D)

• Alpha or gamma haemolytic
• Grows in 6.5% NaCl and bile esculin positive
• Intrinsically resistant to many antibiotics
• VRE (Vancomycin-Resistant Enterococcus) - major hospital pathogen
• Diseases: UTI, endocarditis, biliary infections

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SECTION 3: GRAM-POSITIVE BACILLI

Bacillus species (Aerobic, Spore-forming)

Bacillus anthracis

• Bamboo-cane appearance (jointed rods)
• Non-motile (unlike other Bacillus)
• Non-haemolytic on blood agar
• Capsule made of poly-D-glutamic acid (not polysaccharide)
• Medusa head / Frosted glass colonies
• String of pearls test (penicillin inhibition forms spheroplasts)
• Toxins: PA + EF (oedema toxin), PA + LF (lethal toxin)

• Cutaneous (most common, 95%) - malignant pustule → black eschar
• Inhalational (Woolsorter's disease) - widened mediastinum on CXR
• GI anthrax - from ingestion of spores

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Bacillus cereus

• Food poisoning - 2 types:
  1. Emetic type (1-5 hrs, vomiting) - rice dishes (cereulide toxin, heat stable)
  2. Diarrhoeal type (8-16 hrs, diarrhoea) - meat/vegetables (enterotoxin, heat labile)

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Clostridium species (Anaerobic, Spore-forming)

C. tetani

• Terminal spore (drumstick/tennis racket appearance)
• Tetanospasmin (plasmid) → retrograde to spinal cord → blocks GABA/glycine → spastic paralysis
• Tetanolysin - haemolysin
• Generalised tetanus: trismus → risus sardonicus → opisthotonus
• Neonatal tetanus - umbilical stump infection, poor immunisation of mother

C. botulinum

• Subterminal spore
• Most potent biological toxin (LD50 ~1 ng/kg)
• Blocks ACh at NMJ → flaccid descending paralysis
• Infant botulism - most common form in USA; honey → spores germinate in gut
• Home-canned food - classic adult botulism (type A, B, E)

C. perfringens

• Stormy fermentation in litmus milk (rapid gas production)
• Nagler reaction positive (lecithinase activity on egg-yolk agar)
• Double zone of haemolysis on blood agar
• Alpha toxin (lecithinase) - most important
• Type A: gas gangrene, food poisoning
• Type C: Necrotising enteritis (Pig-bel disease, Papua New Guinea)

C. difficile

• Yellow, horse-manure smell colonies on CCFA medium
• Toxin A (enterotoxin) + Toxin B (cytotoxin)
• Glucosylates Rho GTPases → cytoskeletal disruption
• Pseudomembrane on colonoscopy (yellow plaques)
• Associated with clindamycin, fluoroquinolones, broad-spectrum antibiotics
• Diagnosis: Stool PCR (most sensitive), EIA for toxins
• Treatment: Oral vancomycin or fidaxomicin (first line), bezlotoxumab (prevents recurrence)

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Corynebacterium diphtheriae

• Club-shaped (Chinese letter arrangement)
• Albert's stain - metachromatic (volutin) granules at poles
• Tellurite medium - black/grey colonies (reduces tellurite)
• Elek's test - immunodiffusion to detect toxin production
• Toxin only produced in lysogenic strains (infected by β-corynephage)
• Toxin: ADP-ribosylates EF-2 → blocks protein synthesis → myocarditis, neuropathy

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Listeria monocytogenes

• Small Gram-positive rod
• Tumbling motility at room temperature (22°C), non-motile at 37°C
• Cold enrichment - grows at 4°C (refrigerator temperature)
• Actin rocket motility inside host cells
• Umbrella-shaped motility in semi-solid agar

• Neonatal meningitis + sepsis (along with GBS)
• Meningitis in elderly + immunocompromised
• Granulomatosis infantiseptica (disseminated in neonates)
• Food-borne (soft cheeses, deli meats, raw vegetables)
• Treatment: Ampicillin + Gentamicin (NOT cephalosporins - intrinsically resistant)

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SECTION 4: GRAM-NEGATIVE COCCI

Neisseria

N. meningitidis

• Diplococci (kidney-shaped pairs), intracellular in CSF
• Requires chocolate agar or blood agar with CO₂
• Polysaccharide capsule - key virulence factor (13 serogroups: A, B, C, W, Y most important)
• Ferments glucose + maltose (distinguishes from N. gonorrhoeae)
• IgA protease

• Meningitis (most common bacterial meningitis in meningitis belt Africa)
• Meningococcaemia with Waterhouse-Friderichsen syndrome (bilateral adrenal haemorrhage, purpuric rash, DIC)
• Petechiae/purpura is the hallmark
• Terminal complement deficiency (C5-C9) → recurrent Neisseria infections

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N. gonorrhoeae

• No polysaccharide capsule
• Ferments glucose only (not maltose)
• Thayer-Martin medium (chocolate agar + antibiotics)
• Pili - type IV, antigenic variation (pilE gene)
• Protein II (Opa proteins) - mediate attachment to epithelial cells
• IgA protease - cleaves secretory IgA
• Beta-lactamase (plasmid) - penicillin resistance

• Urethritis, cervicitis
• PID, salpingitis (Fitz-Hugh-Curtis syndrome - perihepatitis)
• Ophthalmia neonatorum (treated with erythromycin eye ointment)
• Disseminated gonococcal infection (DGI): septic arthritis, skin lesions, tenosynovitis
• Treatment: Ceftriaxone IM (DOC now due to widespread resistance)

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SECTION 5: GRAM-NEGATIVE BACILLI

Enterobacteriaceae (Lactose fermenters vs Non-fermenters)

• Pink colonies (lactose fermenters): E. coli, Klebsiella, Enterobacter, Citrobacter
• Colourless (non-fermenters): Salmonella, Shigella, Proteus

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Escherichia coli

• UTI (most common cause) - fimbriae, P pili (uropathogenic)
• Neonatal meningitis (K1 capsular antigen)
• Neonatal meningitis: E. coli K1 + GBS = top 2 causes

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Klebsiella

• Large mucoid colonies, thick capsule (mucoviscosity)
• Currant jelly sputum (haemorrhagic, mucoid)
• Friedländer's pneumonia - upper lobe, alcohol/diabetes
• UTI (hospital-acquired, catheter)
• K. granulomatis (formerly Calymmatobacterium) → Granuloma inguinale (Donovanosis)
  • Donovan bodies in macrophages

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Salmonella

Salmonella typhi (Typhoid fever)

• Ingested → invades Peyer's patches (ileum) → M cells → macrophages → blood
• Bacteraemia → seeded to liver, spleen, bone marrow, Peyer's patches

• Week 1: Fever, step-ladder pattern, headache, relative bradycardia
• Week 2: Rose spots (anterior chest), splenomegaly, hepatomegaly
• Week 3: Complications - intestinal haemorrhage/perforation, myocarditis
• Week 4: Resolution

• Week 1: Blood culture (most sensitive early)
• Week 2-3: Stool + urine culture
• Widal test: O agglutinins (active disease), H agglutinins (past infection/vaccination)
  • Significant: O titre ≥1:160; H titre ≥1:320

Non-typhoidal Salmonella

• Food poisoning (poultry, eggs)
• Gastroenteritis (self-limiting, 2-3 days)
• Bacteraemia in sickle cell disease (Salmonella osteomyelitis)

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Shigella

• S. dysenteriae (most severe, Shiga toxin, HUS) > S. flexneri > S. boydii > S. sonnei (mildest, most common in developed world)

• Very small inoculum (10-100 organisms)
• Invades colonic mucosa → intracellular spread via actin rockets
• Causes dysentery (bloody diarrhoea + mucus + pus)

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Vibrio

Vibrio cholerae

• Comma-shaped, oxidase positive
• TCBS agar - yellow colonies (sucrose fermenter)
• Serotype O1 (classic + El Tor biotypes) and O139 cause epidemics
• Darting motility (shooting star appearance)
• Dark-field microscopy - characteristic motility
• Toxin: Cholera toxin (CT) - phage-encoded (CTXφ), ↑cAMP
• Rice-water diarrhoea, severe dehydration, "washerwoman's hands"
• Treatment: Oral rehydration salts (primary); Doxycycline (antibiotic shortens duration)

V. parahaemolyticus

• Seafood consumption (raw shellfish, crabs)
• Watery or bloody diarrhoea
• Blue-green colonies on TCBS (non-sucrose fermenter)

V. vulnificus

• Most virulent Vibrio
• Necrotising soft tissue infections in coastal areas
• Liver disease patients → fatal septicaemia from raw oysters

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Campylobacter

Campylobacter jejuni

• Most common bacterial cause of food-borne diarrhoea globally
• S-shaped / gull-wing-shaped rods
• Microaerophilic (5% O₂)
• 42°C optimal growth temperature (selective advantage)
• Darting motility (corkscrew)
• Campy-BAP medium (blood agar + antibiotics, 42°C)

• Bloody diarrhoea (invasive)
• Post-infectious complications:
  • Guillain-Barré syndrome (GBS) - molecular mimicry, ganglioside antibodies
  • Reactive arthritis
  • C. jejuni serotype O:19 most associated with GBS

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Helicobacter pylori

• Spiral-shaped, microaerophilic
• Urease positive (most important virulence factor - produces ammonia, neutralises acid)
• CLO test (Campylobacter-like organism test) - biopsy urease test

• Urease, flagella, adhesins
• CagA (cytotoxin-associated gene A) - associated with gastric cancer + peptic ulcer
• VacA (vacuolating cytotoxin) - mucosal damage

• Peptic ulcer disease (duodenal 95%, gastric 70%)
• Chronic gastritis (type B antral gastritis)
• Gastric adenocarcinoma (IARC Group 1 carcinogen)
• MALT lymphoma (eradication alone can cure early MALT lymphoma)

• Urea breath test (UBT) - best non-invasive test, best for test of cure
• Stool antigen test (non-invasive)
• Serology (IgG ELISA) - cannot distinguish active vs past
• Endoscopic biopsy: CLO test + histology + culture (most specific)

• PPI + Clarithromycin + Amoxicillin (or Metronidazole) for 14 days

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Pseudomonas aeruginosa

• Oxidase positive, non-fermenter
• Blue-green pigment (pyocyanin) + fluorescent pigment (pyoverdin)
• Grape-like/fruity odour (2-aminoacetophenone)
• Grows at 42°C (selective advantage)
• Mucoid strains in cystic fibrosis (alginate capsule)

• Nosocomial pneumonia (ventilator-associated)
• Burn wound infections
• Malignant otitis externa (diabetics, elderly)
• Cystic fibrosis lung infections
• Hot tub folliculitis
• UTI (catheterised patients)
• Ecthyma gangrenosum (black necrotic skin lesion in immunocompromised)

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Haemophilus influenzae

• Small pleomorphic Gram-negative coccobacillus
• Requires Factor X (haemin) + Factor V (NAD) for growth
• Chocolate agar (blood heated to 80°C releases X and V factors)
• Satellitism around Staph aureus colonies on blood agar
• Type b capsule (polyribose ribitol phosphate) - most virulent, vaccine-preventable

• Meningitis (before Hib vaccine - most common in children)
• Epiglottitis (type b) - "thumb sign" on lateral neck X-ray
• Pneumonia (non-typeable strains, adults with COPD)
• Otitis media, sinusitis
• Conjunctivitis (non-typeable)

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Bordetella pertussis

• Small Gram-negative coccobacillus
• Bordet-Gengou medium (potato blood glycerol agar) - mercury drop colonies
• Filamentous haemagglutinin (FHA) - major adhesin
• Pertussis toxin (PT), tracheal cytotoxin, adenylate cyclase toxin

1. Catarrhal phase (1-2 weeks) - most infectious, mild cold symptoms
2. Paroxysmal phase (2-6 weeks) - paroxysmal cough + inspiratory whoop + post-tussive vomiting
3. Convalescent phase (weeks-months) - gradual recovery

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Legionella pneumophila

• BCYE agar (L-cysteine + iron required)
• Cannot be seen on Gram stain easily (takes up safranin poorly)
• Dieterle silver stain used for tissue
• Intracellular pathogen (multiplies in macrophages + protozoa)
• Source: Air conditioning cooling towers, water heaters, hospital water

• Severe pneumonia (especially in middle-aged men, smokers, immunocompromised)
• Relative bradycardia, hyponatraemia, elevated LFTs, diarrhoea, confusion
• "Pontiac fever" = mild flu-like illness (same organism, no pneumonia)

• Urinary antigen test (most rapid, detects serogroup 1)
• Culture on BCYE (gold standard, slow)
• DFA (direct fluorescent antibody)

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Brucella

• Obligate intracellular (facultative)
• Gram-negative coccobacillus
• Zoonosis - from cattle (B. abortus), goat/sheep (B. melitensis - most virulent), pigs (B. suis), dogs (B. canis)
• Transmission: unpasteurised milk/cheese, contact with infected animals

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Yersinia

Yersinia pestis (Plague)

• Gram-negative coccobacillus, bipolar staining (safety-pin appearance) with Wayson's stain
• Reservoir: Rodents; Vector: Rat flea (Xenopsylla cheopis)
• Forms: Bubonic (most common, bubo = inguinal lymph node), Pneumonic (most dangerous, droplet spread), Septicaemic

Y. enterocolitica

• Cold-enrichment, grows at 4°C
• Mimics acute appendicitis (mesenteric lymphadenitis)
• Bloody diarrhoea, fever

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Francisella tularensis (Tularaemia)

• Most infectious bacterium (10 organisms cause disease)
• Gram-negative coccobacillus
• Reservoir: Rabbits, rodents; Vector: Ticks, deer flies
• Transmission: tick bite, handling infected animals, inhalation
• Requires cysteine for growth
• Forms: Ulceroglandular (most common), Pneumonic, Oculoglandular, Typhoidal

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SECTION 6: ANAEROBIC BACTERIA

Bacteroides fragilis

• Most common anaerobe in human colon
• Polysaccharide capsule (only anaerobe with a capsule)
• Metronidazole - drug of choice
• Important in intra-abdominal infections, peritonitis

Fusobacterium

• Long pointed rods
• Associated with Lemierre's syndrome (septic thrombophlebitis of internal jugular vein after pharyngitis)
• Also in periodontal disease (along with Treponema - ANUG)

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SECTION 7: SPIROCHETES

Treponema pallidum (Syphilis)

• Cannot be cultured on artificial media
• Too thin for Gram stain
• Dark-field microscopy (corkscrew motility)
• Silver stain (Warthin-Starry, Levaditi) for tissue sections

• Non-treponemal (screening): VDRL, RPR - become negative after treatment (used for monitoring)
• Treponemal (confirmatory): TPHA, FTA-ABS, TPPA - remain positive lifelong
• Biological false positives (VDRL): SLE, antiphospholipid syndrome, malaria, pregnancy, TB, infectious mononucleosis

• Hutchinson's teeth, interstitial keratitis, sensorineural deafness (Hutchinson's triad)
• Saddle nose, sabre tibia, Clutton's joints

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Leptospira (Leptospirosis)

• Hooked ends (question mark appearance)
• Fletcher's medium (semi-solid)
• Dark-field microscopy

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Borrelia

Borrelia burgdorferi (Lyme disease)

• Vector: Ixodes tick (deer tick)
• Giemsa stain, Barbour-Stoenner-Kelly (BSK) medium

1. Stage 1: Erythema migrans (bulls-eye rash) at tick bite site
2. Stage 2: Dissemination - Bell's palsy, meningitis, carditis (heart block)
3. Stage 3: Arthritis (large joints, esp. knee), chronic neurological (Lyme encephalopathy)

Borrelia recurrentis (Relapsing fever)

• Vector: Body louse (epidemic relapsing fever)
• Giemsa stain during febrile episodes
• Antigenic variation of OspC protein → relapsing fever

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SECTION 8: INTRACELLULAR BACTERIA

Rickettsia

• Scrub typhus - eschar at bite site, characteristic; Indian Ocean islands, Asia
• Q fever - atypical pneumonia + hepatitis + no rash + no vector; phase I/II antigen; Weil-Felix negative
• Epidemic typhus - louse-borne, war/crowded conditions, Brill-Zinsser disease (recrudescence)
• RMSF - petechial rash starts on wrists and ankles → spreads centrally

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Chlamydia

• Elementary body (EB) - infectious, metabolically inert, extracellular
• Reticulate body (RB) - replicating, intracellular, metabolically active

Chlamydia trachomatis (serovars)

C. pneumoniae (TWAR strain)

• Atypical pneumonia (mild, walking pneumonia)
• Associated with atherosclerosis

C. psittaci

• Psittacosis/Ornithosis - from birds (parrots, pigeons)
• Atypical pneumonia + systemic features

• Trachoma: Azithromycin single dose (SAFE strategy)

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Mycoplasma

Mycoplasma pneumoniae

• Cold agglutinins (IgM against I antigen on RBCs) - positive in ~50%
• Causes autoimmune haemolytic anaemia
• Atypical pneumonia ("walking pneumonia")
• Eaton agent - grows on Eaton's medium (SP4 medium)
• Fried-egg colonies on Eaton's medium

Mycoplasma genitalium

• NGU (non-gonococcal urethritis)
• Emerging resistance to azithromycin; moxifloxacin used

Ureaplasma urealyticum

• NGU, splits urea
• Associated with premature delivery

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SECTION 9: MYCOBACTERIUM

Mycobacterium tuberculosis

• Strict aerobe
• Slow growth (generation time 16-20 hrs)
• LJ medium (eggs + glycerol + malachite green) - 4-8 weeks
• Buff, rough, dry, crumbly colonies

• Cord factor (Trehalose 6,6'-dimycolate) - inhibits PMN migration, toxic to mitochondria, causes serpentine cord growth
• Wax D (mycolic acid) - acid-fastness, adjuvant property
• Sulfatides - inhibit phagolysosome fusion
• Lipoarabinomannan (LAM) - scavenges free radicals, inhibits T cell activation

• Droplet nuclei (<5 μm) → alveoli → ingested by macrophages (but resists killing)
• Primary complex (Ghon focus = parenchymal lesion + hilar lymph node = Ranke complex)
• Hypersensitivity (Type IV, delayed, Th1-mediated) = tuberculin sensitivity
• Caseation necrosis, granuloma (epithelioid cells, Langhan's giant cells)

• Sputum AFB smear (ZN stain, most rapid, but needs 5,000-10,000 bacilli/mL)
• Culture on LJ medium (gold standard, but slow)
• BACTEC/MGIT (liquid culture, fastest - 1-3 weeks)
• Xpert MTB/RIF (PCR-based, detects TB + rifampicin resistance simultaneously, 2 hours) - WHO recommended first test
• Tuberculin skin test (Mantoux) - inject 5TU PPD intradermally, read at 48-72 hrs
  • ≥5 mm: HIV, recent contact, fibrotic lesion on CXR
  • ≥10 mm: High-risk groups (healthcare workers, immigrants, homeless)
  • ≥15 mm: No risk factors

• Intensive phase (2 months): HRZE (Isoniazid + Rifampicin + Pyrazinamide + Ethambutol)
• Continuation phase (4 months): HR (Isoniazid + Rifampicin)

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Mycobacterium leprae (Leprosy)

• Cannot be cultured on artificial media (like T. pallidum)
• Grown in armadillo footpads (in vivo)
• Acid-fast (ZN stain, also Wade-Fite stain)
• Fite-Faraco stain used in tissue sections

• Tests cell-mediated immunity, not diagnosis
• Positive = TT (good prognosis), Negative = LL (poor prognosis)

• Type 1 reaction (reversal reaction) - upgrading or downgrading, treat with prednisolone
• Type 2 reaction (ENL - Erythema Nodosum Leprosum) - immune complex, treat with thalidomide/prednisolone

• Paucibacillary (PB): Rifampicin (monthly supervised) + Dapsone (daily) × 6 months
• Multibacillary (MB): Rifampicin + Clofazimine (monthly supervised) + Dapsone + Clofazimine (daily) × 12 months

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Non-Tuberculous Mycobacteria (NTM)

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SECTION 10: VIROLOGY

DNA Viruses (mnemonic: HHAPPPY)

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Herpes Viruses (HHV 1-8)

• Fever + pharyngitis + lymphadenopathy + splenomegaly
• Monospot test (heterophile antibodies) - positive
• Atypical lymphocytes (Downey cells) on peripheral smear
• Ampicillin/amoxicillin → maculopapular rash in EBV (avoid!)
• Associated: Burkitt's lymphoma, Nasopharyngeal carcinoma, Post-transplant lymphoproliferative disorder, CNS lymphoma in AIDS

• Most common congenital viral infection causing hearing loss
• Periventricular calcifications (congenital CMV) vs cortical calcifications (Toxoplasma)
• Owl-eye inclusions in infected cells
• CMV retinitis (AIDS, CD4 <50) - "pizza pie" or "ketchup & cheese" appearance

• Chickenpox: Centripetal distribution, "dew drop on rose petal" vesicles, all stages simultaneously
• Herpes zoster: Dermatomal, painful, unilateral; Ramsay Hunt syndrome (VII nerve + ear)
• Tzanck smear - multinucleated giant cells (both HSV and VZV)
• Treatment: Aciclovir (all herpesviruses), Valaciclovir (higher bioavailability)

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Hepatitis Viruses

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HIV

• CCR5 - used by macrophage-tropic strains (M-tropic, R5 strains) - early infection
• CXCR4 - used by T-cell tropic strains (T-tropic, X4 strains) - late disease
• Delta 32 mutation in CCR5 → resistance to HIV (homozygous protective)

• ELISA (4th generation - detects IgG + p24 antigen) - screening
• Western blot - confirmatory (bands at gp120, gp41, p24)
• HIV RNA PCR - viral load (monitors treatment), used in neonates (maternal antibodies confound serology for 18 months)

• Standard first-line: 2 NRTIs + 1 INSTI (e.g., TDF + FTC + Dolutegravir)

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Respiratory Viruses

• Antigenic drift (minor changes in HA/NA, point mutations) → seasonal epidemics
• Antigenic shift (major reassortment of genome segments) → pandemics
• Reassortment between human + animal (avian/swine) strains
• Treatment: Oseltamivir (Tamiflu) - neuraminidase inhibitor, within 48 hours of symptoms
• Amantadine/Rimantadine (M2 inhibitors) - only influenza A, widespread resistance

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Childhood Exanthems

• Cataracts, patent ductus arteriosus (PDA), sensorineural deafness
• "Blueberry muffin" baby (dermal haematopoiesis)
• Prevention: MMR vaccine (live attenuated, avoid in pregnancy)

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Enteroviruses (Picornaviridae)

• Poliovirus, Coxsackievirus, Echovirus, Enterovirus
• Faeco-oral transmission, replicate in intestine
• Poliovirus: Anterior horn cells → lower motor neurone lesion → flaccid paralysis
  • OPV (oral, live attenuated) vs IPV (injectable, killed)
  • Vaccine-associated paralytic poliomyelitis (VAPP) - rare, only with OPV
• Coxsackievirus A16 - Hand-foot-mouth disease, herpangina
• Coxsackievirus B - Myocarditis (most common cause of viral myocarditis), pleurodynia (Bornholm disease), neonatal sepsis

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SECTION 11: MYCOLOGY (FUNGI)

Classification

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Key Fungi

Candida albicans

• Dimorphic - yeast at 37°C, hyphae/pseudohyphae in tissue
• Germ tube test (positive) - forms germ tubes in serum at 37°C
• Chlamydoconidia - on cornmeal agar
• Thrush (oral, oesophageal), vulvovaginitis, diaper rash, systemic candidiasis
• Risk factors: antibiotics, diabetes, immunosuppression, catheters
• Treatment: Fluconazole (superficial), Amphotericin B or Echinocandins (systemic)

Cryptococcus neoformans

• Encapsulated yeast, India ink - halo capsule
• Mucicarmine positive capsule (pink staining)
• Urease positive, phenol oxidase positive (melanin production)
• Source: Pigeon droppings (dried pigeon faeces)
• Meningitis in AIDS (CD4 <100) - "soap bubble" lesions in basal ganglia
• India ink - direct CSF exam
• Serum/CSF cryptococcal antigen (CrAg) - most sensitive
• Treatment: Amphotericin B + Flucytosine (induction) → Fluconazole (consolidation/maintenance)

Aspergillus fumigatus

• Septate hyphae with acute angle branching (45°)
• Conidiophore with vesicle and phialides (fruiting body)
• Source: Decaying vegetation, construction sites
• Diseases:
  • Allergic bronchopulmonary aspergillosis (ABPA) - asthma/CF patients, IgE↑, central bronchiectasis
  • Aspergilloma ("fungus ball") - in pre-existing cavity (old TB), aerial hyphae on CT
  • Invasive aspergillosis - immunocompromised (neutropenic), "halo sign" on CT chest
• Treatment: Voriconazole (first line for invasive), Amphotericin B, Caspofungin

Mucor / Rhizopus (Zygomycetes/Mucormycosis)

• Non-septate (aseptate/pauci-septate) hyphae with right-angle (90°) branching
• Ribbon-like hyphae
• Risk factors: Diabetic ketoacidosis (DKA), iron overload, deferoxamine treatment, neutropenia
• Rhinocerebral mucormycosis (most common form) - black eschar on nasal turbinates, invades orbit
• Treatment: Amphotericin B (first line), surgical debridement

Pneumocystis jirovecii

• NOT a true fungus (originally thought to be a protozoan, reclassified)
• Cannot be cultured in standard media
• GMS (Gomori methenamine silver) stain - black cysts with "helmet" or "crushed ping-pong ball" appearance
• Causes PCP (Pneumocystis pneumonia) in AIDS (CD4 <200)
• CXR: bilateral interstitial infiltrates ("ground glass"), perihilar
• LDH elevated (marker of severity)
• Treatment: Co-trimoxazole (TMP-SMX) - first line, also prophylaxis when CD4 <200
• Alternatives: Pentamidine, Atovaquone, Primaquine + Clindamycin

Sporothrix schenckii

• Dimorphic - mould in environment, yeast in tissue
• Rose thorn injury (florists, gardeners)
• Lymphocutaneous sporotrichosis - nodules along lymphatics
• Treatment: Itraconazole (potassium iodide for cutaneous)

Histoplasma capsulatum

• Dimorphic - mould (25°C), yeast (37°C, intracellular in macrophages)
• Ohio-Mississippi River valley (bird + bat droppings)
• Resembles leishmaniasis on tissue (small intracellular yeasts)
• Treatment: Itraconazole (mild), Amphotericin B (severe)

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Antifungal Drugs

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SECTION 12: PARASITOLOGY

Malaria

• Peripheral blood smear (thick = sensitivity, thin = species identification)
• RDT (Rapid Diagnostic Test) - HRP-2 antigen for P. falciparum
• PCR (most sensitive)

• Uncomplicated P. falciparum: Artemisinin-based Combination Therapy (ACT) - Artemether-lumefantrine
• Severe malaria: IV Artesunate (first line, replaced quinine)
• P. vivax/ovale (radical cure): Chloroquine + Primaquine (clears hypnozoites; check G6PD first!)
• Prophylaxis: Doxycycline, Mefloquine, Atovaquone-proguanil (Malarone)

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Leishmania

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Trypanosomiasis

African (Sleeping sickness)

• T. brucei gambiense (West Africa, chronic) + T. brucei rhodesiense (East Africa, acute)
• Vector: Tsetse fly (Glossina)
• Chancre at bite → stage 1 (blood, lymph, winterbottom's sign = posterior cervical lymphadenopathy) → stage 2 (CNS)
• Treatment: Pentamidine/suramin (stage 1), Melarsoprol (stage 2)

American (Chagas disease)

• T. cruzi
• Vector: Triatomine bug (kissing bug/Reduviid bug), infects via faeces
• Chagoma, Romaña's sign (periorbital oedema)
• Chronic: Cardiomyopathy, megaoesophagus, megacolon
• Treatment: Benznidazole or Nifurtimox (acute phase)

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Intestinal Parasites (Rapid Fire)

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Tissue/Blood Parasites

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SECTION 13: STERILISATION & DISINFECTION

Key Definitions

• Sterilisation: Destruction of ALL microorganisms including spores
• Disinfection: Destruction of most pathogens (not necessarily spores)
• Antiseptic: Used on living tissues
• Disinfectant: Used on inanimate objects
• Bactericidal: Kills bacteria
• Bacteriostatic: Inhibits growth

Methods

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SECTION 14: IMMUNOLOGY (Micro-related)

Complement System

• C3b - Opsonisation (most important)
• C3a, C5a - Anaphylatoxins (mast cell degranulation)
• C5a - Chemotaxis (PMN recruitment), most potent
• C5b-9 (MAC) - Lysis of Gram-negative bacteria
• C1q - clearance of immune complexes

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Hypersensitivity (Gell & Coombs)

• PSGN → Type III (streptococcal antigen-antibody complexes)
• Tuberculin test → Type IV
• Rheumatic fever → Type II (molecular mimicry) + Type III

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Immunoglobulins

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SECTION 15: HIGH-YIELD ONE-LINERS (NEET PG Favourite Facts)

• T. pallidum (dark-field microscopy)
• M. leprae (armadillo footpad)
• Rickettsia (cell culture only)
• Chlamydia (cell culture only)
• P. jirovecii (GMS stain)

• Viruses (all), Rickettsia, Chlamydia, Coxiella, Mycobacterium leprae (facultative), Leishmania, Toxoplasma, Plasmodium

• Most common bacterial meningitis (adults) → S. pneumoniae
• Most common bacterial meningitis (neonates) → GBS (S. agalactiae) + E. coli K1
• Most common meningitis (meningitis belt Africa) → N. meningitidis
• Most common UTI → E. coli
• Most common CAP → S. pneumoniae
• Most common food-borne diarrhoea (globally) → Campylobacter jejuni
• Most common nosocomial infection → UTI (CAUTI)
• Most common cause of osteomyelitis → S. aureus
• Most common organism in diabetic foot → S. aureus (polymicrobial in chronic)
• Most common cause of SBE → Viridans streptococci
• Most common cause of acute endocarditis → S. aureus
• Most common cause of prosthetic valve endocarditis (early, <60 days) → S. epidermidis
• Most common fungal infection in AIDS → Candida (oral thrush earliest)
• Most common cause of infectious blindness → Trachoma (C. trachomatis)
• Most common STI globally → HPV
• Most common STI in India → Trichomonas vaginalis

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💉 Anesthesia Complete Revision

NEET PG Master Guide

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SECTION 1: GENERAL PRINCIPLES

MAC (Minimum Alveolar Concentration)

• Old age
• Hypothermia
• Hypothyroidism
• Hypotension
• Pregnancy
• Opioids, benzodiazepines, alpha-2 agonists
• Anaemia (severe)
• Increased CO₂

• Children (peak at ~6 months)
• Hyperthermia
• Hyperthyroidism
• Chronic alcohol use
• Red hair (genetically higher MAC)

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Blood-Gas Partition Coefficient (Solubility)

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Second Gas Effect & Diffusion Hypoxia

• At end of N₂O anaesthesia, N₂O rapidly diffuses from blood into alveoli
• Dilutes alveolar O₂ and CO₂
• → Hypoxia + hypoventilation
• Prevention: Give 100% O₂ for 5-10 minutes at end of anaesthesia

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SECTION 2: INHALATIONAL AGENTS

Nitrous Oxide (N₂O)

• Colourless, sweet smell, non-flammable (but supports combustion)
• MAC = 105% (cannot produce anaesthesia alone at 1 atm)
• Blood-gas coefficient 0.47 → fast induction
• Diffuses into air-containing cavities (30x more soluble than N₂)

• Pneumothorax (expands)
• Bowel obstruction (expands bowel)
• Middle ear surgery (expands middle ear)
• Air embolism (expands gas)
• Pneumocephalus (after neurosurgery)
• Retinal detachment surgery (SF6 gas in eye)
• Tympanoplasty

• Analgesic (strongest analgesic among volatile agents)
• Entonox = 50% N₂O + 50% O₂ (obstetric analgesia, labour pain)
• Inhibits methionine synthase (Vitamin B12-dependent enzyme) → megaloblastic anaemia with prolonged use
• "Second gas effect"

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Halothane

• Sweetish, non-irritant, good for mask induction
• MAC 0.75%, blood-gas 2.4 (slow induction)
• Sensitises myocardium to catecholamines → arrhythmias (avoid adrenaline with halothane)
• Halothane hepatitis (type II - immune-mediated) - rare but fatal (~1:35,000)
  • More common with repeated exposure
  • Trifluoroacetyl chloride (metabolite) acts as hapten → autoantibodies
• Causes malignant hyperthermia (trigger agent)
• Uterine relaxation (tocolytic) - avoid in obstetrics (PPH risk)

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Sevoflurane

• Non-pungent, non-irritant → gold standard for gaseous induction in children
• Fast (blood-gas 0.69)
• Minimal cardiovascular effects

• Compound A (degradation product in soda lime) → nephrotoxicity (theoretical, high-flow anaesthesia recommended)
• Fluoride ions released (renal concerns, but clinical nephrotoxicity rare)

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Isoflurane

• Pungent smell → avoid for induction (use IV induction)
• Most common volatile agent used
• Causes coronary steal phenomenon (dilates normal coronaries, steals from diseased areas)
• Potent respiratory depressant
• Good muscle relaxation

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Desflurane

• Lowest blood-gas coefficient (0.42) after N₂O
• Fastest wake-up (ideal for outpatient/day surgery)
• Highly pungent - CANNOT be used for induction (laryngospasm, bronchospasm)
• Requires special heated vaporiser (boils at 23.5°C near room temp)
• ↑ Heart rate and BP on rapid increase in concentration (sympathomimetic)
• Minimal metabolism (least hepatotoxicity)

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Ether (Historical but asked)

• Blood-gas coefficient = 12 (slowest)
• Excellent muscle relaxant (used to be sole agent)
• Analgesia without muscle relaxation → Stage 1 analgesia
• Stages of anaesthesia described for ether (Guedel's stages)
• Flammable, explosive
• Safest agent - wide therapeutic index, cardiovascular stability
• Still used in some resource-poor settings

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SECTION 3: GUEDEL'S STAGES OF ANAESTHESIA

• Plane 1: Eyeballs moving, some reflexes
• Plane 2: Eyeballs fixed, loss of corneal reflex
• Plane 3: Intercostal paralysis begins, ideal for most surgery
• Plane 4: Complete intercostal paralysis, diaphragmatic only

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SECTION 4: IV ANAESTHETIC AGENTS

Thiopentone (Thiopental)

• Ultrashort-acting barbiturate (highly lipid soluble → rapid brain uptake)
• Onset 30 sec, duration 5-10 min (redistribution, NOT metabolism)
• Gold standard for rapid sequence induction (RSI) historically
• pH 10.5 (highly alkaline) - precipitates with acidic drugs (e.g., suxamethonium - never mix in same syringe)
• Anticonvulsant (drug of choice for status epilepticus - IV)
• ↓ ICP, ↓ cerebral O₂ consumption → used in raised ICP
• NOT analgesic - anti-analgesic in subanaesthetic doses

• Porphyria (absolute - precipitates acute porphyric crisis)
• Airways obstruction
• Asthma (histamine release)

• Intra-arterial injection → white precipitate → intense vasospasm → gangrene
  • Management: Papaverine (vasodilator) intra-arterially, heparin, sympathetic block

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Propofol

• Milky white emulsion (soybean oil, egg lecithin, glycerol)
• Onset 30-40 sec, smooth, pleasant induction
• Fastest recovery among IV agents (ideal for day-case surgery)
• Context-sensitive half-life very low with infusion
• Antiemetic properties (reduces PONV - post-operative nausea/vomiting)
• ↓ ICP (used in neurosurgery TIVA)

• Prolonged high-dose infusion (>4 mg/kg/hr for >48 hrs)
• Features: Metabolic acidosis, rhabdomyolysis, cardiac failure, renal failure, lipidaemia
• Most common in children and critically ill adults
• Mechanism: Impaired mitochondrial electron transport chain

• Pain on injection (use large vein/lidocaine pretreatment)
• No analgesic properties
• Anti-epileptic in high doses, pro-convulsant in low doses
• Contraindicated: Egg/soya allergy (relative), children <3 years for ICU sedation

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Ketamine

• Phencyclidine derivative
• Dissociative anaesthesia - unique state (analgesia + amnesia + sedation, eyes open, purposeless movements)
• Mechanism: NMDA receptor antagonist (non-competitive)

• Potent analgesic (unique among induction agents)
• Bronchodilator (increases catecholamines → β₂ stimulation) → drug of choice in asthmatic patients
• Maintains airway reflexes (protective reflexes maintained)
• ↑ BP, ↑ HR, ↑ cardiac output (sympathomimetic) → DOC in haemodynamically unstable/shocked patients
• Can be given IM (useful in uncooperative children, field conditions)

• ↑ ICP, ↑ IOP → contraindicated in head injury, glaucoma, hypertensive patients
• Emergence phenomena (hallucinations, delirium, nightmares) - on recovery
  • Prevented by benzodiazepines (midazolam) given before ketamine
• Hypersalivation (give atropine premedication)
• Not suitable for ophthalmic surgery (↑ IOP)

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Etomidate

• Imidazole derivative
• Most cardiovascular stable induction agent → DOC in cardiovascular disease, cardiogenic shock
• Minimal effect on BP, HR, cardiac output

• Adrenocortical suppression (inhibits 11β-hydroxylase → ↓ cortisol production)
  • Even a single induction dose causes 4-8 hrs of adrenal suppression
  • AVOID in sepsis/critically ill (controversial)
• Involuntary muscle movements (myoclonus)
• Pain on injection
• Nausea/vomiting

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Midazolam

• Benzodiazepine, water-soluble at acidic pH, lipid-soluble at body pH
• GABA-A receptor agonist (increases Cl⁻ conductance)
• Uses: Premedication, anxiolysis, sedation, conscious sedation, anticonvulsant
• Anterograde amnesia (ideal for premedication)
• Reversal: Flumazenil (competitive antagonist at BZD site of GABA-A receptor)
• Safe, minimal cardiovascular effects

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Dexmedetomidine

• Selective α-2 agonist (8x more selective than clonidine)
• Sedation without respiratory depression (unique!)
• Analgesic, anxiolytic
• Decreases anaesthetic/opioid requirements
• Uses: ICU sedation (allows rousable sedation), awake fibreoptic intubation, MAC procedures
• Causes: Bradycardia, hypotension (dose-dependent)

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SECTION 5: NEUROMUSCULAR BLOCKING AGENTS (NMBAs)

Classification

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Suxamethonium (Succinylcholine)

• Only depolarising NMBA in clinical use
• Fastest onset (60-90 sec), shortest duration (5-10 min)
• Drug of choice for rapid sequence intubation (RSI) and emergency intubation
• Hydrolysed by pseudocholinesterase (plasma cholinesterase)

• Due to depolarisation of motor end-plate
• Cause post-op myalgia (muscle pains)
• Prevented by small dose of non-depolarising agent (pre-curarisation)

• Burns (>72 hours post-burn)
• Crush injuries, rhabdomyolysis
• Denervation injuries (paraplegia, spinal cord injury)
• Hyperkalaemia
• Personal/family history of malignant hyperthermia
• Pseudocholinesterase deficiency

• Dibucaine inhibits normal pseudocholinesterase by 80% (dibucaine number = 80)
• Atypical pseudocholinesterase inhibited only 20% (dibucaine number = 20)
• Low dibucaine number = atypical enzyme = prolonged suxamethonium action

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Non-Depolarising NMBAs

• Prolonged/repeated suxamethonium doses
• Block character changes from depolarising to non-depolarising (reversible with neostigmine)

Atracurium

• Intermediate duration
• Hofmann elimination (spontaneous degradation at body pH/temp) - not dependent on liver/kidney
• DOC in hepatic + renal failure
• Releases histamine (avoid in asthmatics/allergy-prone)
• Laudanosine (metabolite) - CNS excitatory, seizures (at high doses)

Cisatracurium

• Isomer of atracurium
• Same Hofmann elimination
• Less histamine release than atracurium
• Better choice in ICU

Vecuronium

• Intermediate duration, steroid-based
• Minimal cardiovascular effects (no histamine)
• Hepatically metabolised (avoid in liver disease)

Rocuronium

• Fastest onset among non-depolarising agents (90 sec at high dose)
• Can be used instead of suxamethonium for RSI (at 1.2 mg/kg)
• Reversed by Sugammadex (selective relaxant binding agent)
• Minimal cardiovascular effects

Pancuronium

• Long-acting
• ↑ HR, ↑ BP (vagolytic + sympathomimetic) - useful in bradycardia but problem in hypertension/CAD
• Renal elimination (avoid in renal failure)

Mivacurium

• Shortest-acting non-depolarising agent
• Hydrolysed by pseudocholinesterase (like suxamethonium)
• Releases histamine

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Reversal of NMBAs

Anticholinesterases (reverse non-depolarising)

• Neostigmine (0.05 mg/kg) - most commonly used
• Mechanism: Inhibits acetylcholinesterase → ↑ ACh at NMJ → competes with non-depolarising agent

• Bradycardia, increased secretions, bronchospasm, increased GI motility
• Must give with atropine or glycopyrrolate (antimuscarinic)

Sugammadex

• Modified γ-cyclodextrin - encapsulates rocuronium/vecuronium
• Reverses even profound (deep) neuromuscular block
• Works for rocuronium and vecuronium only (not suxamethonium, atracurium)
• Fastest reversal (deep block reversed within 3 minutes)
• Dose: 2 mg/kg (moderate block), 4 mg/kg (deep), 16 mg/kg (immediate after suxamethonium-like dose of rocuronium)

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SECTION 6: LOCAL ANAESTHETICS

Classification

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Mechanism

• Block voltage-gated Na⁺ channels from inside the cell
• Bind to open/inactivated channels (use-dependent/frequency-dependent block)
• Preferentially block small, myelinated fibres first

• Small unmyelinated (C fibres - pain/temperature) blocked first
• Large myelinated (Aα - motor) blocked last

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Individual Agents

Lidocaine (Lignocaine)

• Most widely used
• Amide, intermediate duration (1-2 hrs)
• Maximum dose: Plain = 3 mg/kg; With adrenaline = 7 mg/kg
• IV lidocaine = antiarrhythmic (Class IB)
• Topical on trachea before intubation (attenuates pressor response)

Bupivacaine

• Long-acting (4-8 hrs) - ideal for postop analgesia
• Maximum dose: 2 mg/kg (plain); 2.5 mg/kg (with adrenaline)
• Cardiotoxic (blocks cardiac Na⁺ and K⁺ channels, causes refractory VF)
• Treatment of bupivacaine cardiotoxicity: 20% Intralipid (lipid emulsion rescue)
• 0.5% heavy bupivacaine used for spinal anaesthesia (hyperbaric = with glucose)

Ropivacaine

• Newer amide, long-acting
• Less cardiotoxic than bupivacaine (S-enantiomer, larger molecule, slower cardiac binding)
• Motor-sparing at lower concentrations (good for labour epidurals)

Cocaine

• Only local anaesthetic that is vasoconstrictor (inhibits noradrenaline reuptake)
• Used in ENT (nasal surgery) - combines anaesthesia + vasoconstriction
• All other LAs are vasodilators (except cocaine)

Prilocaine

• Causes methaemoglobinaemia (metabolite o-toluidine oxidises Hb to MetHb)
• Treatment: Methylene blue IV
• EMLA cream = Eutectic Mixture of LAs = Prilocaine + Lidocaine (topical for PICC, children)

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Adrenaline with Local Anaesthetics

• Ring block (digits/penis/ear/nose) - end arteries, risk of ischaemia/gangrene
• IV regional anaesthesia (Bier's block)
• Cocaine (already vasoconstrictive)

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Local Anaesthetic Toxicity

• Mild: Perioral tingling, tinnitus, metallic taste, lightheadedness
• Moderate: Slurred speech, diplopia, muscle twitching
• Severe: Convulsions → CNS depression → Coma

• Cardiac arrhythmias, bradycardia
• Bupivacaine → refractory VF (most cardiotoxic)

1. Stop injection, 100% O₂
2. Treat convulsions: Midazolam or Thiopentone
3. Cardiac arrest: CPR
4. 20% Intralipid (lipid emulsion) - for severe CVS toxicity (especially bupivacaine)

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SECTION 7: REGIONAL ANAESTHESIA

Spinal Anaesthesia (Subarachnoid Block)

• Heavy solution settles in dependent areas → position determines block level

• Absolute: Patient refusal, infection at site, coagulopathy, raised ICP, hypovolaemia (relative)
• Relative: Systemic sepsis, pre-existing neurological disease, severe aortic stenosis

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Epidural Anaesthesia

• Contains: Epidural fat, venous plexus (Batson's plexus), nerve roots
• Negative pressure in epidural space (hanging drop technique or loss of resistance technique)

• Can be topped up (catheter) → prolonged/continuous anaesthesia
• Can control level more precisely
• Less hypotension than spinal (slower sympathetic block)

• Intravascular injection → tachycardia (adrenaline)
• Intrathecal injection → rapid dense block

• Labour analgesia (most common use)
• Thoracic/abdominal surgery (combined spinal-epidural)
• Post-operative analgesia
• Cancer pain management

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Brachial Plexus Blocks

• Phrenic nerve palsy (ipsilateral hemidiaphragm) - always occurs → avoid in respiratory compromise
• Recurrent laryngeal nerve palsy
• Stellate ganglion block → Horner's syndrome
• Vertebral artery injection

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SECTION 8: MALIGNANT HYPERTHERMIA

Triggers

• All volatile anaesthetic agents (halothane, isoflurane, sevoflurane, desflurane)
• Suxamethonium

Pathophysiology

• Autosomal dominant mutation in ryanodine receptor (RYR1) gene on chromosome 19
• Uncontrolled Ca²⁺ release from sarcoplasmic reticulum
• Massive muscle contraction → heat production

Clinical Features

• ↑ End-tidal CO₂ (FIRST sign) - most sensitive early indicator
• Hyperthermia (may rise 1°C every 5 minutes)
• Muscle rigidity (masseter spasm first - "jaws of steel")
• Tachycardia, arrhythmias
• Dark urine (myoglobinuria)
• Metabolic and respiratory acidosis
• DIC

Treatment

1. Stop all triggers immediately (turn off volatile agents)
2. Dantrolene (2.5 mg/kg IV bolus, repeat up to 10 mg/kg) - specific treatment
   • Mechanism: Blocks RYR1 receptor → prevents Ca²⁺ release from SR
3. Active cooling (ice packs, cold IV fluids)
4. Correct acidosis, hyperkalaemia
5. Maintain urine output (rhabdomyolysis → renal failure)
6. ICU admission

MH vs NMS

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SECTION 9: OPIOIDS

Classification

Receptors

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Key Opioids

Morphine

• Gold standard opioid
• Active metabolite: Morphine-6-glucuronide (M6G) - potent, accumulates in renal failure → prolonged sedation
• Histamine release → hypotension, bronchospasm
• Avoid in renal failure (M6G accumulation)

Fentanyl

• 100x more potent than morphine
• Highly lipid-soluble → rapid onset, short duration (redistribution)
• No histamine release → preferred in asthmatics and haemodynamically unstable
• Fentanyl patches (transdermal) for chronic pain

Remifentanil

• Ultra-short-acting opioid
• Hydrolysed by non-specific esterases in plasma and tissues (NOT pseudocholinesterase)
• Context-insensitive - duration same regardless of infusion length
• Recovery in minutes even after prolonged infusion → ideal for TIVA
• No histamine release
• Caution: acute tolerance and hyperalgesia after prolonged infusion

Tramadol

• Weak μ agonist + inhibits reuptake of serotonin and noradrenaline
• "Atypical opioid"
• Less respiratory depression than traditional opioids
• Lowers seizure threshold
• Can cause serotonin syndrome (especially with SSRIs/MAOIs)
• Metabolised by CYP2D6 to O-desmethyltramadol (active)

Pethidine (Meperidine)

• Metabolite: Norpethidine - CNS excitatory, causes seizures (accumulates in renal failure)
• Anticholinergic effects (dry mouth, tachycardia)
• Serotonin syndrome risk with MAOIs (absolute contraindication)
• Historically used in shivering (reduces shivering threshold)
• Least likely to cause spasm of sphincter of Oddi (relatively) among opioids

Buprenorphine

• Partial μ agonist + κ antagonist
• Ceiling effect on respiratory depression (safer in overdose)
• High receptor affinity → difficult to reverse with naloxone
• Used in opioid dependence (sublingual)

Methadone

• Long-acting (24-36 hrs), oral bioavailability ~80%
• NMDA antagonist (helps neuropathic pain)
• Used for opioid substitution therapy
• QTc prolongation risk

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Opioid Adverse Effects

Opioid Reversal - Naloxone

• Pure μ, κ, δ antagonist (competitive)
• IV, IM, intranasal
• Duration 30-45 min (shorter than most opioids → may need repeat dosing or infusion)
• Can precipitate acute withdrawal in dependent patients
• "Naloxone challenge" - diagnosis of opioid dependence

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SECTION 10: AIRWAY MANAGEMENT

ASA Difficult Airway Algorithm

• LEMON law:
  • Look externally (facial hair, obesity, anatomy)
  • Evaluate (3-3-2 rule: 3 finger mouth opening, 3 finger thyromental, 2 finger hyoid-thyroid)
  • Mallampati
  • Obstruction/Obesity
  • Neck mobility

Mallampati Classification

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Laryngoscopy & Intubation

• Grade I: Full glottis visible
• Grade II: Arytenoids visible
• Grade III: Epiglottis only visible
• Grade IV: Nothing visible

• Adult male: 8.0-9.0 mm ID
• Adult female: 7.0-8.0 mm ID
• Children: (Age/4) + 4 for uncuffed; (Age/4) + 3.5 for cuffed

1. Capnography (ETCO₂) - gold standard
2. Bilateral breath sounds
3. Chest rise
4. CXR (tube tip 2-4 cm above carina)

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Rapid Sequence Intubation (RSI)

1. Preoxygenation (3 min tidal breathing or 8 vital capacity breaths)
2. Cricoid pressure (Sellick's manoeuvre) - compresses oesophagus against C6 vertebra, prevents regurgitation
3. Induction agent (Thiopentone or Propofol)
4. Suxamethonium 1.5 mg/kg (or Rocuronium 1.2 mg/kg if MH risk)
5. Intubation (no bag-mask ventilation before intubation)
6. Release cricoid after cuff inflated and placement confirmed

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Laryngeal Mask Airway (LMA)

• Supraglottic airway device (sits above larynx, no cuff in trachea)
• Does NOT protect against aspiration (unlike ETT)
• Size 3 = small adult (females), Size 4 = average adult, Size 5 = large adult

• Full stomach/aspiration risk
• Upper airway obstruction
• Need for high airway pressures (morbid obesity, poor compliance)

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SECTION 11: MONITORING

ASA Standard Monitoring (Mandatory for all GA)

1. Pulse oximetry (SpO₂) - continuous
2. NIBP - every 5 minutes minimum
3. ECG - continuous
4. Capnography (ETCO₂) - mandatory during intubation
5. Temperature - for cases >30 minutes
6. Inspired O₂ concentration (FiO₂)

Capnography (ETCO₂)

Pulse Oximetry

• Measures SpO₂ (oxygen saturation of Hb) using Beer-Lambert law
• Measures ratio of absorbance at 660 nm (red, deoxyHb) and 940 nm (infrared, oxyHb)

• COHb (carbon monoxide) - falsely HIGH SpO₂ (CO-Hb absorbs like OxyHb)
• MetHb - SpO₂ reads ~85% regardless of actual saturation
• Nail polish (dark colours), motion artefact, hypoperfusion

Bispectral Index (BIS)

• Processed EEG monitor for depth of anaesthesia
• Scale 0-100: 40-60 = adequate anaesthesia; >80 = awake/light sedation; <40 = deep (burst suppression)
• Reduces awareness under anaesthesia

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SECTION 12: PREOPERATIVE ASSESSMENT

ASA Physical Status Classification

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Preoperative Fasting (Nil By Mouth - NBM)

• 2 hours - Clear fluids (water, tea, coffee without milk)
• 4 hours - Breast milk
• 6 hours - Light meal (toast), formula milk, non-human milk
• 8 hours - Full meal

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Premedication

• Anxiolysis (benzodiazepines)
• Analgesia (opioids, NSAIDs)
• Antisialagogue - dry mouth (atropine, glycopyrrolate)
• Antiemetic (ondansetron, metoclopramide)
• Antacid (ranitidine, proton pump inhibitors)
• Aspiration prophylaxis (sodium citrate)

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SECTION 13: SPINAL/EPIDURAL COMPARISON

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SECTION 14: COMPLICATIONS OF ANAESTHESIA

Awareness Under Anaesthesia

• Incidence: ~1-2 per 1000 GA cases
• Risk factors: RSI, cardiopulmonary bypass, trauma/obstetrics, muscle relaxants without adequate hypnotics
• Prevention: BIS monitoring, adequate TIVA dosing, volatile agent monitoring (MAC)

Post-Operative Nausea and Vomiting (PONV)

1. Female sex
2. Non-smoker
3. History of PONV/motion sickness
4. Post-op opioids

• 5-HT₃ antagonists (Ondansetron) - first line
• Dexamethasone (8 mg IV)
• Droperidol (small doses)
• Propofol TIVA (reduces PONV vs volatile agents)
• Transdermal scopolamine
• Total IV anaesthesia (TIVA) significantly reduces PONV

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SECTION 15: HIGH-YIELD RAPID FIRE

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• Most common complication of spinal = Hypotension
• Most common cause of failed intubation = Obesity
• Most common cause of PONV = Opioids + volatile agents + female sex
• Most common nerve injury in lithotomy position = Common peroneal nerve
• Most common nerve injury in prone position = Brachial plexus

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• Opioids → Naloxone
• Benzodiazepines → Flumazenil
• Non-depolarising NMBAs → Neostigmine (+ atropine)
• Rocuronium/Vecuronium → Sugammadex (also works against neostigmine failure)
• Heparin → Protamine
• Warfarin → Vitamin K / FFP / PCC

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