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DNB Final / Post-Diploma FAT 2025 — Complete Answers

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Q1. Oxygen Cascade and Oxygen–Haemoglobin Dissociation Curve

Oxygen Cascade

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Oxygen–Haemoglobin Dissociation Curve (ODC)

• Shape: Sigmoid (S-shaped), due to cooperative binding of O₂ to haem groups
• P50 (PO₂ at which Hb is 50% saturated) = 26.8 mmHg under standard conditions (pH 7.4, 37°C, PaCO₂ 40 mmHg)

• PO₂ 100 mmHg → SpO₂ ~97% (arterial plateau — flat portion — large PO₂ changes = small change in saturation)
• PO₂ 60 mmHg → SpO₂ 90% (critical point — below this, steep fall)
• PO₂ 40 mmHg → SpO₂ 75% (mixed venous)
• PO₂ 27 mmHg → SpO₂ 50% (P50)

• Pulse oximetry becomes unreliable below SpO₂ 70% and cannot distinguish HbCO/MetHb
• Preoxygenation uses the flat portion to maximise O₂ stores (FRC reservoir)
• In hypothermia, left shift reduces O₂ tissue delivery despite high SpO₂

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Q2. Desflurane & Remifentanil

Desflurane (Miller's Anesthesia, 10e)

• CNS: Dose-dependent depression; ↑↑ CMRO₂ suppression; ↑ CBF and ICP (vasodilator) — avoid in raised ICP. At >1 MAC, may cause EEG burst suppression. No seizure activity.
• CVS: Dose-dependent ↓ SVR → ↓ BP. At rapid increases in concentration, causes sympathetic stimulation → tachycardia, hypertension (uniquely among volatile agents). Mild negative inotropy. Does NOT sensitise myocardium to catecholamines (unlike halothane). Coronary vasodilation — theoretical "steal" (minimal clinical significance).
• Respiratory: ↓ Tidal volume, ↑ RR; ↓↓ hypoxic ventilatory drive (at 0.1 MAC). Upper airway irritant — coughing, laryngospasm, bronchospasm. Not used for inhalational induction.
• Neuromuscular: Potentiates NDNMBAs
• Hepatic/Renal: Minimal metabolism (<0.02%) → negligible hepatotoxicity. No nephrotoxicity.

• Environmentally most potent greenhouse gas (GWP 2540 × CO₂) — many institutions phasing out
• Requires dedicated vaporiser (Tec 6 or equivalent) due to low boiling point
• Rapid emergence — useful in neurosurgery and day-case surgery
• Airway irritant — not used for inhalation induction

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Remifentanil (Miller's Anesthesia, 10e)

• Equivalent µ-receptor agonist potency to fentanyl (~100× morphine)
• Rapid onset (1–2 min); peak effect in 1–3 min
• Titratable: can turn off and on rapidly — ideal for TIVA with propofol
• Unique advantage: Predictable, context-insensitive offset regardless of infusion duration

• TIVA (Propofol + Remifentanil — TCI or manual infusion at 0.1–0.5 µg/kg/min)
• Awake fibre-optic intubation (sub-anaesthetic doses)
• Blunt haemodynamic response to laryngoscopy
• Cardiac surgery, neurosurgery, bariatric surgery
• Labour analgesia (PCA)

• Bradycardia and hypotension (dose-dependent; treat with glycopyrrolate/ephedrine)
• Chest wall rigidity at high doses
• Post-operative hyperalgesia (opioid-induced hyperalgesia — OIH) — important limitation; transition to morphine/NSAIDs before ending infusion
• Apnoea; no histamine release
• No reversal with naloxone is needed given rapid offset, but is possible

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Q3. Capnography and Neuromonitoring

Capnography

• Mainstream (sensor at airway) — faster response, heavier
• Sidestream (aspirates gas to analyser) — lighter, can be used with face mask/nasal prong; slight delay

• Phase I (A–B): Baseline — dead space gas, CO₂ ≈ 0
• Phase II (B–C): Rapid rise — mixing of dead space and alveolar gas
• Phase III (C–D): Alveolar plateau — predominantly alveolar gas; slight upslope due to V/Q mismatch
• D: Peak (EtCO₂) = PetCO₂ (normally 35–45 mmHg)
• Phase IV (D–E): Rapid downstroke — inspiration

1. Confirm ETT placement (gold standard — sustained waveform over ≥6 breaths)
2. Monitor ventilation (titrate RR/TV)
3. Detect metabolic changes (MH — first sign is ↑↑ EtCO₂)
4. Detect circuit faults, disconnections
5. Guide CPR quality (EtCO₂ <10 mmHg = poor CPR; ≥35–40 mmHg = ROSC)
6. Assess neuromuscular block reversal (patient effort)
7. Apnoea monitoring during sedation (nasal prong sampling)

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Neuromonitoring (Intraoperative Neurophysiological Monitoring — IONM)

• Monitors cortical electrical activity
• Used in: carotid endarterectomy, epilepsy surgery, deep hypothermic circulatory arrest
• Anaesthetic effects: burst suppression, isoelectric EEG with deep anaesthesia
• Bispectral Index (BIS): Processed EEG parameter (0–100); target 40–60 for general anaesthesia; reduces awareness risk; useful in TIVA

• Measure conduction from peripheral nerve → spinal cord → cortex
• Used in: spinal surgery (scoliosis correction, spinal cord tumour), vascular surgery, TKR
• Warning criteria: >50% ↓ amplitude or >10% ↑ latency
• Suppressants: volatile agents (>0.5 MAC problematic), nitrous oxide

• Transcranial electrical stimulation → motor cortex → corticospinal tract → peripheral nerve/muscle
• Most sensitive for motor pathway integrity
• Contraindicated: pacemaker, cochlear implant, skull defects, seizure history
• TIVA (propofol + remifentanil) preferred — volatiles suppress MEPs

• Free-run EMG: continuous monitoring of nerve irritation
• Triggered EMG: for pedicle screw placement, cranial nerve monitoring (facial nerve)

• Monitor VIII nerve and brainstem during posterior fossa surgery, acoustic neuroma, cochlear implant

• Prefer TIVA (propofol ± remifentanil) — least suppression of evoked potentials
• Avoid volatile agents >0.5–1 MAC during critical monitoring periods
• Avoid NMBAs during MEP/EMG monitoring (except intubation)
• Maintain stable temperature, BP, haematocrit (all affect signal quality)
• Avoid N₂O (suppresses MEPs and SSEPs)

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Q4. Shockable/Non-Shockable Rhythms & Management of Pulseless Rhythms

Shockable Rhythms (Require Defibrillation)

1. Ventricular Fibrillation (VF) — chaotic, irregular, no coordinated electrical activity
2. Pulseless Ventricular Tachycardia (pVT) — regular wide-complex tachycardia, no pulse

Non-Shockable Rhythms

1. Pulseless Electrical Activity (PEA) — organised electrical activity on ECG with no palpable pulse
2. Asystole — flat line (confirm in 2 leads; rule out lead disconnection)

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Management of Pulseless Rhythms — ACLS Algorithm

1. Call for help, start CPR: 30 compressions : 2 breaths (100–120/min, 5–6 cm depth, full recoil)
2. Apply defibrillator/monitor as soon as available
3. Minimise interruptions (<10 sec for each rhythm check)
4. IV/IO access, airway management
5. Adrenaline (epinephrine) 1 mg IV every 3–5 minutes (for ALL pulseless rhythms)
6. Identify and treat reversible causes: 4Hs and 4Ts

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1. Immediate defibrillation: 200 J biphasic (or 360 J monophasic) — single shock
2. Resume CPR immediately for 2 minutes (do NOT check pulse right after shock)
3. Reassess rhythm after 2 min
4. Adrenaline 1 mg IV after 3rd shock, then every 3–5 min
5. After 3rd shock: Amiodarone 300 mg IV bolus (or Lidocaine 1–1.5 mg/kg if amiodarone unavailable); second dose amiodarone 150 mg after 5th shock
6. Continue cycles: shock → CPR 2 min → reassess

1. Continue CPR
2. Adrenaline 1 mg IV every 3–5 minutes (first dose as soon as possible)
3. Search for and treat reversible causes
4. Reassess rhythm every 2 minutes
5. If converting to VF/pVT — defibrillate
6. Do NOT defibrillate PEA/asystole

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Q5. Fascia Iliaca Block

Anatomy

Indications

• Hip fracture analgesia (NICE guidelines recommend as first-line — superior to systemic opioids)
• Total hip arthroplasty and total knee arthroplasty analgesia
• Femoral shaft fractures, knee surgery
• Reduces opioid consumption and improves rehabilitation

Nerves Blocked

Techniques

• Draw line from ASIS to pubic tubercle (inguinal ligament)
• Mark a point 1/3 lateral from pubic tubercle (lateral third)
• Insert needle — feel two 'pops' (fascia lata, then fascia iliaca)
• Inject 30–40 mL local anaesthetic

• Probe below inguinal ligament; identify femoral vessels, then trace laterally to sartorius
• Target: beneath fascia iliaca, lateral to femoral artery
• Visualise spread under fascia
• 30–50 mL of LA injected

• Probe in parasagittal orientation just medial to ASIS, cephalad to inguinal ligament
• More proximal deposition → better obturator nerve and hip articular branch blockade
• Volume 30–40 mL
• Preferred for hip arthroplasty

Local Anaesthetic

• Ropivacaine 0.2–0.375% or Bupivacaine 0.25–0.375%, 30–40 mL
• Maximum doses must be respected (ropivacaine 3 mg/kg, bupivacaine 2 mg/kg)
• Dexamethasone 8 mg or dexmedetomidine can be added as adjuvants to prolong block

Complications

• Haematoma (femoral vessel puncture)
• LAST (local anaesthetic systemic toxicity) — use US guidance, aspirate before injecting
• Femoral nerve palsy (transient)
• Failed block (~10% with landmark technique; lower with US)
• Infection (rare)

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Q6. Methods to Reduce ICP and Cerebral Perfusion Pressure

Tier 1 — First-Line Measures (Applied Immediately)

Tier 2 — Second-Line Measures

Tier 3 — Salvage (Refractory ICP)

• ↓ ICP: Propofol, thiopental, etomidate, benzodiazepines, opioids (if ventilation controlled), lidocaine
• ↑ ICP: Ketamine (controversial — preserves autoregulation but historically avoided in TBI; recent data suggest safe if airway controlled), volatile agents (all cause dose-dependent cerebral vasodilation; sevoflurane safest; desflurane worst)
• Succinylcholine: transient ↑ ICP (acceptable for RSI if airway at risk)

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Q7. Anaesthesia Management — 80-Year-Old Diabetic Hypertensive for Unilateral TKR

Pre-operative Assessment

• Age 80 years: Reduced physiological reserve; ↓ MAC; altered pharmacokinetics (↓ protein binding, ↓ hepatic/renal clearance, ↑ Vd for lipid-soluble drugs); ↑ risk of POCD; fragile vasomotor reflexes
• Diabetes mellitus: Assess glycaemic control (HbA1c), autonomic neuropathy (silent ischemia, gastroparesis), peripheral neuropathy (affects block assessment), chronic kidney disease, ischaemic heart disease
• Hypertension: Assess end-organ damage (cardiac, renal, cerebrovascular); medication review (continue antihypertensives except ARBs/ACEi on day of surgery if desired by cardiologist); risk of haemodynamic swings

• Check anticoagulants (TKR requires bridging decisions)
• Antidiabetics: Stop SGLT-2 inhibitors 3–4 days prior (risk of euDKA); metformin hold if contrast used; insulin management per protocol
• Continue beta-blockers, statins, calcium channel blockers

Anaesthetic Technique Options

• Advantages in this patient: Avoids airway manipulation, reduces aspiration risk (gastroparesis), excellent analgesia, reduces blood loss (~30–50% vs GA), reduces DVT/PE risk, reduces POCD in elderly, allows tourniquet tolerance
• Spinal: Heavy bupivacaine 0.5% 2–2.5 mL (12.5 mg) ± opioid (fentanyl 25 µg or morphine 100 µg intrathecal for prolonged analgesia)
• Target level T12–L1 for TKR; careful BP monitoring (vasopressor infusion — phenylephrine or noradrenaline preferred over ephedrine in diabetics/elderly to avoid tachycardia)

Peripheral Nerve Blocks (TKR Analgesia)

• Blocks saphenous nerve (sensory only from knee medially)
• Preserves quadriceps strength → earlier ambulation
• 20–30 mL ropivacaine 0.5%

• Targets sensory branches to posterior knee capsule
• 20 mL ropivacaine 0.25%

Intraoperative Management

• Positioning: Supine with tourniquet on thigh
• Tourniquet: Inflate to 100–150 mmHg above SBP; max 90 min (note ischaemia-reperfusion on deflation — ↑ K⁺, ↓ BP, ↑ EtCO₂, pain)
• Blood pressure targets: Keep within 20% of baseline; use vasopressors (phenylephrine infusion) for spinal hypotension
• Glucose monitoring: Every 1–2 h intraoperatively; target 7–10 mmol/L; avoid hypoglycaemia (hypoglycaemia unawareness in autonomic neuropathy)
• Bone cement: BCIS (Bone Cement Implantation Syndrome) — hypotension, hypoxia, arrhythmia at cement insertion; warn surgeon, increase FiO₂, fluid bolus, vasopressors ready
• DVT prophylaxis: LMWH, compression stockings, early mobilisation
• Temperature management: Warm IV fluids, Bair Hugger (hypothermia worsens coagulopathy, ↑ POCD risk)

Post-operative

• Multimodal analgesia: Paracetamol 1g QID + NSAIDs (if renal function allows) + adductor canal block + pregabalin 75 mg (cautiously in elderly — sedation) + PCA morphine or tramadol
• PONV prophylaxis: Ondansetron + dexamethasone 8 mg
• VTE prophylaxis: Rivaroxaban 10 mg OD (or LMWH) for 10–14 days
• Physiotherapy: Next day ambulation essential

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Q8. Equipment Used in OLV — DLT (Indications, Types, Complications)

Indications for One-Lung Ventilation (OLV)

1. Infection/abscess — prevent contamination of healthy lung
2. Haemorrhage — massive haemoptysis (>600 mL/24h)
3. Bronchopleural or bronchopleural cutaneous fistula
4. Unilateral bronchopulmonary lavage (pulmonary alveolar proteinosis)
5. Giant unilateral lung cyst/bulla — risk of rupture with positive pressure
6. Tracheobronchial disruption

• Thoracic aortic surgery
• Pneumonectomy, lobectomy, segmentectomy
• Oesophagectomy
• Thoracoscopic surgery (VATS)
• Minimally invasive cardiac surgery

Equipment for OLV

• Carlens (left-sided, carinal hook — now obsolete)
• White (right-sided, carinal hook — now obsolete)
• Robertshaw (no carinal hook; left or right; most common)
• Bronchocath (disposable; left or right; currently most widely used)

1. Tracheal lumen — white/clear coloured cuff (proximal)
2. Bronchial lumen — blue coloured cuff (distal; goes into mainstem bronchus)
3. Bronchial cuff — blue, inflated to seal the mainstem bronchus
4. Tracheal cuff — white/clear, inflated in trachea above carina
5. 15 mm connector (standard) at both ports (tracheal and bronchial)
6. 4 ports: Tracheal pilot balloon, bronchial pilot balloon, tracheal lumen connector, bronchial lumen connector
7. Y-connector with 2 swivel elbows

• Left-sided DLT preferred in >95% of cases (longer left mainstem bronchus — 4–5 cm — easier placement; 2.5 cm right mainstem is too short for right DLT without occluding RUL orifice)
• Right-sided DLT used when: Left pneumonectomy, left mainstem bronchial tear, left lung transplant, distorted left anatomy, thoracic aortic aneurysm compressing left mainstem

• After blind placement: initial auscultation
• FOB through tracheal lumen: carina visible, blue bronchial cuff just below carina in left mainstem
• FOB through bronchial lumen: carina of left bronchus visible distally

• FUJI, COHEN, LARNDT, LUNIVANT, SLT, LEZ (as listed in image notes) — these are video bronchoscopes and endobronchial tube systems used for OLV

• Used when DLT cannot be placed (difficult airway, small child, tracheostomy, rigid spine)
• Arndt blocker — wire-guided; threaded through FOB
• Cohen blocker — tip-deflecting; steerable
• Fuji Uniblocker — self-positioning
• EZ-Blocker (Y-shaped) — sits at carina, occludes either bronchus
• Advantage: Used with standard ETT; easier in difficult airway
• Disadvantage: Slower deflation, can dislodge, no suction of blocked lung

Complications of DLT

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Q9. Difficult Airway Algorithm & Blocks for Awake Fibre-Optic Intubation (AFOI)

Difficult Airway Algorithm (DAS 2015 / ASA 2022 Guidelines)

• Look externally: beard, obesity, trauma, radiation
• Evaluate 3-3-2: mouth opening (3 fingers), hyoid-chin (3 fingers), hyoid-thyroid (2 fingers)
• Mallampati III/IV
• Obstruction (Ludwig's angina, epiglottitis, goitre)
• Neck mobility

• Optimise: BURP/ELM, bougie, change blade, head position
• Maximum 3 attempts

• If Plan A fails
• Allows ventilation; consider ILMA (intubating LMA) for blind or FOB-assisted intubation through SGA

• If Plan B fails; maintain oxygenation

• If "can't intubate, can't oxygenate" (CICO) declared
• Surgical cricothyroidotomy (scalpel-bougie-tube technique — DAS recommended) as primary CICO technique
• Needle cricothyroidotomy as bridge only (high failure rate in adults)
• Identify cricothyroid membrane (CTM): anatomically 1–1.5 cm below thyroid notch; US or palpation

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Awake Fibre-Optic Intubation (AFOI) — Technique and Blocks

• Anticipated difficult intubation (Mallampati III/IV, reduced mouth opening, unstable cervical spine, TMJ ankylosis, awake craniotomy setup, oropharyngeal masses)
• History of failed intubation
• Full stomach with suspected difficult airway (cannot proceed with RSI)
• High cervical cord lesion
• Patient refusing GA

• Lignocaine spray or atomiser to oropharynx, tongue base
• "Spray-as-you-go" technique via fibreoptic scope: instil 2–4 mL 2% lignocaine down suction channel at each anatomical level (vocal cords, trachea)
• Lidocaine nebulisation (4% lidocaine 4 mL via nebuliser — covers entire airway)
• MAPLESON circuit insufflation with lidocaine

• Blocks posterior tongue, vallecula, anterior epiglottis, posterior pharyngeal wall
• Technique: Tonsillar pillar injection (anterior pillar); or transcutaneous approach at styloid process base
• Use 2 mL 2% lignocaine

• Blocks mucosa from epiglottis to vocal cords (internal branch of SLN)
• Technique: Perichondrial injection at greater cornu of hyoid bone bilaterally; or transcutaneous at thyrohyoid membrane
• Use 2 mL 2% lignocaine bilaterally
• Abolishes gag reflex at laryngeal inlet

• Blocks subglottic mucosa and vocal cord undersurface
• Technique: Through cricothyroid membrane; aspirate air to confirm; inject 2–4 mL 4% lignocaine rapidly (provokes cough — disperses LA)
• Maximum total lidocaine ≤9 mg/kg (topical) or 4 mg/kg (injectable)

• Mucosal atomisation device (MAD) — aerosolises LA to mucosa
• Krause's forceps — applies pledgets soaked in LA to nasal mucosa/turbinates (for nasal route)
• Nasal route: Co-phenylcaine spray (lidocaine + phenylephrine) for vasoconstriction and anaesthesia

• Goal: conscious, cooperative, breathing, protecting airway
• Dexmedetomidine infusion 0.5–1 µg/kg over 10 min then 0.2–0.7 µg/kg/h — produces anxiolysis, mild sedation, maintains airway tone and respiratory drive; preferred for AFOI
• Remifentanil TCI (Minto model, Ce 1–2 ng/mL) — blunts airway reflexes
• Midazolam 1–2 mg IV for anxiolysis (use cautiously — can cause airway obstruction in high doses)
• Ketamine 0.5 mg/kg — dissociative sedation, preserves airway tone (useful in paediatrics)

1. Preoxygenation via nasal prongs (high-flow)
2. Apply LA (topical ± blocks)
3. Thread ETT over flexible bronchoscope
4. Advance scope: nasal or oral route → pharynx → visualise cords → pass through cords → confirm carina
5. Railrail ETT over scope into trachea
6. Confirm position (EtCO₂, bilateral breath sounds)
7. Induce anaesthesia

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Q10. Malignant Hyperthermia & Compartment Syndrome

Malignant Hyperthermia (MH) — Miller's Anesthesia, 10e

• Autosomal dominant (variable penetrance); chromosome 19q13.2

• 230 mutations in RyR1 gene (ryanodine receptor type 1 — SR Ca²⁺ release channel) — 50–80% of MH-susceptible patients

• 3 mutations in CACNA1S (dihydropyridine receptor/Cav1.1)

• Triggering agent → uncontrolled release of Ca²⁺ from SR via abnormal RyR1 → sustained high myoplasmic [Ca²⁺] → hypermetabolism of skeletal muscle → ↑↑ O₂ consumption, ↑↑ CO₂ production, lactic acidosis, hyperthermia, muscle contracture → rhabdomyolysis

• ↑↑ EtCO₂ (earliest and most sensitive sign — masseter spasm can precede this)
• Tachycardia (from image: "Tachycardia, Tachypnea")
• Masseter muscle spasm — especially after succinylcholine; may be sole presentation
• Mixed respiratory and metabolic acidosis
• Cyanosis, generalised muscle rigidity

• Hyperthermia — rise of 1–2°C per 5 minutes (image: "↑ 1°C/5 min")
• Rhabdomyolysis → myoglobinuria → acute renal failure
• ↑ K⁺ → cardiac arrhythmias
• Coagulopathy / DIC

• ABG — mixed acidosis (metabolic + respiratory)
• Serum electrolytes — hyperkalaemia
• Serum CK — markedly elevated (may reach >20,000 IU/L)
• Urine myoglobin — myoglobinuria (cola-coloured urine)
• Coagulation profile — DIC screen
• Serum calcium (hypocalcaemia)

• Clinical: Classic triad of ↑ EtCO₂ + rigidity + hyperthermia in context of trigger agent
• Caffeine-Halothane Contracture Test (CHCT / In Vitro Contracture Test — IVCT): Gold standard for susceptibility testing; biopsy of thigh muscle (vastus lateralis); European (EMHG) or North American (NAMHG) protocol; MHS, MHN, MHEq classification
• Genetic testing: RyR1 and CACNA1S mutations (if positive = MHS; negative does not exclude)

1. Stop all trigger agents immediately — disconnect vaporisers
2. Hyperventilate with 100% O₂ — ×2–3× minute ventilation, ↑ FiO₂ to 1.0 to wash out volatile agent; flush circuit (high FGF ≥10 L/min)
3. Dantrolene sodium — MAINSTAY of treatment
   • Initial dose: 2.5 mg/kg IV bolus (rapid)
   • Repeat every 5 minutes as needed
   • Total dose up to 10 mg/kg (occasionally more)
   • Mechanism: Inhibits RyR1 → blocks Ca²⁺ release from SR
   • Reconstitution: Each vial = 20 mg dantrolene + 3 g mannitol in 60 mL water (labour-intensive; newer formulation: Ryanodex 250 mg lyophilised)
4. Transition to non-triggering anaesthetic — TIVA (propofol + remifentanil)
5. Treat hyperthermia:
   • Actively cool: IV cold saline (not LR — K⁺), ice packs to axilla/groin/head, nasogastric cold water lavage, bladder irrigation
   • Stop cooling when temperature reaches 38°C
6. Treat hyperkalaemia: Calcium gluconate IV; sodium bicarbonate; glucose-insulin; avoid CCBs (interact fatally with dantrolene — cardiac arrest)
7. Treat arrhythmias: Amiodarone preferred; beta-blockers; avoid calcium channel blockers
8. Urine output: Maintain >1–2 mL/kg/h with IV fluids (cold saline); furosemide/mannitol for myoglobinuria (mannitol already in dantrolene)
9. Monitor: Invasive BP, CVP, urine output, core temperature (oesophageal/rectal), ABG, CK, K⁺, coagulation every 15–30 min
10. ICU admission — continue dantrolene 1 mg/kg IV q6h for 24–48h to prevent recurrence

• Counsel patient and family; genetic testing for patient and first-degree relatives
• MH alert bracelet; register with MHAUS
• Document trigger avoidance in records

• Central core disease (CCD) — most strongly associated
• King-Denborough syndrome, Multiminicore disease
• NOT associated: Duchenne/Becker MD (risk of rhabdomyolysis with succinylcholine but not RyR1-based MH); neuroleptic malignant syndrome (NMS) is a separate syndrome via dopamine pathway

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Compartment Syndrome (from image notes — "Intra-abdominal Compartment Syndrome" also noted)

• Trauma (long bone fractures — tibia/fibula most common)
• Crush injury, reperfusion injury, burns
• Tight casts/dressings
• Intracompartmental haemorrhage, excessive IV fluid extravasation
• Prolonged lithotomy position → lower limb compartment syndrome

1. Pain out of proportion to injury; pain on passive stretch (earliest and most sensitive sign)
2. Pressure — tense, woody swelling
3. Paraesthesia — nerve ischaemia
4. Paralysis (late)
5. Pallor (late — arterial compromise)
6. Pulselessness (very late — do not wait for this)

• Clinical primarily
• Compartment pressure measurement: Using Stryker device or arterial line manometer
• Treatment threshold: Compartment pressure >30 mmHg OR ΔP (diastolic BP − compartment pressure) <30 mmHg

• Intra-abdominal pressure (IAP) >20 mmHg with new organ dysfunction
• Measured via bladder pressure (Foley catheter with 25 mL saline instilled)
• Normal IAP <5 mmHg; intra-abdominal hypertension (IAH) = IAP ≥12 mmHg
• ACS effects: Lung → ↓ FRC, ↑ airway pressures; Kidney → oliguria/ARF; Heart → ↓ CO; Bowel → ischaemia; Intracranial → ↑ ICP
• Treatment: Decompressive laparotomy; temporary abdominal closure (vacuum-assisted wound closure)

• Often emergency; may have rhabdomyolysis/hyperkalaemia → avoid succinylcholine
• Haemodynamic instability (reperfusion after tourniquet)
• Pain management: Neuraxial if coagulation normal; nerve blocks; opioids
• After tourniquet deflation during TKR → watch for emboli (fat, cement, thrombus) and compartment syndrome post-operatively

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Complete References — DNB FAT 2025 Answers

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Primary Textbooks Consulted (via Medical Library Database)

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1. Miller's Anesthesia, 10th Edition

• Malignant Hyperthermia — Block 12, lines 4101–4250 (Chapter on Neuromuscular Disorders and MH)
• Remifentanil pharmacokinetics and pharmacodynamics — Block 8 (Opioid Pharmacology chapter), references lines 2311–2335; Block 9 lines 299–309
• Desflurane pharmacology — Block 30 (Inhalational Anaesthetics references); Block 6 (Inhaled Anaesthetics chapter)
• MH treatment protocol (dantrolene, triggers, pathophysiology) — Block 12, lines 4103–4250

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2. Barash, Cullen, and Stoelting's Clinical Anesthesia, 9th Edition

• Oxygen supply and cascade — Block 8, lines 2874–2876 (Chapter: Anaesthesia Machines and Safety Devices)
• Absolute indications for DLT / One-lung ventilation — Block 13, lines 270–280 (Thoracic Anaesthesia Key Points)
• Desflurane references — Block 6, lines 2641–2657 (Inhalational Anaesthetics references)

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3. Morgan & Mikhail's Clinical Anesthesiology, 7th Edition

• Fascia Iliaca Plane Block — Block 7, lines 3390–3430 (Chapter 46: Regional Anaesthesia)
  • Infrainguinal fascia iliaca block technique (lines 3400–3406)
  • Suprainguinal fascia iliaca block (lines 3414–3422)
  • Included anatomical ultrasound images (Figures 46–43, 46–44)
• Techniques for One-Lung Ventilation / DLT indications — Block 4, lines 2594–2603 (Chapter 25: Thoracic Anaesthesia)
• Femoral Nerve Block table — Block 7, lines 3348–3350

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Supporting Guidelines Cited

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4. AHA/ERC Resuscitation Guidelines 2021

• Shockable/non-shockable rhythm classification
• ACLS algorithm: VF/pVT defibrillation sequence, amiodarone 300 mg dose, adrenaline 1 mg every 3–5 min
• PEA/Asystole management
• Post-ROSC targeted temperature management (TTM 32–36°C)
• EtCO₂ ≥35–40 mmHg as ROSC indicator during CPR
• Circulation 2021;142(16 Suppl 2)

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5. Difficult Airway Society (DAS) Guidelines 2015

• Plan A/B/C/D difficult airway algorithm
• Surgical cricothyroidotomy (scalpel-bougie-tube) as preferred CICO technique
• Maximum 3 laryngoscopy attempts
• Second-generation SGA as Plan B
• BJA 2015 Full Guideline

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6. ASA Practice Guidelines for Management of the Difficult Airway 2022

• Awake intubation pathway
• Confirmation of airway placement with EtCO₂
• Anesthesiology 2022

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7. MHAUS (Malignant Hyperthermia Association of the United States) Treatment Protocol

• Dantrolene 2.5 mg/kg initial dose; repeat to max 10 mg/kg
• Stop cooling at 38°C
• Avoid CCBs with dantrolene
• Maintain urine output >1–2 mL/kg/h
• ICU dantrolene continuation 1 mg/kg q6h × 24–48h
• www.mhaus.org emergency protocol

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8. NICE Guideline NG111 — Hip Fracture: Management (2023 update)

• Fascia iliaca block as first-line analgesia for hip fracture (recommended before surgical repair)
• NICE NG111

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9. European Malignant Hyperthermia Group (EMHG) Guidelines

• In Vitro Contracture Test (IVCT/CHCT) methodology
• MHS/MHN/MHEq classification criteria
• RyR1 and CACNA1S genetic testing standards

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10. Intraoperative Neuromonitoring — Practice Advisory

• SSEP warning criteria (>50% amplitude reduction, >10% latency increase)
• TIVA preferred over volatile agents for MEP monitoring
• Contraindications to MEP monitoring

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Additional Landmark Papers Directly Referenced

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Summary Table — Which Reference Covers Which Question

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