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Surgery MedEx - Complete Study Guide

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PART 1 - APPLIED SURGICAL ANATOMY

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1. Nervous System: Head and Neck (Level 3)

• S - Skin
• C - Connective tissue (dense, contains vessels)
• A - Aponeurosis (galea aponeurotica)
• L - Loose areolar tissue (danger layer - infection/blood can spread here)
• P - Pericranium

Surgical relevance: Scalp lacerations bleed profusely because vessels in the connective tissue layer are tethered and cannot retract. The loose areolar layer is the "danger space" - pus/blood can spread widely here.

• Extradural haematoma: torn middle meningeal artery (temporal bone fracture) - biconvex on CT, lucid interval classic
• Subdural haematoma: torn bridging veins - crescent-shaped on CT, older/alcoholic patients
• Subarachnoid haemorrhage: ruptured berry aneurysm at Circle of Willis - sudden "thunderclap" headache
• Raised ICP signs: Cushing's triad (hypertension + bradycardia + irregular breathing), papilloedema, ipsilateral pupil dilatation (CN III compression)

• Sympathetic: T1-L2 origins, thoracolumbar outflow
• Parasympathetic: CN III, VII, IX, X + S2-S4 (craniosacral)
• Surgical relevance: damage to cervical sympathetic chain → Horner's syndrome (ptosis, miosis, anhidrosis, enophthalmos)

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2. Cardiovascular System Anatomy (Level 3)

• Right coronary artery (RCA): supplies SA node (60%), AV node (90%), inferior LV
• Left anterior descending (LAD): supplies anterior LV, anterior septum - "widow maker"
• Circumflex (LCx): supplies posterior/lateral LV
• Pericardium: fibrous outer + serous inner. Pericardial tamponade → Beck's triad (hypotension + muffled heart sounds + raised JVP)

• Aorta exits left ventricle via aortic valve (3 cusps)
• SVC/IVC drain into right atrium
• Pulmonary veins (4) drain to left atrium
• Great saphenous vein runs anterior to medial malleolus - used for coronary bypass grafting

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3. Respiratory System Anatomy (Level 3)

• Mediastinum divisions: superior/anterior/middle/posterior
• Trachea bifurcates at sternal angle (T4/5) → carina → left and right main bronchi
• Right main bronchus: shorter, wider, more vertical → foreign bodies preferentially go right
• Pleural anatomy: parietal (pain-sensitive) + visceral (insensate)
• Pneumothorax: air in pleural space → mediastinal shift away from affected side if tension
• Tension pneumothorax: tracheal deviation AWAY from side, absent breath sounds, hypotension → needle decompression at 2nd intercostal space, midclavicular line

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4. Gastro-intestinal System Anatomy (Level 4 - HIGH PRIORITY)

• Inguinal canal: contains spermatic cord (male) / round ligament (female)
• Hesselbach's triangle (direct inguinal hernia): inferior epigastric artery (lateral), rectus sheath (medial), inguinal ligament (inferior)
• Direct hernia: through Hesselbach's triangle - medial to inferior epigastric
• Indirect hernia: through deep inguinal ring - lateral to inferior epigastric, follows spermatic cord

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5. Breast and Endocrine Anatomy

• Lymph drainage: 75% to axillary nodes (levels I-III), 25% to internal mammary
• Blood supply: internal thoracic, lateral thoracic, intercostal
• Axillary contents: axillary vein, brachial plexus cords, long thoracic nerve (serratus anterior - injury = winged scapula), thoracodorsal nerve (latissimus dorsi)

• H-shaped; isthmus overlies 2nd-4th tracheal rings
• Blood supply: superior thyroid (from ECA), inferior thyroid (thyrocervical trunk of subclavian)
• Recurrent laryngeal nerve: runs in tracheo-oesophageal groove → injury → hoarseness
• Parathyroids: 4 glands, posterior to thyroid, at risk during thyroidectomy

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6. Genito-Urinary System Anatomy

• Kidney: retroperitoneal, T12-L3, right lower than left (liver)
• Ureter: 3 points of narrowing (pelviureteric junction, pelvic brim, vesicoureteric junction) - where stones get stuck
• Bladder: posterior = rectum (male), uterus (female); trigone between ureteric orifices and internal urethral orifice
• Prostate: surrounds urethra; posterior lobe = site of carcinoma; lateral lobe = BPH

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7. Musculoskeletal System Anatomy (Level 3)

• Brachial plexus roots: C5-T1
• Axillary nerve: from C5/6, winds around surgical neck humerus → deltoid. Injury in shoulder dislocation
• Radial nerve: spiral groove of humerus → wrist drop
• Ulnar nerve: medial epicondyle → claw hand
• Median nerve: carpal tunnel → loss of thumb opposition + lateral 3.5 fingers sensation
• Femoral nerve: anterior thigh; obturator nerve: medial thigh; sciatic nerve: posterior thigh + entire leg below knee

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PART 2 - APPLIED PHYSIOLOGY

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1. General Physiology (Level 3)

• Na+ = main extracellular cation (135-145 mmol/L)
• K+ = main intracellular cation (3.5-5.0 mmol/L)
• Normal daily requirements: Na+ 1-2 mmol/kg, K+ 0.5-1 mmol/kg

• Ebb phase (0-24h): shock, reduced metabolism, vasoconstriction, hypothermia
• Flow phase (1-5 days): hypermetabolism, catabolism, fever, raised cortisol/glucagon, negative nitrogen balance
• Anabolic phase: recovery, weight gain

• Innate: neutrophils, macrophages, complement, immediate
• Adaptive: T and B lymphocytes, specific, memory
• Surgical infection: most common = gram-negative bacteria (E. coli, Klebsiella); anaerobes in bowel surgery (Bacteroides)

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2. Cardiovascular Physiology (Level 3)

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3. Respiratory Physiology (Level 3)

• Tidal volume: ~500 mL; FRC = ~2.5L (residual capacity after normal expiration)
• Oxygen delivery (DO2) = CO × CaO2; CaO2 = (Hb × 1.34 × SpO2) + (0.003 × PaO2)
• Hypoxaemia causes: V/Q mismatch (most common - PE, pneumonia), shunt, diffusion defect, hypoventilation
• ARDS criteria: Acute onset, bilateral infiltrates, PaO2/FiO2 < 300, non-cardiogenic
• O2 therapy targets: SpO2 94-98% (general), 88-92% (COPD type II)
• Ventilator modes: pressure-controlled vs volume-controlled; PEEP = prevents alveolar collapse

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4. Blood and Reticulo-endothelial System (Level 3)

1. Primary: platelet plug (platelet adhesion via vWF → aggregation)
2. Secondary: coagulation cascade → fibrin

• Intrinsic: XII → XI → IX → X (measured by APTT)
• Extrinsic: tissue factor + VII → X (measured by PT/INR)
• Common pathway: X → thrombin → fibrin

• Indications: Hb <7 g/dL (general), <8-10 in cardiac disease
• ABO and Rh cross-matching required
• Complications: TRALI (transfusion-related acute lung injury), TACO (circulatory overload), haemolytic reaction (ABO incompatibility), febrile non-haemolytic, infection

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5. Nervous System Physiology (Level 2)

• Action potential: depolarisation (Na+ influx) → repolarisation (K+ efflux)
• Neurotransmitters: acetylcholine (NMJ, parasympathetic), noradrenaline (sympathetic), dopamine, serotonin
• Cerebral autoregulation: CBF constant at MAP 60-150 mmHg
• Monro-Kellie doctrine: skull = fixed volume; ICP rises if brain + blood + CSF increases

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6. Gastro-intestinal Physiology (Level 2-3)

• Gastric acid: secreted by parietal cells (HCl + intrinsic factor); stimulated by gastrin (G-cells), ACh, histamine
• Pancreatic enzymes: amylase, lipase, trypsinogen (activated by enterokinase)
• Bilirubin: haemoglobin → unconjugated bilirubin (fat-soluble) → liver conjugation → conjugated (water-soluble) → bile
• Liver: glycogen storage, gluconeogenesis, protein synthesis (albumin, clotting factors), drug metabolism
• Enterohepatic circulation: bile salts reabsorbed in terminal ileum

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7. Genito-Urinary Physiology (Level 2-3)

• GFR normal: ~120 mL/min; measured by creatinine clearance
• Tubular reabsorption: Na+ reabsorbed throughout, K+ mainly in distal tubule
• ADH: released by posterior pituitary, acts on collecting duct → water reabsorption
• Aldosterone: zona glomerulosa, Na+ retention / K+ excretion, released by angiotensin II
• Creatinine rises significantly only when GFR falls <50%

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PART 3 - APPLIED GENERAL PATHOLOGY

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1. Cell Structure, Cycle and Response to Injury (Level 2)

• Cell cycle: G1 → S (DNA synthesis) → G2 → M (mitosis)
• Cell injury responses: atrophy, hypertrophy, hyperplasia, metaplasia, dysplasia
• Necrosis types: coagulative (heart), liquefactive (brain/abscess), caseous (TB), fat (pancreatitis), gangrenous

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2. Acute and Chronic Inflammation (Level 3)

• Vascular phase: vasodilation → increased permeability
• Cellular phase: neutrophil margination → diapedesis → chemotaxis → phagocytosis
• Mediators: histamine (mast cells), prostaglandins, leukotrienes, cytokines (IL-1, TNF-α)

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3. Immunology (Level 2-3)

• HLA matching important for organ transplantation
• Rejection types:
  • Hyperacute: minutes, preformed antibodies
  • Acute: days-weeks, T-cell mediated
  • Chronic: months-years, antibody + T-cell, obliterative vasculopathy
• Immunosuppression: calcineurin inhibitors (tacrolimus, ciclosporin), steroids, azathioprine, MMF

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4. Wound Healing (Level 3) - HIGH YIELD

1. Haemostasis (0-24h): platelet plug, vasoconstriction, clot
2. Inflammatory (1-4 days): neutrophils (day 1-2), then macrophages (day 3+) - debride
3. Proliferative (4 days - 3 weeks): fibroblasts lay collagen (type III initially), angiogenesis, granulation tissue
4. Remodelling (weeks-months): type III → type I collagen; max tensile strength ~80% of original at 3 months

• Primary intention: clean wound, edges apposed
• Secondary intention: wound left open, heals by granulation
• Tertiary (delayed primary): wound left open then closed after 3-5 days

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5. Neoplasia (Level 3) - HIGH YIELD

• Oncogenes: normally promote growth; mutated → uncontrolled proliferation (e.g., RAS, c-myc, HER2)
• Tumour suppressor genes: normally inhibit growth; loss → cancer (e.g., p53, Rb, APC, BRCA1/2)
• Two-hit hypothesis (Knudson): both alleles of tumour suppressor must be lost

1. Self-sufficiency in growth signals
2. Insensitivity to anti-growth signals
3. Evading apoptosis
4. Limitless replication (telomerase)
5. Sustained angiogenesis (VEGF)
6. Tissue invasion and metastasis (↓ E-cadherin, matrix metalloproteinases)

• Haematogenous: lung, liver, bone, brain most common sites
• Lymphatic: regional lymph nodes first
• Transcoelomic: peritoneum (GI/ovarian cancers) → Krukenberg tumour (gastric → ovary)
• Direct invasion

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6-14. Other Pathology Topics

• Virchow's triad: stasis + hypercoagulability + endothelial damage
• DVT Prophylaxis: LMWH, TED stockings, early mobilisation
• PE: pleuritic chest pain, dyspnoea, haemoptysis; Wells score → CTPA

• Reperfusion injury: free radicals, Ca2+ overload, neutrophil activation
• Gangrene: dry (arterial occlusion) vs wet (venous/infection) vs gas (Clostridium - crepitus)

• Albumin: oncotic pressure (2.5 g/dL = 20-25 mmHg); half-life 20 days
• CRP: acute phase protein, rises within 6h of inflammation
• Alpha-1-antitrypsin: serine protease inhibitor; deficiency → emphysema + liver disease

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PART 4 - PRINCIPLES OF SURGERY: PERI-OPERATIVE CARE

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1. Assessment of Fitness for Surgery (Level 4 - HIGH PRIORITY)

• ASA classification:
  • I: Healthy
  • II: Mild systemic disease
  • III: Severe systemic disease (but not incapacitating)
  • IV: Severe systemic disease, constant threat to life
  • V: Moribund - not expected to survive without operation
  • VI: Brain-dead organ donor
• P-POSSUM / POSSUM: Physiological and Operative Severity Score for enumeration of Mortality and Morbidity
• Goldman Cardiac Risk Index: points for cardiac history, ECG, haemodynamic status

• ECG: men >40, women >50, or known cardiac disease
• CXR: respiratory symptoms, known cardiopulmonary disease
• FBC, U&E, clotting: as indicated by history

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2. Management of Associated Medical Conditions (Level 3)

• Warfarin: stop 5 days pre-op; bridge with LMWH if high thrombotic risk; reverse with Vitamin K / FFP / PCC
• DOACs: stop 24-48h (48-72h if renal impairment); no bridging usually needed
• Aspirin: continue for cardiac stents; stop 7-10 days if risk of bleeding

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3. Preparation for Surgery (Level 3)

• Patient must have capacity (understand, retain, weigh, communicate)
• Elements: procedure, indications, risks (serious + common), alternatives, consequences of not having it
• Cannot be given for someone else (except emergency or Power of Attorney)

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4. Principles of Anaesthesia (Level 3)

1. Hypnosis (unconsciousness) - propofol, thiopentone
2. Analgesia - fentanyl, morphine
3. Muscle relaxation - suxamethonium (depolarising), vecuronium/atracurium (non-depolarising)

• Mechanism: Na+ channel blockade
• Agents: lignocaine (max 3 mg/kg, 7 mg/kg with adrenaline), bupivacaine (longer acting, max 2 mg/kg)
• Toxicity: tingling lips, tinnitus → seizures → arrhythmias → cardiac arrest; treat with 20% lipid emulsion

• Spinal (intrathecal): subarachnoid space, fast, short-acting
• Epidural: epidural space, catheter for prolonged/labour analgesia
• Complications of both: hypotension (sympathetic block), headache (post-dural puncture - spinal)

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5. Monitoring the Anaesthetised Patient (Level 3)

• SpO2 (pulse oximetry), ECG, NIBP, EtCO2 (capnography), temperature

• Arterial line: beat-to-beat BP + ABG sampling (radial artery most common)
• CVP line: monitors preload, gives central venous access (normal CVP: 3-8 mmHg)
• Pulmonary artery catheter (Swan-Ganz): PCWP, CO, SvO2 - reserved for high-risk cases

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PRACTICE TRUE/FALSE QUESTIONS

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Block 1 - Anatomy

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Block 2 - Physiology

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Block 3 - Pathology

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Block 4 - Principles of Surgery

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QUICK SUMMARY TABLE - HIGH-YIELD MNEMONICS

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Study tip: The exam is 60 True/False questions with no negative marking. For any statement you are unsure about, guess - there is no penalty. Focus on Level 4 topics (GI anatomy, breast/thyroid, perioperative assessment) as these carry higher competency expectations. Level 2-3 topics need basic concept recall only.

Sources drawn from: Schwartz's Principles of Surgery (11e), Sabiston Textbook of Surgery, Mulholland & Greenfield's Surgery, Robbins & Kumar Basic Pathology, Guyton & Hall Medical Physiology, Miller's Anesthesia (10e).