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General Surgery Four-Station OSCE: High-Yield Study Guide

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TOPIC 1: SHOCK AND BLOOD TRANSFUSION

Station 1 - Initial Assessment

• Airway: ensure patency; intubate if GCS <8 or airway compromise
• Breathing: check RR, SpO2; give high-flow O2 via non-rebreather mask
• Circulation: assess pulse rate/quality, BP, CRT, skin temperature/color, JVP
• Disability: GCS, pupils, blood glucose
• Exposure: look for obvious hemorrhage, distended abdomen, long-bone fractures

• Cold, clammy, pale skin + tachycardia = shock until proven otherwise
• Altered mental status (anxiety, confusion) is an early, sensitive sign of poor cerebral perfusion
• Urine output <0.5 mL/kg/hr = inadequate organ perfusion

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Station 2 - Clinical Assessment and Diagnostic Reasoning

• Hypovolemic: ↓ CO, ↑ SVR, ↓ CVP, ↓ PCWP
• Cardiogenic: ↓ CO, ↑ SVR, ↑ CVP, ↑ PCWP
• Distributive (septic/anaphylactic): ↑ CO (early), ↓ SVR, ↓ CVP
• Neurogenic: ↓ CO, ↓ SVR, relative bradycardia (distinguishes from hypovolemic)
• Obstructive (tension PTX, tamponade): ↓ CO, ↑ SVR, ↑ CVP

• FBC, coagulation (PT/aPTT/fibrinogen), metabolic panel, lactate, ABG
• Lactate >2 mmol/L = tissue hypoperfusion; >4 mmol/L = severe shock
• Base deficit on ABG correlates with shock severity
• Type & crossmatch, blood cultures if septic source suspected
• ECG, echo if cardiogenic shock suspected

• Hb <7 g/dL in stable patients (restrictive strategy)
• Hb <8-10 g/dL in active cardiac disease or active hemorrhage
• Massive transfusion protocol (MTP): >10 units pRBC in 24h, or >4 units in 1h
• MTP ratio: pRBC : FFP : Platelets = 1:1:1 (damage control resuscitation)

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Station 3 - Recognition of Critical Findings

• Class IV hemorrhagic shock: >40% blood volume lost, imminent cardiac arrest
• Tension pneumothorax mimicking obstructive shock (see Chest Injuries)
• Cardiac tamponade: Beck's triad (hypotension, muffled heart sounds, JVD)
• Distributive shock with anaphylaxis: urticaria, bronchospasm, angioedema

• Acute hemolytic reaction (ABO incompatibility): fever, back/flank pain, hemoglobinuria, DIC - STOP transfusion immediately
• TRALI (Transfusion-Related Acute Lung Injury): acute hypoxia within 6h of transfusion - bilateral infiltrates on CXR, non-cardiogenic pulmonary edema
• TACO (Transfusion-Associated Circulatory Overload): pulmonary edema, hypertension - give furosemide
• Massive transfusion complications: hypothermia, hypocalcemia (citrate toxicity), hyperkalemia, dilutional coagulopathy

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Station 4 - Management Plan

1. Bolus: 1-2L crystalloid (warmed Ringer's Lactate preferred over normal saline) in Class II-III
2. Hemorrhagic shock: control source first (surgery > interventional radiology > external compression)
3. "Permissive hypotension" (SBP 80-90 mmHg) until surgical hemorrhage control - avoid over-resuscitation
4. Activate MTP early for Class III-IV hemorrhagic shock
5. Tranexamic acid (TXA) 1g IV over 10 min within 3 hours of injury (CRASH-2 trial evidence)

• Norepinephrine: first-line for septic shock
• Epinephrine: first-line for anaphylactic shock (0.5 mg IM)
• Vasopressin: adjunct in refractory septic shock

• MAP >65 mmHg, UO >0.5 mL/kg/hr, lactate clearance >10%/2h, normalization of base deficit

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TOPIC 2: ABDOMINAL TRAUMA

Station 1 - Initial Assessment

• Mechanism matters: blunt (MVA, fall) vs. penetrating (stab vs. gunshot - higher energy = more visceral injury)
• Abdomen in "E" (Exposure): look for seat belt sign, tire marks, entrance/exit wounds, evisceration
• Hemodynamic status determines speed of workup: unstable = OR, stable = CT
• Log-roll: check posterior abdomen and spine

• Blunt: spleen (most common) > liver > mesentery > small bowel
• Penetrating anterior abdomen: small bowel most common; liver (most common solid organ)
• Penetrating flank/back: retroperitoneal structures (kidneys, duodenum, colon)

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Station 2 - Clinical Assessment and Diagnostic Reasoning

• Peritonism (guarding, rigidity, rebound) = peritoneal contamination - surgical emergency
• Seat belt sign / ecchymosis: high association with small bowel and mesenteric injury
• Cullen's sign (periumbilical bruising) / Grey Turner's sign (flank bruising): retroperitoneal hemorrhage (delayed)
• Kehr's sign: left shoulder tip pain = diaphragmatic irritation from splenic hemorrhage

• FAST (Focused Assessment with Sonography in Trauma): 4 windows (pericardial, hepatorenal, splenorenal, pelvic) - detects free fluid (hemoperitoneum) in minutes; does NOT diagnose organ injury
• FAST limitations: operator-dependent, misses retroperitoneal injuries, bowel injuries
• eFAST: adds bilateral chest windows for pneumo/hemothorax
• CT abdomen/pelvis with IV contrast: gold standard for stable patients; grading organ injuries, identifies active extravasation
• Diagnostic Peritoneal Lavage (DPL): largely replaced by FAST/CT; positive if >100,000 RBC/µL (blunt) or >10,000 RBC/µL (penetrating); used when CT unavailable

• Grade I-II: non-operative management usually possible
• Grade III: selective management based on hemodynamics
• Grade IV-V: usually operative; Grade V = major vascular involvement

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Station 3 - Recognition of Critical Findings

• Hemodynamic instability with positive FAST (free fluid)
• Evisceration of bowel or omentum
• Signs of peritonitis (generalized guarding/rigidity)
• Gunshot wound to abdomen (mandatory exploration)
• Impalement
• Diaphragmatic rupture
• Ruptured hollow viscus (free air on CXR/CT)

• pH <7.2, temp <35°C, base deficit > -8, coagulopathy, >10 units pRBC
• Strategy: stop bleeding + contamination → ICU resuscitation → delayed definitive repair (48-72h)

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Station 4 - Management Plan

• Criteria: hemodynamically stable, no peritoneal signs, CT confirms isolated solid organ injury, ICU monitoring available
• Spleen: success rate >85% overall; fails with higher grade and age >55
• Liver: most lacerations managed non-operatively; angioembolization for active extravasation
• Serial abdominal exams, repeat CT at 48-72h if concern for progression
• Delayed splenic rupture: can occur up to 2 weeks post-injury

• Damage control laparotomy: pack all four quadrants, clip/ligate bleeding vessels, temporary bowel diversion, close abdomen temporarily (Bogota bag or wound vac)
• Splenectomy vs. splenorrhaphy: splenectomy for high-grade/unstable; vaccinate post-splenectomy (pneumococcal, meningococcal, Hib)
• Hollow viscus: primary repair if clean, limited contamination; resection + ostomy if devascularized/contaminated

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TOPIC 3: WOUNDS AND TISSUE REPAIR

Station 1 - Initial Assessment

• Location: proximity to vital structures, joints, neurovascular bundles
• Mechanism: clean incision (knife) vs. laceration (blunt) vs. crush vs. bite vs. blast
• Time since injury: <6h = primary closure usually safe; >6h or contaminated = delayed closure
• Contamination level:
  • Clean (Class I): elective, no viscus entered - infection rate <2%
  • Clean-contaminated (II): controlled viscus entry - infection rate 5-15%
  • Contaminated (III): spillage, traumatic - infection rate 15-25%
  • Dirty (IV): established infection/perforated viscus - infection rate >30%
• Tetanus status: document and immunize if <3 doses or >5 years since last booster

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Station 2 - Clinical Assessment and Diagnostic Reasoning

1. Hemostasis (minutes): platelet plug + coagulation cascade; vasoconstriction then vasodilation
2. Inflammatory (0-5 days): neutrophils (first 24-48h) → macrophages (day 3+, the master orchestrators); growth factors (PDGF, TGF-β, VEGF) released
3. Proliferative (5 days - 3 weeks): fibroblasts lay collagen (type III initially), angiogenesis, granulation tissue, epithelialization; myofibroblasts cause wound contraction
4. Remodeling (3 weeks - 2 years): type III collagen replaced by type I; maximum tensile strength = 80% of original (never 100%)

• Primary intention: edges approximated at time of injury
• Secondary intention: allowed to granulate; best for infected/contaminated wounds
• Tertiary (delayed primary): closure at 4-5 days after initial observation (ideal for contaminated traumatic wounds)

• Local: infection, ischemia, foreign body, radiation, tension
• Systemic: malnutrition (low protein/vitamin C/zinc), diabetes, steroids, chemotherapy, anemia, uremia

• Hypertrophic scar: raised, stays within wound margins, may regress
• Keloid: extends beyond wound margins, does not regress, recurs after excision; more common in dark skin; ear/sternum/shoulder predilection

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Station 3 - Recognition of Critical Findings

• Superficial: manage with Steri-strips/secondary healing
• Fascial dehiscence: serosanguinous "salmon-pink" drainage from wound - check fascia immediately; risk of evisceration
• Evisceration: cover with moist saline gauze; emergency return to OR

• Early infection (<48h): Streptococcal or Clostridial (gas gangrene) - thin brown watery discharge, crepitus = emergency
• Gas gangrene (Clostridium perfringens): severe pain disproportionate to appearance, crepitus, bronze skin discoloration, tachycardia, shock - emergency debridement + penicillin G

• Type I (polymicrobial) vs. Type II (Group A Streptococcus)
• LRINEC score ≥6: high risk for necrotizing soft tissue infection
• "Dishwater" fluid, skin necrosis, severe pain then anesthesia (nerve destruction), rapid spread
• Treatment: immediate surgery (wide debridement), broad-spectrum IV antibiotics, ICU

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Station 4 - Management Plan

1. Irrigate copiously (min 250 mL per cm of laceration) with normal saline under pressure
2. Debride devitalized tissue
3. Select closure method based on contamination and time
4. Suture material selection:
   • Absorbable (Vicryl, PDS): deep layers, contaminated wounds
   • Non-absorbable (Prolene, Nylon): skin closure, vascular anastomosis
   • Rapidly absorbable (plain gut, fast-absorbing Vicryl): mucosal surfaces, children
5. Antibiotic prophylaxis: cefazolin for clean/clean-contaminated wounds; broader coverage for contaminated

• Indications: open abdomen, large traumatic wounds, dehisced wounds, diabetic foot
• Mechanism: removes exudate, reduces edema, promotes granulation, draws wound edges together

• Pressure garments, silicone gel sheets (first-line)
• Intralesional triamcinolone injection
• Surgical excision + adjuvant therapy (radiation or steroids) for keloids

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TOPIC 4: SURGICAL INFECTION

Station 1 - Initial Assessment

• Temperature >38°C or <36°C (fever or hypothermia both indicate sepsis)
• HR >90, RR >20, WBC >12,000 or <4,000, bands >10%
• Sepsis (Sepsis-3 definition): life-threatening organ dysfunction caused by dysregulated host response; SOFA score increase ≥2
• Septic shock: sepsis + vasopressor requirement to maintain MAP ≥65 + lactate >2 mmol/L
• Look for source: wound (erythema, warmth, fluctuance), IV line site, chest (crackles), abdomen (tender), urinary (dysuria/CVA tenderness)

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Station 2 - Clinical Assessment and Diagnostic Reasoning

• CBC, metabolic panel, CRP, procalcitonin, blood cultures (x2 before antibiotics), lactate
• Wound swab/drainage culture
• Imaging: USS for abscess/biliary; CT abdomen/pelvis for intra-abdominal source

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Station 3 - Recognition of Critical Findings

• RR ≥22, altered mentation, SBP ≤100
• Act within 1 hour (Surviving Sepsis Campaign "1-hour bundle")

• Disproportionate pain, skin changes (erythema → bullae → necrosis → gray)
• Crepitus on palpation = surgical emergency
• CT: gas in soft tissues (pathognomonic), but do NOT delay surgery for CT if clinical picture clear

• Incubation 12-24h post-injury
• Severe pain, bronze/bronze-blue skin, crepitus, thin brown exudate, sweet/foul odor
• Systemic toxicity rapid: fever, tachycardia, renal failure, shock
• Emergency: wide surgical debridement, high-dose penicillin G (24 million units/day), hyperbaric O2 adjunct

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Station 4 - Management Plan

1. Measure lactate; re-measure if >2 mmol/L
2. Blood cultures before antibiotics (2 sets)
3. Broad-spectrum antibiotics within 1 hour
4. Crystalloid 30 mL/kg for hypotension or lactate >4 mmol/L
5. Vasopressors (norepinephrine) for MAP <65 mmHg

• Prophylaxis: single dose of cefazolin 30-60 min pre-incision; redose if >3h surgery
• Empiric therapy: guided by suspected source; cover gram-negatives + anaerobes for abdominal (piperacillin-tazobactam, or ceftriaxone + metronidazole)
• De-escalate based on cultures; typical duration 4-7 days for surgical infections
• MRSA risk: add vancomycin for healthcare-associated or severe infections

• Abscess: drain (percutaneous or surgical) - antibiotics alone insufficient
• Peritonitis: urgent laparotomy
• Infected prosthetic material: usually requires removal
• Devitalized/infected tissue: debride promptly

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TOPIC 5: NUTRITION AND FLUID THERAPY

Station 1 - Initial Assessment

• Assess: recent weight loss (>5% in 1 month or >10% in 6 months), poor oral intake, BMI <18.5
• NRS-2002 or MUST score to identify patients at nutritional risk
• Signs of malnutrition: temporal wasting, edema (hypoalbuminemia), muscle wasting, poor wound healing

• Volume depletion: dry mucous membranes, ↑ HR, ↓ BP postural, ↓ skin turgor, sunken eyes, ↓ UO
• Volume overload: pulmonary crackles, JVD, peripheral edema, S3 gallop
• Daily maintenance fluid: 30-35 mL/kg/day; add for ongoing losses (fever +10-15% per °C above 37.5, NG output, fistula output)

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Station 2 - Clinical Assessment and Diagnostic Reasoning

• Water: 30-35 mL/kg
• Na+: 1-2 mmol/kg
• K+: 0.5-1 mmol/kg
• Calories: 25-30 kcal/kg (post-surgical stress: up to 35 kcal/kg)
• Protein: 1.2-2 g/kg (higher in critically ill, burns, major surgery)

• Hyponatremia post-op: excess hypotonic fluids, SIADH - restrict free water, correct slowly
• Hypokalemia: GI losses (vomiting, NG suction, fistula), diuretics - replace KCl (max 20 mmol/h IV)
• Hypocalcemia post-thyroidectomy/parathyroidectomy: perioral tingling, Chvostek's, Trousseau's signs
• Hypomagnesemia: causes refractory hypokalemia; correct Mg first

• Enteral (preferred): "If the gut works, use it"; maintains gut mucosal integrity, cheaper, safer; start within 24-48h post-op if possible
• Parenteral (TPN): gut not usable (ileus, fistula, short bowel, bowel obstruction); via central line; complications: line sepsis, hyperglycemia, liver dysfunction, refeeding syndrome

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Station 3 - Recognition of Critical Findings

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Station 4 - Management Plan

1. Pre-op: correct deficits; avoid prolonged pre-op fasting (clear fluids up to 2h before surgery - current guidelines)
2. Intra-op: replace insensible losses (4-6 mL/kg/h for laparotomy) + blood loss + deficit
3. Post-op: target euvolemia; avoid "fluid creep" (excessive crystalloid associated with ileus, abdominal compartment syndrome, pulmonary edema)

• Simple procedures: restart oral intake within hours (ERAS protocol)
• Major GI surgery: nasojejunal tube feeding or early enteral within 24h
• Critical illness: TPN only if enteral not tolerated by day 3-7
• Target: positive nitrogen balance; protein 1.5-2 g/kg in ICU

• Oral carbohydrate loading 2-3h pre-op (reduces insulin resistance)
• Early post-op oral feeding
• Avoid nasogastric tubes routinely
• Multimodal analgesia to reduce opioid-induced ileus

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TOPIC 6: CHEST INJURIES

Station 1 - Initial Assessment

1. Tension pneumothorax
2. Open pneumothorax (sucking chest wound)
3. Massive hemothorax
4. Flail chest
5. Cardiac tamponade
6. Airway obstruction

• Airway: hoarseness, stridor, tracheal deviation (tension PTX = away from side; atelectasis = toward)
• Breathing: symmetry of chest movement, RR, percussion, auscultation
• Circulation: HR, BP, JVP (↑ in tension PTX and tamponade; ↓ in hemorrhagic)
• eFAST: pericardial window + bilateral pleural windows for pneumo/hemothorax

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Station 2 - Clinical Assessment and Diagnostic Reasoning

• Pulmonary contusion: commonest serious blunt chest injury; CXR shows patchy infiltrates; hypoxia worsens 24-48h
• Myocardial contusion: arrhythmias post sternal trauma; ECG + troponin
• Diaphragmatic rupture: left > right; bowel loops in chest; nasogastric tube coiling in chest = pathognomonic
• Esophageal rupture: Mackler's triad (vomiting + chest pain + subcutaneous emphysema); Hamman's crunch on auscultation

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Station 3 - Recognition of Critical Findings

• Tracheal deviation away from affected side (late sign)
• Absent breath sounds + hyperresonance on affected side
• Hemodynamic collapse (↑ HR, ↓ BP, ↑ JVP)
• Treatment: immediate needle decompression (2nd ICS, MCL) → chest tube (4th/5th ICS, anterior axillary line)

• Air preferentially enters through wound if wound diameter >2/3 tracheal diameter
• Treatment: 3-sided occlusive dressing (valve effect) immediately → formal chest tube at separate site

• Beck's triad: hypotension + muffled heart sounds + JVD
• ECG: electrical alternans; echo: pericardial fluid + RV collapse
• Treatment: pericardiocentesis (subxiphoid approach) as temporizing measure → surgical drainage

• 1500 mL blood in chest cavity (or >200 mL/h for 2-4h after chest tube)

• Treatment: large-bore chest tube + fluid resuscitation; operative indication if >200 mL/h drainage

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Station 4 - Management Plan

• Size: 28-32F for blood; 24-28F for pneumothorax
• Position: 4th/5th ICS, anterior axillary line (safe triangle: anterior border latissimus dorsi, lateral pectoralis major, above 5th ICS)
• Connect to underwater seal; monitor drainage
• Autotransfusion if massive hemothorax (collect + reinfuse blood)

• 1-2 ribs: adequate analgesia (NSAIDs + opioids), incentive spirometry
• ≥3 ribs or age >65: consider admission, aggressive pain control
• Flail segment: PPV/CPAP for underlying pulmonary contusion; surgical fixation for refractory respiratory failure
• Epidural analgesia or paravertebral block: most effective for multiple rib fractures; reduces pneumonia risk

• Supportive: O2, cautious fluid management (avoid fluid overload worsening hypoxia), incentive spirometry
• Intubation if: RR >35, SpO2 <90% on O2, PaO2/FiO2 <300

• Hemodynamic instability: emergency surgery
• Stable: CT angiography to grade → endovascular stent grafting (TEVAR) preferred over open repair

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TOPIC 7: ANESTHESIA AND PAIN MANAGEMENT

Station 1 - Initial Assessment

• ASA Physical Status Classification:
  • I: Healthy patient
  • II: Mild systemic disease
  • III: Severe systemic disease
  • IV: Severe, constant life-threatening disease
  • V: Moribund (not expected to survive without surgery)
  • VI: Brain-dead organ donor
• ASA III-IV = higher risk; consider cardiology/pulmonology consultation

• L: Look externally (obesity, short neck, facial trauma)
• E: Evaluate 3-3-2 rule (mouth opening 3 fingers, hyoid-chin 3 fingers, thyroid-floor of mouth 2 fingers)
• M: Mallampati score (I-IV; III-IV predict difficult laryngoscopy)
• O: Obstruction/Obesity
• N: Neck mobility

• NPO status: solids 6-8h, liquids 2h, clear fluids 2h
• Trauma, pregnancy, bowel obstruction, diabetic gastroparesis: assume full stomach → rapid sequence induction (RSI)

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Station 2 - Clinical Assessment and Diagnostic Reasoning

• General: IV induction (propofol/thiopental) + inhalational maintenance (sevoflurane, desflurane) ± neuromuscular blockade
• Regional: spinal (intrathecal; fast, dense block; headache risk), epidural (catheter; titratable), peripheral nerve blocks
• Local: infiltration, topical; used for minor procedures

• Induction: propofol (1.5-2.5 mg/kg) or ketamine (1-2 mg/kg for hemodynamically unstable/bronchospasm)
• Neuromuscular blockade: succinylcholine (1.5 mg/kg; caution: hyperkalemia risk in burns/crush) or rocuronium (1.2 mg/kg with sugammadex reversal available)
• Cricoid pressure (Sellick maneuver) during RSI

• Step 1: Non-opioid (paracetamol 1g q6h + NSAID/COX-2 inhibitor)
• Step 2: Add weak opioid (tramadol, codeine)
• Step 3: Add strong opioid (morphine, oxycodone, fentanyl)
• Adjuvants at any step: gabapentin, ketamine infusion (opioid-sparing), dexamethasone
• Regional blocks: gold standard for thoracic/abdominal/orthopedic surgery

• Amides (metabolized by liver): lidocaine, bupivacaine, ropivacaine
• Esters (metabolized by plasma cholinesterase): cocaine, benzocaine, procaine
• Maximum doses: lidocaine 3 mg/kg (plain), 7 mg/kg with epinephrine; bupivacaine 2 mg/kg

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Station 3 - Recognition of Critical Findings

• Triggered by: succinylcholine + volatile anesthetic agents (halothane, sevoflurane)
• Mechanism: RYR1 mutation → uncontrolled Ca²⁺ release → skeletal muscle hypermetabolism
• Features: rapidly rising temperature (>2°C/h), masseter spasm, tachycardia, muscle rigidity, dark urine (myoglobinuria), EtCO2 rising despite increased ventilation
• Treatment: dantrolene 2.5 mg/kg IV (repeat up to 10 mg/kg), stop triggering agents, hyperventilate with 100% O2, active cooling, treat hyperkalemia

• CNS: circumoral tingling → tinnitus → confusion → seizures
• CVS: PR prolongation → wide QRS → ventricular arrhythmia → cardiac arrest
• Treatment: lipid emulsion therapy 20% intralipid (1.5 mL/kg bolus then infusion); standard ACLS

• Declare CICO immediately if 3 failed attempts + SpO2 falling
• Emergency front-of-neck airway (FONA): cricothyrotomy (surgical or needle)

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Station 4 - Management Plan

• Continuous ECG, SpO2, ETCO2, NIBP every 5 min, temperature for procedures >30 min
• Invasive arterial line: major/vascular surgery, hemodynamic instability
• Central venous access: major surgery, vasopressor administration

• Pre-emptive analgesia: give before incision
• Paracetamol + NSAID as baseline
• Regional block where possible (epidural for thoracic/abdominal; femoral/sciatic block for lower limb; pec/serratus block for breast)
• Minimize opioids: use opioid-sparing techniques
• PCA (Patient-Controlled Analgesia): morphine or fentanyl; better patient satisfaction

• Risk factors: female, non-smoker, motion sickness history, opioid use
• Prophylaxis: ondansetron (4-8 mg) + dexamethasone (4-8 mg) at induction
• Avoid: neostigmine without anticholinergic, nitrous oxide in high-risk

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TOPIC 8: BURNS

Station 1 - Initial Assessment

• Airway: most critical - singed nasal hairs, eyebrows, carbonaceous sputum, hoarseness, stridor = inhalation injury - intubate EARLY (airway edema progresses rapidly)
• Breathing: circumferential chest burns → escharotomy if restricted breathing
• Circulation: 2 large-bore IVs (can insert through burned tissue if needed); start Parkland formula
• Disability: carbon monoxide (CO) poisoning: high-flow O2 (SpO2 unreliable - measure COHb); cyanide poisoning (house fires) - hydroxocobalamin
• Exposure: remove all clothing/jewelry; estimate TBSA

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Station 2 - Clinical Assessment and Diagnostic Reasoning

• Rule of Nines (adults): Head 9%, each arm 9%, anterior trunk 18%, posterior trunk 18%, each leg 18%, perineum 1%; do NOT include 1st degree burns
• Palmar method: patient's palm = 1% TBSA (for scattered burns)
• Lund-Browder chart: most accurate; adjusts for age (children have larger heads)

• 4 mL × weight (kg) × %TBSA burned (Ringer's Lactate, first 24 hours)
• Half in first 8h (counted from time of burn, not hospital arrival)
• Remaining half over next 16h
• Children: add maintenance fluid (D5LR or D5 0.45% saline)
• Monitor: UO 0.5-1 mL/kg/hr in adults; 1 mL/kg/hr in children

• Clinical: hoarseness, stridor, carbonaceous sputum, facial burns
• Bronchoscopy: gold standard; soot below cords, mucosal erythema/edema
• CO poisoning: COHb level; symptoms at >20% (headache, confusion), >40% (coma, death)

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Station 3 - Recognition of Critical Findings

• Circumferential full-thickness extremity burn → escharotomy (release eschar) to prevent limb ischemia
• Check: pain with passive stretch, pulselessness, paraesthesia, pallor, paralysis (5 Ps)
• Circumferential chest burn → chest escharotomy for ventilatory compromise

• Combined injury dramatically worsens prognosis
• Early intubation (before airway edema closes airway), lung-protective ventilation

• Change of wound appearance: black/dark green discoloration, rapid eschar separation, edema at wound margins
• Systemic SIRS + wound changes = burn wound sepsis - topical (silver sulfadiazine, mafenide acetate) + systemic antibiotics

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Station 4 - Management Plan

1. Airway: early intubation if inhalation injury suspected
2. CO poisoning: 100% O2 via non-rebreather (reduces CO half-life from 5h to 1h); hyperbaric O2 if COHb >25%, neurological symptoms, pregnancy, or cardiac involvement
3. Fluid resuscitation: Parkland formula (RL preferred); reassess hourly with UO
4. Pain: IV morphine + anxiolytic (ketamine excellent for burn wound care procedures)
5. Wound care: cool (not cold) water for ≤20 min if within 3h; cling film as temporary dressing

• Superficial partial thickness: conservative management, non-adherent dressings (mepilex, biobrane)
• Deep partial/full thickness: surgical debridement + split-thickness skin grafting (STSG)
• Temporary coverage: cadaveric allograft, xenograft (pig skin), synthetic dermal substitutes (Integra)
• Topical antimicrobials: silver sulfadiazine (SSD), silver-containing dressings, mafenide acetate (penetrates eschar)

• 10% TBSA partial thickness (>5% in children/elderly)

• Any full-thickness burn
• Burns involving face, hands, feet, genitalia, perineum, major joints
• Electrical/chemical burns
• Inhalation injury
• Burns with pre-existing medical conditions
• Circumferential burns

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TOPIC 9: BASIC SURGICAL SKILLS AND ANASTOMOSIS

Station 1 - Initial Assessment

• Nutritional status: albumin <3 g/dL = significantly increased anastomotic leak risk
• Bowel preparation: mechanical bowel prep + oral antibiotics for elective colorectal surgery (ERAS)
• Anastomosis-specific risk factors for leak: emergency surgery, obesity, steroid use, prior radiation, ischemia, tension on anastomosis, poor technique, low rectal anastomosis

• Clip (do not shave) hair at incision site
• Antiseptic skin prep: chlorhexidine-alcohol preferred over povidone-iodine (lower SSI rate)
• Antibiotic prophylaxis: within 60 min of incision; redose if >3h operative time

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Station 2 - Clinical Assessment and Diagnostic Reasoning

• End-to-end (ETE): bowel of similar caliber; used for small bowel, colon
• End-to-side (ETS): differing calibers; pancreaticojejunostomy, biliary-enteric anastomosis
• Side-to-side (STS): functional anastomosis; gastrojejunostomy bypass
• Stapled vs. hand-sewn: equivalent leak rates overall; stapled faster; hand-sewn may be preferred in small caliber/tension situations

1. Adequate blood supply (no tension, viable ends)
2. No tension
3. Mucosa-to-mucosa apposition
4. Watertight closure
5. Absence of infection or distal obstruction

• Absorbable:
  • Polyglycolic acid (Dexon), Polyglactin (Vicryl): 60-90 day absorption; GI anastomosis, fascial closure
  • Polydioxanone (PDS): 180 days; fascial/abdominal wall closure
  • Poliglecaprone (Monocryl): subcuticular skin closure
• Non-absorbable:
  • Polypropylene (Prolene): vascular anastomosis, hernia repair
  • Polyester (Ethibond): cardiac, prosthetic
  • Nylon (Ethilon): skin closure
  • Steel wire: sternal closure

• Square knot (reef knot): two throws in opposite directions; most common surgical knot
• Surgeon's knot: first throw doubled; used under tension
• Minimum 3 throws for synthetic monofilament

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Station 3 - Recognition of Critical Findings

• Early (day 3-4): tachycardia + fever + elevated WBC + pain = leak until proven otherwise
• Late (day 5-7): purulent drain output, peritonitis, or "failure to thrive" post-op
• CT with rectal contrast (colorectal) or CT with oral contrast: confirms leak location
• Contained leak: IR-guided drainage, bowel rest, IV antibiotics
• Free perforation/peritonitis: emergency re-laparotomy

• Post-op bleeding: bright red blood per rectum + tachycardia + ↓ Hb
• Intraluminal hemorrhage: colonoscopy to identify and treat
• Extraluminal: CT angiography + IR embolization or re-operation

• Ileus: diffuse, no transition point on CT, resolves with conservative management
• SBO: colicky pain, distended loops with transition point, requires intervention if complete or strangulated

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Station 4 - Management Plan

1. Optimize nutrition pre-operatively (immunonutrition, protein supplementation)
2. Avoid mechanical bowel prep alone (combined oral antibiotics more evidence-based)
3. Minimize perioperative vasopressors (maintain perfusion)
4. Avoid over-transfusion/over-resuscitation
5. Diverting stoma (loop ileostomy) for high-risk anastomoses (low rectal, immunosuppressed, emergency)

• Mass closure (looped PDS 1 or 0): 4:1 suture-to-wound ratio; best evidence for midline laparotomy
• Interrupted sutures for infected/contaminated wounds
• Prophylactic mesh: high-risk patients for incisional hernia (obesity, re-do surgery)

• Repair indications: symptoms (pain, obstruction), enlargement, cosmesis
• Mesh repair (Lichtenstein for inguinal; Rives-Stoppa or laparoscopic for incisional) - lower recurrence than primary repair

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TOPIC 10: ARTERIAL DISORDERS

Station 1 - Initial Assessment

• Pain (severe, sudden)
• Pallor
• Parasthesia (early sensory loss = urgent)
• Paralysis (late, motor loss = limb loss imminent)
• Pulselessness
• Poikilothermia (cold limb)

• Class I (Viable): No immediate threat, no sensory/motor loss - duplex/angiography
• Class IIa (Marginally threatened): Minimal sensory loss, no motor deficit - urgent intervention
• Class IIb (Immediately threatened): Sensory + motor loss - emergency intervention
• Class III (Irreversible): Complete sensory + motor loss, infarction - amputation consideration

• Duration >2 weeks
• Ischemic rest pain or tissue loss (ulcer/gangrene)
• ABI <0.4

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Station 2 - Clinical Assessment and Diagnostic Reasoning

• Fontaine Classification:
  • Stage I: Asymptomatic
  • Stage II: Intermittent claudication (IIa: >200m; IIb: <200m)
  • Stage III: Rest pain
  • Stage IV: Tissue loss (ulcer/gangrene)
• ABI (Ankle-Brachial Index):

  • 0.9: Normal

  • 0.71-0.90: Mild PAD
  • 0.41-0.70: Moderate PAD
  • <0.40: Severe/critical ischemia

  • 1.3: Non-compressible vessels (calcification, diabetes) - falsely elevated

• Abdominal Aortic Aneurysm (AAA): diameter >3 cm (normal <2 cm); >5.5 cm or rapidly expanding (>1 cm/year) or symptomatic = repair
• Classic triad of ruptured AAA: sudden severe abdominal/back pain + hypotension + pulsatile abdominal mass; high mortality (~80%)
• USS screening: men >65 who have ever smoked (UK NHS AAA Screening)
• Repair options: endovascular (EVAR) preferred in suitable anatomy; open repair for younger/active patients

• Symptomatic stenosis ≥50%: carotid endarterectomy (CEA) within 2 weeks of TIA/minor stroke (NASCET criteria)
• Asymptomatic stenosis ≥60-70%: CEA or carotid artery stenting (CAS) in selected patients

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Station 3 - Recognition of Critical Findings

• Immediate resuscitation (target SBP 70-90 mmHg - permissive hypotension)
• Emergency vascular surgery team activation
• EVAR if available and suitable anatomy; otherwise open repair
• DO NOT delay for extensive imaging if patient is crashing

• Type A (involves ascending aorta): emergency surgery
• Type B (descending only): medical management (beta-blockade, BP control) unless complicated (ischemia, rupture)
• "Tearing" chest pain radiating to back, unequal arm BPs, pulse deficits

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Station 4 - Management Plan

1. Immediate anticoagulation: heparin 5000 units IV bolus → infusion (prevents propagation, micro-thrombi)
2. Imaging: urgent CT angiography (or operative angiography for Class IIb)
3. Revascularization within 6 hours (viability window):
   • Embolism: surgical embolectomy (Fogarty balloon catheter) under local anesthesia
   • Thrombosis on PAD: bypass grafting (preferred) or catheter-directed thrombolysis
4. Post-reperfusion: monitor for compartment syndrome (fasciotomy prophylactically if >6h ischemia); hyperkalemia, myoglobinuria (renal failure risk)

• Risk factor modification: smoking cessation (most effective), statin therapy, antiplatelet (aspirin or clopidogrel), BP control, glycemic control
• Exercise rehabilitation: structured supervised exercise program - first-line for claudication
• Revascularization: endovascular (angioplasty ± stenting) for iliac/femoropopliteal disease; surgical bypass for complex multi-level disease
• Bypass conduit: autologous great saphenous vein > synthetic (PTFE or Dacron) for below-knee reconstruction

• Neuropathic vs. ischemic vs. mixed (most common)
• Wagner classification for ulcer severity
• Multidisciplinary approach: vascular surgery, diabetology, podiatry, infectious diseases
• Osteomyelitis: probe-to-bone test positive = osteomyelitis until proven otherwise; MRI gold standard

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Quick OSCE Reference - Critical Actions Across All Topics

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General Surgery Four-Station OSCE

High-Yield Guide from Bailey and Love's Short Practice of Surgery (28th Edition)

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TOPIC 1: SHOCK AND BLOOD TRANSFUSION

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COMMON OSCE CASES

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STATION 1 - Initial Assessment

• A: Airway patency; stridor/snoring sounds; jaw thrust or oropharyngeal airway needed
• B: RR >20 (compensatory respiratory alkalosis from metabolic acidosis); SpO2; apply 15 L/min O2 via non-rebreather mask
• C: Heart rate and quality; BP; capillary refill time; skin temperature; JVP
• D: GCS; "Mild anxiety" = compensated shock; "Drowsy" = moderate shock; "Comatose" = severe
• E: Expose fully - look for sites of haemorrhage (external and concealed)

• Compensated shock: tachycardia + cool peripheries + maintained BP - "Apart from a tachycardia and cool peripheries, there may be no other clinical signs of hypovolaemia"
• "Blood pressure is usually well maintained and only falls after 30-40% of circulating volume has been lost" - a normal BP does NOT exclude significant haemorrhage

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STATION 2 - Clinical Assessment and Diagnostic Reasoning

• Hypovolaemic: "Absolute or relative hypovolaemia must be excluded or treated in the management of the shocked state, regardless of cause"
• Cardiogenic: "Due to primary failure of the heart to pump blood to the tissues. Causes include myocardial infarction, cardiac dysrhythmias, valvular heart disease, blunt myocardial injury and cardiomyopathy"
• Obstructive: "Reduction in preload owing to mechanical obstruction of cardiac filling. Common causes include cardiac tamponade, tension pneumothorax, massive pulmonary embolus or air embolus"
• Distributive (septic/anaphylactic/neurogenic): "Vascular dilatation with hypotension, low systemic vascular resistance, inadequate afterload and a resulting abnormally high cardiac output." In neurogenic shock: "failure of sympathetic outflow and adequate vascular tone"
• Endocrine shock: Adrenal insufficiency / thyroid crisis

• ABG: lactate + base deficit (Bailey & Love: "the base deficit and/or lactate should be measured routinely in these patients until they have returned to normal levels")
• FBC, coagulation, U&E, crossmatch
• FAST/eFAST (abdominal and chest free fluid)
• ECG (exclude acute MI as cause of cardiogenic shock)

• Normal: 50-70%
• <50% = inadequate O2 delivery → hypovolaemic or cardiogenic shock
• >70% in sepsis: "disordered utilisation of oxygen at the cellular level and arteriovenous shunting"

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STATION 3 - Recognition of Critical Findings

• Coagulopathy (ATC) → worsened by dilution from transfusion
• Hypothermia → worsened by cold fluids, open body cavities
• Acidosis → worsened by ongoing ischaemia
• "These then lead to further bleeding and a downward spiral, leading to physiological exhaustion and death"

• ABO incompatibility → immediate intravascular haemolysis
• Back pain + fever + haemoglobinuria + hypotension within minutes
• STOP transfusion immediately - send bag + patient sample to lab
• Risk of DIC and acute renal failure

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STATION 4 - Management Plan

1. Two large-bore IV cannulae (14-16G)
2. Warmed Ringer's Lactate / Hartmann's solution (crystalloid)
3. Activate Massive Transfusion Protocol (MTP) for Class III-IV: balanced 1:1:1 ratio (pRBC : FFP : Platelets)
4. Tranexamic acid (TXA): 1g IV bolus within 3 hours of injury (targets hyperfibrinolysis in ATC)
5. Source control is the definitive treatment - not further fluids: "Haemorrhage is treated by arresting the bleeding"
6. Permissive hypotension (SBP 80-90 mmHg) until surgical haemostasis achieved - avoid dilutional coagulopathy

• Urine output: 0.5-1 mL/kg/hr
• Lactate clearance (serial ABG)
• Base deficit returning toward zero
• SvO2 >50%

• Hb <7 g/dL in stable patients (restrictive)
• Active haemorrhage / cardiac disease: Hb <8-10 g/dL
• Massive transfusion: target correction of coagulopathy + hypothermia + acidosis

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TOPIC 2: ABDOMINAL TRAUMA

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COMMON OSCE CASES

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STATION 1 - Initial Assessment

1. Physiologically 'normal' - investigation can be completed before treatment is planned
2. Physiologically 'non-compromised' - limited investigation; establish if non-operative, angioembolisation, or surgery required
3. Physiologically 'compromised' - investigations suspended; immediate surgical correction of bleeding required

• Blunt trauma: seat belt sign (high risk of small bowel + mesenteric injury), handlebar injury, steering wheel impact
• Penetrating: stab vs. gunshot (place metal markers on wounds for CT); "Bullets have a shock wave and when they pass through a solid structure they cause significant damage some distance from the actual track"
• Bailey & Love: "Blood is not an irritant and does not initially cause any abdominal pain. Distension is subjective, and a drop in the blood pressure may be a very late sign in a young fit patient"

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STATION 2 - Clinical Assessment and Diagnostic Reasoning

• Seat belt sign / bruising: bowel/mesenteric injury
• Cullen's sign (periumbilical bruising): retroperitoneal haemorrhage
• Grey Turner's sign (flank bruising): retroperitoneal haemorrhage (both are delayed signs)
• Kehr's sign: left shoulder tip pain = splenic injury with diaphragmatic irritation

• CT abdomen/pelvis with IV contrast: "In torso trauma, the best and most sensitive modality is a CT scan with intravenous contrast; however, in the unstable patient, this is generally not possible"
• FAST/eFAST (Bailey & Love): "The FAST examination has several advantages over DPL in the assessment of blunt abdominal trauma"; 4-window examination; identifies free fluid in Morrison's pouch, splenorenal fossa, pelvis, pericardium
• DPL: largely superseded; used when imaging unavailable; positive: >100,000 RBC/µL (blunt)
• Laparoscopy (Bailey & Love): "Laparoscopy may be a valuable screening investigation in physiologically non-compromised patients with penetrating trauma to detect or exclude peritoneal penetration and/or diaphragmatic injury. There is no place for laparoscopy in the unstable patient."

• Liver (Bailey & Love): "Most injuries are relatively minor and can be managed non-operatively." Graded using AAST ISS. In non-compromised patient, CT is investigation of choice.
• Spleen: Most commonly injured solid organ in blunt trauma; selective non-operative management
• Hollow viscus (bowel): Look for free air on CT; peritonitis on exam

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STATION 3 - Recognition of Critical Findings

• Haemodynamic instability + free fluid on FAST
• Peritonitis / evisceration
• Gunshot wound to abdomen (mandatory)
• Ruptured hollow viscus (free air)
• Ongoing haemorrhage as "transient responder"

• Pressure - manual compression
• Pringle - portal triad clamping (hepatic inflow occlusion)
• Plug - packing with surgical haemostats
• Parenchymal repair - suture, argon beam, topical haemostats

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STATION 4 - Management Plan

• Haemodynamically stable
• No peritonitis
• CT-confirmed solid organ injury (grade I-III typically)
• ICU-level monitoring available
• Regular serial abdominal examinations

• Stab wounds: selective approach - evisceration / haemodynamic instability = immediate laparotomy; stable patients with anterior wounds may undergo diagnostic laparoscopy
• GSW: mandatory laparotomy

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TOPIC 3: WOUNDS AND TISSUE REPAIR

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COMMON OSCE CASES

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STATION 1 - Initial Assessment

1. Location: proximity to vessels, nerves, tendons, joints, body cavities
2. Mechanism: incised (sharp, clean edges) vs. laceration (ragged) vs. crush vs. bite vs. blast
3. Time since injury: primary closure safe <6h for most wounds; face/scalp can close up to 24h
4. Contamination class:
   • Class I (Clean): elective, no viscus entered, infection rate <2%
   • Class II (Clean-contaminated): controlled viscus entry, 5-15%
   • Class III (Contaminated): open fracture, traumatic wounds, spillage, 15-25%
   • Class IV (Dirty): established infection / perforated viscus, >30%
5. Tetanus status: document; immunise if incomplete or >5 years since booster; give tetanus immunoglobulin for tetanus-prone wounds

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STATION 2 - Clinical Assessment and Diagnostic Reasoning

• Primary intention: edges approximated immediately; cleanest result
• Secondary intention: left to granulate; for infected or heavily contaminated wounds
• Tertiary (delayed primary) closure: wound left open 4-5 days, then closed; ideal for contaminated traumatic wounds (Case A is a candidate for this given 8-hour delay)

• Serosanguinous fluid draining from abdominal wound = fascial disruption until proven otherwise
• Bailey & Love: Risk factors include obesity, malnutrition, infection, poor technique, excessive tension, steroid use

• Local: infection (the most common cause), ischaemia, haematoma, foreign body, radiation
• Systemic: malnutrition (protein, vitamin C, zinc deficiency), uncontrolled diabetes, steroids, immunosuppressants, uraemia, jaundice

• Hypertrophic scar: raised but stays within original wound margins; may regress; responds to pressure/silicone
• Keloid: extends beyond wound margins; never regresses; recurs after excision; more common in pigmented skin; locations: ear, sternum, shoulder, deltoid

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STATION 3 - Recognition of Critical Findings

• Salmon-pink serosanguinous discharge = fascial dehiscence
• Expose wound immediately; check integrity of fascia
• Evisceration = emergency return to OR; cover bowel with moist warm saline gauze

• Clostridium perfringens; incubation 12-24h post-contaminated wound
• Severe disproportionate pain → rapidly spreading bronze/dark skin → crepitus (gas in tissues) → thin brown "dishwater" exudate → shock
• Treatment: Emergency wide surgical debridement + high-dose IV penicillin G + hyperbaric O2 (adjunct)
• Do NOT wait for imaging if clinical picture is clear

• LRINEC score ≥6 = high risk
• Type I (polymicrobial) or Type II (Group A Streptococcus)
• "Dishwater" fluid at surgery; rapid tracking along fascial planes
• Treatment: immediate radical surgical debridement, broad-spectrum IV antibiotics, ICU

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STATION 4 - Management Plan

1. Irrigate: copious high-pressure saline irrigation (minimum 250 mL per cm of wound)
2. Debride: all devitalised, ischaemic, and contaminated tissue
3. Haemostasis: electrocautery, ties, topical agents
4. Select closure:
   • <6h, clean: primary closure

   • 6h, contaminated: delayed primary or secondary intention

5. Suture selection:
   • Skin: non-absorbable (nylon/prolene) for tension-free; monocryl subcuticular for cosmesis
   • Deep layers: absorbable (Vicryl/PDS)
   • Abdominal fascia: mass closure with PDS loop (4:1 suture-to-wound length ratio)
6. Prophylactic antibiotics: cefazolin 1-2g IV within 60 min of incision; single dose unless contaminated

• Indications: open abdomen, large traumatic wounds, dehisced wounds, diabetic foot ulcers
• Mechanism: removes exudate, reduces bacterial load, promotes granulation, draws edges together

• Intralesional triamcinolone acetonide (first-line)
• Silicone gel sheets / pressure garments
• Surgical excision only with adjuvant therapy (radiation or steroid injection) to reduce recurrence

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TOPIC 4: SURGICAL INFECTION

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COMMON OSCE CASES

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STATION 1 - Initial Assessment

• SIRS criteria: Temperature >38°C or <36°C; HR >90; RR >20; WBC >12,000 or <4,000
• Sepsis (Sepsis-3): Life-threatening organ dysfunction from dysregulated host response; SOFA increase ≥2
• Septic shock: Sepsis + vasopressor need to maintain MAP ≥65 mmHg + lactate >2 mmol/L

• Wound: erythema, warmth, fluctuance, purulent discharge
• Abdomen: tenderness, rigidity, Murphy's sign, rebound
• Chest: reduced air entry, dullness, crackles
• IV lines: phlebitis, erythema at site
• Urinary: suprapubic tenderness, costovertebral angle tenderness
• Surgical drains: character of output (clear → cloudy → purulent/faeculent)

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STATION 2 - Clinical Assessment and Diagnostic Reasoning

• FBC, CRP, procalcitonin, metabolic panel, lactate
• Blood cultures ×2 before antibiotics
• Wound swab + drain fluid culture
• Imaging: USS (abscess, biliary); CT abdomen/pelvis (intra-abdominal source)

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STATION 3 - Recognition of Critical Findings

• Necrotising fasciitis of the perineum and genitalia
• Rapidly spreading crepitus + skin necrosis + systemic toxicity
• Do not wait for imaging if clinical suspicion is high
• Treatment: Immediate radical surgical debridement (often extensive) + broad-spectrum IV antibiotics (piperacillin-tazobactam + clindamycin + vancomycin for MRSA cover) + ICU + consider hyperbaric O2

• qSOFA ≥2 (RR ≥22 + altered mentation + SBP ≤100)
• Surviving Sepsis Campaign "1-hour bundle:" measure lactate, blood cultures, antibiotics, 30 mL/kg crystalloid, vasopressors for MAP <65

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STATION 4 - Management Plan

• Prophylaxis: cefazolin 1-2g IV 30-60 min before incision; single dose; redose if >3h operative time or EBL >1.5L
• Empirical treatment guided by suspected source:
  • Intra-abdominal: piperacillin-tazobactam OR ceftriaxone + metronidazole
  • MRSA risk: add vancomycin (healthcare-associated, severe)
  • De-escalate at 48-72h based on culture and sensitivity
• Duration: typically 4-7 days for source-controlled surgical infections

• Abscess: drain (percutaneous USS/CT-guided preferred if accessible; surgical if complex)
• Anastomotic leak: contained → drain + antibiotics + NPO; free perforation → emergency re-laparotomy
• Infected prosthetic material (mesh, vascular graft): usually requires removal
• Devitalised infected tissue: debride promptly and radically

• Skin prep: chlorhexidine-alcohol (superior to povidone-iodine)
• Normothermia maintenance intra-operatively
• Tight glycaemic control (target <180 mg/dL intra-op)
• Antibiotic prophylaxis timing
• Wound protector devices in contaminated cases

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TOPIC 5: NUTRITION AND FLUID THERAPY

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COMMON OSCE CASES

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STATION 1 - Initial Assessment

• History: recent weight loss? (>5% in 1 month or >10% in 6 months = significant)
• Reduced food intake? Gastrointestinal symptoms affecting intake?
• Screening tools: NRS-2002 (Nutritional Risk Screening) or MUST (Malnutrition Universal Screening Tool)
• Examination: temporal/thenar muscle wasting, loss of subcutaneous fat, peripheral oedema (hypoalbuminaemia), poor wound healing

• Hypovolaemia: dry mucous membranes, tachycardia, postural hypotension, reduced skin turgor, sunken eyes, oliguria
• Hypervolaemia: pulmonary oedema (crackles, orthopnoea), raised JVP, peripheral oedema
• Daily maintenance: 25-35 mL/kg fluid + 1-2 mmol/kg Na+ + 0.5-1 mmol/kg K+

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STATION 2 - Clinical Assessment and Diagnostic Reasoning

• Hyponatraemia (Case C): Excess hypotonic fluids + SIADH post-surgery; "dilutional" - restrict free water; correct slowly to avoid central pontine myelinolysis (max 8-10 mmol/L/day)
• Hypokalaemia: NG/fistula losses, diuretics; replace KCl (max 20 mmol/h via central line); check Mg²+ (hypomagnesaemia causes refractory hypokalaemia)
• Hypocalcaemia after thyroid/parathyroid surgery: Chvostek's sign (facial nerve tap), Trousseau's sign (carpal spasm with BP cuff); replace IV calcium gluconate

• Enteral preferred: "If the gut works, use it"; maintains mucosal integrity, prevents bacterial translocation, cheaper, safer
• Start within 24-48h post-major surgery when feasible
• Total Parenteral Nutrition (TPN): only when gut non-functional (obstruction, ileus, fistula, short bowel); delivered via central line; risks: line infection, hyperglycaemia, liver dysfunction, refeeding syndrome

• After prolonged starvation + reintroduction of carbohydrates
• Insulin surge → massive cellular uptake of phosphate, potassium, magnesium
• Hypophosphataemia <0.5 mmol/L = hallmark
• Cardiac arrhythmias, respiratory failure (diaphragm weakness), seizures
• Treatment: introduce feeds slowly (10-20 kcal/kg/day initially); supplement phosphate, K+, Mg²+, thiamine before feeding

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STATION 3 - Recognition of Critical Findings

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STATION 4 - Management Plan

1. Pre-op: correct deficits; oral carbohydrate loading 2-3h before surgery (ERAS - reduces insulin resistance)
2. Intra-op: replace insensible losses (4-6 mL/kg/h for open laparotomy) + measured blood loss; use stroke volume variation/pulse pressure variation to guide boluses
3. Post-op: avoid "fluid creep" - excess crystalloid causes ileus, pulmonary oedema, anastomotic oedema; target euvolaemia; use vasopressors instead of excess fluid if hypotensive

• Simple surgery: restart oral intake within hours
• Major GI surgery: nasojejunal feeding or early enteral within 24-48h
• Critical illness: TPN only if enteral not tolerated by day 3-7
• Target: positive nitrogen balance; 1.5-2 g protein/kg/day in critically ill

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TOPIC 6: CHEST INJURIES

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COMMON OSCE CASES

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STATION 1 - Initial Assessment

1. Tension pneumothorax
2. Open pneumothorax (sucking chest wound)
3. Massive haemothorax
4. Flail chest
5. Cardiac tamponade
6. Airway obstruction

• A: Stridor (airway obstruction), hoarseness, tracheal deviation
• B: Symmetry of chest expansion, percussion (resonance vs. dullness), auscultation bilaterally
• C: HR, BP, JVP (raised JVP + hypotension = obstructive shock → tamponade or tension PTX)
• eFAST: pericardial window + bilateral chest windows

• Away from the affected side = tension pneumothorax (or massive haemothorax)
• Toward affected side = major atelectasis / lung collapse

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STATION 2 - Clinical Assessment and Diagnostic Reasoning

• Hypotension + muffled heart sounds + raised JVP
• ECG: electrical alternans (alternating QRS axis)
• Pulsus paradoxus >10 mmHg

• Commonest serious blunt chest injury
• CXR: patchy consolidation, often not apparent immediately
• Hypoxia worsens over 24-48h as oedema develops
• Bailey & Love: "Flail chest is defined as paradoxical movement of a segment of the chest wall where two or more adjacent ribs have each been fractured in at least two places"

• Aortic injury: deceleration mechanism + wide mediastinum (>8 cm) + left haemothorax + unequal arm blood pressures
• Diaphragmatic rupture: left > right; bowel loops in chest on CXR; NG tube coiling in thorax
• Myocardial contusion: sternal fracture mechanism + ECG changes + troponin rise
• Oesophageal rupture: Mackler's triad (vomiting + chest pain + subcutaneous emphysema)

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STATION 3 - Recognition of Critical Findings

• Absent breath sounds + hyperresonance + haemodynamic collapse + tracheal deviation (late sign)
• Immediate treatment: needle decompression (2nd ICS, MCL, large-bore cannula)
• Followed by formal chest drain insertion (4th/5th ICS, anterior axillary line - the "safe triangle")

• Beck's triad + pulsus paradoxus
• Treatment: pericardiocentesis (subxiphoid approach, needle at 45° toward left shoulder) as temporizing measure; definitive = surgical drainage
• In traumatic tamponade (penetrating): emergency left anterolateral thoracotomy with finger release of pericardium

• 1500 mL blood or >200 mL/h for 2-4h after chest drain

• Large-bore chest drain + rapid fluid resuscitation
• Operative indication: initial >1500 mL drainage OR sustained >200 mL/h

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STATION 4 - Management Plan

• Size: 28-32F for blood; 20-24F for pneumothorax
• Position: "safe triangle" - 4th/5th ICS, anterior axillary line (boundaries: anterior latissimus dorsi, lateral pectoralis major, above 5th ICS)
• Connect to underwater seal
• Do not clamp a chest drain in a patient with active haemorrhage

• Underlying pulmonary contusion: O2, fluid restriction, incentive spirometry, physiotherapy
• Analgesia: epidural analgesia or paravertebral block = most effective; reduces pneumonia incidence
• Intubation/PPV: RR >35, SpO2 <90% on O2, PaO2/FiO2 <200, fatigue
• Surgical rib fixation: for refractory respiratory failure or cases requiring thoracotomy for other injuries

• Apply 3-sided occlusive dressing immediately (allows air out on expiration, prevents entry on inspiration)
• Insert formal chest drain at a separate site

• CT angiography in stable patients
• Endovascular stent grafting (TEVAR) preferred over open repair in suitable anatomy
• Descending aortic injuries: medical management (rate control + BP control) until repair

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TOPIC 7: ANAESTHESIA AND PAIN MANAGEMENT

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COMMON OSCE CASES

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STATION 1 - Initial Assessment

• L: Look externally (obesity, short neck, large tongue, facial hair, facial trauma)
• E: Evaluate 3-3-2 rule (inter-incisor gap 3 fingers; hyoid-mental distance 3 fingers; thyroid-floor of mouth 2 fingers)
• M: Mallampati I-IV (open mouth, protrude tongue - if you cannot see uvula = class III/IV = difficult laryngoscopy)
• O: Obstruction/Obesity
• N: Neck mobility (trauma / ankylosing spondylitis)

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STATION 2 - Clinical Assessment and Diagnostic Reasoning

• General anaesthesia (GA): IV induction (propofol 1.5-2.5 mg/kg or ketamine 1-2 mg/kg in haemodynamically unstable) + volatile maintenance (sevoflurane/desflurane) ± neuromuscular blockade
• Spinal anaesthesia: intrathecal injection; dense block; fast onset; risk: post-dural puncture headache, hypotension (sympathetic block)
• Epidural: catheter technique; titratable; excellent for post-operative analgesia; risk: hypotension, motor block, rare epidural haematoma/abscess
• Peripheral nerve blocks: targeted analgesia with minimal systemic effects; ideal for limb surgery + breast + rib fractures

• Induction: propofol (standard) / ketamine (haemodynamically unstable or bronchospasm / thiopentone (obstetrics)
• NMB: succinylcholine 1.5 mg/kg (fastest onset, depolarising) - AVOID in burns >48h, crush injury (hyperkalaemia risk) / rocuronium 1.2 mg/kg (non-depolarising, reversible with sugammadex)
• Cricoid pressure (Sellick manoeuvre) applied from induction until cuff inflated

• Step 1: Paracetamol 1g q6h + NSAID/COX-2 inhibitor (baseline for all)
• Step 2: Add weak opioid (tramadol/codeine) for moderate pain
• Step 3: Add strong opioid (morphine/oxycodone/fentanyl) for severe pain
• Adjuvants: gabapentin/pregabalin (neuropathic), ketamine infusion (opioid-sparing), dexamethasone

• Amides (liver metabolism): lidocaine (max 3 mg/kg plain; 7 mg/kg with epi), bupivacaine (max 2 mg/kg), ropivacaine
• Esters (plasma cholinesterase): cocaine, procaine, benzocaine
• Add epinephrine to increase duration and reduce systemic absorption (NEVER use with epi in digits/penis/ear/nose)

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STATION 3 - Recognition of Critical Findings

• Triggered by: succinylcholine + volatile agents (halothane, sevoflurane, isoflurane)
• Mechanism: RYR1 mutation → uncontrolled sarcoplasmicreticulum Ca²+ release → hypermetabolic crisis
• Features: rapidly rising ETCO2 (earliest sign), masseter spasm, tachycardia, muscle rigidity, hyperthermia (>2°C/h), myoglobinuria, hyperkalaemia
• Treatment:
  1. Call for help; remove all trigger agents; cancel/complete surgery ASAP
  2. Dantrolene 2.5 mg/kg IV (repeat every 5-10 min up to 10 mg/kg); blocks Ca²+ release
  3. Hyperventilate with 100% O2
  4. Active cooling (ice packs, cold IV fluids, cooling blanket)
  5. Treat hyperkalaemia (calcium, insulin-dextrose, bicarbonate)

• CNS: circumoral tingling → tinnitus → visual disturbance → seizures
• CVS: PR prolongation → wide QRS → ventricular arrhythmia → cardiac arrest
• Treatment: 20% lipid emulsion (Intralipid) 1.5 mL/kg IV bolus → infusion; standard ACLS

• Declare CICO after 3 failed attempts + SpO2 falling
• Emergency front-of-neck airway (FONA): surgical cricothyrotomy - vertical skin incision over cricothyroid membrane, horizontal stab incision, insert cuffed ET tube

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STATION 4 - Management Plan

• Cardiology review: echocardiogram, cardiac stress test
• Pulmonology review: pulmonary function tests, optimise COPD
• Anaesthesia review: airway assessment, discuss regional vs. GA
• Blood: FBC, U&E, coagulation, crossmatch, ECG, CXR

• Continuous ECG, SpO2, ETCO2, temperature
• NIBP every 5 minutes (invasive arterial line for major surgery)
• Central venous pressure for major cases; consider cardiac output monitoring (transoesophageal echo or pulse contour analysis)

• Pre-emptive analgesia (give before incision)
• Paracetamol + NSAID as scheduled baseline (not PRN)
• Epidural (thoracic for abdominal) or regional block (TAP block, paravertebral)
• Minimise opioids: opioid-sparing techniques reduce ileus, PONV, respiratory depression
• PCA (Patient-Controlled Analgesia): morphine standard; better pain control than PRN dosing
• For Case C: review PCA settings, add non-opioid adjuncts, consider regional technique

• Risk factors: female sex, non-smoker, PONV history, post-operative opioids
• Prophylaxis: ondansetron 4 mg + dexamethasone 4-8 mg at induction
• Avoid nitrous oxide in high-risk patients

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TOPIC 8: BURNS

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COMMON OSCE CASES

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STATION 1 - Initial Assessment

• A - Airway is the PRIORITY: Singed nasal hairs, singed eyebrows, carbonaceous sputum, hoarseness, stridor = inhalation injury - intubate EARLY before progressive airway oedema closes the airway (oedema peaks at 12-24h)
• B: Circumferential chest burns restrict chest wall movement → escharotomy needed; check SpO2 (unreliable in CO poisoning - measure COHb directly)
• C: 2 large-bore IVs (through burned tissue if necessary); start Parkland formula
• D: CO poisoning → high-flow 100% O2; cyanide poisoning (house fires, burning plastics) → hydroxocobalamin
• E: Remove all clothing/jewellery; estimate TBSA using Rule of Nines (do not include 1st degree/erythema)

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STATION 2 - Clinical Assessment and Diagnostic Reasoning

• Rule of Nines (adults): Head 9%, each arm 9%, anterior trunk 18%, posterior trunk 18%, each leg 18%, perineum 1%
• Case A: Face 4.5% + anterior trunk 18% + right arm 9% = approximately 27-31% TBSA
• Palmar method: patient's palm (with fingers) = 1%; useful for scattered burns

• 4 mL × weight (kg) × %TBSA (Ringer's Lactate) over first 24h - counted from time of burn, not hospital arrival
• Case B: 4 × 70 × 36 = 10,080 mL in first 24h
• Half (5,040 mL) in first 8h; remaining half (5,040 mL) over next 16h
• Monitor: UO 0.5-1 mL/kg/h (35-70 mL/h in Case B)

• COHb >20%: headache, nausea, confusion; >40%: coma, death
• SpO2 is unreliable (reads as oxyhaemoglobin) - measure COHb directly on ABG
• Treatment: 100% O2 via tight-fitting non-rebreather mask (reduces CO half-life from ~5h on room air to ~60-90 min)

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STATION 3 - Recognition of Critical Findings

• Stridor or progressive hoarseness = imminent complete airway obstruction
• Intubate immediately with RSI - do not delay for bronchoscopy
• Post-intubation: lung-protective ventilation (6 mL/kg tidal volumes); bronchoscopy confirms diagnosis (soot below cords, mucosal erythema)

• Circumferential full-thickness extremity burn → oedema within unyielding eschar → elevated compartment pressure → ischaemia
• 5 Ps: Pain (with passive stretch), Pulselessness, Parasthesia, Pallor, Paralysis
• Escharotomy: longitudinal incisions through full-thickness eschar (medial and lateral aspects of limb) to release pressure; performed at bedside under IV analgesia/ketamine
• Chest escharotomy: for circumferential chest burns restricting ventilation

• Change in wound character (dark green/black discolouration), rapid eschar separation, advancing cellulitis, systemic SIRS
• Topical: silver sulfadiazine, mafenide acetate (penetrates eschar), silver-containing dressings
• Systemic: anti-pseudomonal antibiotic (piperacillin-tazobactam or cefepime)

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STATION 4 - Management Plan

1. Airway: early intubation if inhalation injury
2. CO: 100% O2; hyperbaric O2 if COHb >25%, neurological involvement, pregnancy, cardiac effects
3. Fluids: Parkland formula with Ringer's Lactate; reassess hourly with UO; adjust rate (not boluses)
4. Analgesia: IV morphine titrated; ketamine ideal for burn wound dressing changes (dissociative agent, preserves airway reflexes, excellent analgesia)
5. Wound: cool (not cold, not ice) running water for ≤20 min if burn within 3h; cling film as initial dressing (non-adherent, allows assessment)
6. NGT: for large burns (>20% TBSA); ulcer prophylaxis (Curling's ulcer)

• Superficial partial: conservative + non-adherent dressings (Mepitel, Biobrane)
• Deep partial/full thickness: early tangential excision (within 48-72h) + split-thickness skin grafting (STSG)
• Temporary coverage: cadaveric allograft (gold standard), xenograft (pig skin), Integra (dermal substitute)

• 10% TBSA partial thickness (>5% in children/elderly)

• Any full-thickness burn
• Face, hands, feet, genitalia, perineum, major joints involvement
• Electrical or chemical burns
• Inhalation injury
• Circumferential burns
• Burns with significant comorbidities

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TOPIC 9: BASIC SURGICAL SKILLS AND ANASTOMOSIS

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COMMON OSCE CASES

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STATION 1 - Initial Assessment

• Nutritional status: albumin <3 g/dL = high risk
• Comorbidities: diabetes (impaired healing), steroids (inhibit fibroblasts), immunosuppressants
• Operation: emergency vs. elective; degree of contamination; tension or ischaemia at anastomosis
• Bowel preparation: combined mechanical + oral antibiotics for elective colorectal (ERAS)

• Open wound after appendicectomy: was this a dirty (Class IV) case? (gangrenous appendix = Class IV)
• Inspect: depth, base tissue (granulation/slough/necrosis), signs of infection, undermining
• Check fascia integrity: probe the wound; serosanguinous fluid = suspect fascial dehiscence

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STATION 2 - Clinical Assessment and Diagnostic Reasoning

• Tachycardia + fever + drain output change on days 3-7 = leak until proven otherwise
• CT abdomen/pelvis with oral + IV contrast: confirms leak, identifies free fluid/air, guides drainage
• Drain fluid: check pH (low = bowel content), creatinine (high = urine leak), amylase (high = pancreatic fistula)

1. Adequate blood supply to both ends (no tension, no ischaemia)
2. No tension - the commonest cause of leakage
3. Mucosa-to-mucosa apposition
4. Water-tight closure
5. No distal obstruction
6. Absence of infection

• End-to-end: similar calibre bowel; small bowel, colon
• End-to-side: differing calibres; ileocolic, bilioenteric
• Side-to-side: bypass; gastrojejunostomy
• Stapled vs. hand-sewn: equivalent anastomotic leak rates; stapled faster; hand-sewn preferred in small calibre or difficult locations

• Absorbable: Vicryl (Polyglactin 910, 60-90 days) - GI anastomosis, soft tissue; PDS (Polydioxanone, 180 days) - fascial closure
• Non-absorbable: Prolene (Polypropylene) - vascular; Nylon - skin; Steel wire - sternal closure
• Abdominal mass closure: looped #1 PDS or nylon; 4:1 suture-to-wound length ratio (evidence-based, reduces incisional hernia)

• Square (reef) knot: two throws in opposite directions = flat, secure
• Surgeon's knot: first throw doubled for tension; use under tissue tension
• Minimum 3 throws for monofilament synthetic sutures; 2 throws adequate for multifilament

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STATION 3 - Recognition of Critical Findings

• Contained leak (drain output changed, CT shows pericolic collection): conservative - bowel rest + IV antibiotics + CT-guided drainage
• Free perforation / faecal peritonitis: emergency re-laparotomy - Hartmann's procedure (resect + end colostomy) is the safest option in peritonitis
• Do NOT perform a primary anastomosis in faecal peritonitis (Case B) - carry out Hartmann's procedure; restore continuity at 3-6 months

• Intraluminal: PR bleeding + ↓ Hb post-op; colonoscopy to identify and treat
• Extraluminal (mesenteric vessel): CT angiography → IR embolisation or re-operation

• Class IV wound (dirty): should have been left open for delayed primary closure or secondary healing
• Fascial dehiscence: emergency; evisceration = return to OR

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STATION 4 - Management Plan

• Early (Day 3-4, tachycardia + fever): CT first to characterise
• Contained: NPO + IV antibiotics (piperacillin-tazobactam) + CT-guided/surgical drainage; consider TPN
• Free perforation: emergency laparotomy; Hartmann's for left colon; primary repair ± defunctioning ileostomy for right colon
• Anastomotic disconnection: take down anastomosis, form stomas

• Low rectal anastomosis (<5 cm from anal verge)
• Emergency surgery in peritonitis
• Immunosuppressed / malnourished / steroid use
• Technical difficulty at anastomosis

• Should not be primarily closed at original operation
• Pack loosely with saline-moistened gauze; delayed primary closure at 4-5 days if no infection
• Or allow secondary healing with NPWT (wound VAC)

• Mass closure technique; PDS loop #1 suture
• 4:1 suture-to-wound ratio (take 1 cm bites, 1 cm apart)
• Avoid strangulating bites (causes ischaemia → necrosis → failure)
• Prophylactic mesh in high-risk patients (obesity, chronic cough, re-do surgery)

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TOPIC 10: ARTERIAL DISORDERS

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COMMON OSCE CASES

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STATION 1 - Initial Assessment

1. Pain - sudden, severe, unrelenting
2. Pallor - waxy white/mottled skin
3. Paraesthesia - early sensory loss (anterior compartment first); early = still salvageable
4. Paralysis - late motor loss; paralysis = immediately threatened or irreversible
5. Pulselessness - absent distal pulses
6. Poikilothermia - cold limb

• A: Patent
• B: Tachypnoea
• C: Shock + pulsatile abdominal mass → do not delay for extensive imaging if crashing
• Target SBP 70-90 mmHg (permissive hypotension) until aortic control in theatre

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STATION 2 - Clinical Assessment and Diagnostic Reasoning

• Stage I: Asymptomatic
• Stage II: Claudication (IIa >200m; IIb <200m)
• Stage III: Rest pain (nocturnal, relieved by hanging leg down)
• Stage IV: Tissue loss (ulcer/gangrene)
• Case C = Stage IV (rest pain + ulcer)

• 0.9: Normal

• 0.71-0.90: Mild disease
• 0.41-0.70: Moderate disease
• <0.40: Critical limb ischaemia (Case C = ABI 0.38 = severe/critical)

• 1.3: Non-compressible (calcified vessels, diabetes - falsely elevated, use toe-brachial index instead)

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STATION 3 - Recognition of Critical Findings

• Mortality without surgery approaches 100%; overall (including pre-hospital) ~80%
• Permissive hypotension: target SBP 70-90 mmHg; avoid over-resuscitation (raises BP → dislodges clot → re-bleeding)
• Do NOT delay for extensive workup in unstable patient
• Activate vascular surgery team and OR simultaneously
• EVAR (endovascular) if suitable anatomy + haemodynamic stability allows; otherwise emergency open repair

• Paralysis present = Rutherford IIb = 6-hour window for revascularisation before irreversible muscle death
• Reperfusion injury after revascularisation: myoglobinuria → acute renal failure; hyperkalaemia; compartment syndrome
• Prophylactic four-compartment fasciotomy if ischaemia >6h or evidence of compartment syndrome

• Type A (involves ascending aorta): emergency cardiac surgery; risk of tamponade, coronary occlusion, aortic regurgitation
• Type B (descending only): medical (IV labetalol + nitroprusside, target SBP 100-120, HR <60) unless complicated (ischaemia, rupture, rapid expansion)
• Presentation: sudden tearing chest pain radiating to back + unequal arm blood pressures + pulse deficits

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STATION 4 - Management Plan

1. Immediate anticoagulation: heparin 5,000 units IV bolus → infusion (prevents propagation)
2. Imaging: CT angiography (stable patients; provides roadmap) or operative angiography (unstable Class IIb)
3. Revascularisation within 6h:
   • Embolism: Fogarty balloon catheter embolectomy under local anaesthesia; longitudinal arteriotomy over common femoral artery
   • Thrombosis on PAD: surgical bypass (preferred) or catheter-directed thrombolysis (stable, <14 days)
4. Post-revascularisation monitoring:
   • 4-compartment leg fasciotomy if >6h ischaemia
   • Monitor for reperfusion syndrome: myoglobinuria (dark urine) → aggressive IV hydration + alkalinise urine
   • Hyperkalaemia: ECG monitoring, treat if >6 mmol/L
5. Long-term: investigate + treat source (AF → anticoagulate; cardiac thrombus → echocardiography)

• Risk factor modification (most effective intervention): smoking cessation, statin, antiplatelet (aspirin 75 mg or clopidogrel 75 mg), BP control (<140/90), tight glycaemic control
• Supervised exercise programme: first-line for claudication (Stage II); 3×/week for ≥12 weeks
• Cilostazol (phosphodiesterase inhibitor): modest benefit for claudication
• Revascularisation for CLTI (Case C - rest pain + ulcer):
  • Endovascular (angioplasty ± stenting): first-line for iliac/femoropopliteal lesions; less invasive, faster recovery
  • Surgical bypass: for complex multi-level disease; autologous great saphenous vein = preferred conduit (superior patency, especially below-knee)
  • PTFE/Dacron synthetic graft: for above-knee popliteal; poor patency below knee

• <5.5 cm: USS surveillance (3-monthly if 4.5-5.4 cm; 6-monthly if 4-4.4 cm; annually if 3-4 cm)
• ≥5.5 cm or symptomatic: EVAR (endovascular) preferred in suitable anatomy; open repair for younger/active patients or unsuitable EVAR anatomy
• Post-EVAR: lifelong CT surveillance for endoleak

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MASTER QUICK-REFERENCE TABLE - All 10 Topics

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