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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