Preoperative risk stratification

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your exam.

Perioperative Care and Surgical Patient Safety is the seventh content block in the Surgery section of the Saudi GP Board, carrying about 3% of the total score. It spans preoperative risk stratification, intraoperative discipline, and postoperative complication surveillance.

ASA I–VI grades the patient, not the operation: I = healthy, II = mild systemic disease, III = severe but not incapacitating, IV = constant threat to life, V = moribund, VI = brain-dead organ donor.
Wound classes run I (clean) → II (clean-contaminated) → III (contaminated) → IV (dirty-infected), each predicting surgical site infection (SSI) risk and guiding antibiotic duration.
The 5 Ws of postoperative fever by post-op day (POD): Wind POD 1–2, Water POD 3–5, Wound POD 5–7, Walking POD 4–6, Wonder drugs POD >7.
Parkland formula = 4 × weight (kg) × %TBSA burned; half in the first 8 hours from the time of burn, the rest over the next 16 hours.

Mnemonic: “A Surgical Wound Classifies Infection Risk” → clean (I) <1.5%, dirty (IV) >25%.

🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months.

Preoperative risk stratification

Combine ASA Physical Status with functional capacity in METs. A patient able to climb two flights of stairs (≥4 METs) generally tolerates non-cardiac surgery without further cardiac testing, even with stable coronary disease. Add the Revised Cardiac Risk Index (Lee criteria) when METs are low: high-risk factors include ischemic heart disease, heart failure, cerebrovascular disease, diabetes on insulin, creatinine >2 mg/dL, and high-risk surgery.

Intraoperative safety scaffolding

The WHO Surgical Safety Checklist runs three mandatory phases:

Sign-in — before anaesthesia: identity, site, consent, allergy, airway, blood loss risk.
Time-out — before skin incision: team members introduced, procedure confirmed, antibiotic given within 60 minutes of incision, imaging displayed.
Sign-out — before the patient leaves theatre: instrument/swab/needle count, specimen labelling, recovery concerns.

Common stem: a “missed sponge count” or a “wrong-site surgery” question almost always tests the correct phase of the checklist.

Wound classification and antibiotic timing

Class	Example	SSI risk	Antibiotic strategy
I Clean	Inguinal hernia repair	<1.5%	Single pre-op dose if prosthesis
II Clean-contaminated	Elective cholecystectomy	2–9%	Pre-op dose, ≤24 h
III Contaminated	Open bowel resection with spill	5–15%	Therapeutic course
IV Dirty-infected	Perforated appendicitis	>25%	Full treatment course

Postoperative complication patterns

Track vital signs against post-op day:

POD 1–2: atelectasis, pneumonia, primary haemorrhage.
POD 3–5: UTI, anastomotic leak (rising CRP, disproportionate tachycardia), intra-abdominal collection.
POD 4–6: DVT/PE, ileus resolution.
POD 5–7+: wound infection, dehiscence, drug fever, line sepsis.

Fluid and analgesia framework

MAP ≥65 mmHg is the perfusion target (formula: MAP = DBP + ⅓[SBP − DBP]). Use multimodal analgesia (paracetamol + NSAID + opioid-sparing regional) and an ERAS bundle: carbohydrate loading 2 h pre-op, early mobilisation on POD 0, oral fluids within hours, and opioid-sparing discharge criteria.

🔴 Extended — Deep Study (3mo+)

Comprehensive coverage for students on a longer study timeline.

VTE prophylaxis selection

Use the Caprini score (surgical patients) or Padua score (medical inpatients) to choose mechanical vs pharmacologic prophylaxis. Caprini ≥5 warrants LMWH + mechanical; hold LMWH 12–24 h before spinal or epidural needle placement or catheter removal to prevent spinal haematoma. Mechanical prophylaxis alone is acceptable when bleeding risk dominates (e.g., neurosurgery, active GI bleed).

Burn resuscitation: getting Parkland right

Formula: total volume (mL) = 4 × weight (kg) × %TBSA burned. Pitfall: the “first half” time window is measured from the time of the burn, not from hospital arrival. Common error: infusing the entire calculated volume in 8 hours after admission → abdominal compartment syndrome and pulmonary oedema. Use lactated Ringer’s, titrate to urine output 0.5 mL/kg/h (adults) and 1 mL/kg/h (children <30 kg), and reduce rate if MAP or CVP rises disproportionately.

Anastomotic leak: the high-yield alert pattern

Subtle presentation on POD 3–5:

Tachycardia >110/min not explained by volume status.
New abdominal distension or shoulder-tip pain.
CRP rising after an initial fall; WBC often lagging.
Fecal output in a drain, or sudden watery wound discharge.

CT abdomen with rectal contrast is the confirmatory test; management is resuscitation, source control (percutaneous or re-laparotomy), and antibiotics.

Exam trap: candidates who anchor on “wound infection” and miss the leak on POD 4 lose marks — always rank differentials by POD timing first.

Practice prompts

Scenario: A 68-year-old diabetic with METs 3 is booked for elective colectomy. His ECG shows old Q-waves; creatinine is 1.9 mg/dL. What is his perioperative plan? → Optimise cardiac status (functional capacity borderline, so consider stress testing), correct electrolytes, hold metformin the morning of surgery, and stratify with RCRI = 4 (high risk).
Scenario: A patient on POD 5 after sigmoid resection has a temperature of 38.4 °C and pulse 118/min, wound looks clean, urinalysis normal. CXR clear. What is your first step? → Suspect anastomotic leak or intra-abdominal collection; arrange CT abdomen with rectal contrast before chasing “wound” or “urine” sources.

Adjacent topics worth linking

Cardiac risk: Goldman/Lee indices bridge this topic to internal medicine.
Antibiotic stewardship: perioperative prophylaxis is a common SCFHS stewardship stem.
Patient blood management (PBM): EBV calculation pre-op guides transfusion triggers.

High-yield reminder: the Saudi GP Board loves single-best-answer MCQs that combine POD timing, vital sign trends, and a single discriminating intervention — practise by sorting every complication into the 5-W grid first.

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Preoperative risk stratification