5.1 Surgical Evaluation, Preoperative Clearance, & Postoperative Complications
Key Takeaways
- Functional capacity >= 4 METs (climbing two flights of stairs without symptoms) indicates acceptable perioperative cardiac risk for non-cardiac surgery.
- Discontinue SGLT2 inhibitors 3-4 days prior to surgery due to the risk of euglycemic diabetic ketoacidosis (e-DKA).
- Postoperative fever follows the '5 Ws' timeline: Wind (atelectasis 24-48h), Water (UTI 48-72h), Wound (SSI 5-7d), Walking (DVT/PE 7-10d), and Wonder drugs/wound deep space (>7d).
- Surgical site infections are classified as superficial incisional, deep incisional, or organ/space; superficial infections require suture removal and drainage rather than routine parenteral antibiotics.
- Acute postoperative oliguria (<0.5 mL/kg/h for 2 consecutive hours) requires immediate physical evaluation and bladder scan to rule out urinary catheter obstruction before administering IV fluid boluses.
Preoperative Evaluation, Risk Stratification, & Postoperative Complications
Preoperative evaluation balances surgical urgency against patient-specific physiological risks. The primary objective is not to 'clear' a patient for surgery, but to quantify perioperative risk, optimize chronic medical conditions, and implement risk-reduction strategies. Postoperatively, systematic monitoring enables early recognition of life-threatening surgical complications.
Preoperative Risk Stratification & Medical Optimization
Cardiovascular Risk Assessment
Cardiovascular complications are the leading cause of perioperative mortality in non-cardiac surgery. The Canadian Cardiovascular Society (CCS) perioperative guidelines recommend measuring baseline NT-proBNP or BNP in patients aged $\ge 65$ years, or aged 45–64 years with significant cardiovascular disease, to refine risk estimation.
Risk stratification relies on the Revised Cardiac Risk Index (RCRI), which assigns 1 point for each of the following six independent predictors:
- High-risk surgery (intraperitoneal, intrathoracic, or suprainguinal vascular surgery)
- History of ischemic heart disease (myocardial infarction, positive exercise test, Q waves, angina)
- History of congestive heart failure (pulmonary edema, paroxysmal nocturnal dyspnea, bilateral crackles, S3)
- History of cerebrovascular disease (stroke or transient ischemic attack)
- Preoperative insulin therapy for diabetes mellitus
- Preoperative serum creatinine $> 170\ \mu\text{mol/L}$ ($> 2.0\ \text{mg/dL}$)
| RCRI Score | Risk Class | Major Cardiac Event Rate (%) | Management Strategy |
|---|---|---|---|
| 0 Points | Class I | 0.4% | Proceed to elective surgery |
| 1 Point | Class II | 0.9% | Proceed with close monitoring; measure post-op troponins |
| 2 Points | Class III | 6.6% | Optimize medical therapy; consider cardiology consultation |
| $\ge 3$ Points | Class IV | 11.0% | Formal cardiology workup; reconsider surgical risk vs. benefit |
Functional capacity is assessed in Metabolic Equivalents of Task (METs):
- $< 4$ METs (Poor): Unable to walk 2 blocks on level ground or climb one flight of stairs. High perioperative risk.
- $\ge 4$ METs (Good to Excellent): Can climb two flights of stairs carrying groceries, heavy house cleaning, or light sports. Indicates acceptable functional reserve.
💡 MCCQE1 Exam Tip: Patients with poor functional capacity ($< 4$ METs) and an elevated RCRI score requiring non-urgent surgery should undergo non-invasive stress testing (dobutamine echocardiography or myocardial perfusion imaging). If surgery is emergency or urgent, proceed directly to the operating room with invasive hemodynamic monitoring.
Pulmonary Risk Assessment & ASA Physical Status
Postoperative pulmonary complications (atelectasis, pneumonia, respiratory failure) occur at rates comparable to cardiac events. Risk factors include upper abdominal or thoracic incisions, age $> 60$ years, COPD, smoking, and obstructive sleep apnea (OSA).
Screening for OSA is performed using the STOP-BANG questionnaire (Snoring, Tiredness, Observed apnea, High Blood Pressure, BMI $> 35$, Age $> 50$, Neck circumference $> 40\text{ cm}$, Male Gender). High risk (score $\ge 5$) warrants perioperative continuous positive airway pressure (CPAP) planning.
ASA Physical Status Classification System
- ASA I: Normal healthy patient
- ASA II: Mild systemic disease without substantive functional limitations (e.g., controlled HTN, controlled DM, smoker)
- ASA III: Severe systemic disease with substantive functional limitations (e.g., poorly controlled DM/HTN, stable angina, history of MI $> 3$ months ago)
- ASA IV: Severe systemic disease that is a constant threat to life (e.g., recent MI $< 3$ months ago, ongoing unstable angina, severe valve dysfunction)
- ASA V: Moribund patient not expected to survive without the operation (e.g., ruptured AAA, massive trauma)
- ASA VI: Declared brain-dead patient whose organs are being harvested
- 'E' Modifier: Added for emergency procedures (e.g., ASA III-E)
Perioperative Medication Management
Appropriate management of chronic medications prevents acute withdrawal, excessive surgical bleeding, and metabolic crises.
| Medication Category | Preoperative Hold Period | Perioperative Management & Rationale |
|---|---|---|
| Warfarin | Hold 5 days prior | Target INR $< 1.5$ for surgery. Bridge with LMWH/UFH if high VTE or mechanical heart valve risk. |
| DOACs (Apixaban, Rivaroxaban, Dabigatran) | Hold 24–48 hours prior | Extend hold to 72 hours for impaired renal function ($CrCl < 50\text{ mL/min}$) or neuraxial anesthesia. |
| Aspirin | Continue in secondary prevention | Continue for ischemic heart disease/stents. Hold 7 days only for high-bleed risk neurosurgery or posterior eye surgery. |
| Clopidogrel / Ticagrelor | Hold 5–7 days prior | Hold 5 days for clopidogrel, 7 days for prasugrel. Consult cardiology if drug-eluting stent placed within 12 months. |
| Metformin | Hold day of surgery | Prevent lactic acidosis during intraoperative hypoperfusion or contrast administration. |
| SGLT2 Inhibitors (Empagliflozin, Dapagliflozin) | Hold 3–4 days prior | Mandatory hold due to severe risk of euglycemic diabetic ketoacidosis (e-DKA) under surgical stress. |
| Insulin | Reduce morning dose | Give 50% of NPH/long-acting insulin on morning of surgery. Hold short-acting bolus insulin while NPO. |
| ACE Inhibitors / ARBs | Hold 24 hours prior | Discontinue morning of surgery to prevent refractory post-induction vasoplegic hypotension. |
| Beta-Blockers & Statins | CONTINUE | Never stop abruptly. Continue on morning of surgery with a sip of water to avoid withdrawal ischemia. |
Postoperative Complications & Diagnostic Timelines
Postoperative Fever: The "5 Ws"
Postoperative fever is defined as a temperature $> 38.0^\circ\text{C}$ ($100.4^\circ\text{F}$). Causes cluster predictably by postoperative day (POD):
| Postoperative Day (POD) | Cause ("W") | Common Etiology & Pathophysiology | Key Diagnostic Workup & Management |
|---|---|---|---|
| POD 1–2 | Wind | Atelectasis (most common), early hospital-acquired pneumonia | Incentive spirometry, chest physiotherapy, early ambulation. Chest X-ray if hypoxemic. |
| POD 3–5 | Water | Urinary tract infection (UTI), catheter-associated UTI | Urinalysis and urine culture. Remove Foley catheter; targeted IV/oral antibiotics. |
| POD 5–7 | Wound | Surgical site infection (SSI - superficial or deep incisional) | Inspect incision for erythema, warmth, purulence. Open wound, drain fluid, send Gram stain/culture. |
| POD 7–10 | Walking | Deep vein thrombosis (DVT), Pulmonary embolism (PE) | Bilateral leg duplex US; CT pulmonary angiography (CTPA). Anticoagulation if confirmed. |
| POD $> 7$ / Any time | Wonder Drugs / What we did | Drug fever, intra-abdominal abscess, anastomotic leak, line infection | Abdominal CT scan with IV/oral contrast for deep abscess. Blood cultures, line tip cultures. |
⚠️ Clinical Scenario: A 62-year-old male on POD 6 following anterior resection develops a temperature of $38.8^\circ\text{C}$, tachycardia (115 bpm), and localized lower abdominal tenderness with cloudy purulent fluid leaking between skin staples. Next Step: Remove skin staples bedside, open the incision, obtain wound cultures, and dress with wet-to-dry packing. Parenteral antibiotics are reserved for surrounding cellulitis, systemic sepsis, or deep fascial involvement.
Surgical Site Infections (SSI)
SSIs are categorized into three anatomical tiers:
- Superficial Incisional: Involves skin and subcutaneous tissue only. Managed by suture/staple removal, drainage, and local wound care.
- Deep Incisional: Involves fascia and muscle layers. Requires operative debridement, tissue cultures, and systemic antibiotics.
- Organ/Space: Involves intra-abdominal, intrathoracic, or joint cavities (e.g., intra-abdominal abscess post-colectomy). Requires percutaneous image-guided catheter drainage or surgical re-exploration plus IV broad-spectrum antibiotics.
Postoperative Oliguria & Acute Kidney Injury
Oliguria is defined as urine output $< 0.5\ \text{mL/kg/h}$ for 2 consecutive hours. The approach requires rapid differentiation between obstructive (postrenal), hypovolemic (prerenal), and intrinsic renal etiologies.
- Step 1 (Rule out obstruction): Inspect catheter for kinks. Perform a bedside bladder scan or flush the Foley catheter with $30\text{ mL}$ sterile saline.
- Step 2 (Evaluate volume status): Assess blood pressure, heart rate, CVP, skin turgor, and fluid balance records.
- Step 3 (Fluid challenge): Administer a $500\text{ mL}$ isotonic crystalloid bolus over 30 minutes if prerenal azotemia is suspected.
- Step 4 (Investigate intrinsic failure): If urine output does not respond to fluid resuscitation, order serum electrolytes, creatinine, urinalysis, fractional excretion of sodium ($FE_{Na}$), and renal ultrasound.
Wound Dehiscence vs. Evisceration
- Wound Dehiscence: Separation of fascial layers without protrusion of intra-abdominal contents. Classic sign: profuse salmon-pink, serosanguinous wound discharge on POD 4–8. Managed with abdominal binder, bed rest, and surgical repair of fascia.
- Evisceration: Surgical emergency defined as fascial separation with protrusion of abdominal viscera (bowel loops) through the skin incision.
- Immediate Management: Cover exposed bowel with warm, sterile saline-soaked gauze, place patient in low Fowler position with knees flexed, keep strictly NPO, administer IV broad-spectrum antibiotics, and notify the surgical team for emergent return to the operating room.
A 68-year-old male with a history of hypertension, type 2 diabetes mellitus, and a prior ischemic stroke 2 years ago is evaluated prior to an elective laparoscopic hemicolectomy for colon cancer. He walks 3 miles daily without chest pain or dyspnea. His preoperative serum creatinine is 110 umol/L. Which of the following is the most appropriate next step in his cardiovascular risk management?
A 54-year-old female on POD 6 following an open total abdominal hysterectomy develops a fever of 38.6°C. Physical examination reveals an erythematous, warm, and exquisitely tender lower abdominal incision. A small amount of foul-smelling purulent liquid is draining between the skin staples. What is the single most appropriate initial management step?
On POD 5 after an exploratory laparotomy, a nurse calls the physician because a 60-year-old patient's dressing is soaked with copious salmon-pink, serosanguinous fluid. When removing the dressing, several loops of small intestine are visualized protruding beyond the abdominal wall. What is the most appropriate immediate bedside intervention?