Risk Stratification

Risk Stratification - Setting the Stage

Preoperative risk stratification estimates adverse outcome likelihood, guiding anesthetic plans and consent.

ASA Physical Status Classification System:

General Factors Influencing Risk:

• Age: Extremes (e.g., >70 yrs, neonates)
• Comorbidities: Cardiac, pulmonary, renal, endocrine.
• Surgical Factors:
  • Type (major vs. minor)
  • Urgency (emergency)
  • Duration (prolonged)

⭐ ASA class strongly correlates with perioperative mortality. An ASA III patient has ~5-7x higher 30-day mortality risk vs. ASA I.

Risk Stratification - Prime Suspects

Identifying patients at high risk for perioperative cardiac & pulmonary complications.

• Cardiac Risk: Revised Cardiac Risk Index (RCRI/Lee Index)

  • Predicts MACE (MI, pulm edema, VF/arrest, CHB).
  • 6 Predictors (1 point each):
    • High-risk surgery (vascular, intraperitoneal/thoracic)
    • Hx of Ischemic Heart Disease (IHD)
    • Hx of Congestive Heart Failure (CHF)
    • Hx of Cerebrovascular disease (CVA/TIA)
    • Insulin for Diabetes
    • Serum Creatinine >2 mg/dL
  • MACE Risk Score:
    • 0 pts: 0.4%
    • 1 pt: 0.9%
    • 2 pts: 6.6%
    • ≥3 pts: 11%

  ⭐ Hx CHF: strongest independent RCRI predictor for MACE.

  • Key Cardiac Conditions:
    • IHD: Recent MI (<30 days high risk).
    • HF: EF <40%, NYHA Class III/IV.
    • Valvular: Severe Aortic Stenosis (AVA <1 cm²).
    • Arrhythmias: High-grade AV block, uncontrolled AF.

• Pulmonary Risk

  • Risk Factors: Age, smoking (>4wks cessation beneficial), COPD, asthma, OSA, surgical site (thoracic/upper abd.), duration >2h, emergency.
  • ARISCAT Score: Predicts PPCs. Factors: Age, SpO₂ <96%, recent resp. infection (<1mo), anemia (Hb <10g/dL), surgical site, duration, emergency.
  • 📌 STOP-BANG (OSA Screen): Snoring, Tired, Observed apnea, Pressure (HTN), BMI >35, Age >50, Neck >40cm, Gender (Male). Score ≥3 high OSA risk.

Risk Stratification - Wider Net

• Functional Capacity: METS (Metabolic Equivalents)
  • Definition: 1 MET = $3.5 \text{ mL O}_2/\text{kg/min}$ (basal O₂ use).
  • Examples: Self-care (1 MET); climb stairs, light housework (4 METs); strenuous sports e.g., swimming (>10 METs).
  • Significance: Capacity >4 METs implies adequate reserve for surgery.

  ⭐ Poor functional capacity (<4 METs) is a strong predictor of major post-op cardiopulmonary complications.

• Other Systemic Risks:
  • Renal: Assess eGFR (target >60 $mL/min/1.73m^2$); identify AKI risk factors (e.g., CKD, diabetes).
  • Hepatic: Child-Pugh score (uses bilirubin, albumin, INR, ascites, encephalopathy) for cirrhosis severity.
  • DVT/PE: Caprini score stratifies VTE risk, guides prophylaxis.
• Elderly Patient Considerations:
  • Increased vulnerability; assess frailty (gait speed), cognitive function, nutritional status, polypharmacy.
• Preoperative Biomarkers:
  • HbA1c: Long-term glycemic control (target <8%).
  • BNP/NT-proBNP: Elevated levels indicate cardiac strain, ↑ perioperative cardiac risk.
  • Troponin: Baseline for high-risk cardiac patients or suspected Acute Coronary Syndrome (ACS).

High-Yield Points - ⚡ Biggest Takeaways

• ASA classification is fundamental for overall patient risk.
• RCRI (Revised Cardiac Risk Index) identifies patients at ↑ risk for MACE post-surgery.
• Functional capacity: <4 METs indicates poor reserve, ↑ risk.
• Active cardiac conditions (e.g., unstable angina, recent MI) necessitate preoperative optimization.
• Major pulmonary risk factors include smoking, COPD, and OSA (screen with STOP-BANG).
• Continue chronic beta-blockers; consider for RCRI ≥2 if benefits outweigh risks.
• Manage anticoagulants/antiplatelets balancing bleeding vs. thrombotic risk perioperatively.