Risk Stratification

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Risk Stratification - Setting the Stage

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

ASA Physical Status Classification System:

ClassDescriptionExample
ASA IHealthy patientNormal, healthy
ASA IIMild systemic diseaseControlled HTN/DM; smoker, obesity
ASA IIISevere systemic diseasePoorly controlled HTN/DM; MI >3mo, COPD
ASA IVSevere systemic disease, constant threat to lifeRecent MI <3mo; CVA, sepsis, ARDS
ASA VMoribund, not expected to survive without opRuptured aneurysm; massive trauma
ASA VIDeclared brain-dead, organ donor-
EEmergency surgeryAdded to ASA class (e.g., ASA II E)

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). METs Associated With Different Activities

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.

Practice Questions: Risk Stratification

Test your understanding with these related questions

Which of the following signs of congestive cardiac failure constitute a major risk to the surgical patient undergoing anaesthesia ?

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Flashcards: Risk Stratification

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A patient with >3 month hx of MI, CVA, TIA or CAD would be classified under ASA _____

TAP TO REVEAL ANSWER

A patient with >3 month hx of MI, CVA, TIA or CAD would be classified under ASA _____

III

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