What is the recommended approach for a functional capacity risk assessment?

Recommended Approach for Functional Capacity Risk Assessment

The recommended approach for functional capacity risk assessment is to use the Duke Activity Status Index (DASI) or similar validated questionnaire to determine if a patient can achieve ≥4 METs, with exercise stress testing reserved for cases where functional capacity remains unknown or poor. 1

Determining Functional Capacity: A Stepwise Approach

Step 1: Initial Assessment Using Validated Questionnaires

• Use the Duke Activity Status Index (DASI) as the primary tool to estimate functional capacity 1
• Alternative validated tools include the Specific Activity Scale 1
• Ask specific questions about daily activities that correspond to MET levels:
  • Can the patient walk 4 blocks on level ground? (≥4 METs)
  • Can the patient climb 2 flights of stairs? (≥4 METs)
  • Can the patient do moderate activities like moderate cycling, climbing hills, singles tennis? (≥4 METs) 1

Step 2: Interpreting Functional Capacity Results

• ≥4 METs = Adequate functional capacity
  • Proceed with surgery without further cardiac evaluation 1
  • Low risk of perioperative complications 1
• <4 METs = Poor functional capacity
  • Associated with increased perioperative cardiac risk and long-term mortality 1
  • Consider further evaluation based on clinical risk factors and surgery type 1

Step 3: When Functional Capacity is Unknown or Poor

• If functional capacity remains unknown or is poor (<4 METs), consider:
  • The number of clinical risk factors present
  • The specific type of surgery planned
  • Whether further testing will impact decision-making or perioperative care 1

Exercise Testing When Indicated

When objective measurement of functional capacity is needed:

Protocol Selection

• Choose a protocol tailored to yield 8-12 minutes of fatigue-limited exercise 1, 2
• Prefer protocols with modest increases in workload:
  • Balke and Ware protocol
  • Naughton protocol
  • Ramp protocols with small increments 1, 2
• Bruce protocol may be appropriate when expecting >12 minutes of exercise capacity 2

Test Administration

• Minimize handrail support during treadmill testing to avoid overestimation of capacity 1, 2
• Consider direct measurement of oxygen consumption (ventilatory expired gas analysis) when accuracy is critical, such as in heart failure patients 1, 2

Common Pitfalls and Caveats

1. Overestimation of capacity: Self-reported functional capacity may be inaccurate; validate with specific activity questions 1

2. Inappropriate protocol selection: Large stage-to-stage increments in workload can lead to inaccurate estimation of functional capacity 1

3. Misinterpretation of METs: Remember that 1 MET equals the resting oxygen consumption of a 70-kg, 40-year-old man (3.5 mL/kg/min) 1

4. Ignoring non-cardiac limitations: Orthopedic issues, neurological conditions, or respiratory problems may limit exercise capacity independent of cardiac function 1

5. Assuming all patients need exercise testing: For many patients, questionnaire-based assessment is sufficient; reserve formal testing for cases where results will change management 1

By following this structured approach to functional capacity assessment, clinicians can effectively stratify perioperative risk and make informed decisions about the need for additional cardiac evaluation before noncardiac surgery.