How is a patient's surgical fitness determined?

Determining Surgical Fitness

Surgical fitness is primarily determined by assessing a patient's functional capacity, with the ability to perform activities requiring at least 4 METs (metabolic equivalents) being a critical threshold for lower surgical risk. 1

Functional Capacity Assessment

Functional capacity is the cornerstone of surgical fitness evaluation:

• 4 METs threshold: Patients who cannot meet a 4-MET demand during normal daily activities have significantly higher perioperative cardiac risk 1
• Practical assessment methods:
  • Ask if patient can walk 4 blocks or climb 2 flights of stairs
  • Determine if patient can perform activities like moderate cycling, climbing hills, singles tennis
  • Duke Activity Status Index questionnaire can estimate functional capacity 1
  • The likelihood of serious complications is inversely related to blocks walked (p<0.006) or flights of stairs climbed (p<0.01) 1

Risk Stratification Algorithm

1. Determine urgency of surgery:

   • If emergency, proceed with appropriate monitoring based on clinical assessment 1
   • If urgent/elective, continue evaluation

2. Assess for active cardiac conditions (unstable coronary syndromes, decompensated heart failure, severe arrhythmias, severe valvular disease):

   • If present, consider delaying surgery for cardiac stabilization 1

3. Evaluate surgery-specific risk:

   • High risk (>5%): Vascular, major abdominal procedures
   • Intermediate risk (1-5%): Intraperitoneal, intrathoracic, orthopedic, prostate surgery
   • Low risk (<1%): Endoscopic procedures 1

4. Assess functional capacity:

   • If ≥4 METs without symptoms, proceed to surgery 1
   • If <4 METs or unknown, evaluate clinical risk factors

5. Evaluate clinical risk factors:

   • If no clinical risk factors: proceed with surgery
   • If 1-2 clinical risk factors: consider proceeding with beta blockade or testing if it will change management
   • If ≥3 clinical risk factors: consider further cardiac testing based on surgery-specific risk 1

Special Population Considerations

Obese Patients

• Calculate Obesity Surgery Mortality Risk Score (OS-MRS) considering BMI ≥50 kg/m², male gender, hypertension, pulmonary embolism risk factors, and age ≥45 years 2
• Scores of 4-5 indicate highest risk (Class C: 2.4-3.0% mortality) 2
• Consider cardiopulmonary exercise testing (CPET) for obese patients with poor exercise tolerance 2

Elderly Patients

• Evaluate overall "frailty" including cognitive, functional, social, and nutritional status 3
• Consider that preventive vascular procedures in asymptomatic elderly patients require realistic estimates of life expectancy and patient goals 3

Objective Testing When Indicated

• Cardiopulmonary exercise testing (CPET): Provides objective metrics of cardiorespiratory fitness when functional capacity is unclear 4
• Stress testing: Recommended if patient unable to achieve 4 METs, has multiple cardiac risk factors, or requires pharmacological stress testing 1, 2
• Laboratory tests: Comprehensive metabolic panel, coagulation studies, and other tests based on patient comorbidities 2

Common Pitfalls to Avoid

• Overreliance on subjective assessment: Clinical questionnaires only estimate functional capacity and are not as objective as exercise testing 1
• Ignoring procedure-specific risk: The type of surgery itself may identify patients with greater likelihood of underlying heart disease 1
• Overlooking frailty factors: Traditional risk assessments may miss important geriatric risk factors 3
• Neglecting patient goals: Decision to pursue surgery should consider not just mortality risk but also patient's primary goals (prolongation of life vs. maintenance of independence) 3, 5

By systematically evaluating these factors, clinicians can make informed decisions about a patient's fitness for surgery, potentially reducing perioperative morbidity and mortality.