Preoperative Evaluation and Management of Functional Capacity in Anesthesiology

Patient Evaluation and Risk Stratification

The American College of Cardiology recommends that patients with poor functional capacity (<4 METs) or those who are symptomatic should be evaluated for clinical risk factors, and considers beta-blockade for heart rate control 6, 7
The American Society of Anesthesiologists (ASA) physical status classification system stratifies patients based on their physical health and comorbidities, not chronological age, with ASA IV being a predictor of high risk for major adverse cardiac events (MACE) 5
The Duke Activity Status Index (DASI) is superior to subjective anesthesiologist evaluation for predicting 30-day mortality or myocardial infarction, with a score ≤34 associated with increased risk 2
Patients with a DASI score ≤34 have a higher risk of 30-day mortality or myocardial infarction, and should be evaluated further 2
The American College of Cardiology recommends that patients with good functional capacity (>4 METs) without symptoms can proceed with scheduled surgery without additional cardiovascular testing, as it rarely changes management 6, 7

The American College of Cardiology recommends that arterial blood gas analysis should be considered in patients with saturation <95% on room air, forced vital capacity <3 liters, or forced expiratory volume <1.5 liters 6, 8, 9
A PCO₂ >6 kPa (45 mmHg) indicates respiratory insufficiency and significantly increases anesthetic risk 8, 9

The American College of Cardiology recommends that patients with high cardiovascular risk (ASA ≥3) and poor functional capacity (<2 flights of stairs) have a 1.63-fold increased risk of 30-day mortality, myocardial infarction, acute heart failure, or potentially fatal arrhythmias 2
The American College of Cardiology recommends that preoperative NT-proBNP levels >100 pg/mL are independently associated with all-cause mortality, but adding NT-proBNP to traditional risk scores does not significantly improve risk prediction beyond combined scores with self-reported functional status measures 1, 2

The American Society of Anesthesiologists recommends that target-controlled infusion (TCI) of propofol using the Marsh and Schnider models becomes unreliable in patients >140-150 kg, and commercial pumps do not allow weights >150 kg with Marsh or BMI >35 kg/m² (women) or >42 kg/m² (men) with Schnider 8, 9
The American Society of Anesthesiologists strongly recommends monitoring anesthetic depth when using TCI with neuromuscular blockers due to the significant risk of intraoperative awareness 8, 9

Obesity alone is not a clinical indication for high-dependency postoperative care, but consider level 2 or 3 care if there are significant pre-existing comorbidities or high risk indicated (e.g., OS-MRS 4-5 or limited function) 8, 9