Patient-specific Risk Factors

“Never treat a stranger.” Identification of patient-specific risk factors is predicated on data obtained from the physical evaluation.¹ Past and present illnesses; major hospitalizations; review of organ systems; family history; social history; history of drug allergies and other adverse drug effects; medications, vitamins and other dietary supplements (including special diets) currently taken by the patient must be considered in determining perioperative risk.

Since the stress-response is mediated primarily by the sympathoadrenal system, the history should also seek to determine the patient’s functional capacity (FC).¹³ FC relates to a person’s functional reserve, which correlates well with maximum oxygen uptake during treadmill testing and is expressed in metabolic equivalents (METs). One MET equals the resting or basal oxygen requirement (i.e., 3.5 ml of O2 per kg per minute) of a 40–year-old, 70-kg man.

A validated method to determine FC, predicated on a person’s ability to perform a spectrum of common daily activities, is presented in Box A.^14-16 FC is classified as excellent (>10 METs), good (7 METs to 10 METs), moderate (6 METs to 4 METs), or poor (<4 METs). The inability of a person to climb two flights of stairs or to run a short distance indicates poor functional capacity (<4 METs). When functional capacity is low, the risk of a medical emergency is high.¹³

For example, a person with no evidence of coronary artery disease (CAD), but who reports a history of sedentary lifestyle and has poor FC may benefit from a preoperative evaluation. Conversely, a patient considered high-risk because of a history of CAD who is asymptomatic and runs 30 minutes daily may need no further cardiovascular testing before proceeding with planned dental procedures, i.e., when functional capacity is high, the risk of a medical emergency is low.

Physical examination is also part of risk assessment.^1,13 A patient’s mental state and general appearance, e.g., cyanosis, pallor, diaphoresis, shortness of breath, tightness and/or pain in the chest with minimal activity, tremor, anxiety, and peripheral edema are signs and symptoms that provide invaluable clues regarding the patient’s overall health status. Critically, the physical examination must also include a determination of the patient’s baseline vital signs.^1,13

Predicated on patient-specific risk factors identified during the physical evaluation, the American Society of Anesthesiology (ASA) Physical Status (PS) Classification system provides a practical method to quantify perioperative risk for patients undergoing surgical (and by extension dental) procedures (Box B).^17,18 The rate of perioperative complications in medicine has been shown to correlate closely to the ASA PS classification and ranges from 0.4/1000 for ASA PS I to 9.6/1000 for ASA PS IV.¹⁹