Patient-specific problems, which may interfere with the clinical process and/or patients’ quality of life, must be identified. The ability of a patient to undergo dental procedures is predicated on his/her medical history.8 Past and present illnesses, major hospitalizations, review of organ systems, drug allergies, other adverse drug effects, medications, vitamins, dietary supplements, or special diets must be considered in determining perioperative risk.9
Since the main physiologic stimulus to epinephrine secretion is exercise, the history should also seek to determine the patient’s functional capacity.8 Functional capacity relates to a person’s functional reserve and correlates well with maximum oxygen uptake by treadmill testing. Functional capacity is expessed 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.
Functional capacity is reflected in a person’s ability to perform a spectrum of common daily activities (Box 2).10-12 It is classified as excellent (>10 METs), good (7 METs to 10 METs), moderate (6 METs to 4 METs), or poor (< 4 METs). The inability to climb two flights of stairs or run a short distance indicates poor functional capacity (< 4 METs). A functional capacity of 4 METs is predictive of increased incidence of perioperative and long-term cardiac events.8
< 4 METs
|Can you…||2 METs|
> 10 METs
When functional capacity is high, the risk of MACE is low. For example, a patient classified as having elevated-risk because of age or known coronary artery disease (CAD), but who is asymptomatic and runs 30 minute daily may need no further cardiovascular testing before proceeding with planned non-cardiac procedures. In contrast, a sedentary patient without a history of CAD, but with poor functional capacity may benefit from a preoperative evaluation.
The cardiovascular effects of infiltration anesthesia compared with those produced by ergometric exercising have been evaluated.13 The hemodynamic effects of infiltration anesthesia with 0.045 mg of epinephrine (4.5 cc of a local anesthetic agent with epinephrine 1:100,000) were found to be less than those produced by ergometric-stress testing at 25 watts in young patients and at 15 watts in older subjects. The workload of ergometric-stress testing at these levels is >4 METs.12-15
Consequently, patients whose functional capacity is ≥4 METs can safely be administered at least 4.5 cc of a local anesthetic agent with epinephrine 1:100,000. In this study, there were no differences in hemodynamic responses (evaluated by echocardiography) between normotensive and hypertensive patients. This is of note because hypertension and structural coronary arterial abnormalities are the cause of 90-95% of the arrhythmias, which lead to sudden cardiac death.
Physical examination is also part of risk assessment.8,9 The general appearance of the patient provides invaluable clues regarding his/her overall cardiac status. 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 of underlying CVD. Critically, the physical examination must also include a determination of the patient’s vital signs Box 3.
Predicated on patient-specific risk factors the American Society of Anesthesiology (ASA) Physical Status (PS) Classification system provides a practical method to determine perioperative risk for patients undergoing surgical (and by extension dental) procedures (Box 4).16,17 The rate of perioperative medical complications correlates closely to the ASA PS classification of patients and ranges from 0.4/1000 for ASA PS I to 9.6/1000 for ASA PS IV.18