Body mass index: risk predictor for cosmetic day surgery.

Body mass index (BMI; weight per unit surface area) is the scientific yardstick by which overweight is gauged relative to the population norm. The contrary association between obesity and diabetes or hypertension is only too well known. Less appreciated is the heightened sensitivity to respiratory depressants such as sedatives and analgesics in the obese (BMI >/= 30) and the increased incidence of sleep apnea in the morbidly obese (BMI >/= 35)-either or both of which raise the risk of cosmetic surgery when sedation or anesthesia is contemplated. Guided by the BMI, a gender-independent measure of fatness, the surgeon now can inform the patient of her or his relative operative risk and offer an objective rationale for advising overnight hospitalization rather than office-based day surgery. The BMI is readily calculated when height and weight are expressed in metric units, much less so when measured in foot-pound units. In fact, the calculations are sufficiently cumbersome that the BMI remains underused in U.S. office surgery. The author's complimentary "BMI Calculator"-an Excel workbook available on-line to society members-is designed so that office staff need enter only height (in feet and inches) and weight (in pounds) to print the BMI for the patient's permanent record. The BMI places patient weight relative to height in proper perspective for aesthetic surgery, whether with sedation or under general anesthesia. The BMI ought to be as routine a part of the preoperative assessment as blood pressure or hemoglobin content.