Some Cautionary Tales About Ideal Body Weight Dosing of Anesthetic Medications: It Is Not All That Ideal!

Abstract

Studies utilizing ideal body weight (IBW) dosing of perioperative medications are being increasingly published (1–3). One major reason for the increasing interest in weight-based medication dose adjustment is the relentless surge in obesity prevalence across every age spectrum in the United States (US) and many Western Countries (4). Current estimates are that about 12 million (approximately 16.9%) children in the US are obese, defined as age and gender-specific body mass index (BMI) ≥95th percentile using the year 2000 Centers for Disease Control and Prevention (CDC) growth charts (5). A predictable result of the secular trend in childhood obesity prevalence is that an increasing proportion of patients undergoing non-bariatric surgery are overweight, obese or severely obese (6). Since weight-based dosing is used for virtually every medication in children (7), the potential for dosing errors in obese patients is enormous. Because many anesthetic drugs are administered intravenously, overdose of these drugs could cause significant side effects, especially in children with lower internal reserves to buffer dosing errors. Conversely, under-dose of anesthetic medications could cause insufficient anesthesia, pain, suffering during, and long after surgery. The overarching question that perioperative clinicians ask on a fairly regular basis is: should actual body weight be used to select perioperative drug doses in obese individuals? The relative dearth of standardized dosing recommendations in obese individuals (children and adults) and a near absence of clear guidelines regarding optimal dosing of anesthetic medications for obese patients is a critical source of concern (7).