Abstract
We thank Dr. Smith for her insightful comments on our review of drug dosing in obese patients receiving neuromuscular blocking agents (NMBA).1,2 Dr. Smith eloquently illustrates the variability with different lean body mass (LBM) calculations, which can be clinically significant particularly at higher weight classes. We agree with these points, which highlight some of the many challenges with medication dosing in this population. As stated by Dr. Smith, many of these formulae were derived from patient cohorts that included limited number of patients with more extreme forms of obesity (body mass index ≥40 kg/m2). Furthermore, much of the data originate from the operating rooms where goals of care may be different from that observed in the intensive care unit (ICU). Current uses for NMBA in the ICU include facilitation of mechanical ventilation in patients with acute respiratory distress syndrome, treatment of head injury patients with elevated intracranial pressure, and reduction of shivering in patients undergoing therapeutic hypothermia. Widespread use of NMBAs has most recently been recognised throughout the coronavirus disease 2019 pandemic, where obesity has been highly prevalent.
Most importantly, LBM formulae may be cumbersome to perform at the bedside and prone to calculation error. While many online calculators are available, these calculators do not integrate with electronic medical records (EMR), further limiting their use. Common metrics for weight available in EMRs are typically restricted to total body weight, ideal body weight, and adjusted body weight. EMR developers and the information technology industry are strongly encouraged to adapt their platforms to include LBM as an option for dosing calculations. Further research is required to finetune LBM formulas to reduce variance and improve accuracy.
