Anaesthetists' drug dosing practices in class III obese surgical patients: A bi-national survey

Class III obese (body mass index >= 40 kg/m² ) patients, now regularly encountered clinically, have increased perioperative risks, including potentially from suboptimal drug dosing. However, current dosing guidelines are based on low-level evidence and may not be widely accepted. This study aimed to investigate anaesthetists' dosing practices for class III obese surgical patients, explore if they had experienced an increased incidence of adverse events potentially related to drug dosing with these patients and assess which resources they consulted for dosing advice in this population. An electronic survey was emailed to 1000 randomly selected members of the Australian and New Zealand College of Anaesthetists. Data were summarised and the Pearson's _χ² test was used to compare respondents' genders, geographic locations and seniority designations with the greater Australian and New Zealand College of Anaesthetists' membership. There were 230 completed responses (response rate 23%). A large proportion (46%-76%) of respondents indicated they dose class III obese patients in keeping with current recommendations; however, substantial heterogeneity in dosing practices was found. Lean body weight was the most frequently used regimen for dosing propofol, non-depolarising muscle relaxants, sugammadex and opioids, whereas total body weight was most frequently used for suxamethonium. Nearly 70% of respondents reported using at least one resource to assist their dosing practices in obesity. Importantly, increased incidences of adverse events in class III obese patients related to drug dosing were commonly experienced by respondents. Until higher-level evidence is available for dosing class III obese patients, anaesthetists should consider current recommendations and exercise increased attention to dosing. Further clinician education may assist in optimising dosing in this patient group.