Peri -and Postoperative Drug Therapy Schedules for Morbidly Obese Patients

Rationale: Obesity is an increasing health risk worldwide, with the USA recording prevalence in adults of around 20%. The mean body weight of obese patients is also increasing. One of the strategies to treat extreme obesity (Body Mass Index (BMI) \> 40 kg/m2) is weight-reducing surgery like laparoscopic gastric banding or gastric bypass. During anaesthesia, morbidly obese patients are exposed to an increased risk at developing postoperative wound infections, apnoea and thrombotic events and may be more difficult to intubate. Routinely, amongst others, cefazolin, morphine, nadroparin and atracurium are administered in standard dosages. However, it is not known to what extend the pharmacokinetics and/or -dynamics of these drugs are affected in morbidly obese patients. Therefore, evidence-based dosing schedules for these drugs in morbidly obese patients should be developed. Objective: The study is performed in order to develop population pharmacokinetic and/or pharmacodynamic models of the routinely used drug therapies during bariatric surgery in morbidly obese patients (BMI \> 40 kg/m2): cefazolin, morphine, nadroparin and atracurium. A covariate analysis will be performed in order to account for variability in pharmacokinetic and/or pharmacodynamic parameters. This covariate analysis will take into account procedure and patient bound covariates, with specific interest for body weight as a covariate. Whenever possible, non-obese patients will be included in the covariate analysis. The results will be used to develop individualised dosing schemes for routinely used drugs peri-operatively in morbidly obese patients. Study design: A randomised, prospective, observational, therapeutic and invasive study. Study population: Morbidly obese patients with a Body Mass Index \> 40 kg/m2 undergoing laparoscopic banding or gastric bypass surgery, 18-60 years old. A total of 20 patients will be included in the study. Intervention (if applicable): All measurements and data col