Peri -and Postoperative Drug Therapy Schedules for Morbidly Obese Patients

Overview

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 collection will take place around administration of drugs that are given according to routine clinical practice (cefazolin 2 grams for prophylaxis of infections, morphine 10 mg intravenously at the end of surgery, a patient-controlled analgesia (PCA) pump with morphine for postoperative pain relief and nadroparin 0,6 ml for trombo-embolic prophylaxis). For muscle relaxation, patients are randomised to receive one of two generally accepted dosing regimen of atracurium (0.5 mg/kg based on ideal body weight or 0.5 mg/kg based on total body weight). Peri- and postoperatively, a maximum amount of 70 ml of blood will be collected from an indwelling arterial line for measurement of concentrations of cefazolin, morphine, and anti-Xa (nadroparin). One week after surgery the patient will be checked for thrombosis using ultrasonography. Main study parameters/endpoints: Primary endpoints to evaluate in morbidly obese patients are; – pharmacokinetic parameters of cefazolin in blood; – pharmacokinetic parameters of morphine and metabolites in blood; – time course of anti-factor Xa levels in blood following nadroparin; – time course of the pharmacodynamic effect of atracurium. Secondary endpoints to evaluate in morbidly obese patients are: – to compare primary endpoints (obtained in morbidly obese patients) with data of non-obese patients – the occurrence of postoperative wound infections; – postoperative pain scores, sedation scores and nausea scores; – the occurrence of bleedings or thrombotic events ; – required amounts of morphine (PCA); – to compare the time course of the pharmacodynamic effect of two different doses of atracurium.

Study Type

  • Study Type: Interventional
  • Study Design
    • Allocation: Randomized
    • Intervention Model: Parallel Assignment
    • Primary Purpose: Diagnostic
    • Masking: Triple (Participant, Care Provider, Investigator)
  • Study Primary Completion Date: April 2010

Interventions

  • Drug: Atracurium, TBW
    • Dose atracurium 0.5 mg/kg based on total body weight

Arms, Groups and Cohorts

  • Active Comparator: Atracurium, TBW
    • Dose of atracurium 0.5 mg/kg based on total body weight
  • Active Comparator: Atracurium IBW
    • dose 0.5 mg/kg based on ideal body weight

Clinical Trial Outcome Measures

Primary Measures

  • Time course of the pharmacodynamic effect of atracurium
    • Time Frame: 6 months
  • Pharmacokinetic parameters of cefazolin in blood
    • Time Frame: 6 months
  • Pharmacokinetic parameters of morphine and metabolites in blood
    • Time Frame: 6 months
  • Time course of anti-factor Xa levels in blood following nadroparin
    • Time Frame: 6 months

Secondary Measures

  • Dosing of atracurium based on total or ideal body weight
    • Time Frame: 6 months
  • To compare primary endpoints (obtained in morbidly obese patients) with data of non-obese patients
    • Time Frame: 6 months
  • The occurrence of postoperative wound infections
    • Time Frame: 6 months
  • Postoperative pain scores, sedation scores and nausea scores
    • Time Frame: 6 months
  • The occurrence of bleedings or thrombotic events
    • Time Frame: 6 months
  • Required amounts of morphine (PCA)
    • Time Frame: 6 months

Participating in This Clinical Trial

Inclusion Criteria

  • Morbidly obese patients undergoing bariatric surgery with a BMI > 40 kg/m2, ASA I-III Exclusion Criteria:

  • Epilepsy, pregnancy, breastfeeding and known allergy allergies to cefazolin, morphine, nadroparin, atracurium, or benzene sulphonic acid. History of coagulation disorder or history of heparin/LMWH induced thrombocytopenia.

Gender Eligibility: All

Minimum Age: 18 Years

Maximum Age: 65 Years

Are Healthy Volunteers Accepted: No

Investigator Details

  • Lead Sponsor
    • St. Antonius Hospital
  • Provider of Information About this Clinical Study
    • S. van Kralingen, St. Antonius Hospital
  • Overall Official(s)
    • Simone van Kralingen, MD, Principal Investigator, St. Antonius Hospital

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