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Abstracts and Programme, EUROANAESTHESIA 2008: Pharmacology

Effects of obesity on wash-in and wash-out kinetics of desflurane


Papaioannou, A.; Metaxari, M.; Fakiris, K.; Melissa, I.; Askitopoulou, H.

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European Journal of Anaesthesiology (EJA): May-June 2008 - Volume 25 - Issue - p 150
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Background and Goal of Study: Desflurane is the least lipid-soluble inhaled anaesthetic. However reports comparing its kinetics in obese and non-obese patients are lacking. The aim of this study was to evaluate the effects of morbid obesity on the wash-in and wash-out curves of desflurane.

Materials and Methods: The wash-in and wash-out curves of desflurane were determined in seven morbidly obese patients undergoing laparoscopic gastric banding. These curves were compared to measurements in seven non-obese patients undergoing laparoscopic cholecystectomy. All patients were premedicated with midazolam 0.05 mg kg-1. Induction to anaesthesia was achieved with propofol 2 mg kg-1, fentanyl 2 mcg kg-1 and rocuronium 0.6 mg kg-1. Maintenance of anaesthesia was achieved with desflurane and remifentanil, whereas morphine 0.1 mg kg-1 was administered 20 minutes before the end of surgery for postoperative analgesia. After endotracheal intubation and stabilization of the ventilatory variables, (FiO2 50%, RR 12 min-1, FGF 5 L min-1, Vt 8 ml kg-1, PEEP 5 mBar) desflurane was administered at an inspired concentration (Fi) of 7%. This concentration was chosen to maintain anaesthesia with 1mac of desflurane. The end-tidal (FA) concentration of deslfurane was measured with the Agent Analyser IRIA of the anaesthetic apparatus (Primus Draëger) whose function is based on infrared absorption. The Fi/FA ratio of desflurane was measured for 10 minutes. At that point a steady state of the end-tidal concentration of desflurane was achieved. At the end of the operation desflurane was discontinued and the FA/FA0 ratio was recorded until the patients of both groups made purposeful movements or opened their eyes. Statistical analysis was performed with two-way ANOVA for repeated measures and Bonferroni post hoc test.

Results and Discussion: The Fi/FA ratio was significantly higher in the obese patients on the 1 and 1.5 minute of the wash-in curve. Regarding the wash-out curve, the FA/FA0 was significantly greater for non-obese patients only at 0.5 minutes after discontinuation of the agent.

Conclusion(s): Due to low lipid solubility, desflurane displays similar wash-in and wash-out kinetics in obese and non-obese patients.

© 2008 European Society of Anaesthesiology