Increased lung clearance of isoflurane shortens emergence in obesity: a prospective randomized-controlled trial

• Published in: Acta anaesthesiologica Scandinavica Vol. 55; no. 8; pp. 995 - 1001
• Main Authors: KATZNELSON, R., NAUGHTON, F., FRIEDMAN, Z., LEI, D., DUFFIN, J., FEDORKO, L., WASOWICZ, M., VAN RENSBURG, A., MURPHY, J., FISHER, J. A.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-09-2011; Blackwell
• Subjects: Aged; Airway Management; Anesthesia; Anesthesia Recovery Period; Anesthesia, General; Anesthesia, Inhalation; Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Anesthetics, Inhalation - pharmacokinetics; Biological and medical sciences; Critical Care; Endpoint Determination; Female; Gynecologic Surgical Procedures; Humans; Isoflurane - pharmacokinetics; Lung - metabolism; Male; Medical sciences; Middle Aged; Obesity - complications; Obesity - physiopathology; Postoperative Complications - epidemiology; Postoperative Nausea and Vomiting - epidemiology; Posture; Prospective Studies; Volatile compound; Obesity; General anesthetic; Nutrition disorder; Anesthesia; Nutritional status; Isoflurane; Halogen Organic compounds
• ISSN: 0001-5172; 1399-6576
• DOI: 10.1111/j.1399-6576.2011.02486.x

Background: There is a concern that obesity may play a role in prolonging emergence from fat‐soluble inhalational anaesthetics. We hypothesized that increased pulmonary clearance of isoflurane will shorten immediate recovery from anaesthesia and post‐anaesthesia care unit (PACU) stay in obese patients.
Methods: After Ethics Review Board approval, 44 ASA I–III patients with BMI>30 kg/m2 undergoing elective gynaecological or urological surgery were randomized after completion of surgery to either an isocapnic hyperpnoea (IH) or a conventional recovery (C) group. The anaesthesia protocol included propofol, fentanyl, morphine, rocuronium and isoflurane in air/O2. Groups were compared using unpaired t‐test and ANOVA.
Results: Minute ventilation in the IH group before extubation was 22.6±2.7 vs. 6.3±1.8 l/min in the C group. Compared with C, the IH group had a shorter time to extubation (5.4±2.7 vs. 15.8±2.7 min, P<0.01), initiation of spontaneous ventilation (2.7±2.3 vs. 6.5±4.5 min, P<0.01), BIS recovery >75 (3.2±2.3 vs. 8.9±5.8 min, P<0.01), eye opening (4.6±2.9 vs. 13.6±7.1 min, P<0.01) and eligibility for leaving the operating room (7.1±2.9 vs. 19.9±11.9 min, P<0.01). There was no difference in time for eligibility for PACU discharge.
Conclusion: Increasing alveolar ventilation enhances anaesthetic elimination and accelerates short‐term recovery in obese patients.