title: Increased lung clearance of isoflurane shortens emergence in obesity: a prospective randomized-controlled trial.
abstract: 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/m(2) 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/O(2) . 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.
  
  
  CONCLUSIONS
  Increasing alveolar ventilation enhances anaesthetic elimination and accelerates short-term recovery in obese patients.
authors.affiliation: Department of Anesthesia and Pain Management, University Health Network, Toronto General Hospital, ON, Canada. rita.katznelson@uhn.on.ca
authors.forename: R
authors.initials: R
authors.lastname: Katznelson
authors.forename: F
authors.initials: F
authors.lastname: Naughton
authors.forename: Z
authors.initials: Z
authors.lastname: Friedman
authors.forename: D
authors.initials: D
authors.lastname: Lei
authors.forename: J
authors.initials: J
authors.lastname: Duffin
authors.forename: L
authors.initials: L
authors.lastname: Fedorko
authors.forename: M
authors.initials: M
authors.lastname: Wasowicz
authors.forename: A
authors.initials: A
authors.lastname: Van Rensburg
authors.forename: J
authors.initials: J
authors.lastname: Murphy
authors.forename: J A
authors.initials: JA
authors.lastname: Fisher
mesh_terms: D000368:Aged; D058109:Airway Management; D000762:Anesthesia Recovery Period; D000768:Anesthesia, General; D000769:Anesthesia, Inhalation; D018685:Anesthetics, Inhalation / Q000493:pharmacokinetics*; D003422:Critical Care; D023381:Endpoint Determination; D005260:Female; D013509:Gynecologic Surgical Procedures; D006801:Humans; D007530:Isoflurane / Q000493:pharmacokinetics*; D008168:Lung / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000503:physiopathology*; D011183:Postoperative Complications / Q000453:epidemiology; D020250:Postoperative Nausea and Vomiting / Q000453:epidemiology; D011187:Posture; D011446:Prospective Studies
chemical_list: D018685:Anesthetics, Inhalation; D007530:Isoflurane