title: Post-operative hypercapnia-induced hyperpnoea accelerates recovery from sevoflurane anaesthesia: a prospective randomised controlled trial.
abstract: BACKGROUND
  The time to recovery from vapour anaesthesia is shortened by an increase in ventilation while maintaining normocapnia. Hypercapnia during emergence from anaesthesia in spontaneously breathing patients also increases anaesthetic clearance from the brain by increasing cerebral blood flow. We hypothesised that hypercapnia-induced hyperpnoea accelerates emergence from sevoflurane anaesthesia compared to the standard anaesthesia protocol.
  
  
  METHODS
  After Ethics Review Board approval, 44 ASA I-III patients undergoing elective gynaecological surgery were randomised after surgery to either hypercapnic hyperpnoea or control groups. In the hypercapnic hyperpnoea group, the end-tidal CO2 was adjusted to a range of 6.0-7.3 kPa to maintain a minute ventilation of 10-15 l/min. Recovery indices were compared using unpaired t-tests and ANOVA.
  
  
  RESULTS
  Prior to extubation, minute ventilation and end-tidal CO2 in hypercapnic hyperpnoea and control groups were 10.3 ± 1.7 l/min vs. 5.4 ± 1.2 l/min (P < 0.001) and 6.6 ± 0.6 kPa and 5.2 ± 0.5 kPa (P < 0.001), respectively. Compared to control, the study group had shorter time to extubation [4.4 ± 1.3 (SD) vs. 9.8 ± 4.4 min, P < 0.01], BIS recovery to > 75 (2.4 ± 0.9 vs. 6.1 ± 3.1 min, P < 0.01), eye opening (3.9 ± 1.6 vs. 9.8 ± 6.2 min, P < 0.01), eligibility for leaving operating room (5.1 ± 1.2 vs. 11.1 ± 4.6 min, P < 0.01), and post-anaesthesia care unit (73.9 ± 14.2 vs. 89.4 ± 22.6)
  
  
  CONCLUSIONS
  Hypercapnic hyperpnoea in spontaneously breathing patients halves the time of recovery from sevoflurane-induced anaesthesia in the operating room.
authors: Department of Anesthesia and Pain Management, University Health Network, University of Toronto, Toronto, ON, Canada. rita.katznelson@uhn.ca
authors: R
authors: R
authors: Katznelson
authors: G
authors: G
authors: Djaiani
authors: F
authors: F
authors: Naughton
authors: M
authors: M
authors: Wasowicz
authors: T
authors: T
authors: Ragoonanan
authors: J
authors: J
authors: Duffin
authors: L
authors: L
authors: Fedorko
authors: J
authors: J
authors: Murphy
authors: J A
authors: JA
authors: Fisher
mesh_terms: D000704:Analysis of Variance; D000762:Anesthesia Recovery Period; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology*; D006985:Hyperventilation / Q000503:physiopathology*; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology*; D008875:Middle Aged; D011446:Prospective Studies; D000077149:Sevoflurane; D013997:Time Factors
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane