• Carlo Pancaro, Simone Giovannoni, Adelchi Toscano, and Vito Aldo Peduto.
• Department of Anesthesiology and Perioperative Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA. carlopancaro@hotmail.com.
• Can J Anaesth. 2005 Jun 1;52(6):591-4.

PurposeThe incidence and duration of apnea during sevoflurane anesthesia have not been fully characterized. We hypothesized that sevoflurane at slowly increasing concentrations reduces incidence and shortens the duration of apnea compared to administration of a highly concentrated anesthetic mixture.Methods131 women were randomly assigned to receive 35% oxygen in air and sevoflurane at: incremental concentrations of 1%, from 1% to 8% (group 1-8%, n = 42); decremental-incremental concentrations of 2%, from 8% to 4% and then from 4% to 8% (group 8-4-8%, n = 36); or fixed concentrations of 8% for induction of anesthesia (group 8%, n = 53). A blinded investigator observed whether and for how long patients stopped breathing.ResultsAll groups reached 2.5 minimum alveolar concentration of end-tidal sevoflurane. Although apnea was observed in all groups, it was more frequent in the 8% group than in 1 to 8% (68% vs 21%, P < 0.05) or 8 to 4 to 8% groups (68% vs 20%, P < 0.05). Duration of apnea was also more pronounced in the 8% group than in 1 to 8% and 8 to 4 to 8% groups ( 58 +/- 25 s vs 32 +/- 18 sec, P < 0.05 and vs 35 +/- 16 sec, P < 0.05, respectively).ConclusionsSevoflurane induces apnea more frequently and for longer duration at a fixed high concentration compared to incremental or decremental-incremental concentrations. Decremental-incremental concentrations offer the additional advantage of a speed of induction similar to that elicited by the 8% concentration.

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