Canadian Journal of Anesthesia 53:885-890 (2006)
© Canadian Anesthesiologists' Society, 2006
General Anesthesia
Preparation of the Dräger Primus anesthetic machine for malignant hyperthermia-susceptible patients
[La préparation de l’appareil à anesthésie Dräger Primus pour les patients susceptibles d’hyperthermie maligne]
Heike Prinzhausen, FRCA, Mark W. Crawford, MBBS FRCPC, James O’Rourke, MBBCh FFARCSI and Guy C. Petroz, MD
From the Department of Anesthesia, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada.
Address correspondence to: Dr. Crawford, Department of Anesthesia, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada. Phone: 416-813-6466; Fax: 416-813-7543; E-mail: mark.crawford@sickkids.ca
Purpose: Preparation of anesthesia machines for patients who are susceptible to malignant hyperthermia includes flushing the machine with vapour-free fresh gas to washout residual anesthetic agents. To establish guidelines for the preparation of the Dräger Primus machine, we compared the washout profiles for isoflurane and sevoflurane in the Dräger Primus and Ohmeda Excel 210 anesthesia machines.
Technical features: The machines were primed with 1.5% isoflurane or 2.5% sevoflurane. Fresh gas flow (FGF) was set at 10 L·min–1 during the early washout phase, and subsequently reduced to 3 L·min–1 during the late washout phase. A Miran ambient air analyzer measured the anesthetic concentration every minute during washout until a concentration of 5 ppm was achieved in the inspiratory limb of the circle circuit. We found that at a FGF of 10 L·min–1, maximum washout times for isoflurane and sevoflurane in the Primus, 70 and 74 min, respectively, were approximately tenfold greater than for isoflurane in the Excel 210 (7.0 min). Increasing the FGF to 18 L·min–1 decreased the washout time for isoflurane in the Primus, only moderately, to 52 min. We observed a threefold increase in anesthetic concentration in the Primus during the late washout phase.
Conclusion: We conclude that the Primus must be flushed for at least 70 min to decrease the anesthetic concentration to 5 ppm when using a FGF of 10 L·min–1. We recommend maintaining a FGF of 10 L·min–1 for the duration of anesthesia in order to prevent the rebound increase in anesthetic concentration in the FGF.
Reprinted with permission from the Canadian Journal of Anesthesia.
