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Coasting after overpressure induction with sevoflurane
J F Hendrickx1, D M Vandeput, A M De Geyndt
1Department of Anesthesiology, Intensive Care and Pain Therapy, Onze Lieve Vrouwziekenhuis, Aalst, Belgium.
Study Objective:
To evaluate the clinical feasibility of using a coasting technique to temporarily maintain anesthesia after overpressure induction with sevoflurane.
Study Design:
Prospective clinical study.
Setting:
Large teaching hospital.
Patients:
12 ASA physical status I, II, and III patients receiving general anesthesia for a variety of peripheral procedures.
Interventions:
After overpressure induction of anesthesia with sevoflurane (8%) in an O(2)/N(2)O mixture, the fresh gas flow (FGF) was lowered to 0.5 L/min and the vaporizer was turned off (coasting).
Measurements And Main Results:
After priming a circle system with sevoflurane (8% sevoflurane vaporizer setting in 6 L/min O(2)/N(2)O [33%/66%] for 30 s), patients took several vital capacity breaths from the mixture until loss of consciousness. After 3.4 +/- 0.7 min, depth of anesthesia was considered adequate for laryngeal mask airway (LMA) insertion, and FGF was reduced to 0.5 L/min (33% O(2), 66% N(2)O) and the sevoflurane vaporizer was turned off. The end-expired sevoflurane concentration (Et(sevo)) decreased from 5.8 +/- 1.3% just before insertion of the LMA to 0.97 +/- 0.22% at 20 minutes.
Conclusions:
After overpressure induction with sevoflurane, coasting during minimal flow anesthesia (FGF 0.5 L/min) is a simple technique that can maintain anesthesia for short procedures (less than 15 to 20 min), or can be used as a bridge or an adjunct to other low-flow techniques.