TY - JOUR
T1 - Maintaining sevoflurane anesthesia during low-flow anesthesia using a single vaporizer setting change after overpressure induction
AU - Hendrickx, Jan F.A.
AU - Vandeput, Dirk M.
AU - De Geyndt, Axel M.
AU - De Ridder, Koen P.
AU - Haenen, Johan S.
AU - Deloof, Thierry
AU - De Wolf, Andre M.
PY - 2000/6
Y1 - 2000/6
N2 - Study Objective: A sevoflurane vaporizer dial setting of 1.9% was previously found to maintain the end-expired sevoflurane concentration (Et(sevo)) at 1.3% during maintenance of anesthesia for procedures up to one hour with an O2 FGF of 1 L/min. We examined whether applying these parameters could simplify low-flow sevoflurane anesthesia after overpressure induction using two slightly different techniques. Design: Prospective clinical study. Setting: Large teaching hospital. Patients: Sixteen patients receiving general anesthesia for a variety of peripheral procedures. Interventions: Anesthesia was induced with overpressure with sevoflurane (8%) in an 8 L · min-1 O2/N2O mixture (30%/70%). After a laryngeal mask airway (LMA) was placed, fresh gas flow (FGF) was lowered to 1 L · min-1 using O2 and N2O (FiO2 30%) with patients breathing spontaneously. In group I patients (n = 8), the vaporizer dial was set at 1.9% at the same time the FGF was lowered. In group II patients (n = 8), the vaporizer was turned off until Et(sevo) had decreased to 1.3%, after which the dial was set at 1.9%. The course of Et(sevo) in the two groups was examined. Measurements and Main Results: In group I, Et(sevo) after 3 min was 4.88 ± 1.12%. Et(sevo) decreased slowly after reduction of FGF to 1.83 ± 0.19%, 1.59 ± 0.18%, and 1.52 ± 0.19% at 10, 20, and 30 min, respectively. In group II, Et(sevo) after 3 min was 4.34 ± 0.84%, and decreased more rapidly after reduction of FGF to 1 L · min-1 than in group I. Et(sevo) was 1.40 ± 0.09%, 1.40 ± 0.11%, and 1.38 ± 0.13% at 10, 20, and 30 min, respectively. Conclusions: After high-flow overpressure induction with sevoflurane, a single change in vaporizer setting (to 1.9%) and FGF (to 1 L · min-1) suffices for the Et(sevo) to approach the predicted Et(sevo) (1.3%) within 10-15 min; thereafter the Et(sevo) remains nearly constant. As expected, the predicted Et(sevo) is attained slightly faster when the vaporizer is temporarily turned off. Clinically applying previously derived pharmacokinetic parameters simplifies low-flow sevoflurane anesthesia after overpressure induction. (C) 2000 Elsevier Science Inc.
AB - Study Objective: A sevoflurane vaporizer dial setting of 1.9% was previously found to maintain the end-expired sevoflurane concentration (Et(sevo)) at 1.3% during maintenance of anesthesia for procedures up to one hour with an O2 FGF of 1 L/min. We examined whether applying these parameters could simplify low-flow sevoflurane anesthesia after overpressure induction using two slightly different techniques. Design: Prospective clinical study. Setting: Large teaching hospital. Patients: Sixteen patients receiving general anesthesia for a variety of peripheral procedures. Interventions: Anesthesia was induced with overpressure with sevoflurane (8%) in an 8 L · min-1 O2/N2O mixture (30%/70%). After a laryngeal mask airway (LMA) was placed, fresh gas flow (FGF) was lowered to 1 L · min-1 using O2 and N2O (FiO2 30%) with patients breathing spontaneously. In group I patients (n = 8), the vaporizer dial was set at 1.9% at the same time the FGF was lowered. In group II patients (n = 8), the vaporizer was turned off until Et(sevo) had decreased to 1.3%, after which the dial was set at 1.9%. The course of Et(sevo) in the two groups was examined. Measurements and Main Results: In group I, Et(sevo) after 3 min was 4.88 ± 1.12%. Et(sevo) decreased slowly after reduction of FGF to 1.83 ± 0.19%, 1.59 ± 0.18%, and 1.52 ± 0.19% at 10, 20, and 30 min, respectively. In group II, Et(sevo) after 3 min was 4.34 ± 0.84%, and decreased more rapidly after reduction of FGF to 1 L · min-1 than in group I. Et(sevo) was 1.40 ± 0.09%, 1.40 ± 0.11%, and 1.38 ± 0.13% at 10, 20, and 30 min, respectively. Conclusions: After high-flow overpressure induction with sevoflurane, a single change in vaporizer setting (to 1.9%) and FGF (to 1 L · min-1) suffices for the Et(sevo) to approach the predicted Et(sevo) (1.3%) within 10-15 min; thereafter the Et(sevo) remains nearly constant. As expected, the predicted Et(sevo) is attained slightly faster when the vaporizer is temporarily turned off. Clinically applying previously derived pharmacokinetic parameters simplifies low-flow sevoflurane anesthesia after overpressure induction. (C) 2000 Elsevier Science Inc.
KW - Anesthetic techniques
KW - Anesthetics, volatile
KW - Low-flow anesthesia
KW - Pharmacokinetics
KW - Sevoflurane
UR - http://www.scopus.com/inward/record.url?scp=0034209610&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0034209610&partnerID=8YFLogxK
U2 - 10.1016/S0952-8180(00)00159-8
DO - 10.1016/S0952-8180(00)00159-8
M3 - Article
C2 - 10960203
AN - SCOPUS:0034209610
SN - 0952-8180
VL - 12
SP - 303
EP - 307
JO - Journal of Clinical Anesthesia
JF - Journal of Clinical Anesthesia
IS - 4
ER -