title: Changes in sevoflurane plasma concentration with delivery through the oxygenator during on-pump cardiac surgery.
abstract: BACKGROUND
  It is unclear what factors affect the uptake of sevoflurane administered through the membrane oxygenator during cardiopulmonary bypass (CPB) and whether this can be monitored via the oxygenator exhaust gas.
  
  
  METHODS
  Stable delivery of sevoflurane was administered to 30 elective cardiac surgery patients at 1.8 vol% (inspiratory) via the anaesthetic circuit and ventilator. During CPB, sevoflurane was administered in the oxygenator fresh gas supply (Compactflo Evolution™; Sorin Group, Milano, Italy). Sevoflurane plasma concentration (SPC) was measured using gas chromatography. Changes were correlated with bispectral index (BIS), patient temperature, haematocrit, plasma albumin concentration, oxygenator fresh gas flow, and the sevoflurane concentration in the oxygenator exhaust at predefined time points.
  
  
  RESULTS
  The mean SPC pre-bypass was 54.9 µg ml(-1) [95% confidence interval (CI): 50.6-59.1]. SPC decreased to 43.2 µg ml(-1) (95% CI: 40.3-46.1; P<0.001) after initiation of CPB, and was lower still during rewarming and weaning from bypass, 39.4 µg ml(-1) (95% CI: 36.6-42.3; P<0.001). BIS did not exceed a value of 55. SPCs were higher during hypothermia (P<0.001) and with an increase in oxygenator fresh gas flow (P=0.015), and lower with haemodilution (P=0.027). No correlation was found between SPC and the concentration of sevoflurane in the oxygenator exhaust gas (r=-0.04; 95% CI: -0.18 to 0.09; P=0.53).
  
  
  CONCLUSIONS
  The uptake of sevoflurane delivered via the membrane oxygenator during CPB seems to be affected by hypothermia, haemodilution, and changes in the oxygenator fresh gas supply flow. Measuring the concentration of sevoflurane in the exhaust from the oxygenator is not useful for monitoring sevoflurane administration during bypass.
authors: Department of Anaesthesiology, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, Hamburg 20246, Germany. r.nitzschke@uke.de
authors: R
authors: R
authors: Nitzschke
authors: J
authors: J
authors: Wilgusch
authors: J F
authors: JF
authors: Kersten
authors: C J
authors: CJ
authors: Trepte
authors: S A
authors: SA
authors: Haas
authors: D A
authors: DA
authors: Reuter
authors: A E
authors: AE
authors: Goetz
authors: M S
authors: MS
authors: Goepfert
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018685:Anesthetics, Inhalation / Q000097:blood*; D006348:Cardiac Surgical Procedures; D002315:Cardiopulmonary Bypass; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008738:Methyl Ethers / Q000008:administration & dosage / Q000097:blood*; D008875:Middle Aged; D010107:Oxygenators, Membrane; D011446:Prospective Studies; D000077149:Sevoflurane
chemical_list: D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane
keywords: anaesthetics; cardiopulmonary bypass; inhalation; oxygenators, membrane; sevoflurane; solubility