Probability to tolerate laryngoscopy and noxious stimulation response index as general indicators of the anaesthetic potency of sevoflurane, propofol, and remifentanil.
BACKGROUND
The probability to tolerate laryngoscopy (PTOL) and its derivative, the noxious stimulation response index (NSRI), have been proposed as measures of potency of a propofol-remifentanil drug combination. This study aims at developing a triple drug interaction model to estimate the combined potency of sevoflurane, propofol, and remifentanil in terms of PTOL. We compare the predictive performance of PTOL and the NSRI with various anaesthetic depth monitors.


METHODS
Data from three previous studies (n=120) were pooled and reanalysed. Movement response after laryngoscopy was observed with different combinations of propofol-remifentanil, sevoflurane-propofol, and sevoflurane-remifentanil. A triple interaction model to estimate PTOL was developed. The NSRI was derived from PTOL. The ability of PTOL and the NSRI to predict observed tolerance of laryngoscopy (TOL) was compared with the following other measures: (i) effect-site concentrations of sevoflurane, propofol, and remifentanil (CeSEVO, CePROP, and CeREMI); (ii) bispectral index; (iii) two measures of spectral entropy; (iv) composite variability index; and (v) surgical pleth index.


RESULTS
Sevoflurane and propofol interact additively, whereas remifentanil interacts in a strongly synergistic manner. The effect-site concentrations of sevoflurane and propofol at a PTOL of 50% (Ce50; se) were 2.59 (0.13) vol % and 7.58 (0.49) µg ml(-1). A CeREMI of 1.36 (0.15) ng ml(-1) reduced the Ce50 of sevoflurane and propofol by 50%. The common slope factor was 5.22 (0.52). The PTOL and NSRI predict the movement response to laryngoscopy best.


CONCLUSIONS
The triple interaction model estimates the potency of any combination of sevoflurane, propofol, and remifentanil expressed as either PTOL or NSRI.
Department of Anaesthesiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands.
L N
LN
Hannivoort
Department of Anaesthesiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands h.e.m.vereecke@umcg.nl.
H E M
HE
Vereecke
Department of Anaesthesiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands.
J H
JH
Proost
Department of Anaesthesia, Ghent University, Gent, Belgium.
B E K
BE
Heyse
Department of Anaesthesiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands.
D J
DJ
Eleveld
Consulting Scientist, Arlesheim, Switzerland.
T W
TW
Bouillon
Department of Anaesthesiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands Department of Anaesthesia, Ghent University, Gent, Belgium.
M M R F
MM
Struys
Department of Anaesthesiology, Spital Tiefenau, University of Bern, Bern, Switzerland.
M
M
Luginbühl
D000293:Adolescent; D000328:Adult; D019162:Anesthetics, Combined / Q000008:administration & dosage / Q000494:pharmacology*; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000494:pharmacology; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000494:pharmacology; D004334:Drug Administration Schedule; D004347:Drug Interactions; D016903:Drug Monitoring / Q000379:methods; D004357:Drug Synergism; D004569:Electroencephalography / Q000187:drug effects; D005260:Female; D006801:Humans; D007828:Laryngoscopy; D008297:Male; D008738:Methyl Ethers / Q000008:administration & dosage / Q000494:pharmacology; D008875:Middle Aged; D008954:Models, Biological; D009068:Movement / Q000187:drug effects; D010880:Piperidines / Q000008:administration & dosage / Q000494:pharmacology; D015742:Propofol / Q000008:administration & dosage / Q000494:pharmacology; D000077208:Remifentanil; D000077149:Sevoflurane; D055815:Young Adult
D019162:Anesthetics, Combined; D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D008738:Methyl Ethers; D010880:Piperidines; D000077149:Sevoflurane; D000077208:Remifentanil; D015742:Propofol
drug interactions; laryngoscopy; propofol; remifentanil; sevoflurane