BIS response to tamponade and dobutamine in swine varies with hypnotic/opiate ratio.
OBJECTIVE
This study in swine assessed BIS stability in response to decreases and increases in cardiac output under two propofol/remifentanil dosage combinations, both producing the same depth of surgical anaesthesia.


METHODS
Eight anaesthetized-paralyzed ventilated adult swine were studied using a random-order cross-over design. Four received a P low/R high combination (P, 8.4+/-0.9 mg/kg/h; and R, 0.54+/-0.02 microg/kg/min) and then a P high/R low combination (P, 26.7+/-2.1mg/kg/h; and R, 0.34+/-0.01 microg/kg/min). The other four had these two combinations in the reverse order. Under each P/R combination, and after a 60-minutes steady state, a 15-minute stable cardiac tamponade was induced by intrapericardial gelatine infusion. Then, after returning to pre tamponade condition, a 15 minutes period with dobutamine was allowed.


RESULTS
Tamponade induced falls in average mean arterial pressure (MAP) (from 79+/-18 to 47+/-9 mm Hg; p<0.05) and cardiac output (Qc) (from 1.90+/-0.46 l/min to 1.20+/-0.38 l/min, p<0.05). Conversely, dobutamine increased both MAP and Qc (p<0.05). During each type of hemodynamic challenges, changes in anaesthesia depth as assessed by BIS differed dramatically between the two drug combinations, despite observing the same percent change in P and R effect-site concentration. With P high/R low and tamponade, BIS fell from 65+/-5 to 29+/-10 (p<0.05); dobutamine produced opposite effects. With P low/R high, in contrast, BIS was not influenced by either of the hemodynamic challenges.


CONCLUSIONS
Conversely to a high propofol/low remifentanil combination, a low propofol/high remifentanil combination allows constant anaesthetic depth in the face of haemodynamic challenges.
Beydon
L
L
Pôle d'Anesthésie-Réanimation, CHU d'Angers, 49933 Angers cedex 9, France. lbeydon.angers@invivo.edu
Desfontis
J C
JC
Ganster
F
F
Petres
J
J
Gautier
F
F
Ferec
S
S
Cailleux
A
A
Dussaussoy
C
C
Liu
N
N
Chazot
T
T
Fischler
M
M
Gogny
M
M
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000771:Anesthesia, Intravenous; D018686:Anesthetics, Intravenous / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D002305:Cardiac Tamponade / Q000139:chemically induced* / Q000503:physiopathology*; D002316:Cardiotonic Agents / Q000494:pharmacology*; D004280:Dobutamine / Q000494:pharmacology*; D004338:Drug Combinations; D004569:Electroencephalography / Q000187:drug effects*; D006993:Hypnotics and Sedatives / Q000494:pharmacology*; D016343:Monitoring, Intraoperative; D010880:Piperidines / Q000494:pharmacology; D015742:Propofol / Q000494:pharmacology; D000077208:Remifentanil; D013552:Swine
D000701:Analgesics, Opioid; D018686:Anesthetics, Intravenous; D002316:Cardiotonic Agents; D004338:Drug Combinations; D006993:Hypnotics and Sedatives; D010880:Piperidines; D004280:Dobutamine; D000077208:Remifentanil; D015742:Propofol