Remifentanil and nitrous oxide reduce changes in cerebral blood flow velocity in the middle cerebral artery caused by pain.
BACKGROUND
Cerebral blood flow is affected by painful stimuli, and analgesic agents may alter the response of cerebral blood flow to pain. We set out to quantify the effects of remifentanil and nitrous oxide on blood flow changes caused by experimental pain.


METHODS
We simulated surgical pain in 10 conscious volunteers using increasing mechanical pressure to the tibia. We measured changes in cerebral blood flow velocity in the middle cerebral artery (CBFV(MCA)) caused by the pain, using transcranial Doppler sonography. We gave increasing doses of remifentanil (0.025, 0.05 and 0.1 micro g kg(-1) min(-1)) or nitrous oxide [20%, 35% and 50% end-tidal concentration (FE'(N(2)O))] and compared these effects on blood flow changes.


RESULTS
Nitrous oxide increased CBFV(MCA) only when given at 50% FE'(N(2)O). Remifentanil did not affect CBFV(MCA). Pain increased CBFV(MCA). Both agents attenuated this pain-induced change in CBFV(MCA) with the exception of nitrous oxide at 20% FE'(N(2)O).


CONCLUSIONS
Inhalation of nitrous oxide or adminstration of remifentanil attenuated pain-induced changes in CBFV(MCA).
Lorenz
I H
IH
Department of Anaesthesia and Intensive Care Medicine, University of Innsbruck, A-6020 Innsbruck, Anichstrasse 35, Austria.
Kolbitsch
C
C
Hinteregger
M
M
Bauer
P
P
Spiegel
M
M
Luger
T J
TJ
Schmidauer
C
C
Streif
W
W
Pfeiffer
K P
KP
Benzer
A
A
D000293:Adolescent; D000328:Adult; D018712:Analgesics, Non-Narcotic / Q000627:therapeutic use*; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000627:therapeutic use*; D018685:Anesthetics, Inhalation / Q000627:therapeutic use*; D001783:Blood Flow Velocity / Q000187:drug effects; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D006801:Humans; D007263:Infusions, Parenteral; D007432:Intraoperative Period; D008297:Male; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000503:physiopathology*; D009609:Nitrous Oxide / Q000627:therapeutic use*; D010146:Pain / Q000000981:diagnostic imaging / Q000188:drug therapy*; D010880:Piperidines / Q000008:administration & dosage / Q000627:therapeutic use*; D000077208:Remifentanil; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods
D018712:Analgesics, Non-Narcotic; D000701:Analgesics, Opioid; D018685:Anesthetics, Inhalation; D010880:Piperidines; D009609:Nitrous Oxide; D000077208:Remifentanil