title: Hypocapnia reverses the fentanyl-induced increase in cerebral blood flow velocity in awake humans.
abstract: Investigations on the effects of opioids on cerebrovascular dynamics have repeatedly demonstrated mild to moderate increases in cerebral blood flow velocity in the middle cerebral artery (CBFVMCA), cerebral blood flow, and cerebrospinal fluid pressure in humans and animals. However, the influence of hypocapnia on these fentanyl effects has not been investigated. We compared mean CBFVMCA during normo- and hypocapnia before and after administration of fentanyl (2.5 micrograms/kg i.v.) in 20 awake humans. During normocapnia (end-tidal carbon dioxide [ETCO2] 40 mmHg) fentanyl significantly increased mean CBFVMCA (60 +/- 10 cm/s vs. 81 +/- 12 cm/s [mean +/- SD]; p < 0.01), whereas during hypocapnia (ETCO2 25 mmHg) mean CBFVMCA values were identical (40 +/- 7 cm/s vs. 40 +/- 7 cm/s) before and after fentanyl administration. These results confirm previous findings that administration of fentanyl increases CBFVMCA, but, more importantly, clearly indicate that hypocapnia reverses this potentially undesirable effect.
authors.affiliation: Department of Anesthesia, University of Innsbruck, Austria.
authors.forename: C
authors.initials: C
authors.lastname: Kolbitsch
authors.forename: C
authors.initials: C
authors.lastname: Hörmann
authors.forename: C
authors.initials: C
authors.lastname: Schmidauer
authors.forename: M
authors.initials: M
authors.lastname: Ortler
authors.forename: J
authors.initials: J
authors.lastname: Burtscher
authors.forename: A
authors.initials: A
authors.lastname: Benzer
mesh_terms: D000328:Adult; D000701:Analgesics, Opioid / Q000009:adverse effects*; D001794:Blood Pressure / Q000187:drug effects; D002536:Cerebral Arteries / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000187:drug effects* / Q000502:physiology*; D005260:Female; D005283:Fentanyl / Q000009:adverse effects*; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D016857:Hypocapnia / Q000503:physiopathology*; D007432:Intraoperative Period; D008297:Male; D008875:Middle Aged; D017585:Ultrasonography, Doppler, Transcranial; D014851:Wakefulness / Q000502:physiology
chemical_list: D000701:Analgesics, Opioid; D005283:Fentanyl