Normocapnia improves cerebral oxygen delivery during conventional oxygen therapy in carbon monoxide-exposed research subjects.
OBJECTIVE
We determine whether maintaining normocapnia during hyperoxic treatment of carbon monoxide-exposed research subjects improves cerebral oxygen delivery.


METHODS
This experiment used a randomized, single-blinded, crossover design. We exposed 14 human research subjects to carbon monoxide until their carboxyhemoglobin levels reached 10% to 12%. We then treated each research subject with 60 minutes of hyperoxia with or without normocapnia. Research subjects returned after at least 24 hours, were reexposed to carbon monoxide, and were given the alternate treatment. Relative changes in cerebral oxygen delivery were calculated as the product of blood oxygen content and middle cerebral artery velocity (an index of cerebral blood flow) as measured by transcranial Doppler ultrasonography.


RESULTS
Maintaining normocapnia during hyperoxic treatment resulted in significantly higher cerebral oxygen delivery compared with standard oxygen treatment (P <.05; 95% confidence interval at 60 minutes 2.8% to 16.7%) as a result of the prevention of hypocapnia-induced cerebral vasoconstriction and more rapid elimination of carbon monoxide due to increased minute ventilation.


CONCLUSIONS
If severely poisoned patients respond like our research subjects, maintaining normocapnia during initial hyperoxic treatment of carbon monoxide poisoning may lead to increased oxygen delivery to the brain. Determining the effect of such a change in conventional treatment on outcome requires clinical studies.
Rucker
Joshua
J
Department of Anesthesia, University Health Network, University of Toronto, Toronto, Ontario, Canada.
Tesler
Janet
J
Fedorko
Ludwik
L
Takeuchi
Akinori
A
Mascia
Luciana
L
Vesely
Alex
A
Kobrossi
Sasha
S
Slutsky
Arthur S
AS
Volgyesi
George
G
Iscoe
Steve
S
Fisher
Joseph A
JA
D000328:Adult; D001783:Blood Flow Velocity; D002249:Carbon Monoxide Poisoning / Q000188:drug therapy* / Q000503:physiopathology; D002560:Cerebrovascular Circulation; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000008:administration & dosage* / Q000097:blood / Q000627:therapeutic use; D016037:Single-Blind Method
D010100:Oxygen