Effects of propofol, etomidate, and pentobarbital on critical oxygen delivery.
OBJECTIVE
To test the hypothesis that propofol, etomidate, and pentobarbital increase critical oxygen delivery in a dose-dependent manner during progressive hemorrhage.


METHODS
Prospective, randomized laboratory investigation.


METHODS
University laboratory.


METHODS
A total of 40 anesthetized, paralyzed, and mechanically ventilated dogs weighing 29.2+/-4.6 kg.


METHODS
Dogs were randomly assigned to be anesthetized with propofol (n = 13), etomidate (n = 13), or pentobarbital (n = 14) at either low or high dosages. At 30 mins after splenectomy, the dogs underwent progressive hemorrhage by successive withdrawals of 3-5 mL/kg arterial blood.


RESULTS
At each step of hemorrhage, oxygen consumption and oxygen delivery were determined. Oxygen consumption was obtained from expired gas analysis, and oxygen delivery was determined from thermodilution cardiac output and calculated arterial oxygen content. In each animal, critical oxygen delivery and critical oxygen consumption were obtained from a plot of oxygen consumption vs. oxygen delivery as the point of intersection of the two best-fit regression lines determined by a least sum of squares method. Critical oxygen extraction was obtained by dividing critical oxygen consumption by critical oxygen delivery. In the three groups, animals receiving the higher anesthetic infusion had a significantly higher critical oxygen delivery (propofol: 10.5+/-0.8 vs. 13.9+/-2.5 mL/min/m2, p < .05; etomidate: 10.1+/-0.7 vs. 13.4+/-3.0 mL/min/m2, p < .05; pentobarbital: 7.8+/-1.0 vs. 12.3+/-2.5 mL/min/m2, p < .01) attributable to a lower critical oxygen extraction ratio (propofol: 41.1+/-6.4% vs. 54.2+/-2.5%, p < .01; etomidate: 42.7+/-10.2% vs. 60.6+/-7.1%, p < .01; pentobarbital: 42.2+/-7.2% vs. 64.3+/-8.8%, p < .01).


CONCLUSIONS
This study indicates that propofol, etomidate, and pentobarbital increased critical oxygen delivery in a dose-dependent manner. This effect was mainly related to a decrease in tissue oxygen extraction capabilities.
Van der Linden
P
P
Department of Cardiac Anesthesia, Centre Hospitalier Universitaire, Charleroi, Belgium.
Schmartz
D
D
Gilbart
E
E
Engelman
E
E
Vincent
J L
JL
D018686:Anesthetics, Intravenous / Q000494:pharmacology*; D000818:Animals; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005045:Etomidate / Q000494:pharmacology*; D005260:Female; D006439:Hemodynamics / Q000187:drug effects*; D007773:Lactates / Q000097:blood; D008297:Male; D010101:Oxygen Consumption / Q000187:drug effects*; D010424:Pentobarbital / Q000494:pharmacology*; D015742:Propofol / Q000494:pharmacology*
D018686:Anesthetics, Intravenous; D007773:Lactates; D010424:Pentobarbital; D015742:Propofol; D005045:Etomidate