Nitric oxide does not play a major role in the regulation of systemic hemodynamic responses to acute normovolemic hemodilution.
BACKGROUND
The mechanisms of cardiovascular changes following acute normovolemic hemodilution (ANH) have not been fully elucidated. We tested the hypothesis that inhibition of nitric oxide synthesis attenuates ANH-induced cardiovascular responses.


METHODS
We observed the effects of N(omega)-nitro-L-arginine methyl ester (L-NAME) pretreatment on ANH-induced cardiovascular responses and compared these effects with those elicited by phenylephrine (PHE). Twenty dogs anesthetized with isoflurane were divided into two groups: one group was pretreated with L-NAME and the other with PHE. Both groups were normovolemically hemodiluted using 6% hydroxyethyl starch to reduce the hemoglobin concentration to approximately 50% of the pretreatment value.


RESULTS
Pretreatment with either L-NAME or PHE caused a significant increase in mean aortic blood pressure (MAP) and systemic vascular resistance (SVR) with a significant decrease in cardiac output (CO) and stroke volume (SV). However, no remarkable differences in these variables were seen between groups. In both groups ANH produced increases in heart rate, CO, SV, and maximal left ventricular dP/dt with a significant decrease in SVR. No significant differences in these variables were apparent after ANH except that MAP was decreased in the PHE group but not in the L-NAME group.


CONCLUSIONS
Our results suggest that nitric oxide does not play a major role in mediation or modulation of the systemic vascular responses to ANH.
Hirose
Y
Y
Department of Anesthesia, Fukuoka Tokushukai Hospital, Kasuga, Japan.
Kimura
H
H
Kitahata
H
H
Kawahito
S
S
Oshita
S
S
D000818:Animals; D004285:Dogs; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006438:Hemodilution; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology*; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*
D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D019331:NG-Nitroarginine Methyl Ester