Je. Chelly et al., CARDIAC AND REGIONAL HEMODYNAMIC INTERACTIONS BETWEEN HALOTHANE AND NITRIC-OXIDE SYNTHASE ACTIVITY IN DOGS, Anesthesiology, 85(1), 1996, pp. 142-149
Background: In vitro, halothane appears to affect the role played by n
itric oxide in the regulation of vascular tone and cardiac function. I
n vivo the results of the interactions between halothane and the nitri
c oxide pathway remain controversial. The authors investigated the eff
ects of halothane on the cardiac and regional hemodynamic properties o
f N-methyl-L-arginine (NMA), a specific nitric oxide synthase inhibito
r, in dogs. Methods: Twenty-five dogs were chronically instrumented. A
ortic pressure, the first derivative of left ventricular pressure, car
diac output, heart rate, and carotid, coronary, mesenteric, hepatic, p
ortal and renal blood flows were continuously recorded. N-methyl-L-arg
inine was infused intravenously at 20 mg/kg over 1 min in awake dogs (
n = 11) and in 1.2% halothane-anesthetized dogs (n = 10). As a control
group, the remaining four dogs were studied awake and during 1.2% hal
othane for 2 h in the absence of NMA. Results: In awake dogs, NMA prod
uced a sustained presser response (34%) and systemic vasoconstriction
(40%) associated with a decrease In cardiac output (16%). Regional cir
culation changes included an immediate and transient increase in carot
id (43%) and coronary (237%) blood flows and a subsequent decrease in
carotid blood flow (25%). Hepatic and mesenteric blood flows also decr
eased, by 43% and 16%, respectively. Except for the coronary circulati
on, regional vascular resistance increased significantly. Halothane di
d not affect the presser response to NMA but did blunt the cardiac out
put changes. Consequently, the systemic vasoconstriction after nitric
oxide synthase inhibition was of shorter duration and of lesser magnit
ude during halothane anesthesia. Halothane also blunted the carotid, m
esenteric, and renal vasoconstriction induced by NMA. Finally, in 1.2%
halothane-anesthetized dogs, NMA induced a coronary vasoconstriction.
Conclusions: Halothane minimally interferes with the systemic and reg
ional hemodynamic consequences of nitric oxide synthase blockade. The
nature and magnitude of the interaction depend on the territory in whi
ch they occur.