Effects of dobutamine, norepinephrine, and vasopressin on cardiovascular function in anesthetized neonatal foals with induced hypotension.
OBJECTIVE
To determine the effects of dobutamine, norepinephrine, and vasopressin on cardiovascular function and gastric mucosal perfusion in anesthetized foals during isoflurane-induced hypotension.


METHODS
6 foals that were 1 to 5 days of age.


METHODS
6 foals received 3 vasoactive drugs with at least 24 hours between treatments. Treatments consisted of dobutamine (4 and 8 Sang/kg/min), norepinephrine (0.3 and 1.0 Sang/kg/min), and vasopressin (0.3 and 1.0 mU/kg/min) administered IV. Foals were maintained at a steady hypotensive state induced by a deep level of isoflurane anesthesia for 30 minutes, and baseline cardiorespiratory variables were recorded. Vasoactive drugs were administered at the low infusion rate for 15 minutes, and cardiorespiratory variables were recorded. Drugs were then administered at the high infusion rate for 15 minutes, and cardiorespiratory variables were recorded a third time. Gastric mucosal perfusion was measured by tonometry at the same time points.


RESULTS
Dobutamine and norepinephrine administration improved cardiac index. Vascular resistance was increased by norepinephrine and vasopressin administration but decreased by dobutamine at the high infusion rate. Blood pressure was increased by all treatments but was significantly higher during the high infusion rate of norepinephrine. Oxygen delivery was significantly increased by norepinephrine and dobutamine administration; O2 consumption decreased with dobutamine. The O2 extraction ratio was decreased following norepinephrine and dobutamine treatments. The gastric to arterial CO2 gap was significantly increased during administration of vasopressin at the high infusion rate.


CONCLUSIONS
Norepinephrine and dobutamine are better alternatives than vasopressin for restoring cardiovascular function and maintaining splanchnic circulation during isoflurane-induced hypotension in neonatal foals.
Valverde
Alexander
A
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610, USA.
Giguère
Steeve
S
Sanchez
L Chris
LC
Shih
Andre
A
Ryan
Clare
C
D018685:Anesthetics, Inhalation / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004280:Dobutamine / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005753:Gastric Mucosa / Q000098:blood supply / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006736:Horses / Q000378:metabolism*; D007022:Hypotension / Q000139:chemically induced*; D007530:Isoflurane / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000008:administration & dosage / Q000494:pharmacology*; D013566:Sympathomimetics / Q000008:administration & dosage / Q000494:pharmacology; D014662:Vasoconstrictor Agents / Q000008:administration & dosage / Q000494:pharmacology; D014667:Vasopressins / Q000008:administration & dosage / Q000494:pharmacology*
D018685:Anesthetics, Inhalation; D013566:Sympathomimetics; D014662:Vasoconstrictor Agents; D014667:Vasopressins; D004280:Dobutamine; D007530:Isoflurane; D009638:Norepinephrine