Effects of norepinephrine and a combined norepinephrine and dobutamine infusion on systemic hemodynamics and indices of renal function in normotensive neonatal thoroughbred foals.
BACKGROUND
Norepinephrine is a potent vasopressor that increases arterial blood pressure but may have adverse effects on renal blood flow. The combination of norepinephrine and dobutamine may lead to improved renal perfusion compared to an infusion of norepinephrine alone. The effects of these drugs in the normotensive neonatal foal have not been reported.


OBJECTIVE
Norepinephrine increases arterial blood pressure. Adding dobutamine to a norepinephrine infusion will change the renal profile during the infusions without changing the arterial blood pressure.


METHODS
Eight conscious Thoroughbred foals were used in this study.


METHODS
Each foal received norepinephrine (0.1 microg/kg/min), combined norepinephrine (0.1 microg/kg/min) and dobutamine (5 microg/kg/min), and a control dose of saline in a masked, placebo-controlled study. Heart rate, arterial blood pressure (direct), and cardiac output (lithium dilution) were measured, and systemic vascular resistance, stroke volume, cardiac index, and stroke volume index were calculated. Urine output, creatinine clearance, and fractional excretion of sodium, potassium, and chloride were measured.


RESULTS
Norepinephrine and a combined norepinephrine and dobutamine infusion increased arterial blood pressure and systemic vascular resistance and decreased heart rate and cardiac index as compared to saline. The combination resulted in higher arterial pressure than norepinephrine alone. There was no significant difference in urine output, creatinine clearance, or fractional excretion of electrolytes with either infusion as compared to saline.


CONCLUSIONS
These data suggest that norepinephrine and a combined norepinephrine and dobutamine infusion cause unique hemodynamic effects without affecting indices of renal function, and this effect warrants further investigation.
Hollis
A R
AR
Royal Veterinary College, London, United Kingdom.
Ousey
J C
JC
Palmer
L
L
Stoneham
S J
SJ
Corley
K T T
KT
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects; D003404:Creatinine / Q000652:urine; D004280:Dobutamine / Q000494:pharmacology*; D004338:Drug Combinations; D004573:Electrolytes / Q000652:urine; D006339:Heart Rate / Q000187:drug effects; D006736:Horses / Q000502:physiology*; D007262:Infusions, Intravenous / Q000662:veterinary; D007668:Kidney / Q000187:drug effects* / Q000502:physiology; D007677:Kidney Function Tests / Q000662:veterinary; D009638:Norepinephrine / Q000494:pharmacology*; D013566:Sympathomimetics / Q000494:pharmacology*; D014655:Vascular Resistance / Q000187:drug effects
D004338:Drug Combinations; D004573:Electrolytes; D013566:Sympathomimetics; D004280:Dobutamine; D003404:Creatinine; D009638:Norepinephrine