Hemodynamic effects of ionized calcium in horses anesthetized with halothane or isoflurane.
OBJECTIVE
To evaluate the effects of halothane and isoflurane on cardiovascular function and serum total and ionized calcium concentrations in horses, and to determine whether administration of calcium gluconate would attenuate these effects.


METHODS
6 clinically normal adult Thoroughbreds.


METHODS
Catheters were inserted for measurement of arterial blood pressures, pulmonary arterial blood pressures, right ventricular pressure (for determination of myocardial contractility), right atrial pressure, and cardiac output and for collection of arterial blood samples. Anesthesia was then induced with xylazine hydrochloride and ketamine hydrochloride and maintained with halothane or isoflurane. An i.v. infusion of calcium gluconate was begun 75 minutes after anesthetic induction; dosage of calcium gluconate was 0.1 mg/kg of body weight/min for the first 15 minutes, 0.2 mg/kg/min for the next 15 minutes, and 0.4 mg/kg/min for an additional 15 minutes. Data were collected before, during, and after administration of calcium gluconate.


RESULTS
Halothane and isoflurane decreased myocardial contractility, cardiac index, and mean arterial pressure, but halothane caused greater depression than isoflurane. Calcium gluconate attenuated the anesthetic-induced depression in cardiac index, stroke index, and maximal rate of increase in right ventricular pressure when horses were anesthetized with isoflurane. When horses were anesthetized with halothane, a higher dosage of calcium gluconate was required to attenuate the depression in stroke index and maximal rate of increase in right ventricular pressure; cardiac index was not changed with calcium administration.


CONCLUSIONS
I.v. administration of calcium gluconate may support myocardial function in horses anesthetized with isoflurane.
Grubb
T L
TL
Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Champaign-Urbana 61801, USA.
Benson
G J
GJ
Foreman
J H
JH
Constable
P D
PD
Thurmon
J C
JC
Olson
W O
WO
Tranquilli
W J
WJ
Davis
L E
LE
D000769:Anesthesia, Inhalation / Q000662:veterinary; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002118:Calcium / Q000097:blood*; D002302:Cardiac Output / Q000187:drug effects; D005260:Female; D006221:Halothane / Q000494:pharmacology*; D006439:Hemodynamics / Q000187:drug effects* / Q000502:physiology; D006736:Horses / Q000502:physiology*; D007530:Isoflurane / Q000494:pharmacology*; D008297:Male; D009919:Orchiectomy; D011651:Pulmonary Artery / Q000187:drug effects; D013318:Stroke Volume / Q000187:drug effects; D013997:Time Factors
D007530:Isoflurane; D002118:Calcium; D006221:Halothane