Thiopental and halothane dose-sparing effects of magnesium sulphate in dogs.
OBJECTIVE
To evaluate the effect of pre- and intraoperatively administered magnesium sulphate (MgSO(4)) on the induction dose of thiopental and of halothane for maintenance of anaesthesia in dogs undergoing ovariohysterectomy (OHE).


METHODS
Prospective, double-blind, randomized, placebo-controlled study.


METHODS
Forty-six healthy, ASA physical status 1 dogs, scheduled for elective OHE.


METHODS
The dogs were randomly assigned to receive a bolus of 50 mg kg(-1) MgSO(4) intravenously (IV), just before induction of anaesthesia, followed by a constant rate infusion (CRI) of 12 mg kg(-1) hour(-1) MgSO(4) intraoperatively (group Mg, n = 27) or a placebo bolus and CRI of 0.9% sodium chloride (NaCl) (group C, n = 19), approximately 30 minutes after premedication with acepromazine (0.05 mg kg(-1), intramuscularly, IM) and carprofen (4 mg kg(-1), subcutaneously, SC). Anaesthesia was induced with thiopental administered to effect and maintained with halothane in oxygen. End-tidal halothane (ET(hal)) was adjusted to achieve adequate depth of anaesthesia. Blood samples were obtained pre- and postoperatively for measurement of total serum magnesium concentration.


RESULTS
The mean dose of thiopental was statistically lower (p < 0.0005) and the mean standardized ET(hal) concentration and end-tidal carbon dioxide partial pressure (Pe'CO(2)) areas under the curve were statistically smaller (p < 0.0005 and 0.014 respectively) in group Mg. Postoperatively the mean total serum magnesium concentration was statistically higher than the preoperative value (p < 0.0005) in group Mg, but not in group C. Nausea, associated with the MgSO(4) bolus injection, was observed in six dogs in group Mg, two of which vomited prior to induction of anaesthesia.


CONCLUSIONS
Magnesium sulphate administration reduced the induction dose of thiopental and ET(hal) concentration for maintenance of anaesthesia in dogs undergoing OHE. Observed side effects were nausea and vomiting.
Anagnostou
Tilemahos L
TL
Anaesthesia and Intensive Care Unit, Companion Animal Clinic, Department of Clinical Sciences, Faculty of Veterinary Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece.
Savvas
Ioannis
I
Kazakos
George M
GM
Raptopoulos
Dimitris
D
Ververidis
Haralabos
H
Roubies
Nikolaos
N
D000758:Anesthesia / Q000662:veterinary*; D000777:Anesthetics / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D018685:Anesthetics, Inhalation / Q000008:administration & dosage / Q000493:pharmacokinetics; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000493:pharmacokinetics; D000818:Animals; D019540:Area Under Curve; D004285:Dogs / Q000378:metabolism / Q000502:physiology* / Q000601:surgery; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D006221:Halothane / Q000008:administration & dosage / Q000493:pharmacokinetics; D007044:Hysterectomy / Q000662:veterinary; D007262:Infusions, Intravenous / Q000662:veterinary; D008278:Magnesium Sulfate / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D011446:Prospective Studies; D013874:Thiopental / Q000008:administration & dosage / Q000493:pharmacokinetics
D000777:Anesthetics; D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D008278:Magnesium Sulfate; D013874:Thiopental; D006221:Halothane