Effect of H1- and H2-receptor antagonists on the hemodynamic changes induced by the intravenous administration of ketamine in sevoflurane-anesthetized cats.
OBJECTIVE
The anesthetic ketamine has been reported to cause both an increase of the plasma histamine concentration, notably in cats, and a cardiovascular depression. The latter has been described in humans and in other species. However the relevance of the histamine fluctuation for the ketamine-induced hemodynamic changes has not been determined.


METHODS
We studied the contribution of histamine to the hemodynamic effects induced by IV ketamine (7 mg/kg) in 12 sevoflurane anesthetized cats, of which half had been pre-treated with combined H(1)- and H(2) -receptor antagonists.


METHODS
The mean arterial pressure (MAP) and the heart rate (HR) from both untreated (group C) and pre-treated (group AH) cats were recorded before and after the ketamine administration. The plasma histamine concentration was also measured.


RESULTS
Plasma histamine fluctuations in the control and the antihistamine-treated group followed a similar pattern (no statistical differences); an initial rise that peaked 2 min after ketamine injection (from 0.63 +/- 0.11 ng/ml to 2.22 +/- 0.69 ng/ml in the C group, and from 0.71 +/- 0.10 ng/ml to 1.09 +/- 0.28 ng/ml in the AH group) followed by an immediate decrease in plasma concentrations. As for the hemodynamic variables under analysis, in the control group ketamine administration was followed by an early 30.3 +/- 8.1% reduction (p < 0.005) in the MAP with no associated changes in the HR. In the antihistamine pre-treated group, ketamine caused a further decrease of the MAP (41.7 +/- 2.3%), and a significant (p < 0.01) 11.6 +/- 2.9% reduction of the HR.


CONCLUSIONS
Ketamine in anesthetized cats triggers histamine release and induces cardiovascular depression. The depression is more pronounced under the blockade of histamine activity through histamine receptor antagonists.
Costa-Farré
C
C
Department of Medicine and Surgery, Veterinary School, Universitat Autònoma de Barcelona, 08193, Bellaterra, Barcelona, Spain.
García
F
F
Andaluz
A
A
Torres
R
R
de Mora
F
F
D000777:Anesthetics / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D003331:Coronary Vessels / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D006632:Histamine / Q000378:metabolism; D006634:Histamine H1 Antagonists / Q000494:pharmacology*; D006635:Histamine H2 Antagonists / Q000494:pharmacology*; D007275:Injections, Intravenous; D007649:Ketamine / Q000008:administration & dosage* / Q000494:pharmacology*; D008297:Male; D008738:Methyl Ethers / Q000494:pharmacology*; D011969:Receptors, Histamine H1 / Q000378:metabolism; D011970:Receptors, Histamine H2 / Q000378:metabolism; D000077149:Sevoflurane
D000777:Anesthetics; D006634:Histamine H1 Antagonists; D006635:Histamine H2 Antagonists; D008738:Methyl Ethers; D011969:Receptors, Histamine H1; D011970:Receptors, Histamine H2; D000077149:Sevoflurane; D007649:Ketamine; D006632:Histamine