Effect of anaesthetic and rat strain on heart rate responses to simulated haemorrhage.
OBJECTIVE
Haemorrhage is characterized by two distinct responses, sympathoexcitation that evokes tachycardia and supports blood pressure, followed by sympathoinhibition contributing to bradycardia and hypotension. It has been shown that anaesthetics alter the response to haemorrhage and we hypothesized that rat strain may also influence the response. We investigated the effect of simulated haemorrhage on heart rate (HR) responses in three strains of conscious rats, and the effect of three common anaesthetics, by comparing HR responses under anaesthesia to the conscious response. Haemorrhage was simulated by constricting the inferior vena cava. We demonstrate differential effects of anaesthetics, including both maintenance and elimination of HR responses to haemorrhage depending on anaesthetic.


RESULTS
We also show that both phases of the HR response differ in different conscious rat strains, and we have demonstrated a transient increase in HR during the decompensatory phase of haemorrhage, a novel 'second HR peak' with advanced hypotension.


CONCLUSIONS
Both rat strain and anaesthetic influence HR responses to haemorrhage, and some anaesthetics appear less suitable than others for studies of haemodynamic responses in rats. There was evidence of an additional compensatory mechanism that operates at advanced levels of hypotension in the rat.
Holobotovskyy
V V
VV
School of Medicine and Pharmacology, University of Western Australia, Western Australian.
Arnolda
L F
LF
McKitrick
D J
DJ
D000777:Anesthetics / Q000494:pharmacology*; D018685:Anesthetics, Inhalation / Q000494:pharmacology; D018686:Anesthetics, Intravenous / Q000494:pharmacology; D000818:Animals; D001463:Barbiturates / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D006221:Halothane / Q000494:pharmacology; D006339:Heart Rate / Q000187:drug effects*; D006470:Hemorrhage / Q000503:physiopathology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D017207:Rats, Sprague-Dawley; D014520:Urethane / Q000494:pharmacology
D000777:Anesthetics; D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D001463:Barbiturates; D014520:Urethane; D006221:Halothane