Plasma catecholamines, corticosterone, glucose and fatty acids concentrations and mean arterial pressure and body temperature in haemorrhagic hypovolaemia, hypothermia and a combination of these in the rabbit.

Venous plasma noradrenaline, adrenaline, dopamine, corticosterone, glucose and free fatty acid concentrations were measured in anaesthetized rabbits during hypovolaemia, hypothermia and a combination of these. The anaesthetic used was Hypnorm, which contains fentanyl and fluanisone. In the hypovolaemia group blood was shed via the venous cannula until the mean arterial pressure was 50 mmHg. The rabbits in the hypothermia group were cooled in iced water to a central temperature of 32 degrees C, and the rabbits in the combined hypovolaemia-hypothermia group were bled until hypovolaemic and then cooled in iced water to a central temperature of 32 degrees C. Rewarming was done in dry air at 43 degrees C. Bleeding and hypothermia activated the sympathicoadrenal system, causing a rise in the noradrenaline and adrenaline concentrations, as well as a rise in corticosterone. There were no significant differences in plasma noradrenaline and adrenaline values between the groups, whereas hypovolaemia alone also increased the dopamine concentration. In the hypothermia group the amount of corticosterone after cooling and rewarming was higher than in the combined group. Hypothermia and hypovolaemia increased the level of free fatty acids and blood glucose, which in the hypovolaemia group remained higher after volume replacement than in the other groups. Hypothermia in both groups increased the mean arterial pressure. In conclusion, the results suggest that hypothermia may prevent some harmful effects of hypovolaemia, e.g. by correcting mean arterial pressure, thus preventing the mortality seen in the hypovolaemia group.