The effect of haemorrhagic shock on blood pressure and heart rate responses to adrenaline in the conscious dog.

The effects of haemorrhagic shock on blood pressure and heart rate responses to exogenous adrenaline (2 microgram/kg i.v.) were studied in conscious dogs with chronically implanted vascular cannulae. The animals were bled to a mean arterial pressure of 40 mmHg, the duration of hypovolaemia being two hours. Adrenaline was injected before bleeding, at the beginning and at the end of controlled hypotension, before and 15 minutes after reinfusion. Plasma adrenaline and noradrenaline levels were determined by a radioenzymatic method. In shock, blood pressure responses and their duration decreased. Heart rate responses were changed from a bradycardia type before bleeding to a tachycardia during shock. After reinfusion biphasic responses were dominating. A significant negative correlation was found between plasma noradrenaline levels and blood pressure responses to adrenaline.