Autoregulation of myocardial blood flow under controlled hypotension in the dog.
The autoregulation of myocardial blood flow was studied under: (a) haemorrhagic hypotension (mean pressure decrease 40% from baseline); (b) drug-induced hypotension with sodium nitroprusside or trimetaphan (40% pressure decrease); (c) drug-induced hypotension (40% pressure decrease) after moderate blood loss of 20%. Dogs were used in experiments under general anaesthesia with sodium thiopentone and artificially ventilated with N2O/O2 (70%, 30%) and pancuronium. Under haemorrhagic hypotension, the flow was pressure-dependent from the beginning. During nitroprusside hypotension, there was autoregulation of coronary flow to the level of mean pressure decrease 30% from control. Under trimetaphan, a constant flow persisted to the level of mean pressure decrease 20% from the baseline. Identical changes were seen during drug-induced hypotension after moderate blood loss (20%). Central venous pressure, cardiac output, left ventricular stroke work and minute work changes are demonstrated. Blood gas data pH, PO2, PCO2 in the aortic and coronary sinus under drug-induced hypotension are compared with control groups. There is a level of autoregulation of myocardial blood flow under hypotension. This level can be unfavourably changed in cases with hypertension and coronary obstructive diseases.
D000818:Animals; D001784:Blood Gas Analysis; D001794:Blood Pressure; D003326:Coronary Circulation / Q000187:drug effects; D004285:Dogs; D005260:Female; D006470:Hemorrhage / Q000503:physiopathology; D006706:Homeostasis; D007023:Hypotension, Controlled; D008297:Male; D009599:Nitroprusside / Q000494:pharmacology
D009599:Nitroprusside