CHRONIC INSTRUMENTATION TECHNIQUES FOR HAEMODYNAMIC MEASUREMENTS

Most of the knowledge of cardiovascular physi-ology and pharmacology is based on experiments which have been conducted on animals in the anaesthetized state, often with an open chest, and the tacit assumption that general anaesthesia does not modify the conclusions derived from these experiments to a major extent. However, research in chronically instrumented experimental animals has shown that the methodological requirement for basal anaesthesia—that is, the impact of anaesthetic drugs in the absence of the particular anaesthetic under study—may cause a consider-able disruption of the autonomic control of the cardiovascular system [1, 2,4,7,12, 15,16], a pro-found shift in baseline haemodynamics [1,2,4,7, 10-16], and myocardial function and coronary haemodynamics [1,3,10-14,16], variables which are of fundamental importance in studying the impact of various anaesthetics on the cardio-vascular system. It is, therefore, important to conduct sequential haemodynamic measurements enabling comparisons of the conscious v. the anaesthetized states. The goal of the present article is to present some of the chronic instru-mentation techniques for study of the effects of anaesthetic agents on overall haemodynamics, coronary blood flow and regional myocardial function in comparison with the conscious state. METHODS Implantation of instrumentation is carried out in trained, premedicated animals using general anaesthesia with either pentobarbitone 25—30 mg kg"1 i.v. or a volatile anaesthetic after induction o