ANESTHESIA FOR ABDOMINAL VASCULAR-SURGERY IN PATIENTS WITH CORONARY-ARTERY DISEASE (CAD) .1. ISOFLURANE PRODUCES DOSE-DEPENDENT CORONARY VASODILATION

The effects of anaesthesia for major abdominal vascular surgery on cor onary flow regulation and mechanisms of myocardial ischaemia were stud ied in 56 patients with, CAD, using a randomized, partly double-blinde d protocol. After induction with fentanyl (3 mu g.kg(-1)) and thiopent one (2-4 mg.kg(-1)) and tracheal intubation, principal anaesthetics we re nitrous oxide/oxygen (60/40) with isoflurane (n=20), halothane (n=1 9) or fentanyl (15-20 mu g.kg(-1)) (n=17). Conventional invasive techn iques and coronary venous retrograde thermodilution were used to asses s systemic and coronary haemodynamics. Coronary vascular resistance wa s estimated from myocardial oxygen extraction. Myocardial ischaemia wa s diagnosed by 12-lead ECG and/or anterior wall motion abnormalities b y cardiokymography and/or myocardial lactate production. When adjustme nt of anaesthetic dose was insufficient for haemodynamic control, iv p henylephrine and nitroglycerine were adminstered to treat hypotension and hypertension or cardiac failure respectively. Measurements were pe rformed at four specific intervals; awake, before surgery and 10 and 3 0 min after abdominal incision. Comparable changes of systemic haemody namics and myocardial oxygen consumption were observed in the three gr oups. Coronary vasodilation was evidenced in isoflurane patients only and was linearly dose-dependent (P<0.001). Partial Least Squares Proje ctions to Latent Structures modelling with cross validation confirmed this dose-dependency and ruled out a clinically measurable influence b y intervention drugs or simultaneous systemic haemodynamic abnormaliti es. The incidence of myocardial ischaemia during anaesthesia and surge ry was comparable in the three groups (35, 37 and 24%, respectively) a nd there was an association with systemic haemodynamic aberrations in IS of the 27 ischaemic episodes. In contrast to ischaemic halothane an d fentanyl patients, isoflurane patients with ischaemia had significan tly lower myocardial oxygen extraction (P=0.008 and P=0.001, respectiv ely), indicating that the oxygen extraction reserve was not utilized i n a normal way during ischaemia.