ANESTHESIA FOR ABDOMINAL AORTIC-SURGERY IN PATIENTS WITH CORONARY-ARTERY DISEASE .2. EFFECTS OF NITROUS-OXIDE ON SYSTEMIC AND CORONARY HEMODYNAMICS, REGIONAL VENTRICULAR-FUNCTION AND INCIDENCE OF MYOCARDIAL-ISCHEMIA

This study examines the effects of nitrous oxide on haemodynamics, ant erior left ventricular (LV) function and incidence of myocardial ischa emia in abdominal vascular surgical patients with coronary artery dise ase. Forty-seven patients were randomly assigned to isoflurane-fentany l anaesthesia with nitrous erode-oxygen vs air-oxygen (control). Syste mic and coronary haemodynamics, 12-lead ECG, LV anterior wall motion b y cardiokymography (CKG) and myocardial lactate balance were recorded at four intervals: before and during anaesthesia and 10 and 30 minutes into surgery. Systemic haemodynamics were controlled by anaesthetic d ose, and, when insufficient, by iv nitroglycerine (NG) in case of LV f ailure (PCWP >18 mmHg) and by phenylephrine during hypotension. We fou nd that nitrous oxide was associated with greater need for iv nitrogly cerin (patients: P=0.031, episodes P=0.005) and more myocardial ischae mia (patients P=0.012, episodes P=0.001) despite systemic and coronary haemodynamics comparable to the control group. We conclude that nitro us oxide, known to have both sympathomimetic and cardiodepressive acti ons, produced cardiodepression in the face of sympathetic stimulation. Our study design did not allow us to conclude if myocardial ischaemia was the consequence of increased wall stress or a reason for the obse rved LV dysfunction. The higher incidence of introperative myocardial ischaemia and need for IUG did not cause increased cardiac morbidity.