Myocardial metabolism and haemodynamic responses with enflurane anaesthesia for coronary artery surgery

Abstract

The study was supported by the Nova Scotia Heart Foundation and Ohio Medical Anesthetics.Maintenance of myocardial oxygen balance during anaesthesia is essential, particularly for patients with coronary artery disease, to avoid major ischaemic episodes or frank infarction. Increased oxygen consumption due to a hyperdynamic circulation must be avoided. Moderate depression of myocardial contractility by potent anaesthetic drugs is desirable but must be controllable. The adequacy of myocardial oxygenation can now be assessed in the operating room, by measuring coronary sinus blood flow, myocardial oxygen consumption and lactate extraction. Myocardial oxygenation can be maintained in coronary patients with halothaneoxygen but not so with 1 mg.kg -l of morphine, and oxygen. ~ Delaney et al. 2 reported, in patients having coronary vein grafts (CABG), myocardial function and haemodynamic effects of enflurane, but correlation of haemodynamics with CBF, MVO2 and MLE has not been documented. We present the haemodynamic and myocardial metabolic effects of enflurane-oxygen anaesthesia from pre-induction, through anaesthesia and operation for CABG and for 24 hours afterward. Methods Study populationTen male patients gave their informed consent. Mean age was 53.7 years (range 34-62), mean weight 79.2 Kg (68-91); eight had known previous infarction. Their disability by NYHA Class was: 11 -one patient, III -seven and IV -two; all patients were normotensive. Nine were kept on effective beta blockade (average: propranolol dose 40rag q.i.d.) until operation. Although nine had signi-CAN ANAESTH SOC ] 1984 ! 31:6 I pp604-10

Myocardial Ischaemia Associated With General Anaesthesia

“…Hence, myocardial oxygen extraction was reduced. Similar observations were made in comparable patients by Moffitt and colleagues [41] and in vascular surgical patients with CAD by Rydvall and associates [56]. These investigators also studied the regional coronary haemodynamic effects of enflurane by the use of the multiple thermistor, retrograde thermodilution coronary flow technique [48], allowing great cardiac venous blood flow (GCVF)j which represents most of left ventricular blood flow, and total coronary sinus blood flow (CSF) to be assessed separately.…”

Anaesthesia for coronary artery surgery — a plea for a goal-directed approach

“…23.24 For the volatile agents the lack of residual analgesia, when combined with rapid emergence, may exacerbate postoperative hypertension and tachycardia with the potential for myocardial ischaemia and anastamotic suture disruption. 5,6 Changes in clearance following cardiopulmonary bypass for agents such as diazepam and lorazepam, which have long elimination half-times, z~ may produce prolonged residual effects in the postoperative period. Diazepam has active metabolites zs and both lorazepam and diazepam depend on hepatic metabolism for their elimination.…”