A new risk classification for patients undergoing cardiac surgery has been used for the last two years by the anaesthesiologists of the Montreal Heart Institute. The following factors known to be associated with a greater operative morbidity and mortality were selected: (1) poor left ventricular function, (2) congestive heart failure, (3) unstable angina or recent (less than 6 weeks) myocardial infarction, (4) age over 65 years, (5) severe obesity (Body Mass Index greater than 30), (6) reoperation, (7) emergency surgery, (8) other significant or uncontrolled systemic disturbances. Patients with none of the above factors were classified as normal risks; those presenting with one of those selected factors were classified as increased risks, and those with more than one factor were said to carry a high risk. In a prospective study of 500 consecutive open-heart surgery patients classified according to this method, we found that the operated population at normal risk (50 per cent of cases) had a mortality of 0.4 per cent, the patient group with increased risk (32 per cent of cases) had a mortality of 3.1 per cent, and the high risk group (18 per cent of cases) had a 12.2 per cent mortality. Furthermore, 50 deaths following open-heart surgery were assessed retrospectively using the classification; 58 per cent of these patients were classified as high risk, 34 per cent had an increased risk, and only eight per cent were found to be in the normal risk group. Thus, this new risk classification has proven to be a reliable and useful tool for preoperative assessment of patients undergoing open-heart surgery and for teaching purposes.

Mcllvaine et al. reported that morphine anaesthesia (1.5 mg.kg-1) was associated with a lower incidence of postoperative hypertension (3.8 per cent) following coronary artery bypass graft surgery (CABG), compared to 28 per cent when low dosefentanyl (7.5-10 µg.kg-1) and halogenated agents were used for anaesthesia. Since in this earlier study the relative dosage of the narcotics used could not be considered as equivalent we compared the incidence of postoperative hypertension in two groups of 24 patients operated for CABG: one group received morphine 1.5 mg.kg-1 and the other fentanyl 50 µg.kg-1: these doses are considered clinically equivalent. In both groups, patients breathed a mixture of nitrous oxide oxygen (3/2). All patients had normal ventricular function. There was not a single case of postoperative hypertension in the morphine group whereas seven cases occurred in the fentanyl group (29 per cent). The incidence of preoperative hypertension was similar in both groups. During the operation, before the extracorporeal circulation, supplementation of anaesthesia to maintain cardiovascular stability was necessary twice as often in the morphine group as in the fentanyl group (40 vs 19). These results show that morphine anaesthesia prevents postoperative hypertension in CABG; clinically equivalent doses of fentanyl do not. However, during surgery, for the period preceding the extracorporeal circulation, fentanyl seems to be preferable to morphine for the coronary patients. This work suggests that a technique combining both narcotics might be advantageous: fentanyl being used before the extracorporeai circulation and morphine during and after, to prevent the postoperative hypertension, it remains to be determined if such a combination would be effective and would not present untoward effects such as delaying recovery, prolonging intubation period and ICU stay.