The overall incidence of CAD is decreasing in North America; the preventive, diagnostic and therapeutic measures have improved in the last decades as have progressed our knowledge of the disease. Despite these facts, the problem of the patient with CAD presenting for anaesthesia is still serious and likely to increase as the population ages. Therefore, the vigilant anaesthetist must seek out and protect patients at risk of developing periopera-tive MI.

Variations in end-tidal carbon dioxide partial pressure (PetCO2) and temperature were measured for six hours following coronary artery bypass surgery in twenty patients. In the recovery room, the patients were mechanically ventilated with a tidal volume of 12 ml·kg-1. Arterial blood gases were drawn every two hours, and the respiratory frequency was adjusted to maintain arterial carbon dioxide pressure (PaCO2) in the range of 30– 45 mmHg. Naso-pharyngeal temperature was recorded every 30 minutes, andPetCO2 was measured continuously. The mean difference between temperature-corrected arterial and end-tidal CO2 pressure measurements was 3.2 mmHg (SD = 2.8; r = 0.963). This difference did not vary with time, temperature or PCO2. The largest temperature increases (mean 1.7°C/hour) occurred at a mean of 253 minutes after the end of surgery. End-tidal PCO2 increased markedly as temperature rose, in spite of a coincident increase in ventilation and then decreased as temperature stabilized. Large increases in CO2 production, caused by the metabolic demands during rewarming, most likely account for these changes. It is concluded that end-tidal CO2 recordings are reliable, and can help in maintaining normocarbia during the short but unstable period associated with rewarming following cardiac surgery.

Vingt-cinq malades sous traitement bêta-bloquant, sans atteinte sévère de la fonction myocardique, et devant subir un pontage aorto-coronarien ont reçu une induction anesthésique comportant soit du diazépam (groupe D) soit de l'Alfatésine® (groupe A). Les variables hémodynamiques étudiées incluaient la mesure des différentes pressions intravasculaires, du débit cardiaque et des intervalles systoliques. L'étude a porté sur l'effet de chacune des deux drogues employées seules (temps I) et après addition à chacune d'elles de fentanyl, de pancuronium et de protoxyde d'azote (temps II). Les résultats semblent démontrer que l'Alfatésine employée seule déprime la fonction myocardique (baisse de SI de 12,51 % et augmentation de PEP/LVET de 10,79 %), alors que ce n'est pas le cas du diazépam. Toutefois, après l'addition de fentanyl, de pancuronium et de protoxyde d'azote, les deux groupes de malades se comportent de façon à peu près similaire, puisque ces dernières drogues semblent ajouter un effet dépresseur au diazépam (baisse de SI de 13,83 % et augmentation de PEP/LVET de 15,77 %) sans augmenter l'effet inotrope négatif de l'Alfatésine. D'autre part l'utilisation conjointe du cathéter de Swan-Ganz et des intervalles de temps systoliques semble permettre d'apprécier de façon plus précise les différentes composantes de la performance myocardique.

The haemodynamic effects of induction of anaesthesia with diazepam (group D) and Althesin (group A) were studied in 25 coronary patients under betablockers with good myocardial function. Haemodynamic variables monitored were vascular pressures, cardiac output and systolic time intervals. The effects of both drugs were observed when used alone (time I) and in combination with fentanyl, pancuronium and nitrous oxide (time II). The results seemed to show that Althesin (12.51% fall in SI and 10.79% increase in PEP/LVET) depressed myocardial function more than diazepam (no significant difference), but the introduction of fentanyl, pancuronium and nitrous oxide removed the differences between the drugs as to their effect on myocardial performance. These drugs added a depressant effect to diazepam (13.83% fall in SI and 15.77% increase in PEP/LVET) without increasing Althesin's negative inotropic effect. However, in group A at time II, the pulmonary arterial pressure, the wedge pressure and the pulmonary vascular resistance were significantly reduced, while they remained stable in the diazepam group.

Boulanger, Marcel MD; Maillé, Jean-Guy MD; Pelletier, Guy B. MD; Michalk, Suzanne MD Author Information

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.

Boulanger, Marcel MD; Besner, Guy MD; Hudon, Gilles MD; Meere, Claude MD Author Information

Hypertension following coronary surgery is generally reported at an alarmingly high incidence (30 to 75 per cent). A vigilance program carried out in 1977 at the Montreal Heart Institute disclosed a low incidence of 3.5 per cent in 200 consecutive unselected cases. A similar program in 1980 based on 160 cases showed an incidence of 23.7 per cent. This highly significant difference is found to be related to the differences in anaesthetic management which have occurred since 1977 when anaesthesia was primarily morphine 1.0 to 1.5 mg . kg-1 supplemented as needed with low dose halogenated agents and vasodilation therapy. In 1980, only one of the authors (J.T.) still uses this technique. The incidence of hypertension in 40 of his patients was 2.5 per cent. The others use low dose fentanyl (7.5 to 10 micrograms . kg-1) supplemented as needed with halogenated agents and vasodilating therapy; the incidence of hypertension in 160 cases was 23.7 per cent. Would these results be the same with an anaesthetic technique comparing both drugs at equipotent doses? A prospective clinical study is addressing this question.

Ce texte destiné aux résidents d’anesthésie-réanimation en début de stage dans un service cardio-vasculaire, discute du risque opératoire et de certains problèmes courants chez les patients devant subir une intervention chirurgicale cardiaque ou vasculaire. On classifie le risque en risque habituel, accru ou élevé, selon la présence de facteurs aggravants du risque (mauvaise fonction ventriculaire, angor instable, âge, etc. …). On propose une évaluation du risque habituel pour certaines interventions courantes. Parmi les problèmes courants rencontrés chez ces malades, on retrouve entre autres des pathologies pulmonaires, des problèmes de coagulation, le diabète et l’insuffisance rénale. La prémédication utilisée chez ce type de malade et l ’ approche adoptée à l’ Institut de Cardiologie de Montréal y sont discutées.