Abstract
The present clinical study was undertaken to assess the alterations in myocardial metabolism and coronary haemodynamics during weaning from mechanical ventilation in postoperative cardiac surgical patients. Global and regional myocardial blood flow and metabolism were assessed using a dual port coronary sinus-great cardiac vein thermodilution catheter in 17 patients who had undergone coronary revascularization and who were being weaned from mechanical ventilation. Anaerobic myocardial metabolism, as demonstrated by the production of myocardial lactate, manifested in 8 of 17 patients during at least one of the weaning phases. There were no differences in coronary blood flow between patients who produced myocardial lactate and those who maintained aerobic cardiac metabolism. However, lactate producers exhibited larger changes in systemic vascular resistance and mean arterial pressure than the non-lactate producers. This metabolic manifestation of myocardial ischaemia was not accompanied by electrocardiographs changes of ischaemia, nor presence of chest pain, and may represent another form of silent ischaemia. We conclude that despite coronary revascularization, the myocardium may remain vulnerable to ischaemic anaerobic metabolism in the immediate postoperative period.
Résumé
Cette étude clinique a été menée afin d’évaluer les altérations dans le métabolisme du myocarde et l’hémodynamique des coronaires lors du sevrage de la ventilation mécanique chez les patients en période post-opératoire d’une chirurgie cardiaque. Chez 17 patients ayant subi une revascularisation coronarienne et qui étaient en sevrage de la ventilation mécanique, le métabolisme et le débit sanguin myocardique global et régional ont été évalués a l’aide d’un cathéter à thermodilution a double lumière (sinus coronaire et grande veine coronaire). Un métabolisme myocardique anaérobique s’est manifesté chez 8 des 17 patients durant au moins une des phases du sevrage tel que démontré par la production de lactate myocardique. Il n’y a eu aucune différence du débit sanguin coronarien entre les patients qui produisaient du lactate myocardique et ceux qui maintenaient un métabolisme cardiaque aérobique. Cependant, ceux qui produisaient du lactate avaient des changements plus importants de la résistance vasculaire systémique et de la tension artérielle moyenne que ceux qui nen produisaient pas. Cette manifestation métabolique de l’ischémie myocardique n’était pas accompagnée de changements ischémiques à l’électrocar-diogramme ni de douleurs thoraciques, et pourrait représenter une autre forme d’ischémie silencieuse. Nous concluons que le myocarde peut demeurer vulnérable au métabolisme anaérobique ischémique dans la période post-opératoire immédiate, malgré une revascularisation coronarienne.
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Dr. Elia was a Research Fellow of the Canadian Heart Foundation at the Massachusetts General Hospital, and a Recipient of the Canadian Anaesthetists’ Society Research Award.
Dr. Liu was a Fellow of the Medical Research Council of Canada and is now a Research Scholar of the Heart and Stroke Foundation of Ontario.
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Elia, S., Liu, P., Hilgenberg, A. et al. Coronary haemo-dynamics and myocardial metabolism during weaning from mechanical ventilation in cardiac surgical patients. Can J Anaesth 38, 564–571 (1991). https://doi.org/10.1007/BF03008185
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DOI: https://doi.org/10.1007/BF03008185