Canadian Journal of Anesthesia, Vol 21, 181-194, Copyright © 1974 by Canadian Anesthesiologists' Society

Pulmonary Complications and Cardiopulmonary Bypass: A Clinical Study in Adults

¹ Department of Anaesthesiology, Vancouver General Hospital, and Faculty of Medicine, University of British Columbia
² Department of Surgery, St. Paul's Hospital, and the Faculty of Medicine, University of British Columbia, Vancouver, B.C.

Pulmonary complications are extremely frequent after cardiopulmonary bypass. Hypoxic levels of arterial oxygen tension (PaO₂ < 70.0 mm Hg) occurred in more than 50 per cent of the 19 patients studied. Atelectasis or collapse of the left lower lobe is highly characteristic and was seen in more than 50 per cent of the patients studied. Pulmonary function assessment (using PaO₂, a-ADO₂, A-ADCO₂, V_D/V_T and CO diffusing capacity D_COCOSS) suggests that increased physiological shunting in the atelectatic or consolidated lungs is the crucial factor. This study compared pre-operative and post-operative changes in these parameters during the first week after operation. Pulmonary dysfunction was maximal 24 hours post-operatively and gradually improved during the next six days. Anatomical, anaesthetic, and manipulative factors probably predispose to the frequent involvement of the left lower lobe. The use of left ventricle venting, sighs, "PEEP" and humidity during bypass may help to minimize pulmonary complications. Suction of both lower lobe bronchi prior to extubation and postoperative physiotherapy and "stir-up" regimes are also important. The significance of roentgenological and clinical evidence of pulmonary function in this type of patient can best be followed by A-aDO₂ gradients and the PaO₂.