PULMONARY COMPLICATIONS AND CARDIOPULMONARY BYPASS

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Presented at Canadian Anaesthetists' Society Annual Meeting, Vancouver, June, 1973. THE use of eardiopulmonary bypass and of the pump oxygenator has increased as newer surgical techniques have been developed. Pulmonary complications, particularly those of the left lower lobe, have remained frequent following bypass 1 despite the decrease in the post-perfusion syndrome or "pump lung" attributed to improved venting of the left ventricle and atrium s and/or the use of low molecular weight dextran? This study is an attempt to present the nature and frequency of these complications and to correlate these changes with pulmonary function during the first post-operative week. Pulmonary function was assessed using alveolo-arterial oxygen gradients (A-aDO2), arterio-alveolar carbon dioxide gradients (a-ADCO2), steady-state diffusing capacity for carbon monoxide (Dco.~.~), and physiological dead space-tidal volume ratios (VD/VT) in association with the roentgenologic changes. MATERIALS AND METHODS Nineteen patients were studied. They were clinically free of chest disease or overt uncontrolled congestive heart failure with the exception of one (case No. 11). Seventeen had coronary artery bypass grafts for refractory or intractable angina pectoris; one (No. 11) had mitral and aortic valve replacement because of refractory congestive heart failure and the remaining one (No. 15) had an aortic valve replacement. The clinical details are shown in Table I. All patients had cardiopulmonary bypass using a Sarns roller pump with the Bentley "Temptrol" reservoir and bubble oxygenator. Prime consisted of three units of heparinized homologous blood (3-5 days old) mixed with 1.5 to 2.0 litres of two-thirds 5 per cent G/W with one-third N/S. Blood flow was maintained at 9..2 liters/M s minute at 35 ~ C. with a minimum perfusion pressure of 60 mm Hg after adequate venting of left atrium and ventricle. During bypass the lungs were kept statically inflated with a mixture of nitrous oxide and oxygen 50:50 at 10 cm H20 pressure and humidified using an ultrasonic nebulizer. Three "sighs" were administered during most periods of bypass and again after the patient had come off bypass. The clinical and operative records were reviewed for factors which might have