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We measured the changes in energy expenditure in the early postoperative phase after coronary artery bypass operations and the ventilatory response to the increased demand for respiratory gas exchange. Breathing pattern and gas exchange were measured noninvasively by respiratory inductive plethysmography and indirect calorimetry with a canopy. Eighteen patients were studied after weaning from mechanical ventilation. Energy expenditure increased by 18.3%, which is comparable to the response to major injury. Carbon dioxide production increased from 162 +/- 20 to 195 +/- 36 ml/min in the supine position (p less than 0.001), and similar changes were observed in the half-sitting position. Arterial carbon dioxide tension increased marginally (37.5 +/- 2.96 mm Hg preoperatively versus 39.7 +/- 4.87 mm Hg postoperatively; p less than 0.05), while oxygen tension decreased from 89.9 +/- 17.3 mm Hg to 62.9 +/- 13.4 mm Hg (p less than 0.001). Minute ventilation increased by 34% in the supine position (p less than 0.01) and by 28% in the half-sitting position (p less than 0.05), while tidal volume remained unchanged. We conclude that coronary artery bypass operations induce hypermetabolism and substantially increase ventilation and risk of arterial hypoxemia during the phase of compromised cardiovascular reserves.

Breathing pattern was studied non-invasively in 20 coronary artery bypass surgery patients before the operation and post-operatively after weaning from mechanical ventilation. Post-operatively minute ventilation (VE), breathing frequency (Fr) and mean inspiratory flow (VT/TI) increased (28%, 42%, 27%; p less than 0.01, p less than 0.001, p less than 0.01, respectively), while tidal volume (VT) decreased (15%, p less than 0.025). CO2 production (VCO2) and oxygen consumption (VO2) increased postoperatively (p less than 0.001 for both), contributing to the increase in ventilatory demand. Reduced variation of VT and Fr (p less than 0.001, p less than 0.01, respectively) and number of sighs (p less than 0.001) were characteristic of the post-operative breathing pattern. Post-operatively an increase in the contribution of rib cage (%RC) to tidal volume in the supine position was observed suggesting reduced motion of the diaphragm. All patients had atelectasis, 17 had pleural fluid and only 6 normal vascularity post-operatively. The shallow breathing in combination with increased ventilatory demand, impaired gas exchange and the surgical trauma of the thorax predispose to postoperative respiratory complications.

During the years 1977-1980, 47 patients with unstable angina pectoris underwent coronary artery bypass grafting within on an average 16 days after onset of angina. A total of 90 grafts were inserted (1.9 grafts per patient). There were no early deaths in patients operated on for unstable angina. Two late deaths (4.2%) occurred during a follow-up period varying between 14 and 62 months, mean 38 months. Two patients (2.1%) sustained perioperative infarction and two patients (4.2%), late myocardial infarction. All patients were symptomatically improved following operation and 32 (72.7%) are entirely asymptomatic. The authors conclude that patients with unstable angina pectoris can safely undergo early arteriography and semielective operation with results comparable to that for operation in patients with stable angina pectoris.

Reversed left internal mammary artery grafting with retrograde flow to the left anterior descending coronary branch was used in five of 500 consecutive bypass operations. The indications were significant stenosis in the left subclavian artery (3 patients) or the proximal left internal mammary artery (1) and proximal damage to the left internal mammary artery during dissection from the thoracic wall (1). The postoperative clinical course was smooth in all five patients, with no evidence of myocardial ischemia. In follow-up averaging 14 months four patients were asymptomatic. The reversed internal mammary artery graft was visualized with digital subtraction angiography in four cases. Radionuclide imaging during exercise confirmed graft patency in all but the symptomatic patient, who was found to have an area of reversible ischemia anteriorly in the left ventricle.

One hundred patients with high-risk unstable and medication-resistant angina pectoris underwent coronary artery by-pass grafting. In 35 cases the angina was of early post-infarction type, in 60 it was progressive after previous stability and in five it was of recent onset. All had abnormal ECG in association with anginal attacks (ST depression in 76, ST elevation in 5, T-wave inversion in 15 and left bundle branch block in 4). The left main coronary artery was stenosed in 33 patients, and the respective figures for three-vessel, two-vessel and one-vessel disease were 53, 9 and 5. The average number of inserted peripheral grafts/patient was 4.6. The perioperative mortality rate was 1%. Seven patients had confirmed or probable perioperative myocardial infarction and two had late infarction during the hospital stay, but none had angina pectoris on discharge. Of 60 patients re-examined after 1 year, 47 were angina-free. Five had NYHA class III angina, but all were improved. In refractory unstable angina pectoris there is severe coronary artery involvement, but bypass grafting can give good results.