[The influence of cardiopulmonary bypass on respiratory function in an early postoperative period]

To investigate the influence of cardiopulmonary bypass (CPB) on pulmonary function early after the operation by evaluating Qs/Qt.

Twenty one patients after elective myocardial revascularization surgery have been analysed. Group 1 included 11 patients who have undergone cardiac surgery with CPB. Group 2 included 10 patients who have undergone cardiac surgery without CPB. Blood gas analysis for intrapulmonary shunt calculations was made 20 minutes after the induction of anesthesia and 4 hours after surgery. Qs/Qt was also calculated.

Four hours after surgery Qs/Qt increased compared to preoperative data in group 1 (from 8.6 +/- 2.1 to 16.8 +/- 2.6%, p < 0.02). Intrapulmonary shunt was greater in group 1 vs group 2 four hours after the surgery (16.8 +/- 2.6 and 7.8 +/- 2.1%, p < 0.02). In group 1, alterations in a pulmonary function (81.8%) were caused by atelectasis detected by chest x-ray. In group 2 neither increase in intrapulmonary shunt nor atelectasis were determined.

Arterial hypoxemia and an increase in the intrapulmonary shunt (due to atelectasis) have proven that alterations in the pulmonary function occur more often and are more pronounced in patients after surgery with cardiopulmonary bypass.