The influence of cardiopulmonary bypass on respiratory dysfunction in early postoperative period

Pulmonary dysfunction is one of the most serious problems in an early postoperative period after cardiac surgery. This study was designed to reveal the impact of performed cardiopulmonary bypass on pulmonary function during early postoperative period by evaluating the intrapulmonary shunt.

Twenty-one patients undergoing elective myocardial revascularization surgery were analyzed. The patients were divided into two groups. Group 1 included 11 patients who underwent cardiac surgery on cardiopulmonary bypass. Group 2 included 10 patients who underwent cardiac surgery without cardiopulmonary bypass. Preoperative data were similar in the both groups. Blood gas analysis for intrapulmonary shunt calculations was made at 20 minutes after the induction of anesthesia and at 4 hours after the surgery. Intrapulmonary shunt size (Qs/Qt) was also calculated and the records were studied for additional data.

At 4 hours after surgery Qs/Qt increased, compared to the preoperative data in Group 1 (from 8.6+/-2.1 to 16.8+/-2.6%, p<0.02). Intrapulmonary shunt was great in Group 1 compared with Group 2 at four hours after the surgery (16.8+/-2.6 and 7.8+/-2.1%, p<0.02). In Group 1 80 % of alterations in a pulmonary function were caused by atelectasis, detected by chest X-ray. In Group 2 no increase in intrapulmonary shunt and no atelectasis were determined.

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