Influence of PEEP ventilation immediately after cardiopulmonary bypass on right ventricular function

Abstract

Ventilation with positive end-expiratory pressure (PEEP) is often the appropriate therapy for treating patients with impaired pulmonary function after cardiac surgery procedures. Circulatory depression, however, sometimes limits the level of PEEP. This study was conducted to investigate the effects of PEEP ventilation (+15 cmH2O) immediately after weaning from cardiopulmonary bypass 1) period of PEEP application and 45 min thereafter; 2) period of PEEP application on right ventricular hemodynamics using a new thermodilution technique for measuring right ventricular ejection fraction (RVEF), right ventricular end-diastolic and end-systolic volumes (RVEDV, RVESV). Forty patients undergoing aortocoronary bypass grafting were retrospectively divided into two groups: group 1 (n = 24) in which RVEF was reduced significantly (40 → 28 percent), and group 2 (n = 16) in which EVEF remained almost unchanged. In patients in group 1, stenosis of the right coronary artery (RCA) was significantly more pronounced incomparison to the others and was detected to be responsible for the different reaction of RVEF (analysis of co-variance). Application of PEEP immediately after weaning from CPB was followed by an increase in RVESV (+4 percent; RVEDV -1 percent) in group 1, whereas patients of group 2 differed significantly (RVESV -14 percent; RVEDV -15 percent). Cardiac index was decreased only in group 1 (-32 percent). During the second period of PEEP application, no further difference could be observed between the groups. We conclude that hemodynamic changes related to PEEP ventilation are minimal in the intact right ventricle. Abnormalities in right ventricular function due to stenosis of the RCA, however, have had marked clinical influence on the circulatory response. Monitoring of right ventricular function seems to be of benefit for cardiac surgery patients in this situation.