Intraoperative changes in extravascular lung water. Study on heart surgery patients

The intraoperative changes in extravascular lung water (EVLW) were studied in 40 patients undergoing aortic-coronary bypass grafting. The patients were divided into two groups on the basis of preoperative ejection fraction (EF) values (group I: EF greater than 45%; group II: EF less than 45%). EVLW was measured using the double-indicator dilution method (thermo/dye). In a control study, changes in transthoracic impedance (ZoTh) were recorded. The initial EVLW value in group I was 4.3 +/- 0.4 ml/kg body wt. and in group II, 4.4 +/- 0.3 ml/kg body wt. After extracorporeal circulation, significant changes in EVLW could be observed (group I: from 4.5 +/- 0.5 ml/kg body wt. to 7.0 +/- 0.2 ml/kg body wt.; group II: from 5.1 +/- 0.8 ml/kg body wt. to 7.8 +/- 0.9 ml/kg body wt. (p less than 0.001). At the end of the operation, no changes in EVLW were observed in group I. However, in group II EVLW was significantly different to initial values (6.3 +/- 1.0 ml/kg body wt., p less than 0.01). The results obtained using the double-indicator method were identical with those obtained using the transthoracic impedance method. A marked correlation could be seen between length of ECC recording and EVLW values at the end of the operation, especially when the ECC time was 90 min or more (r = 0.84). Based on our results, it must be assumed that intraoperative damage to capillary membranes occurs if the ECC time is above 90 min.