CONTINUOUS BLOOD DENSITY-MEASUREMENTS AND VOLUME CHANGES DURING EXTRACORPOREAL-CIRCULATION IN PATIENTS UNDERGOING CARDIAC-SURGERY

The changes of blood volume and transcapillary fluid shifts during ext racorporeal circulation (ECC) was examined using continuous measuremen ts of blood density by the mechanical oscillator technique. Sixteen pa tients (1 female, 15 male) with a mean age of 61.4 years (+/-7.6 years , 47-70 years) undergoing coronary artery bypass surgery were included in this study. The equipment for continuous measurement of the blood density (DPRT by Paar/Austria) was installed at the arterial line of t he heart-lung bypass. Higher-precision discrete measurements of some p arameters used the DMA 55 equipment produced by the Paar company. Meas urements were taken at 37 degrees C. In 11 patients the transcapillary volume loss (difference of total volume between beginning and end of ECC) during heart-lung bypass (mean observation period of 55 min (+/- 16 min, 28-82 min) was found to be 870 ml/m(2) body surface area (BSA) (+/- 360 ml, 290-1560 ml/m(2)) by the dilution method using the primi ng solution at the beginning and 500 mi lactated Ringer's solution add ed at the end of the ECC. The calculated volume shift using the ''doub le density method'', which takes into account blood density, plasma de nsity, and hematocrit, amounted to 830 ml/m(2) BSA (+/- 200 ml, 450-12 10 ml/m(2)). The density of the transcapillary volume loss into the in terstitial layer was calculated and found to be 1.0026 g/ml (+/- 0.001 7 g/ml, 1.0003-1.0063 g/ml). A significant difference of transcapillar y volume shift correlated with the administered catecholamine (dopamin e, dobutamine) dosage postoperatively. Without catecholamine this diff erence was 260 ml/m(2) BSA, with 3 mu m/kg/min dopamine it rose to > 5 00 ml/m(2) BSA. The mechanical oscillator technique allows the measure ment of blood volume shifts during cardiopulmonary bypass in order to monitor the course of the ECC and the transcapillary volume shift with out increasing the stress on the patient.