Perioperative monitoring of circulating and central blood volume in cardiac surgery by pulse dye densitometry

OBJECTIVE: To determine perioperative changes in circulating (BVI) and central blood volume (CBVI) by a new dye dilution technique using pulse dye densitometry. DESIGN AND SETTING: Prospective observational study in the cardiac anesthesia and intensive care unit of a university hospital. PATIENTS: Sixty-six patients undergoing coronary artery bypass surgery. MEASUREMENTS AND RESULTS: Hemodynamic measurements by the dye dilution method using pulse dye densitometry were performed prior to skin incision and 3.3+/-1.4 h and 17+/-2.7 h after surgery. Based on conventional monitoring the therapeutic goals of hemodynamic therapy were achieved in all of the patients of this study. Despite a marked positive fluid balance which developed during surgery mean BVI decreased significantly after surgery while CBVI remained unchanged. Postoperative BVI deficits vs. preoperative values were observed in 78% of patients; these BVI deficits were profound in 29% of the cases. In contrast, 65% of the individual patients showed no or only minor postoperative changes in CBVI vs. preoperative values. CONCLUSIONS: Changes in the intravascular volume compartments affected BVI to a greater extent than CBVI. Therefore measuring circulating in addition to central blood volume may be useful to ensure a normal circulating blood volume that can compensate for any change in the central vascular compartment.