Influence of hypertonic volume replacement on the microcirculation in cardiac surgery

We have studied the effects of two types of volume replacement on the microcirculation in an open, controlled study in 45 patients undergoing aorto-coronary bypass grafting whose pulmonary capillary wedge pressure (PCWP) was less than 5 mm Hg. Hypertonic saline prepared in hydroxyethylstarch solution (HS-HES, n = 15) and 6% HES 200/0.5 solution (6% HES; n = 15) were infused randomly before operation in order to double the PCWP. Patients not given an infusion served as controls (n = 15). Skin microcirculatory blood flow was investigated by laser Doppler flow (LDF) measured simultaneously at the forearm and forehead before and after cardiopulmonary bypass (CPB). Less HS-HES (3.8 (SD 0.3) ml kg-1) than 6% HES-solution (9.7 (1.5) ml kg-1) was necessary to double baseline PCWP. There were no differences in heart rate and mean arterial pressure (MAP) between the groups. Cardiac index (CI) increased significantly in both volume groups (HS-HES max. +54%; 6% HES max. +30%). Systemic vascular resistance (SVR) decreased after infusion of HS-HES (-30%) and after 6% HES(-19%) and remained almost unchanged in the control group. Plasma viscosity decreased after infusion of HS-HES and increased slightly in control patients (+4%). In comparison with the 6% HES and particularly with the control group, LDF was significantly greater after infusion of HS-HES (forearm +80%; forehead +28%). LDF during CPB and thereafter was always greater than baseline values in the HS-HES group, whereas after bypass LDF was reduced in the 6% HES (-5%) and particularly in the control patients (-30%).(ABSTRACT TRUNCATED AT 250 WORDS)