[Cardiorespiratory and microcirculatory effects following volume replacement using a new hydroxyethyl starch preparation].

Volume therapy is often necessary in cardiac surgery to maintain stable haemodynamics. Various different hydroxyethyl starch (HAES) solutions with different concentrations, mean molecular weights, and degrees of substitution are available for this purpose. In determining the ideal type of volume therapy, not only changes in macrohaemodynamics, but also the influence on microcirculatory blood flow have to be taken into account. The efficacy of a new 10% HAES 130/0.5 solution was studied in cardiac surgery patients in comparison to a standard 10% HAES 200/0.5 preparation. METHODS. In patients scheduled for elective aortocoronary bypass grafting who had a pulmonary capillary wedge pressure (PCWP) of less than 4 mm Hg after induction of anaesthesia, either a new 10% HAES 130/0.5 (n = 15) or a standard 10% HAES 200/0.5 solution (n = 15) was infused to double the reduced PCWP; 15 patients without volume therapy served as controls (n = 15). A two-channel laser Doppler skin blood-flux monitor was used to evaluate microcirculatory alterations. Measurements of laser Doppler flux (LDF) was simultaneously performed at the patient's forehead and forearm before and after volume infusion as well as during and after cardiopulmonary bypass (CPB). In addition, changes in gross haemodynamics were documented using a pulmonary artery catheter. Plasma viscosity and various laboratory parameters, including calculation of intrapulmonary right-to-left shunting (Qs/Qt), were also measured. RESULTS. Cardiac index (CI) increased in both volume groups (HAES 130: max. +38%; HAES 200: +55%). The increases in PCWP and CI were maintained at 40 min after volume infusion only in the HAES 200 patients. Systemic vascular resistance (SVR) decreased most markedly after infusion of HAES 200 (-34%; HAES 130: -18%). No further differences in gross haemodynamics could be seen after CPB. Plasma viscosity and colloid osmotic pressure increased in both HAES groups without significant differences. During the entire investigation period, pulmonary gas exchange (paO2) and Qs/Qt did not differ between the groups. Infusion of both HAES solutions resulted in an increase in LDF that was most pronounced after infusion of HAES 200 (forehead LDF: +81%; HAES 130: +18%) and was evident in the post-bypass period only in these patients (LDF: HAES 200: +82%; HAES 130: -20%; control: -43%). No correlation between LDF values and the other haemodynamic and laboratory parameters could be demonstrated. CONCLUSION. The improvement in macrohaemodynamics was of shorter duration after infusion of the new HAES 130 solution than after standard HAES 200. Volume replacement with HAES 200 resulted in an increase in microcirculatory blood flow that was more pronounced and of longer duration than in the HAES 130 patients. Thus, HAES 130 seems to be less effective than HAES 200 for volume replacement; HAES 200 should be preferred in patients undergoing cardiac surgery.