Volume replacement after cardiac surgery: a comparative study between hydroxyethylstarch (6%, 70/0.5), gelatin (3.5%) and Ringer's solution

Introduction

During hypothermic cardiopulmonary bypass (CPB) patients often experience vasoconstriction and later their peripheral circulations gradually dilate over a period of several hours. The redistribution of circulation produces hypovolemia for which volume loading is necessary. Our aim was to compare 6% hydroxyethylstarch (70/0.5), 3.5% polygelin and Ringer's solution when used for volume restoration during the first 6 h after CPB. We were especially interested in hemodynamic stability, plasma viscosity, bleeding, volume uptake and oxygenation index (PaO₂/FiO₂).

Methods

Ninety adult patients undergoing cardiac surgery and CPB were randomized before surgery to one of three fluid regimens. The groups were comparable with respect to age, sex, heart function and pre-existing diseases. Hemodynamic function, plasma viscosity, mediastinal blood loss, and volume uptake were measured after 30 min, 60 min postoperatively and then every hour during the first 6 h after surgery. The oxygenation index was measured 1, 3 and 6 h after surgery. A P value <0.05 was considered significant.

Results

There were no significant intergroup differences in any of the hemodynamic variables MAP, CVP and HR. There was no significant difference among the three groups in the plasma viscosity after surgery. Mediastinal blood flow increased significantly in the HES group 2–6 h after surgery (P < 0.05) compared with the geline and Ringer's group. The two colloid groups needed significantly less fluid compared with the Ringer's group (P<0.05). There were no differences in diuresis. There were no significant intergroup differences in the oxygenation index. The need for postoperative ventilatory support did not vary between the three groups.

Conclusion

This randomized comparison of two colloid and a Ringer's solution fluid regimens after cardiac surgery shows that there is no difference in hemodynamic stability, plasma viscosity, oxygenation index and duration of intubation. The HES group has a significantly higher blood loss. The Ringer's group has a significant higher volume uptake. The colloid-free regimen did not affect the pulmonary function.

The colloid-free Ringer's solution regimen is clinically fully acceptable and economically more favourable than the two colloid fluid regimens studied.