The variation of volume expansion after infusion of hydroxy ethyl starch 6% in critically ill patients

Background and objectives

Knowledge of the volume expanding effect of colloids is essential in many intensive care unit (ICU) patients. This volume expanding effect is usually evaluated by indirect methods [eg arterial blood pressure, central venous pressure, pulmonary capillary wedge pressure (PCWP), cardiac output, hematocrit and diuresis], albeit these methods only correlate poorly to direct measurements. The scarce amount of data so far available is mainly due to the rather cumbersome methods for direct determination of circulating blood volume (CBV) in ICU patients. We have used a modification of the carbon monoxide (CO) method for estimation of CBV enabling quick bedside determinations. The aim of this study was to evaluate the interindividual variation of volume expansion during the first 8 h after infusion of 500 ml HES 6% in critically ill patients.

Methods

In 20 consecutive patients admitted to the ICU requiring mechanical ventilation and volume expansion. In each patient 500 ml of HES 6% was infused during a period of 30 min. The CBV was measured immediately before the infusion and hourly for 8 h. During this period all efforts were made to keep the fluid balance unchanged.

Results

The mean volume expansion measured immediately after infusion 500 ml HES 6% was 476 ± 310 ml (2SD). The corresponding values after 4 and 8 h were 241 ± 248 ml (2SD) and 104 ± 358 ml (2SD), respectively. The coefficient of variation of the method for estimation of CBV was 3.6%.

Conclusion

The large interindividual variation of the volume expansion after infusion of HES 6% in critically ill patients illustrates the difficulties in optimizing colloid therapy without a direct measurement of the CBV.