Estimation of splanchnic blood flow by the Fick principle in man and problems in the use of indocyanine green.

OBJECTIVES

Measurement of splanchnic blood flow is necessary to evaluate the effect of therapeutic interventions on splanchnic tissue perfusion. Systemic indocyanine green (ICG) clearance has been used to estimate splanchnic blood flow, but the results may be compromised by altered hepatic dye extraction. We evaluated the applicability of simultaneous estimation of splanchnic and femoral blood flow by dye dilution and regional blood sampling in intensive care patients.

METHODS

240 simultaneous determinations of regional blood flow were conducted in different patient groups (cardiac surgery, ARDS, pancreatitis, septic shock, preoperative controls). The measurement protocol consists of catheterizations of hepatic vein, femoral artery and vein and primed constant infusion of two different ICG preparations.

RESULTS

The method was used successfully in a wide variety of patients. Steady-state dye concentration and sufficient dye extraction was achieved in each group of patients. The coefficient of variation of splanchnic blood flow estimation was 7 +/- 1% and of femoral blood flow estimation 6 +/- 0%. There was a great intra- and interindividual variation of ICG extraction. Use of dobutamine modified the extraction in most patients but did not lessen the performance of the method. ICG extraction was markedly lower and the coefficient of variation of both femoral and splanchnic blood flow markedly higher with propylene glycol-dissolved ICG preparation as compared with the freeze-dried.

CONCLUSIONS

The prerequisites for the method of primed, constant infusion of indocyanine green with hepatic vein catheterization are achieved in intensive care patients. The results of splanchnic blood flow estimations based on techniques with peripheral blood sampling should be interpreted with caution, and the use of ICG clearance as a flow-related indicator without the measurement of ICG extraction cannot be justified because of the great variability of dye extraction. Certain indocyanine green preparations may greatly modify the results of the regional blood flow determinations.