Is it feasible to monitor total hepatic blood flow by use of transesophageal echography? A validation in patients

Objective

In critically ill patients total hepato-splanchnic blood flow is usually determined using a primed continuous infusion of indocyanine green (ICG) with hepatic venous sampling [1]. The hepatic venous catheterisation, however, is an invasive procedure and we could recently demonstrate in an animal model that hepato-splanchnic blood flow could be reliably determined with transesophageal echocardiography (TEE) [2]. In this study we investigated whether transesophageal echocardiography is a noninvasive method for bedside assessment of hepatic venous blood flow in clinical practice.

Patients and Methods

Thirteen anesthetized and ventilated critically ill patients in whom hepato-splanchnic blood flow was augmented by a dobutamine infusion were studied.

Hepatic venous blood flow values were derived with TEE using the following calculations: Diameter (d) and velocity time integral (VTI) of all three hepatic veins were determined by TEE, heart rate (HR) was derived from ECG and flow subsequently calculated as Q = p (d/2)² 0.57 VTI HR [2]. These values were compared with hepato-splanchnic blood flow (Qspl) measurements using a primed (12 mg) continuous (0.5 mg/min) infusion of indocyanine green with hepatic venous sampling as described before in detail [1]. Parameters were determined at baseline as well as after modulating splanchnic blood flow by the infusion of dobutamine.

Results

A significant increase in splanchnic blood flow could be determined with TEE (438 [387-555] vs 559 [495-709] ml/min/m²) as well as using the ICG-method (889 [370-2285] vs 1098 [684-3479] ml/min/m²). The Spearman correlation coefficient between both methods, however, was 0.77 at baseline and 0.63 after dobutamine-infusion.

Conclusion

The values of splanchnic blood flow determined by the two different methods had a great variance. TEE, hence, does not seem to offer a noninvasive approach for monitoring changes in hepato-splanchnic blood flow in critically ill patients.