Glucose dilution can detect fluid redistribution following phentolamine infusion in dogs.

OBJECTIVE

We have recently reported that the initial distribution volume of glucose (IDVG) reliably measures the central extracellular fluid (ECF) volume in the presence of fluid gain or loss. However, it is not clear if IDVG consistently reflects central-ECF volume when redistribution of fluid occurs in the absence of fluid gain or loss. This study was designed to investigate changes in fluid volumes during phentolamine infusion in dogs.

DESIGN

Prospective animal study.

SETTING

Institutional animal research laboratory.

SUBJECTS

Fourteen anesthetized and ventilated mongrel dogs.

INTERVENTIONS

Anesthetized animals were mechanically ventilated and received infusions of normal saline (n = 7) or phentolamine (10 microg kg min) (n = 7). Plasma volume was estimated using the indocyanine green (ICG) dilution method (PV-ICG) and IDVG was calculated using a one-compartment model by simultaneous administration of ICG 0.5 mg/kg and glucose 100 mg/kg before, during, and after infusion of either drug.

MEASUREMENTS AND RESULTS

PV-ICG during infusion was not different between groups. However, IDVG significantly decreased (P < 0.05) following phentolamine infusion when compared with normal saline infusion.

CONCLUSION

Our results suggest that IDVG rather than PV-ICG consistently measures central extracellular fluid volume, even when redistribution of fluid occurs.