Plasma volume expansion resulting from intravenous glucose tolerance test

Abstract

Objective. To quantify the degree of plasma volume expansion that occurs during an intravenous glucose tolerance test (IVGTT). Methods. Twenty healthy volunteers (mean age, 28 years) underwent IVGTTs in which 0.3g/kg of glucose 30% was injected as a bolus over 1min. Twelve blood samples were collected over 75min. The plasma glucose and blood hemoglobin concentrations were used to calculate the volume distribution (V d) and the clearance (C L) of both the exogenous glucose and the injected fluid volume. Results. The IVGTT caused a virtually instant plasma volume expansion of 10%. The half-life of the glucose averaged 15min and the plasma volume expansion 16min. Correction of the fluid kinetic model for osmotic effects after injection reduced C L for the infused volume by 85%, which illustrates the strength of osmosis in allocating fluid back to the intracellular fluid space. Simulations indicated that plasma volume expansion can be reduced to 60% by increasing the injection time from 1 to 5min and reducing the glucose load from 0.3 to 0.2g/kg. Conclusion. A regular IVGTT induced an acute plasma volume expansion that peaked at 10% despite the fact that only 50-80mL of fluid were administered. Copyright © 2011 Robert G. Hahn and Thomas Nystrm.