Plasma Volume Expansion Resulting from Intravenous Glucose Tolerance Test

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 0.3 g/kg of glucose 30% was injected as a bolus over 1 min. Twelve blood samples were collected over 75 min. The plasma glucose and blood hemoglobin concentrations were used to calculate the volume distribution (V(d)) and the clearance (CL) 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 15 min and the plasma volume expansion 16 min. Correction of the fluid kinetic model for osmotic effects after injection reduced CL 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 5 min and reducing the glucose load from 0.3 to 0.2 g/kg. CONCLUSION A regular IVGTT induced an acute plasma volume expansion that peaked at 10% despite the fact that only 50-80 mL of fluid were administered.