The effect of an oral glucose load on sodium and water excretion after rapid intravenous infusion of 0.9% (w/v) saline.

BACKGROUND & AIMS: Previous studies have suggested that oral or intravenous glucose enhances salt and water retention following a saline load. To test this, we studied the effects of an oral glucose load on urinary sodium and water excretion and serum biochemistry in response to a 2l intravenous infusion of 0.9% saline in normal subjects.

METHODS

A crossover study was conducted on six male volunteers. On one occasion, they received 2l 0.9% saline intravenously over 1h. A week later, they were given 100ml 50% dextrose orally prior to the same infusion. Subjects passed urine before start of the infusion. Body weight, haematocrit and serum biochemistry were recorded preinfusion and hourly for 6h. Urine was collected for 6h postinfusion and analysed for sodium, potassium and osmolality.

RESULTS

The six subjects had a mean (SE) age of 20.9 (0.4) years and BMI of 22.7 (0.2). Median (IQR) water balance over 6h was 1462 (1005-1650)ml after saline and 1203 (989-1735)ml after glucose and saline (NS). Urinary sodium and potassium excretion on the two occasions over 6h were 76 (69-111) vs 74 (92-174)mmol and 31 (29-40) vs 30 (20-36)mmol, respectively (NS). Using repeated measures testing, there was no significant difference in body weight, haematocrit, serum albumin, sodium, potassium, chloride, osmolality and blood glucose measured at hourly intervals on the two occasions.

CONCLUSIONS

In contrast to previous literature, in normal subjects, an additional oral glucose load does not appear to have an effect on urinary sodium excretion or serum biochemistry after a rapid 2l infusion of 0.9% saline. This does not preclude an effect under conditions of prior starvation or injury.