Changes in body composition, hematologic parameters, and serum biochemistry after rapid intravenous infusion or oral intake of 2 liters of 0.9% saline solution in young healthy volunteers: randomized crossover study.

BACKGROUND

The perioperative infusion of 2 L of saline is associated with weight gain and decreased serum albumin and hematocrit. We hypothesized that these parameters would respond differently to oral administration and intravenous infusion of saline solution.

METHODS

This was a crossover study that included 10 healthy young men (ages 18-26 years). At two times, 8 weeks apart, the participants were randomized to receive 2 L of 0.9% saline over 1 h by intravenous (IV) administration to a forearm vein or by oral intake. The participants were weighed and body masses were calculated. Bioelectrical impedance analysis was performed with a single-frequency device using tetrapolar distal limb electrodes. Blood samples were collected 1 h after the administration period for laboratory assays: hematocrit, hemoglobin, blood glucose, serum electrolytes, albumin, creatinine, osmolality.

RESULTS

There was an increase in body weight (p<0.01), total body water (p<0.01), and lean body mass (p<0.01) after the experiment in both groups, with no difference between them. The volume of urine output was similar in the two experiments. The hemoglobin (oral group from 14.4±0.8 g/dl to 13.8±0.8 g/dl; IV group from 14.4±0.6 g/dl to 12.6±0.6 g/dl) and hematocrit (oral group from 43.2±1.8% to 43.2±2.8%; IV group from 43.6±2.2% to 40.0±2.6%) significantly decreased (p<0.01) with IV saline. Serum albumin remained stable after oral intake but significantly decreased (p=0.04) after IV infusion.

CONCLUSIONS

Oral intake of 2 L of 0.9% saline results in minimal variations in serum albumin, hemoglobin, and hematocrit when compared to IV infusion of the same volume.