EFFECT OF WATER AND SALINE LOAD ON URINARY OUTPUT IN HEALTHY UNDERGRADUATE MEDICAL STUDENTS

Abstract

ABSTRACT
Water and electrolyte balance is a vital homeostatic function. Their excretion depends on various factors –
state of hydration, plasma osmolarity etc. There are rare reports on effect of hypertonic solution on urinary
output. Therefore, the study aimed at investigating the effect of water or saline (especially the hypertonic)
load on urinary output (UO) in healthy undergraduate male medical students (17-20 years). They (n=20)
were randomised into 4 equal groups: control, water, normal and hypertonic saline (1.8%). The study was
a part of undergraduate practical conducted under controlled conditions in the Physiology Department,
BPKIHS. The day before the experiment, all of them were given same instructions. Next day, the experimental
groups drank water/saline solution 12 ml/kg. Then the UO was measured ½-hourly. A non-parametric –
Friedman test was used for intra- and inter-group differences in UO and specific gravity. The data are
presented as median (range). In water group the 60-min UO was significantly higher than the 30-min UO
[178.5 (24-415) vs. 22.5 (21-81) ml, p<0.05]. This group also had significantly higher UO than the control at
90-min [84 (20-250) vs. 19 (18-23) ml, p<0.05)]. The UO of normal-saline group was significantly higher
than that of control at 90-min [40 (22-250) vs. 19 (18-23) ml, p<0.05]. There was no significant difference in
specific gravity. The water and normal saline loads were adequate to elicit physiological response, the
hypertonic solution was not strong enough to show significant physiological response suggesting need of
saline load to be more than twice of the plasma osmolarity.

Key Words: homeostasis, water-electrolyte balance, salt load, water load.