Mc Nab et al, conducted a meta-analysis which included randomized controlled trials comparing isotonic vs hypotonic IV fluids as maintenance fluid in children involving 1109 children aged 3 months to 18 y. The intervention group received isotonic fluid (sodium >125 - 160 meq/l) while the other group received hypotonic fluid (sodium <125 meq/l). The primary outcome of the study was to measure proportion of patients in each treatment group with hyponatremia or hypernatremia at any time point while receiving intravenous fluids. Anti-diuretic hormone level, plasma and urine osmolarity, electrolytes were also measured. A total of 449 patients in the analysis received isotonic fluid, while 521 received hypotonic fluid. Those who received isotonic fluid had substantially lower risk of hyponatraemia (17% versus 34%; RR 0.48; 95% CI 0.38 to 0.60). It was not clear whether there is an increased risk of hypernatraemia when isotonic fluids are used (4% versus 3%; RR 1.24; 95% CI 0.65 to 2.38), although the absolute number of patients developing hypernatraemia was low.