A prospective trial comparing isotonic with hypotonic maintenance fluids for prevention of hospital-acquired hyponatraemia

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Background:Recent literature suggests that hypotonic fluids increase the risk of hospital-acquired hyponatraemia; despite this, hypotonic fluids are widely used.Objectives:To compare the change in serum sodium following the use of hypotonic (0.3% saline, 0.45% saline) or isotonic (0.9% saline) intravenous (IV) maintenance solutions in hospitalised children.Study design:This was a randomised controlled trial. Children aged 3 months to 15 years with medical or surgical disorders were randomised to receive one of three maintenance IV fluids: two hypotonic solutions (3.3% dextrose in 0.3% saline or 5% dextrose in 0.45% saline) and one isotonic solution (5% dextrose in 0.9% saline). The primary outcome was serum sodium levels at 8 hours. Secondary outcomes included the incidence of hospital-acquired hyponatraemia, adverse events attributable to IV solutions and length of hospital stay.Results:151 children were assigned randomly to receive 0.3% saline (n = 49), 0.45% saline (n = 50) or 0.9% saline (n = 52). Baseline characteristics were similar for the three groups. At 8 hours, mean (SD) serum sodium was lower in the hypotonic solutions groups [0.3% saline 134.65 (1.9) mmol/L, 0.45% saline 134.90 (2.3) mmol/L than 0.9% saline 137.98 (2.8) mmol/L] (P < 0.0001). The incidence of hospital-acquired hyponatraemia was higher in the hypotonic groups [0.3% saline 10/49 (20.4%), 0.45% saline 11/50 (22%) than 0.9% saline 1/52 (1.9%), P = 0.006). There were no differences in other adverse effects or length of hospital stay between the groups.Conclusion:Hypotonic IV solutions increase the incidence of hospital-acquired hyponatraemia. Isotonic solutions are a safer alternative.