Coulthard et al, conducted a randomized controlled trial involving 82 patients undergoing spinal instrumentation, craniotomy for tumor resection or cranial vault remodelling. Children were randomized to receive Hartman's solution with 5% dextrose or 0.45% saline with 5% dextrose. The primary outcome was to measure sodium at 16-18 hours postoperatively. Thirty nine children received Hartman's solution and 40 received hypotonic saline. The result showed mean postoperative plasma sodium levels of children receiving 0.45% saline and 5% dextrose were 1.4 mmol/l (95% CI [0.4 to 2.5]) lower than those receiving Hartmann's and 5% dextrose (p=0.008). In the 0.45% saline group, seven patients (18%) became hyponatraemic (Na <135 mmol/l) at 16-18 postoperatively; in the Hartmann's group no patient became hyponatraemic (p=0.01). No child in either fluid group became hypernatraemic.