Many children in hospital need fluid through an intravenous line (or 'drip') because they cannot eat or drink enough and they need to remain hydrated. This fluid can cause rare but serious side effects due to the salt level in the body decreasing. When the salt level in the body decreases quickly brain swelling can occur, which can result in death.
There has been uncertainty regarding how much salt the intravenous fluid should contain.
Traditionally, fluids containing lower salt levels than blood (hypotonic) have been administered. This analysis compared these fluids with fluid containing a similar salt level to blood (isotonic). We aimed to determine how many patients had low salt levels in the blood when an isotonic fluid was used compared with a hypotonic fluid.
Studies conducted prior to 17 June 2013 were reviewed. We included 10 studies in the analysis, involving a total of 1106 children. When isotonic fluids were used, the sodium level in the body was less likely to be low. One hundred and sixty-nine children per 1000 had low sodium levels in the blood when an isotonic fluid was given, compared with 338 children per 1000 when a hypotonic fluid was used. The results for serious adverse events associated with isotonic or hypotonic fluids were uncertain.
This review mainly looked at patients who either had surgery and/or were in intensive care, with most only needing intravenous fluid for less than a day.
Quality of the evidence
The studies included were generally well conducted and were of a high quality.
Isotonic intravenous maintenance fluids with sodium concentrations similar to that of plasma reduce the risk of hyponatraemia when compared with hypotonic intravenous fluids. These results apply for the first 24 hours of administration in a wide group of primarily surgical paediatric patients with varying severities of illness.
Maintenance intravenous fluids are frequently used in hospitalised children who cannot maintain adequate hydration through enteral intake. Traditionally used hypotonic fluids have been associated with hyponatraemia and subsequent morbidity and mortality. Use of isotonic fluid has been proposed to reduce complications.
To establish and compare the risk of hyponatraemia by systematically reviewing studies where isotonic is compared with hypotonic intravenous fluid for maintenance purposes in children.
Secondly, to compare the risk of hypernatraemia, the effect on mean serum sodium concentration and the rate of attributable adverse effects of both fluid types in children.
We ran the search on 17 June 2013. We searched the Cochrane Injuries Group Specialised Register, Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), MEDLINE (OvidSP), Embase (OvidSP), and ISI Web of Science. We also searched clinical trials registers and screened reference lists. We updated this search in October 2014 but these results have not yet been incorporated.
We included randomised controlled trials that compared isotonic versus hypotonic intravenous fluids for maintenance hydration in children.
At least two authors assessed and extracted data for each trial. We presented dichotomous outcomes as risk ratios (RR) with 95% confidence intervals (CIs) and continuous outcomes as mean differences with 95% CIs.
Ten studies met the inclusion criteria, with a total of 1106 patients. The majority of the studies were performed in surgical or intensive care populations (or both). There was considerable variation in the composition of intravenous fluid, particularly hypotonic fluid, used in the studies. There was a low risk of bias for most of the included studies. Ten studies provided data for our primary outcome, a total of 449 patients in the analysis received isotonic fluid, while 521 received hypotonic fluid. Those who received isotonic fluid had a substantially lower risk of hyponatraemia (17% versus 34%; RR 0.48; 95% CI 0.38 to 0.60, high quality evidence). It is unclear 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, nine studies, 937 participants, low quality evidence), although the absolute number of patients developing hypernatraemia was low. Most studies had safety restrictions included in their methodology, preventing detailed investigation of serious adverse events.