Review: hypotonic solutions increase acute hyponatraemia in children receiving standard intravenous maintenance therapy
Q In children receiving standard intravenous (IV) maintenance therapy in hospital, what is the relative safety of hypotonic and isotonic solutions?
Medline, EMBASE/Excerpta Medica (to 2006), Cochrane Library, Current Controlled Trials, conference proceedings and abstracts, reference lists, personal files, and experts in the field.
Study selection and assessment:
controlled trials, cohort studies, and case-control studies that evaluated adverse events (acute plasma sodium derangements and their attributed morbidity) associated with use of hypotonic (containing <0.9% sodium chloride) or isotonic (containing 0.9% sodium chloride or Ringers Lactate) IV maintenance solutions in children 1 month to 17 years of age who had been admitted to hospital for any medical or surgical condition. Patients with pre-existing hyponatraemia or comorbidities that result in sodium derangements were excluded. 6 studies (2 randomised controlled trials, 1 non-randomised controlled trial, 2 cohort studies, and 1 case-control study) (n = 404) met the selection criteria. Quality assessment of individual studies was based on criteria appropriate for the study design.
hyponatraemia (plasma sodium concentration <136 mmol/l), post-treatment plasma sodium concentration, mean change in plasma sodium concentration, and adverse events.
Children who received hypotonic IV maintenance solutions had a greater risk of hyponatraemia than those who received isotonic solutions (table). The mean post-treatment plasma sodium concentration was lower and the mean decrease in plasma sodium concentration (after treatment v before treatment) was greater in the hypotonic group than in the isotonic group (table). Seizures (1 cohort study, n = 56) and increased pulmonary interstitial fluid (1 cohort study, n = 24) were reported more frequently in children receiving hypotonic solutions, but the differences were not significant because of small sample sizes.
In children receiving standard intravenous maintenance therapy in hospital, hypotonic solutions increase the risk of acute hyponatraemia more than isotonic solutions.
- Jennifer Yost, RN, MA
For children who are at risk of fluid and electrolyte imbalances, the current recommendation, based on a publication from 1957, is the prescription of hypotonic IV maintenance solutions.1 However, concern has arisen that this practice may contribute to hyponatraemia and its harmful effects on patient outcomes.
The review by Choong et al has several strengths: a clearly focused clinical question, comprehensive search strategy, specific inclusion and exclusion criteria, and quality assessment by multiple reviewers using standardised tools. However, the review has several limitations. The authors noted the heterogenous designs and variable quality of studies included in the review. In addition, defining hyponatraemia as plasma sodium concentrations <136 mmol/l might have affected the results of the review; normal sodium concentrations are widely documented as ranging from 135–145 mmol/l.2,3 Furthermore, inclusion of a large study with a population comprising patients with gastroenteritis and dehydration might have affected the results of the review. The current standard of practice is to treat patients who are severely dehydrated with isotonic solutions when oral rehydration is not possible;4 thus, treatment with hypotonic solutions would be inappropriate and could affect serum sodium concentrations.
The findings of the review by Choong et al validate challenges to the current standard of practice of prescribing hypotonic solutions in children. However, given the strengths and weaknesses of the review and the individual studies, Choong et al are correct in their conclusion that changes to this standard of practice should not be adopted until more rigorous clinical trials comparing different types of IV fluid therapy in children are completed.
For correspondence: Dr K Choong, Department of Paediatrics, McMaster University, Hamilton, Ontario, Canada.
Source of funding: not stated.