NEW YORK (Reuters Health) – In children having surgery, isotonic parenteral maintenance fluids (PMS) are safer than hypotonic PMS in guarding against postoperative hyponatremia, with six the number needed to treat to prevent one case.

The findings from a randomized controlled study appear in the November issue of Pediatrics.

“The results of this trial confirmed our hypothesis that the current recommendations for routine use of hypotonic fluids in children are inappropriate,” first author Dr. Karen Choong, Associate Professor, Pediatrics and Critical Care Medicine, McMaster University, Hamilton, Ontario, Canada, told Reuters Health.

She noted that this issue has been “furiously debated” in the pediatric literature in recent years. “Part of the problem,” she said, “is that prior to 2006, there was very little evidence, and what available published evidence existed was limited in scope and quality.”

The current study, Dr. Choong said, is the largest pediatric trial of its nature to date, and the findings are consistent with other recent studies. “This emerging evidence should prompt a critical review and update of the current fluid practice guidelines in children, such that we can continue to provide the safest and best evidence based care for our children,” the investigator said.

The study included 258 surgical patients 6 months to 16 years old with an expected postoperative stay of more than 24 hours; 130 were randomly assigned to receive hypotonic PMS (0.45% saline) and 128 to receive isotonic PMS (0.9% saline) for 48 hours following surgery. Baseline characteristics were similar in the two groups.

According to the researchers, the risk of hyponatremia was greater in those who received hypotonic PMS (40.8% vs 22.7%; relative risk, 1.82). Eight patients (6.2%) in the hypotonic PMS group developed severe hyponatremia, compared with one patient (0.8%) in the isotonic group (relative risk, 7.21).

There was no evidence that sicker patients were at increased risk of hyponatremia after adjusting for PMS type and isotonic PMS did not increase the risk of hypernatremia.

In addition, the researchers say the findings confirm that ADH levels are elevated in children after surgery and that isotonic PMS is a safer empiric choice for preventing potential harm.

Dr. Choong said, “The use of hypotonic fluids in children has been dogma and standard of practice for over 50 years, and this study demonstrates why it is so important to perform research on practices that we take for granted on the basis of historical evidence.”

“We now have confirmatory evidence that isotonic fluids are safer than hypotonic fluids, at least in children, after surgery,” Dr. Choong said. “Most importantly, however, clinicians should not assume that ‘one size fits all’ – we should have the same respect for intravenous fluids as we have for any drug that we prescribe, and therefore individualize our prescriptions to each patient’s needs.”

In their paper, the authors note that they did not include patients who required emergency surgery, which limits the generalizability of the results for that population, although there is no evidence to suggest that that group of patients might behave differently.

Reference:

Hypotonic Versus Isotonic Maintenance Fluids After Surgery for Children: A Randomized Controlled Trial

SOURCE: Pediatrics 2011;128:857-866.

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