Post-Op Fluids Key to Sodium Levels in Children

By John Gever, Senior Editor, MedPage Today
Abnormally low sodium levels were much more common in children recovering from surgery when they were given hypotonic maintenance fluids, rather than isotonic fluids, according to the results of a randomized, controlled trial.

The relative risk for hyponatremia associated with hypotonic fluids in the 258-patient trial was 1.82 (95% CI 1.21 to 2.74) compared with isotonic fluids, reported Karen Choong, MB, of McMaster Children's Hospital in Hamilton, Ontario, and colleagues online in Pediatrics.

Some 41% of children in the study developed hyponatremia when given the hypotonic fluids -- the current standard of care for children postoperatively -- versus 23% of those receiving isotonic fluids. That worked out to a number-needed-to-treat of six for isotonic fluids to prevent one case of hyponatremia, the researchers indicated.

"The results of this trial indicate that the current standard for postoperative fluid and electrolyte management for pediatric patients should change," Choong and colleagues concluded.

In an accompanying editorial, two pediatric nephrologists agreed.

"There can no longer be any justification for the routine administration of hypotonic fluids in hospitalized children," wrote Michael L. Moritz, MD, of the University of Pittsburgh, and Juan Carlos Ayus, MD, of Renal Consultants of Houston. They added, "the FDA should review the existing literature on hypotonic fluids and issue a warning about the dangers associated with its use."

As the trial results indicated, hyponatremia is a common occurrence in hospitalized children and especially in those who have undergone surgery.

Hypotonic maintenance fluids have gained currency under a theory that isotonic fluids pose too much risk for excessive sodium and its consequences, such as interstitial fluid overload and hyperchloremic metabolic acidosis.

In the trial, euvolemic patients from 6 months to 16 years old undergoing elective surgery were randomized to fluids with 0.45% saline (hypotonic) or 0.9% saline (isotonic) on a double-blind basis. About 40% of enrolled patients were undergoing orthopedic surgery. Other types of procedures included urologic, plastic, otolaryngologic, and general. Fluids were started as soon as possible after surgery and given for a maximum of 48 hours. Plasma sodium and anti-diuretic hormone (ADH) were monitored.