Intravenous fluids are as much a part of the hospital experience as those oh-so-flattering gowns that open in the back. But while there's little variation in gown design, physicians have considerable choice when it comes to IV fluids. And which fluid to choose – particularly the liquid's sodium content - has become a source of controversy in pediatric healthcare.
The two basic fluid varieties are hypotonic, which is relatively low in sodium compared to blood, and isotonic, with approximately the same sodium level as blood.
Hypotonic IV fluid has long been the standard of care when it comes to delivering maintenance fluids in hospitalized children. It might seem odd that a fluid with less sodium than a child’s blood naturally contains would be the fluid of choice, but doctors in the 1950s had calculated that hypotonic fluids had the optimal composition for maintaining fluid and electrolyte levels.
Concern has been growing, though, about the number of children in hospitals who were developing low sodium levels in their blood – a condition called hyponatremia. If sodium levels get too low, it can cause complications leading to brain swelling, seizures and death.
Some studies have shown an association between hypotonic fluids and the development of hyponatremia, with between 19 and 50 percent of hospitalized children affected, but the majority of these studies have been limited in size, duration, or only examined select patient populations such as the critically ill.
Now physicians at Lucile Packard Children’s Hospital and Stanford, using an innovative approach enabled by the electronic medical record (EMR), have published an analysis of more than a thousand children admitted to Packard Children’s across the entire range of childhood disease. The study appears online in The Journal of Pediatrics.
The researchers found that children who received hypotonic IV fluids were significantly more likely to develop hyponatremia – 39 percent – as opposed to 28 percent of patients receiving isotonic fluids.
“This is by far the largest study to date because we were able to obtain the data from the electronic medical record,” Christopher Longhurst, MD, MS, chief medical information officer at Packard Children’s and one of the authors of the study, told me. Longhurst is also an associate professor of clinical pediatrics at Stanford.
The doctors also found that there were clinical factors, such as certain admitting diagnoses and surgical procedures, that influenced the likelihood a child would develop hyponatremia.
"Our study is unique in that, while we found the use of hypotonic fluids was associated with higher rates of hyponatremia, we also discovered that there were several other factors that may be far more important in determining hyponatremic risk," said Scott Sutherland, MD, a clinical assistant of pediatrics and the senior author of the study. "Our findings suggest that use of isotonic fluids alone won’t solve the problem.”
The study concludes by suggesting that future research in the area should focus on all hyponatremic risk factors, rather than just the sodium content of the fluid. And, given the complexity of hospitalized patients, the authors write, "it is quite possible that a one-size-fits-all approach to IV maintenance fluid management is no longer tenable.”
Photo by Thomas van de Dosse