In a previous post (What’s critical to you | gutsandgrowth), I’ve drawn attention to the problem of hyponatremia. This particular hospital problem is often iatrogenic and often preventable. Two recent studies provide more data to support limiting hypotonic fluids.
The first study that took place between 2009-2011, shows that this remains a common problem at Stanford’s pediatric hospital (J Pediatr 2013; 163: 1646-51). This study was a retrospective study with data extracted from the hospital’s EMR.
From a cohort of 5498 patients receiving intravenous fluids (IVFs) on admission, 1048 were suitable for study due to the availability of serum sodium levels, not having several types of IVFs, and not being neonatal patients. In addition, patients who had abnormal sodiums on admission (n=753) were excluded.
Hypotonic fluids included: D5W, one-quarter normal saline (1/4 NS), D5 1/4 NS, 1/2 NS, D5 1/2 NS, and total parenteral nutrition. No patients received D5W as a maintenance fluid, but its use with medications contributed to total free water delivery.
Isotonic fluids were D5 NS, NS, and Lactated Ringer’s.
- Hyponatremia (Na <135 mEq/L) developed in 260 of 674 (38.6%) who received hypotonic fluids and in 104 of 374 (27.8%) who received isotonic fluids. OR 1.63
- The overall incidence of hyponatremia was 34.7% in this cohort.
- Other factors associated with developing hyponatremia: surgical admission (adjusted OR 1.44), cardiac admitting diagnosis (aOR 2.08), and hematology/oncology admission (aOR 2.37)
The fact that hyponatremia occurred in a large number on isotonic fluids indicates that additional factors like total fluid volume and uncorrected volume deficits contribute as well. Preferential water retention can still occur in the setting of increased ADH levels. This study, like all retrospective studies, has several limitations. However, the basic finding that hypotonic fluids increase the risk of hyponatremia remains solid.
The second study was a recent meta-analysis (Pediatrics 2014; 133: 105-113 -thanks to Seth Marcus for this reference) which included ten randomized controlled trials. It showed that hypotonic maintenance IV fluids were associated with a much higher risk of hyponatremia (RR 2.24) and severe hyponatremia (Na <130) (RR=5.29).
Bottomline from both studies: Isotonic fluids are safer than hypotonic fluids in hospitalized children for maintenance IV fluids in terms of decreasing the risk of hyponatremia.