What’s critical to you

Over the past ten years, there has been increasing scrutiny with regard to iatrogenic hyponatremia.  Specifically, one of the concerns has been that the administration of hypotonic fluids will result in hyponatremia and potential complications.

In our hospital system, several years ago the hospital administration circulated a list of the new critical laboratory values that would be used to notify physicians of severe derangements.  The goal of selecting a critical value is to improve the outcome of patients by allowing a more rapid and direct communication of an abnormality.  At the same time, it takes time to contact physicians and most physicians do not want to be called too often.

I carefully reviewed the critical values list and was very concerned that the value to call for hyponatremia was <120.  When I protested, I was informed that in fact the sodium critical value had not been changed and had been in place “without a problem” for more than ten years.  In addition, the critical value cutoff at several other children’s hospitals was similar (range was between 120-130).

Despite these reassurances, I remained concerned that this was not the right policy, particularly as alterations in sodium are frequently due to physician error and need to be addressed promptly.  This led to a number of discussions with the laboratory and ultimately to a retrospective review (Guarner, J; Hochman, J; Kurbatova, E; Mullins, R.  Study of outcomes associated with hyponatremia and hypernatremia in children.
Pediatric and developmental pathology 2011;14(2):117-23.)  During a six month period, 53,099 sodium tests were reviewed with 166 having sodium values of 124 or less.  Some of the important findings include the following:

  • Mortality was 42% in patients with sodium values <120mmol/L
  • Treatment was instituted more rapidly when physicians were notified
  • Half of the patients with hyponatremia were receiving hypotonic fluids.

At this time, our critical value for sodium has changed so that physicians are now notified if sodium is less than 125.  Do you know your institution’s critical value?  Are your patients receiving hypotonic fluids?  Something to think about.

Another article in Pediatrics adds more insight into the prevention of hyponatremia (Pediatrics 2011; 128: 980 -983).  Moritz and Ayus reiterate their arguments from 2003 that hypotonic fluids should not be used routinely in children due to the risk of hyponatremia and associated complications.  They cite 20 studies completed over the last seven years which indicate that isotonic fluids are safe and prevent hyponatremia.  “There can no longer be any justification for the routine administration of hypotonic fluids in hospitalized children….On the basis of today’s standards, hypotonic fluids would not receive FDA approval for routine use.”  The main concern about hyponatremia is hyponatremic encephalopathy –this remains a common medical emergency (Pediatrics 2008; 121 (6): www.pediatrics.org/cgi/contnet/full/121/e1577).  Early in the hospital course and in the immediate postoperative period are timeframes that have been noted to have increased incidence of hyponatremia.  However, hyponatremia (<135) is common at all times and affects ~25% of hospitalized patients (Arch Dis Child 2008; 93: 285-287).  So, with your next admission, think about lactated ringer’s or normal saline instead of half-normal.

Additional References:

  • -Pediatrics 2011; 128: 857.
  • -J Peds 2008; 153: 444-447 (letters and references on this topic).
  • -Am J Clin Pathol 2007; 127: 56-59.  Critical Na values.
  • -J Pediatr 2008; 152: 33 & 4.  Frequent p-op hyponatremia.
  • -NEJM 2008; 359: 1018.  Hyponatremia associated with poor prognosis in patients awaitng OLT.
  • -Hepatology 2006; 44: 1535.  Hyponatremia (Na <130) associated with increased mortality & ascites reaccumulation.
  • -J Pediatr 2004; 145: 584. Recs 20-80ml/kg of isotonic fluid to correct hypovolemia prior to typical maintenance fluids (to avoid hyponatremia due to hypovolemia).  Says that isotonic fluids for maintenance may be problematic if cardiopulmonary or renal dz.
  • -Pediatrics 2004; 113; 1395.  Advocates use of isotonic saline (0.9%).  States that hypotonic fluids lead to hyponatremia in many cases b/c of excessive ADH in many patients.
  • -NEJM 2005; 352: 1550 & 1613. Hyponatremia related to Boston Marathon & London Marathon

5 thoughts on “What’s critical to you

    • No. Isotonic fluids are the main fluids that we would use to give a fluid bolus as they restore vascular volume without fluid shifts. My understanding is that 0.9% saline and lactated ringer’s are the two main isotonic fluids. D5W is also considered isotonic; however, the dextrose is rapidly metabolized and this leads to the delivery of a significant free water load.

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