Wednesday, December 6, 2017

Testing and Treatment

The 2017 Marine Corps Marathon was the second warmest on record and the second busiest in the medical tents.  Temperatures started at 53.2 degrees F and reached a max of 77.3 degrees F. WBGT readings done every hour at three locations on the course. With a low of 53.2 at 0800 and a high of 73.9 at 1400 on the course. Of our 42 transports 22 were heat related and one runner; a 61 yo female runner presented confused, with several bouts of nausea and vomiting and a serum sodium of 131 mmol/L.

Various references define hyponatremia as a serum sodium <135 mmol/L and critical hypernatremia as <120 mmol/L. Other risk factors include fluid intake, gender, exercise duration > 4 hours, pre-exercise over hydration, easy access to fluids on the course and temperature. Symptoms range from confusion, nausea, vomiting, confusion, seizures and unresponsiveness. Some runners have low serum sodium levels and no visible symptoms.

The discussion point I bring up is testing and treatment. Should all runners presenting with symptoms of hyponatremia have sodium levels tested prior to the introduction of an IV?  In cases where athletes are picked up on the race course and transported immediately by EMS service, should an IV be withheld until testing is complete? There are events that have few if any aid stations and protocols that do not cover all these possibilities. Would you start an IV on a runner in your aid station without a serum sodium level?


  1. Yes...I would definitely want to have a Na level before starting an IV. The short turn around, even if it means transporting a patient, makes it safer for the patient. I would give the runner some salt if I was suspicious of hyponatremia until a Na level was done. Katie Powers RN

  2. Shelly,
    Great question.
    I think the circumstances of the IV start make a difference.
    Having started many before the advent of point of care testing, I think it depends on comfort level with your clinical diagnosis and the ability to transfer quickly if needed. In a situation where dilutional exercise associated hyponatremia is likely, withholding IV fluids until lab studies are available is prudent as any fluid short of hypertonic saline can make the condition worse. I would also withhold oral fluids if EAH is suspected.
    Bill Roberts

  3. Shelly,
    I would agree with the thoughts above, namely, I would hold IV fluids in cases of suspected dilutional exercise associated hyponatremia. Many times we find the point of care machines can malfunction in extreme weather conditions. In these cases a careful neurological exam can help guide you. Also, treatment with hypertonic saline in some one with normal kidney would not be harmful. Whereas it may save a life its they are hyponatremic. I assume your question is regarding normal saline = IV fluids which are hypotonic?