Hypernatremia and intravenous fluid resuscitation in collapsed ultramarathon runners

Clin J Sport Med. 2008 May;18(3):273-8. doi: 10.1097/JSM.0b013e31815eb0b5.


Objective: To determine if a return to normonatremia is required for symptomatology to resolve in collapsed hypernatremic runners and if intravenous (IV) administration of an isotonic solution would adversely affect serum sodium concentration ([Na+]) in collapsed normonatremic runners.

Design: Observational study.

Setting: 2006 Comrades Marathon.

Participants: 103 collapsed runners.

Main outcome measure: Final serum [Na] upon discharge.

Results: 58% of all collapsed runners were hypernatremic. Hypernatremic runners reported significantly more vomiting than normonatremic runners (79 versus 34%; P < 0.001). A significant decrease in serum [Na] in hypernatremic collapsed runners occurred after the IV administration of either 1 L of 0.45% normal saline (150.5 +/- 3.5 versus 148.0 +/- 4.6; P < 0.05) or Ringers lactate solution (147.7 +/- 2.2 versus 146.2 +/- 2.1; P < 0.05). One liter of IV fluid administration caused an increase in plasma volume that was not significantly different between (1) hypernatremic runners receiving a hypotonic solution (13.5 +/- 12.7%) and (2) normonatremic runners receiving an isotonic solution (15.6 +/- 11.3%). The final serum [Na+] of hypernatremic runners was above the range for normonatremia upon discharge (>145 mmol/L).

Conclusions: A return to normonatremia was not required for hypernatremic runners to "recover" and be discharged from the medical tent. Vomiting either aggravated and/or facilitated the development of hypernatremia. IV administration of 1 L of either (1) a hypotonic solution to hypernatremic runners or (2) an isotonic solution to both normonatremic and hypernatremic runners did not produce any adverse biochemical or cardiovascular changes and can therefore be considered a safe and effective treatment for collapsed runners if used in this context.

MeSH terms

  • Female
  • Humans
  • Hypernatremia / etiology
  • Hypernatremia / physiopathology
  • Hypernatremia / therapy*
  • Infusions, Intravenous*
  • Male
  • Observation
  • Physical Exertion / physiology*
  • Running*
  • Sodium / analysis
  • Sodium / blood
  • South Africa


  • Sodium