title: Dysnatremia predicts a delayed recovery in collapsed ultramarathon runners.
abstract: OBJECTIVE
  To assess (1) the incidence of dysnatremia in collapsed runners presenting to the medical tent of the 89-km Comrades Marathon and whether dysnatremia influences time to discharge, and (2) whether intravenous fluids could restore serum sodium concentration ([Na+]) to 140 mM faster than could the administration of oral fluids.
  
  
  METHODS
  Prospective randomized controlled trial.
  
  
  METHODS
  2005 Comrades Marathon.
  
  
  METHODS
  One hundred thirty-three collapsed runners and 31 control-group runners.
  
  
  METHODS
  Collapsed runners presenting to the medical tent at the finish of the 2005 Comrades Marathon were randomized into an intravenous or oral fluid administration group, with the type and amount of fluid administered dictated by initial [Na+].
  
  
  METHODS
  Time to discharge, serum [Na+].
  
  
  RESULTS
  Forty-five percent of collapsed runners were hypernatremic, 2% were hyponatremic, and 53% were normonatremic. Normonatremic runners spent significantly less time in the medical tent (80 +/- 31 minutes) compared with hypernatremic (102 +/- 36 minutes) and hyponatremic (146 +/- 122 minutes) runners. Intravenous fluid therapy produced larger but nonsignificant reductions in [Na+] than oral therapy (-2.1 +/- 3.1 versus -0.7 +/- 1.8 mM); however, 45% of runners assigned to the oral fluid group could not tolerate oral rehydration.
  
  
  CONCLUSIONS
  A slight majority of collapsed runners were normonatremic and spent significantly less time in the medical tent compared with hyper- and hyponatremic athletes. Initial rates of correction of hypernatremia were similar with intravenous and oral hypotonic fluid therapy. Clinicians should be advised that intravenous fluid resuscitation may best benefit hypernatremic collapsed runners who are intolerant to oral fluid ingestion.
authors.affiliation: Department of Human Biology, University of Cape Town, South Africa. thew@sports.uct.ac.za
authors.forename: Tamara
authors.initials: T
authors.lastname: Hew-Butler
authors.forename: Karen
authors.initials: K
authors.lastname: Sharwood
authors.forename: Jeremy
authors.initials: J
authors.lastname: Boulter
authors.forename: Malcolm
authors.initials: M
authors.lastname: Collins
authors.forename: Ross
authors.initials: R
authors.lastname: Tucker
authors.forename: Jonathan
authors.initials: J
authors.lastname: Dugas
authors.forename: Rob
authors.initials: R
authors.lastname: Shave
authors.forename: Keith
authors.initials: K
authors.lastname: George
authors.forename: Timothy
authors.initials: T
authors.lastname: Cable
authors.forename: Joseph G
authors.initials: JG
authors.lastname: Verbalis
authors.forename: Timothy
authors.initials: T
authors.lastname: Noakes
mesh_terms: D000328:Adult; D003681:Dehydration / Q000628:therapy*; D005260:Female; D006359:Heat Exhaustion / Q000503:physiopathology*; D006801:Humans; D006955:Hypernatremia / Q000453:epidemiology* / Q000503:physiopathology; D008297:Male; D005082:Physical Exertion / Q000502:physiology*; D011446:Prospective Studies; D020127:Recovery of Function / Q000502:physiology*; D012420:Running / Q000502:physiology*; D013019:South Africa