HYPONATREMIA: The most serious cause of exercise associated collapse
A potentially fatal condition that can be seen in endurance athletes when their sodium levels drop too low either from hyper-hydration or from dehydration.
Dehydration = a low blood level resulting in low sodium content
Hyper-hydration = diluting the level of sodium
SEVERE Less than 126
Too much H2O (water intoxication) can cause a lethal physiologic reaction where water rushes into cells including brain cells.
Doctors can misdiagnose it as dehydration and mistakenly treat with IV fluids
How it happens:
During high intensity exercise, sodium is lost along with sweat. Athletes can lose up to 2 grams of salt per liter of sweat. An athlete who only replaces the lost fluid with water will have a decreased blood-sodium concentration. Sodium balance is necessary for transmitting nerve impulses and proper muscle function.
Consider a full glass of salt-water. If you dump out half of the contents of the glass (as is lost in sweat), and replace that with water only, the sodium concentration of in the glass is far less and the water is more dilute. This can occur in the bloodstream of an athlete who only hydrates with water during excessive sweating. The result is …… HYPONATREMIA
RUNNER’S PROFILE: Mark Robinson
Completed Boston Marathon at age 27
Drank gallon H2O before race
A cup at every drink station
Drank H20 after finishing race despite vomiting
Collapsed in parents home
Air-lifted to a Boston Hospital
Misdiagnosed with Dehydration, Given fluids
Was in a Coma for 4 days before recovering.
SIGNS OF HYPONATREMIA
Swelling in extremities (fingers and ankles)
FOR ATHLETES: HOW TO AVOID HYPONATREMIA
Use a sodium containing sports drinks during long distance (more than 60-90 minutes long)
Increase salt intake per day several days prior to competition (except for those with hypertension)
Try not to drink more then you sweat
During a marathon a good rule of thumb is to drink about 1 cup of fluid every 20 minutesAvoid use of NSAIDS (like ibuprofen) medicines that contain sodium during event.
FOR PHYSICIANS: HOW TO AVOID PITFALLS IN THE TREATMENT OF HYPONATREMIA
Do not misdiagnose Acute Hyponatremia as Dehydration and give fluids and cause CEREBRAL EDEMA
Do not use Hypertonic saline in patients that do not have signs of CNS involvement
Do not correct Na greater than 4-6 meq/L and cause central pontine myelinolysis.
When serum sodium concentration falls rapidly
Over 24-48 hours
The compensatory mechanism is overwhelmed which can lead to cerebral edema and brainstem herniation
Develops over more than 48hrs
Experience milder degrees of cerebral edema for a given serum sodium level
Brainstem herniation has not been observed
The causes of morbidity and death are status epilepticus (when chronic hyponatremia reaches levels of 110 mEq/L or less) and central pontine myelinolysis
when corrected improperly.
The distinction between ACUTE hyponatremia and CHRONIC hyponatremia has critical differences in proper corrective therapy.
Acute evolution of hyponatremia (as in marathon runners and high endurance athletes) leaves little opportunity for compensatory extrusion of CNS intracellular solutes.
Hypertonic saline (3%) on a rare occasion may be used to rapidly increase serum sodium level in patients with severe acute or chronic hyponatremia if manifested by severe confusion, coma, seizures, or evidence of brainstem herniation
An increase of 4-6 mEq/L over a few hours is sufficient. Further correction is dangerous and must be avoided unless necessary to correct continued seizures or other severe CNS abnormality
Equation for use of Hypertonic Saline.
Required volume = (Na desired - Na current)(TBW) / (Na Fluid- Na Current)