Wilderness and Rescue Medicine 8th Edition

49

Section II: Critical Body Systems

scene may disclose problems like drug overdose, trauma, or hypoxia. Sometimes, people will experience brief seizure activity with head injury at the time of impact. This seems to be more common in children and is not serious if it resolves quickly and there is an early return of normal mental status. However, seizure occurring later as part of a pattern of increasing ICP certainly is serious. In the case of a known epileptic who improves spontaneously post seizure and seems other- wise okay, evacuation need not be an emergency. However, blood levels of medication will need to be checked and adjusted. The patient should not be allowed to perform risky activities or be left alone in dangerous situations. This is not a patient who can be trusted to belay a climbing partner or remain on the deck of a small boat alone. Exercise Associated Hyponatremia Exercise associated hyponatremia is most com- mon with extreme athletes and others who have been working or playing hard and drinking too much water. This dilutes the salt content of the body to a point where function is impaired. The term hyponatremia means low sodium, one of the body’s primary electrolytes. This is the Salts in the STOPEATS mnemonic. Hyponatremia typically causes changes in mental status, particularly slow thinking, confu- sion, and tremors. Serious cases can cause loss of consciousness and seizures. The signs and symp- toms can resemble heat exhaustion with weakness, nausea, and headache, but urine volume is near normal with relatively dilute urine. This can be a difficult diagnosis to make without a device to measure electrolytes.

General Principles

Exercise-Associated Hyponatremia Mechanism: • Excessive fluid replacement dilutes sodium and other salts • Some loss of salts through sweat, but primarily a problem of too much water Signs and Symptoms: • Altered mental state; slow mentation, lethargy, agitation • Nausea, headache, weakness, seizures, tremors • Urine output and core temperature near normal

14

© 2018 WMA

The term dilutional hyponatremia describes the problem in patients who drink too much without significant sweating or vigorous activity. This is uncommon but can affect people using recre- ational drugs like MDMA or people on uncon- ventional diets. Treatment of Exertional Hyponatremia Water restriction is the usual field treatment for hyponatremia. Salty food may help but is not definitive treatment. Evacuation to medical care is ideal. Fluid replacement with normal saline, as is often performed for dehydration, can actually make hyponatremia worse. Hydration should be initiated for hyponatremia only if signs and symp- toms of dehydration are also present and when blood electrolytes can be measured. Worsening of mental status and level of consciousness suggests a serious problem requiring emergency evacuation. Giving an oral solution of 3% saline solution or the equivalent (e.g. ½ teaspoon of salt in 100 ml of water) and repeating in 10 minutes may help.

Treatment: • Rest • Fluid restriction unless there is evidence of volume depletion • Evacuate if not improving, urgently if worse Exercise-Associated Hyponatremia

*

Low Risk

High Risk

!

© 2018 WMA