What is Exercise-Associated Hyponatremia?
Exercise-associated hyponatremia (EAH) is when the levels of sodium in your blood drop below a certain point (135 mmol/L) during or up to 24 hours after physical activity. While it was initially believed to affect only long-distance endurance athletes, it is now recognized to occur in athletes of various sports with a range of symptoms.
It’s very important to quickly identify EAH and separate it from other illnesses that might occur from exerting effort. Sometimes, people might think EAH is a different medical condition and give fluids that can make EAH worse, even becoming a life-threatening situation. Based on how severe the EAH is, it can be treated either by limiting fluid intake or replacing the sodium in the body.
One of the best ways to prevent EAH is by avoiding drinking too much water. Awareness is key; Athletes, coaches, healthcare workers, and sports event staff must be educated about how to prevent EAH and be able to recognize the symptoms when they occur. This can lower the risk of the condition worsening to a serious brain condition (hyponatremic encephalopathy), coma, or even death.
What Causes Exercise-Associated Hyponatremia?
Exercise-associated hyponatremia (EAH) is a condition that occurs when the balance of water to salt in your body is disrupted. Two key factors usually cause this condition to develop when one is exercising intensively.
First, athletes often drink a lot of fluids that don’t have much salt, such as water and sports drinks, both before and during intense physical activities. This increase in fluids can increase the amount of water in the body.
Secondly, intense physical activity itself often results in the body secreting more of a hormone called antidiuretic hormone (ADH). This hormone’s job is to help the body maintain the right amount of water. However, when too much of it’s produced, the body can end up holding onto too much water.
It’s the combination of these two factors – drinking lots of low-salt fluids and secreting too much ADH – that can result in EAH during strenuous physical activities.
Risk Factors and Frequency for Exercise-Associated Hyponatremia
Exercise-associated hyponatremia (EAH) is a condition that can affect athletes participating in a wide range of activities such as marathon and ultramarathon running, triathlons, shorter-distance running, military training operations, team ball sports, recreational hiking, and yoga. The main causes of EAH include drinking excessive amounts of low-sodium fluids, experiencing high temperatures, and exercising for extended periods, typically more than 2 hours. Research has shown that as temperatures rise, so does the incidence of EAH.
Men and women are equally likely to experience EAH when taking into account factors like body mass index and how long they exercise for. Consuming a diet low in sodium, particularly high-sodium foods, can be a contributing factor, as can the use of non-steroid anti-inflammatory drugs, which enhance the water retention effects of ADH in the kidneys.
Most of the time, EAH is found unexpectedly in athletes who don’t show any symptoms. After endurance events, when athletes are routinely checked or their blood is tested for other purposes, EAH is reported in 5-51% of cases. Serious cases of EAH are estimated to affect between 0.1% and 1.0% of endurance athletes, with marathon runners, ultramarathon runners, Ironman athletes, long-distance backpackers, and military service members being most commonly affected. In the military, the incidence is 6.9 cases per 100,000 service members per year.
Signs and Symptoms of Exercise-Associated Hyponatremia
Exercise-associated hyponatremia (EAH) is a health condition that could affect athletes who have undergone intense physical activity. EAH should be considered if an individual has participated in extensive forms of exercises such as marathons, cycling events, triathlons, long walks, backpacking, or extended military field training or combat exercises within the last day. The chances of EAH arise if the exercise duration exceeds two hours or occurs in hot weather.
Symptoms of EAH could vary from being symptom-less to mild to severe. Some symptoms include:
- Lightheadedness
- General discomfort or malaise
- Fatigue
- Irritability
- Overall weakness
- Headache
- Nausea
- Decreased urine output
In severe cases, symptoms could include vomiting, minimal or no urine output, confusion, collapsing, seizures, coma, and potentially death during or shortly after the physical activity.
Evidence of EAH is strengthened when the person shows no signs of heat illness or dehydration, including thirst, dizziness when standing, dry mouth or throat, drop in blood pressure upon standing, and high core body temperature. Identifying EAH from heat-related illness and dehydration is crucial, as those conditions would be treated with isotonic fluid — a solution that could be fatal if the individual was actually suffering from EAH.
During a physical evaluation, patients with mild EAH could exhibit slight fever, rapid heart rate, flushed skin, excessive sweating, and tiredness. In severe cases, EAH may present with altered awareness, from distractedness to full unawareness of surroundings, loss of sweating, low blood pressure, and unusual limb movements.
Testing for Exercise-Associated Hyponatremia
If you’re suspected of having Exertional Hyponatremia (EAH), a condition brought about by low sodium levels in your blood after extensive physical activity, there are several checks that have to be made. These checks include tracking your vital signs such as heart rate and blood pressure, assessing your mental state using something called a Glasgow coma scale, and ensuring your airway is clear, your breathing is sufficient and your circulation is functioning properly. A very important step is getting an accurate measure of your core body temperature, ideally through a rectal temperature reading. This is to identify if you’re suffering from any heat-related illnesses (like heat stroke or heat exhaustion), which can frequently occur alongside EAH.
A key part of diagnosing EAH is determining the level of sodium in your blood. This step, however, isn’t always feasible due to the high cost and temperature limitations of the devices used in such tests. If you’ve been drinking lots of low-sodium fluids during a long period of physical activity, this information will be used as part of the diagnosis process. In general, a diagnosis of EAH is made if your blood sodium level is less than 135 mmol/L and you have a history of excessive fluid intake.
If you’re able to, it’s important to answer all questions about your activity and fluid intake before you started feeling unwell. If you can’t talk or don’t remember, someone who was with you, like a coach or a teammate, can provide these details. Also, a check will be performed to identify your blood glucose levels because low blood glucose, or hypoglycemia, can cause symptoms similar to EAH.
Treatment Options for Exercise-Associated Hyponatremia
If a sportsperson starts to feel unwell during or after exercise, it’s essential to figure out why. Exercise-associated hyponatremia (EAH), where the body has too much water and not enough sodium, could be the cause. However, it can be easily confused with other conditions like heat exhaustion, heatstroke, or exercise collapse associated with sickle cell trait (ECAST), which all require different treatments. So, it’s crucial to figure out what’s going on before starting treatment. Plus, the type of treatment given will depend on the symptoms the patient is experiencing.
If a patient has no symptoms relating to their nervous system (e.g., confusion, seizures, or unconsciousness), their EAH is considered mild. In this case, the patient should drink less fluid to help their body increase sodium levels. This approach works by suppressing a hormone called ADH, which helps the body expel excess water. Some patients may also be advised to take concentrated oral doses of sodium, although they might find this unpalatable or it might cause nausea. This can be taken in various forms, like a small dose of a salty solution, drinking broth made from several bouillon cubes, or eating salted pretzels. Despite feeling unwell, a patient with mild EAH might recover quicker and spend less time in the hospital if they’re treated with these oral methods, rather than receiving intravenous (IV) fluids.
However, if a patient with EAH starts to experience neurological symptoms, their condition is considered severe. The patient should immediately receive a dose of a concentrated saline solution through an IV line, which can be repeated every 10 minutes up to three times. If needed, larger amounts can be given over an hour without any complications, although this does come with an increased risk of correcting sodium levels too quickly and potentially causing damage to the nerves in the brain and spinal cord due to sudden changes in water levels (osmotic demyelination).
When a patient with suspected EAH arrives at a hospital, their sodium levels should be checked straight away. The treatment in the hospital will be similar to the pre-hospital treatment, with severe cases and those showing signs of brain swelling being treated with smaller doses of a concentrated saline solution over a period of time. This often leads to a small increase in sodium levels and alleviation of neurological symptoms. However, if a patient with EAH also has symptoms of encephalopathy (a condition where the brain is affected, leading to altered mental status, personality changes, or memory loss), they might need admission into the intensive care unit, depending on the hospital’s policies and criteria.
What else can Exercise-Associated Hyponatremia be?
EAH, or Exercise-Associated Hyponatremia, is a condition that belongs to a group of injuries that can happen due to physical exertion. There are several other conditions or injuries that can result from intense exercise, like:
- Heat exhaustion
- Heatstroke
- Exercise-associated collapse
- Exertional collapse associated with sickle cell trait (ECAST)
- Low body fluid levels (hypovolemia)
- Low blood sugar (hypoglycemia)
- Irregular heart rhythms (sudden cardiac arrhythmia) such as Wolff-Parkinson-White syndrome, prolonged QT syndrome, and channelopathy
- Heart muscle disease (hypertrophic cardiomyopathy)
- Sudden cardiac death without a known cause
- Seizures
- Fainting due to changes in heart rate or blood pressure (vasovagal syncope)
- Pretending to be sick or injured (malingering)
It’s crucial for healthcare professionals who are responsible for athletes to consider these different possibilities when diagnosing and treating exertional injuries.
What to expect with Exercise-Associated Hyponatremia
Most athletes recover from a mild case of Exercise Associated Hyponatremia (EAH), a condition caused by low sodium levels in the blood, within hours of visiting the emergency room. They usually do not need to stay in the hospital for a prolonged period. After being treated with a salt solution, either orally or via an intravenous drip, they typically stay in the emergency room between 50 and 79 minutes.
However, severe cases of EAH may require the patient to be admitted to a hospital ward or an intensive care unit (ICU), based on the rules of the particular hospital. Those who develop an even more serious condition known as exercise-associated hyponatremia encephalopathy, which is caused by brain damage due to swelling, are at risk of serious health complications and even death. However, we don’t yet know the exact death rate linked to this serious condition.
At this point in time, it’s also unclear whether people who’ve had EAH in the past are more likely to develop it again in the future.
Possible Complications When Diagnosed with Exercise-Associated Hyponatremia
The main negative effects of Exercise-Associated Hyponatremia (EAH) and its treatment are a severe brain condition called Exercise-Associated Hyponatremic Encephalopathy (EAHE), accumulation of fluid in the lungs not related to heart problems, mental disorders due to damage of nerves in the center of the brain, and negative effects due to misdiagnosis and wrong treatment.
If EAH is not treated, mild conditions can worsen severely and lead to a profound change in mental state, seizures, and coma because of brain swelling. This condition is called EAHE and can often result in death, although the exact death rate is not known. The best treatments for EAHE are a quick correction of salt levels in the blood with a concentrated salt solution and supportive care for the resulting conditions, like breathing help and seizure control.
Fluid can accumulate in the lungs unrelated to heart conditions due to imbalances in body’s water regulation system in EAH, leading to breathing difficulties and the need for breathing assistance.
Correcting low salt levels in the blood too quickly may lead to a disasterous permanent nerve damage in the center of the brain, causing neurological deficits despite correction of the salt levels in the blood.
If EAH is wrongly diagnosed when the actual condition is dehydration or heat stroke, treatment with concentrated fluids, restricting fluid intake and lack of cooling can harm the patient.
List of Complications of EAH and its Treatment:
- Severe brain condition (EAHE)
- Fluid accumulation in lungs unrelated to heart problems
- Mental disorders due to damage of nerves in center of brain
- Problems due to misdiagnosis and wrong treatment
- Death from untreated EAHE
- Neurological issues despite correcting salt levels
- Harm due to wrong diagnosis and treatment
Preventing Exercise-Associated Hyponatremia
EAH, which is when the body has too much fluid and too little salt, can be prevented by not drinking too much fluid, taking in enough salt orally, and by teaching athletes, event staff, and healthcare workers about how it can be prevented and how to recognize its symptoms.
The issue with EAH happens when the body takes in more fluid (water) than it loses (through sweat, urine, etc). Therefore, the best way to balance fluid in the body is to only drink when thirsty to prevent drinking too much. Another way to check how much fluid is needed is by seeing if an athlete’s weight changes during exercise, although this might not always be practical. Taking too much of fluid, especially in large quantities, should be discouraged.
In order to balance the salt-water levels in the body during exercise, athletes can also eat salty foods along with drinking fluids if they wish. Taking salt tablets or packets during exercise has not been proven to reduce the chances of getting EAH.
Athletes who take part in long-term events should be informed about the dangers of drinking too much liquid, the need to eat food during these events, and how to spot if they or someone else is showing signs of EAH or other heat related injuries. Event staff, EMS and frontline healthcare workers, and military members also need to be educated on how to recognize EAH and how to prevent it by avoiding drinking too much liquid and making sure enough salt is taken in.
