Introduction

Altitude-related conditions can range from mild and discomforting to severe and life-threatening. Acute mountain sickness (AMS) is a common condition in those with a recent elevation change above 8000 feet. Although it is usually mild, it may be severe enough to warrant emergency medical services (EMS) activation, especially in a challenging environment. High-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE) are life-threatening diagnoses, and EMS will almost certainly be involved in these cases. EMS is uniquely positioned to assist in these cases as evacuation is not simply getting patients to treatment; evacuation, specifically, descent from the affecting elevation and hypoxic environment, is the treatment. Any EMS system that will potentially be operating at altitudes near or over 8000 feet above sea level should be prepared to deal with altitude-related conditions.

Issues of Concern

Medications and Portable Oxygen

Medications used to treat altitude-related conditions are quite specific and often are not a part of EMS formularies. Both ibuprofen and dexamethasone are used for prophylaxis of altitude illness and in the treatment of symptomatic patients. Each medication has met safety standards to use and should be a part of any EMS systems treatment plan and equipment if there is a high likelihood of responding to a patient needing evacuation due to altitude-related conditions. The dose of ibuprofen is 600 mg by mouth every 8 hours, whether for treatment or prophylaxis.[1] The initial dose for dexamethasone is 8 mg orally, then 4 mg orally every 6 hours.[2] Patients with HACE and altered mental status should have dexamethasone administered by the intramuscular route.

For the treatment of HAPE, nifedipine has been recommended; however, studies have shown that it adds no benefit when used to treat modalities of descent from altitude and supplemental oxygen.[3][4] Supplemental oxygen is a mainstay of EMS treatment and, if available, should be given to patients with altitude illness. Although hypoxia is not the sole cause of altitude illness, treating the relative hypoxia at altitude with supplemental oxygen is very beneficial. Although oxygen helps treat patients with AMS and HACE, it is particularly beneficial in patients with HAPE. Patients with HAPE often have a very low oxygen saturation and are in respiratory distress. Recommendations are for supplemental oxygen to be started at a rate of 4 liters per minute via a nasal cannula to keep oxygen saturation over 95%. 

Portable Pressure Bags

Commercially available portable hyperbaric chambers (Gamow bag) can increase the ambient pressure around a patient and be useful for treating severe altitude illness.[5] A pressure of 2 pounds per square inch can be created inside the bag using a foot pump. Although the actual relative pressure increase is based on the altitude at which the device is used, the proper use of this device can achieve pressure increases equivalent to descending well over 1000 meters.[6] Portable hyperbaric chambers have been used successfully by EMS personnel with only minimal training.[7] Although a portable pressure bag is not a substitute for descent from altitude, this is an option when rapid descent is not possible in severe altitude illness. Optimally, a patient can stay in the portable hyperbaric chamber and a positive-pressure environment until an actual descent occurs. 

Descent

Descent from altitude is universally considered the primary treatment for patients with severe or life-threatening altitude-related conditions. In patients with HAPE or HACE, descent is essential. The only legitimate reason to delay is secondary to a lack of an available method or safety concerns that prevent it. Although patients with acute mountain sickness can usually be safely maintained at altitude and only need to halt ascent to acclimatize, any patient with severe symptoms, progressive symptoms, or other concerns that prompted the activation of EMS will most likely require descent. Absent life-threatening symptoms of HAPE or HACE, the descent should be considered urgent rather than emergent. Regardless of whether an available method is available or because of safety concerns, descent from altitude should be the primary focus of all EMS efforts in any patient with HAPE or HACE. The rapidity and absolute elevation decrease of descent are both of utmost importance when considering the optimal process for evacuation from an EMS perspective. Descents of as little as 300m are known to be extremely effective in reversing the effects of altitude-related conditions, and a descent of 1000m is usually effective. A greater degree of descent from altitude is never a problem and is prudent if possible.[8] EMS professionals can find it rewarding to know that a patient can be in a life-threatening condition, and simple, rapid transport from the low-pressure hypoxic environment to a lower altitude is curative. 

Clinical Significance

Preparation

Any EMS system that may potentially respond to altitude-related conditions should be prepared well in advance to manage altitude-related illnesses. Proper pharmacologic options, specific altitude-related equipment, and medical training should all be prepared, available, and familiar to EMS providers well before responding to an EMS call for an altitude-related condition. 

Environmental Concerns

Because altitude illnesses often occur in an austere environment, EMS personnel must be prepared when optimal treatment options are unavailable. Patients experiencing HACE may suffer from significant trauma because the associated altered mental status can lead to poor decision-making. Patients with other forms of altitude illness may have traveled too far and cannot return to their starting point due to symptoms. In cases with significant trauma, only life-threatening treatments should be performed before evacuation. "Load and go" should be the mantra instead of "stay and play." Bad weather and difficult terrain will often make immediate descent dangerous or impossible. These issues are why adjunct treatments should be available in addition to supplemental oxygen and descent. When an EMS professional is dealing with a life-threatening altitude illness, balancing the available options with the feasibility of descent can be difficult. In general, because even relatively small descents can dramatically improve patients, a rapid descent of a small amount is preferred to delay descent for a larger elevation change. 

Diagnosis

For EMS, recognizing the presence of an altitude-related condition is vital, and initiating descent from altitude or alternative treatments should be immediately started. The condition can be challenging to diagnose because acute mountain sickness can present with non-specific symptoms. Fortunately, HACE's more severe condition is easier to diagnose because of specific pathognomonic symptoms. The Lake Louise scoring system can assist EMS providers in diagnosing altitude-related illnesses.[9] The questionnaire evaluates for headache, nausea or vomiting, fatigue or weakness, and dizziness-headedness. To diagnose HACE, a patient should have acute mountain sickness with ataxia or altered mental status.  The presence of ataxia and altered mental status in a patient at high altitude should alert EMS that the patient needs to be assessed for altitude-related conditions. The presence of either of these symptoms should prompt immediate descent. High-altitude pulmonary edema is a different clinical entity that EMS can effectively screen for in a high-altitude environment. Pulse oximetry measurement usually shows readings below what is expected for a given elevation. Vital sign abnormalities are extremely common in HAPE, and the presence of tachycardia and tachypnea in conjunction with dyspnea at rest is usually sufficient to prompt EMS evacuation.[10]  

Differential Diagnosis

EMS providers should be familiar with and understand how to manage patients with different types of high-altitude illnesses when there is a chance that patients with these conditions may be encountered. Patients often call with nonspecific complaints and perhaps even a presumptive alternative diagnosis. Infection, dehydration, hypoglycemia, hyperglycemia, hangover, and migraine are extremely common complaints that can mimic AMS and early HACE. Asthma, pulmonary infection, heart failure, and PE are all in the differential diagnosis of HAPE. When an EMS is called for a complaint consistent with these diagnoses, it must be aware of a high altitude environment and understand the importance of rapid descent in altitude illness. Delay in transport is potentially life-threatening if a patient with HACE is misdiagnosed as dehydrated and given IV fluids in place. Oxygen saturation does not correlate with the degree of AMS/HACE enough to decide if a patient needs immediate evacuation. The decision to evacuate is based on history and clinical presentation, not vital signs. A complete neurological evaluation and mental status exam are of paramount importance when deciding whether immediate evacuation of patients with AMS or HACE is required. EMS providers should consider presenting vital signs, specifically tachycardia and tachypnea, in the presence of dyspnea at rest, which can suggest a diagnosis of HAPE.