Altitude-related conditions can range from mild and discomforting to severe and life-threatening. Acute mountain sickness (AMS) is a common entity in those who have had a recent change in elevation above 8000 ft and is usually mild, but it may be severe enough to warrant 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 in a unique position 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.

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 medicine has met safety standards to use and should be a part of any EMS systems treatment plan and equipment if there is high likelihood of responding to a patient needing evacuation due to altitude-related conditions.  The dosing for ibuprofen is 600mg by mouth every 8 hours whether for treatment or prophylaxis.[1]  The dosing for dexamethasone is 8 mg orally initially and then 4 mg orally every six 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, but studies have shown that it adds no benefit when used in conjunction with the treatment of 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, treatment of the relative hypoxia at altitude with supplemental oxygen is very beneficial. While oxygen is helpful in treating patients with AMS/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 4L/minute via a nasal cannula with a goal of keeping oxygen saturation over 95%.  

Portable Pressure Bags

Commercially available portable hyperbaric chambers (Gamow bag) can increase the ambient pressure around a patient and can be useful for the treatment of severe altitude illness.[5]  By the use of a foot pump, a pressure of 2 PSI can be created inside the bag.  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, in the setting of severe altitude illness, this is an option when rapid descent is not possible.  Optimally a patient will be able to 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 any patient with severe or life-threatening altitude-related conditions.  In patients with HAPE or HACE, descent is essential and the only legitimate reason to delay is secondary to a lack of an available method to do so or safety concerns that prevent it.  While patients with acute mountain sickness can usually 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 most likely will require descent.  Absent life-threatening symptoms of HAPE or HACE, the descent, should be considered urgent rather than emergent.  Regardless, absent an available method 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 a simple, rapid transport from the low-pressure hypoxic environment to a lower altitude is curative. 

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 for situations when the optimal treatment options may be 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 are unable to return to their starting point due to symptoms. In cases with significant trauma, only life-threatening treatments should be performed prior to evacuation. “Load and go” should be the mantra as opposed to “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 life-threatening altitude illness, balancing the available options with the feasibility of descent can be difficult.  In general, because even relatively small descents can have dramatic improvements for patients, a rapid descent of a small amount is preferred to delaying descent for a larger elevation change. 

Diagnosis

For EMS, recognition of the presence of an altitude-related condition is vital and initiate descent from altitude or alternative treatments should be immediately started.  Because acute mountain sickness can present with non-specific symptoms, the condition can be challenging to diagnose.  Fortunately, the much more severe condition of HACE is easier to diagnose because of specific symptoms that are pathognomonic.  The Lake Louise scoring system can assist EMS providers and diagnosing altitude-related illness.[9]  The questionnaire evaluates for the presence of headache, nausea/vomiting, fatigue/weakness, and dizziness-headedness.  To diagnose HACE, a patient should have acute mountain sickness with ataxia and/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 can be effectively screened for by EMS in a high-altitude environment. Measurement of pulse oximetry will usually show 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 will 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 EMS is called for a complaint consistent with these diagnoses, it is essential that EMS have an awareness 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 be used in deciding 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/HACE is required. EMS providers should consider presenting vital signs, specifically tachycardia and tachypnea in the presence of dyspnea at rest, that can suggest a diagnosis of HAPE.