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. Because the low-pressure hypoxic environment is the cause of these altitude related conditions, 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, 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 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 are used in the treatment of patients who are symptomatic. Each medicine is quite safe and should be a part of any EMS system that has a high likelihood of responding to a patient needing evacuation due to altitude-related conditions. Dosing for ibuprofen is 600mg by mouth every 8 hours whether for treatment or prophylaxis. Dosing for dexamethasone is 8 mg initially and then 4 mg every six hours. Because those with HACE have altered mental status, an intramuscular route is recommended for these patients. For the treatment of HAPE, nifedipine has been the recommendation, but studies have shown that it adds no benefit on top of descent and supplemental oxygen. Supplemental oxygen is a mainstay of EMS treatment capabilities and if available should be given to patients with altitude illness. Although the development of altitude illness is not due only to hypoxia, treatment of the relative hypoxia at altitude with supplemental oxygen is very beneficial. While oxygen is helpful in patients with AMS/HACE, it is particularly beneficial in patients with HAPE. These patients often have very low oxygen saturation and are in respiratory distress. A starting rate of 4L/minute via a nasal cannula with a goal of keeping oxygen saturation over 95% is recommended.
Portable pressure bags
Commercially available portable hyperbaric chambers (Gamow bag) can increase the ambient pressure around a patient and have been useful for the treatment of severe altitude illness. Use of a foot pump to a pressure of 2 PSI inside the bag can reduce the effective pressure significantly. Although the actual relative pressure increase is based on the altitude at which the device is used, use of this device can achieve pressure increases equivalent to descending well over 1000 meters. This device has been used successfully by EMS personnel with minimal training. Although a portable pressure bag is not a substitute for descent in the setting severe altitude illness, this is an option when rapid descent is not available. Optimally a patient will be able to stay in the positive pressure environment until an actual descent is possible.
Without question, descent is 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 due to lack of availability or safety concerns that prevent it. While patients with acute mountain sickness can usually safely maintain altitude and only need to halt ascent to acclimatize, any patient with severity of symptoms or other concerns that prompted the activation of EMS most likely will require descent as well. Absent life-threatening symptoms of HAPE or HACE, the descent, in this case, should be considered urgent rather than emergent. Nevertheless, absent availability and 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 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 descent of 1000m is usually considered entirely effective. Of course, a greater descent is never a problem and is prudent if available. As an EMS professional, it is remarkably rewarding to know a patient can be in life-threatening extremes and simple, rapid transport from the low-pressure hypoxic environment is curative.
Any EMS system that is potentially responding to altitude-related conditions should be prepared well in advance to respond to these types of patients. Proper pharmacologic options, specific altitude related treatment equipment, and medical training should all be considered well before responding to an EMS call for an altitude-related condition.
Because altitude illness often occurs in austere environments, EMS personnel must be aware that optimal options may not always be available. Patients experiencing HACE may suffer from significant trauma because the condition causes altered mental status leading to poor decision making. Patients with other forms of altitude illness may have traveled too far into the environment 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. Sometimes that straightforward, optimal option is not available. 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.
For EMS response, the determination of a possible altitude related condition is vital to initiate descent from altitude or alternative treatments. Because acute mountain sickness has a number of non-specific symptoms, it can be challenging to diagnose. Fortunately, the much more severe HACE is also easier to diagnose with specific symptoms. A scoring system has been developed in order to assist with the diagnosis of AMS called the Lake Louise scoring system. For a patient with a recent rise in altitude and the presence of a headache, the questionnaire evaluates the presence of headache, nausea/vomiting, fatigue/weakness, and dizziness. Of note, the diagnosis of HACE is based on a patient with acute mountain sickness who also has ataxia and/or altered mental status. The presence of ataxia and altered mental status in a patient at high altitude should be specifically queried by EMS for altitude-related conditions. The presence of either symptom should prompt immediate descent. High altitude pulmonary edema is a different clinical entity that can be screened effectively by EMS in a high-altitude environment. Measurement of pulse oximetry will usually show readings below that which is expected for the elevation. Vital sign abnormalities are extremely common in this diagnosis and the presence of tachycardia and tachypnea in the presence of dyspnea at rest is usually adequate to prompt EMS evacuation.
When EMS is called to transport a patient with altitude-related conditions, it is extremely important that an understanding of the potential differential diagnoses are known and understood beforehand. 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. Of note, oxygen saturation does not correlate with AMS/HACE specifically 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 solid neurological evaluation and the mental status exam is of paramount importance in the decision to immediately evacuate patients with AMS/HACE. Conversely, as noted above, presenting vital signs, specifically tachycardia and tachypnea in the presence of dyspnea at rest are quite important in evaluating a patient with potential HAPE.
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