Denali Mountain Medicine
By Colin Grissom, MD
(The borders between traveling and mountaineering are becoming blurred as remote mountains become more accessible. Many individuals with little climbing experience and only a vague knowledge of altitude-related illnesses are attempting to reach summits of high peaks for which they are not properly prepared. Many become ill and are injured. Here is the experience of a medical team on one such mountain.)
Denali (formerly known as Mt. McKinley) is the tallest mountain in North America at 6,194 meters, and is unique among the high mountains of the world because of its proximity to the arctic circle at 63 degrees North latitude. During the climbing season of May to July arctic conditions exist higher on the mountain. Temperatures at night during May are -29 to - 40 Celsius at the 4,200 to 5,100 meters level, and storms with winds of 80 to 160+ kilometers per hour can occur during May and June and last for several days. Because of its northern latitude the barometric pressure on Denali is lower for a given altitude than on mountains closer to the equator. This difference becomes noticeable above 3,000 meters and makes the summit of Denali physiologically equivalent to a 6,300 to 6,900 meters peak in the Himalayas.
Climbers on Denali
As one of the "seven summits" (the highest mountain on each continent), Denali is an internationally known mountain that attracts a large number of climbers. Of the 1,110 climbers attempting Denali in 1997 about 90%, or around 1,000 climbers, spent part or all of their expedition on the West Buttress route. Of the 1,110 climbers 51% were successful in reaching the summit; 38% were from outside the USA.
The National Park Service camp on Denali
Because of the large number of climbers that attempt the West Buttress route and stay at 4,200 meter for acclimatization and preparation for summit attempts, the U.S. National Park Service (NPS) maintains a camp there. The camp sits on a large glacial plateau and is at an ideal elevation for acclimatization prior to a move to the 5,100 meter high camp, from which the summit is attempted. Consequently during the peak climbing season of mid May to mid June there are typically 100 to 200 climbers at the 4,200 meter camp at any one time.
This camp consists of two small heated walk-in shelters (a Weatherport TM and a "Clamshell" made by the same company). One shelter is used for cooking and communication equipment and the other for medical care. The NPS camp is occupied by the acclimatized rescue team which consists of an NPS climbing ranger, volunteer climbers, and a volunteer doctor. One or two para-rescue personnel from the Alaska Air National Guard are also part of the rescue team. The Alaska Air National Guard provides support to the camp in terms of medical supplies, tents, and rescue equipment.
The function of the NPS camp are several: 1) to serve as an information resource for climbers on the mountain with questions about acclimatization and strategies for a safe summit attempt, 2) to provide medical care to sick or injured climbers, and 3) to rescue sick or injured climbers higher on the mountain. Medical research on high altitude illness is also conducted at the camp by some of the volunteer doctors under separate funding.
Rescue on Denali
The NPS provides for rescue of climbers who become ill or injured when it is considered appropriate, based on the evaluation of field personnel. Factors considered in mounting a rescue are the degree of urgency of the problem, whether the climber and his party could safely self evacuate and, of paramount importance, the safety of the rescue party. Rescue is sometimes precluded or postponed by storms and cold weather conditions. The NPS mountaineering handbook for Denali states that "Rescue is not automatic. Denali National Park and Preserve expects park users to exhibit a degree of self-reliance and responsibility for their own safety commensurate with the degree of difficulty of the activities they undertake."
Personnel and resources of the NPS available to assist with rescues on Denali include the climbing ranger and volunteers occupying the 4,200 meter camp, the NPS Lama helicopter based in Talkeetna, (which is off the mountain) and the NPS at the ranger station in Talkeetna - where the incident commander for all major rescues is located and where logistics are coordinated.
Utilizing the helicopter for rescue and evacuation is not automatic. The nature of the medical problem (i.e. life threatening) is balanced against risk to the rescuers and weather conditions. For example, a non-life threatening injury, such as a broken ankle, at 5,400 meters, would most likely be evacuated on the ground despite the time and manpower it would require, because the injury does not warrant the risk of landing the helicopter at that altitude. Once ground evacuated to 4,200 meters a broken ankle might be evacuated by helicopter if the weather was good and the patient was not ambulatory. In contrast, a climbing fall, where injuries and problems might include hypothermia, frostbite, long bone fractures, and a closed head injury, would be helicopter evacuated from the nearest safe landing zone at 5,100 to 5,700 meters, weather permitting.
Military rescue personnel that sometimes assist with rescues include the Army High Altitude Rescue Team (HART). HART operates the Chinook helicopter which has the capability to land at altitudes up to 5,900 meters, but has no ground rescue capability. The Alaska Air National Guard also sometimes assists with rescues, and has the personnel to provide ground rescue, but the altitude ceiling for their Pavehawk helicopter is 3,000 to 3,600 meters.
Trauma due to climbing falls
Severe trauma on Denali is almost always the result of a climbing fall. Response time to such events is at least two hours, even for a fall witnessed from the 4,200 meter camp, and may take as long as 12 to 24 hours, depending on the weather. Because of the long response time climbers who have suffered injuries that require surgical intervention within several hours do not survive. Climbers may also die from hypothermia before the rescue team can reach them. Because of these factors, climbers who are injured in climbing falls and survive generally do not have immediate life threatening injuries from the fall, but they all have life threatening hypothermia and usually severe frostbite by the time the rescue team reaches them. Principles of treatment generally involve immobilizing fractured extremities and the spine if clinically indicated, warm IV fluids, supplemental oxygen, and packaging in a sleeping bag and litter for lowering or helicopter evacuation. Helicopter evacuation from the nearest safe landing zone is optimal.
High altitude illnesses on Denali
Acute Mountain Sickness
Acute mountain sickness (AMS) is a symptom complex seen a few hours to a few days after ascent to altitudes above 2500 meters. Most individuals with AMS present with a mild form of the condition, characterized by headache in association with one or more of the following: lassitude, insomnia, anorexia, nausea, dizziness, or peripheral edema. More severe AMS is characterized by an altered level of consciousness, ataxia, or cough with shortness of breath at rest. Such symptoms suggest that AMS has progressed to high altitude cerebral edema (HACE) or high altitude pulmonary edema (HAPE). HACE and HAPE are generally associated with more rapid ascent to higher altitudes. AMS is usually benign and self-limited. HAPE or HACE are potentially life-threatening conditions, especially if further ascent is undertaken.
The incidence of AMS on Denali is about 30 to 50% and is most often mild to moderate in severity. Most climbers treat their AMS by halting ascent, resting, and using analgesics for headache. Descent is always effective therapy, and is recommended in more severe cases. Drug therapy with acetazolamide or dexamethasone may be used to speed resolution of symptoms.
High Altitude Cerebral Edema (HACE)
HACE is characterized clinically by progression of global cerebral signs and symptoms in the setting of AMS. The hallmarks of HACE are truncal ataxia (walking as if one who had too much alcohol to drink), severe lassitude, and altered consciousness. Left untreated, HACE progresses from confusion and impaired mentation, to drowsiness, obtundation, coma and death. The mechanisms leading to HACE are presumably similar to those causing AMS, and HACE may be considered the severe form of AMS. Therefore a person with AMS who becomes confused or starts staggering when they walk is developing HACE. Immediate descent is mandatory to prevent progression and death. Recovery is not as rapid as in AMS or HAPE; ataxia and altered mental status may persist even after descent of several thousand meters. Oxygen, if available, should be administered with descent both to improve oxygenation and because HACE is often associated with HAPE. Dexamethasone should be administered by whatever route available in doses of four to six milligrams every six hours. If descent is impossible because of weather or terrain conditions, a portable hyperbaric chamber is an alternative but should not delay descent.
On Denali patients with HACE are often times recognized at 5,100 meters and are immediately ground evacuated by litter to 4,100 meters (or air evacuated from 4,100 meters, weather permitting). Supplemental oxygen and dexamethosone, 8 mg initially then 4 mg every six hours, are the mainstays of therapy. Patients tend to remain severely ataxic even if other neurologic symptoms resolve, and therefore are helicopter evacuated as soon as weather permits - which may take days. A portable hyperbaric chamber is available in the rescue cache at 5,100 meters if descent to the 4,200 meter medical camp is impossible because of weather or terrain conditions.
High Altitude Pulmonary Edema (HAPE)
HAPE is a form of pulmonary edema that occurs after acute ascent to high altitude greater than 2500 meters. HAPE is a non-cardiogenic pulmonary edema, which by definition means that the flooding of alveoli with fluid is not due to heart failure, but rather to a leak in the pulmonary blood vessels. The incidence of HAPE varies with rate of ascent and ultimate altitude attained. Incidence has been reported as high as 15% in Indian troops airlifted from sea level to altitudes between 3,500 meters and 5,500 meters, but only 2% in climbers making a more gradual ascent to 6,150 meters on Denali, and 0.01% in skiers at 2,500 meters in the Colorado Rockies. Contributing factors to HAPE may include exertion, cold ambient temperature, and a pre-existing upper respiratory infection. The clinical presentation includes symptoms of fatigue, shortness of breath at rest, marked decrease in exercise tolerance, and a dry cough that progresses to a cough productive of white frothy sputum.
Treatment of HAPE consists of improving oxygenation either with descent to a lower altitude or administration of supplemental oxygen. Mild to moderate cases of HAPE respond well to therapy with resolution of symptoms within hours after descent of 1000 meters. Untreated, HAPE may rapidly progress to death in less than 24 hours.
On Denali HAPE is treated with supplemental oxygen via nasal canula or face mask overnight, and arterial oxygen saturation is monitored and maintained above 85%. Patients usually sleep in the medical shelter and then descend with their climbing team the next day to at least the 3,300 meter camp. HAPE is almost always self-evacuated with the help of the patients' climbing team. Helicopter rescue is only used when there is associated cerebral edema. Climbers with HAPE are instructed to descend to at least 3,300 meters, or lower if symptoms are not resolved at that altitude. After at least a three nights stay at 3,300 meters climbers may reascend if they desire, and sometimes eventually reach the summit without recurrence of HAPE.
Colin is a physician for the U.S. National Park Service, 14,000 Ft. Medical Camp, Mt McKinley (Denali), Alaska. He is also an Instructor of Medicine at the University of Utah School of Medicine, Pulmonary and Critical Care Division, LDS Hospital, Salt lake City, Utah. This article is a summary of his presentation at the Winter Wilderness Medical Course in Breckenridge, Colorado. The course was sponsored by the Wilderness Medical Society.
