4 Altitude, Heat, and Cold Problems EDWARD J. S HAHADY Patients may choose to be physically active in environments that can create ill- ness, like high and low attitudes and the extremes of heat and cold. The pri- mary care clinician needs to be aware of how to prevent and treat problems that are associated with these environments. Age, comorbid disease, and use of certain medications increase risk of environmental illness in some patients. A good working knowledge of the physiological responses to changes in alti- tude and temperature, clinical symptoms, and principles of treatment and pre- vention will facilitate effective management of this group of patients. Table 4.1 lists some of the problems that are encountered by the primary care clinician. 1. High-Altitude Sickness 1.1. Acute Mountain Sickness Thirty-four million people travel yearly to high altitudes for some type of recreational activity. Heights above 5000 ft usually produce some mild symp- toms of shortness of breath and mild headache for a few days. Individuals with compromised pulmonary function, the elderly, and those with other chronic diseases may experience more severe symptoms and symptoms at less elevation. Twenty-five percent of those who travel above 8500 ft experience symptoms of high-altitude illness and one in 100 develop serious symptoms. The syndrome of high-altitude illness represents a spectrum of clinical condi- tions that range in severity from mild acute mountain sickness (AMS) with an unpleasant constellation of symptoms to the life-threatening conditions of high-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE). Acute mountain sickness may also be the early presentation of a process that can progress to life-threatening HAPE or HACE. Although most primary care clinicians practice in areas below 5000 ft they still will encounter altitude sickness. Patients will rely on primary care clinicians for advice on pre- vention of altitude illness and if they become ill the telephone and the Internet bring patients and clinicians together no matter what the distance. 35 36 E.J. Shahady TABLE 4.1. Classification of environmental problems. High-altitude illness ● Acute mountain sickness ● High-altitude pulmonary edema ● High-altitude cerebral edema ● Other altitude-related disorders: retinopathy, peripheral edema, venous stasis ● Chronic diseases and altitude Low-altitude illness ● Barotrauma to ears, sinuses, teeth, skin ● The bends Heat injury ● Heat cramps ● Heat exhaustion (heat syncope) ● Heatstroke Cold injury ● Hypothermia—mild, moderate, severe ● Frostbite ● Chilblains The symptoms of mild AMS are similar to a viral syndrome, a hangover, or physical exhaustion. These vague symptoms have led to misdiagnosis in some cases. In a setting of high-altitude exposure, these vague symptoms should be considered AMS until proven otherwise. The diagnosis of AMS can be made when a patient has had a recent exposure to increase in altitude for several hours and complains of a head- ache plus at least one of the following symptoms: nausea, vomiting, loss of appetite, fatigue, dizziness, light-headedness, and difficulty in sleeping. The headache may be mild but is usually bitemporal and throbbing in nature. The other symptoms described may range in severity from mild to incapacitating. Acute mountain sickness symptoms usually develop within a few hours after arrival at high altitude and reach maximum intensity in 24 to 48 h. Most individuals become symptom-free by the third or fourth day. The onset of symptoms may be delayed in some individuals for up to 4 days and a few may have symptoms that may be prolonged for up to 1 month. Most people tol- erate or treat their symptoms by remaining at the same altitude until the ill- ness resolves. Acute mountain sickness is rare below 8000 ft and is more common with rapid ascent to altitudes greater than 10,000 ft. Difficulty with breathing on exertion is common at high altitudes but if the difficulty is present at rest, HAPE may be present. Similarly, any alteration in mentation or signs of ataxia suggests the presence of HACE. Any hint of HAPE or HACE should be taken seriously. 4. Altitude, Heat, and Cold Problems 37 1.1.1. Treatment The mild forms of AMS may not require specific treatment. It usually resolves spontaneously if further ascent and exercise are avoided. Halting ascent or activity to allow further acclimatization may reverse the symptoms; however, continuing the ascent exacerbates the underlying pathologic processes and may lead to disastrous results. Further treatment is indicated if the symptoms become severe enough to interfere with the individual’s activities. Acetazolamide (Diamox) speeds the process of acclimatization and, if given early in the illness, leads to a more rapid resolution of symptoms. A dose of 250 mg of acetazolamide given at the onset of symptoms and repeated twice daily is effective therapy. If AMS does not respond to maintenance of altitude, rest, and pharmacologic intervention within 24 h, the patient should descend to a lower altitude. A descent of 1500 to 3000 ft effectively reverses high- altitude illness in most cases. Oxygen, if available, addresses the primary insult of high-altitude exposure, corrects hypoxemia, and relieves the headache. For persistent difficulty in sleeping, it can be given in small amounts (1 to 2 L/min) during sleep. Insomnia generally results from periodic breathing, which is experienced by most visitors to altitude. This is best treated with the respira- tory stimulant acetazolamide. Doses of acetazolamide as low as 62.5 mg at bedtime may be adequate to prevent periodic breathing and eradicate insom- nia. Avoid the use of benzodiazepines and other sedative hypnotics because of their tendency to decrease ventilation during sleep. Dexamethasone is an effective treatment for AMS. It is usually used for patients who cannot tolerate acetazolamide, or in more advanced cases of AMS. Trials have used 8 mg initially, followed by 4 mg every 6 h. 1.1.2. Prevention The symptoms of AMS can be unpleasant enough to interfere or interrupt travel, business, or vacation plans. The majority of individuals with AMS report a decrease in activity. Allowing adequate time for acclimatization by slow ascent is the best method of prevention. This may not be possible for a short vacation period. The altitude where the individual sleeps is the key alti- tude. The ideal first-night altitude is no higher than 8000 ft, with a subse- quent increase of not more than 2000 ft each night. If the journey begins at 10,000 ft, then three nights should be spent acclimatizing. Daytime excur- sions to higher altitudes with a return to a lower sleeping altitude are accept- able. Mild to moderate exercise aids acclimatization but overexertion may contribute to AMS. Intake of a high-carbohydrate diet and maintenance of adequate hydration are helpful. Acetazolamide (Diamox) is very effective in preventing AMS. Lower dosages provide similar prophylaxis with fewer adverse reactions than higher dosages. The current recommended dosage is 125 mg twice daily starting 24 h before ascent and continuing for the first 2 days at high altitude. The dosage for 38 E.J. Shahady children is 2.5 mg/kg/dose up to 125 mg total, given twice daily. Acetazolamide is a carbonic anhydrase inhibitor that induces a mild diuresis and stimulates res- piration. This respiratory stimulation is particularly important during sleep, when the hypoxemia caused by periodic breathing is eradicated by acetazo- lamide. The diuretic effects reduce fluid retention in AMS. This drug also low- ers cerebrospinal fluid (CSF) volume and pressure, which may play an additional role in prevention and treatment of cerebral edema. The most common adverse reactions to acetazolamide include paresthesias and polyuria. Less common reactions include nausea, drowsiness, tinnitus, and transient myopia. The flavor of carbonated beverages such as soft drinks or beer may change. Acetazolamide is a sulfa drug, so patients allergic to sulfa drugs may have a reaction. Dexamethasone can prevent AMS but should be reserved for individuals who cannot tolerate acetazolamide. The lowest effec- tive dosage is 4 mg every 12 h. Other issues that aid with prevention include carbohydrate ingestion and avoiding alcohol and smoking. Some but not all studies suggest carbohydrates as the most efficient form of fuel for digestion. This fuel consumes less oxygen and may leave more oxygen available for other bodily activities. Avoidance of alcohol and smoking optimizes acclimatization. Alcohol depresses respiration and produces dehydration. Smoking cigarettes decreases oxygen-carrying capacity. 1.2. High-Altitude Pulmonary Edema HAPE is the most common fatal manifestation of severe high-altitude illness. It is uncommon below 10,000 ft but can occur at 8000 ft related to heavy exercise. At higher altitudes, it may also occur at rest or with light activity. The symptoms may start a few hours after reaching the higher altitude but usually begin slowly 2 to 4 days after arrival at high altitude. Dyspnea on exertion, fatigue with min- imal to moderate effort, and dry cough are early manifestations of the disease. These symptoms may be subtle but noticeable when comparing the victim with others in the group. The symptoms of AMS are also usually present. As HAPE progresses the dyspnea intensifies with effort and is unrelieved by rest. The cough becomes productive of copious amounts of clear watery sputum, and with time, hemoptysis. This may be followed by ataxia and altered mentation secondary to hypoxemia and/or cerebral edema. Examination reveals an increased respiratory and heart rate, with audible rhonchi and gurgles. 1.2.1. Treatment Descent to a lower altitude, bed rest, and supplemental oxygen are the most effective methods of therapy. Descents of 1500 to 3000 ft should be adequate to allow for a rapid recovery. After recovery, the victim may be able to reas- cend in 2 or 3 days.