Altitude illness
Altitude Illness is common in higher altitudes, where the amount of oxygen is considerably lesser than sea level. It mostly occurs when the body can’t acclimatize to the new surroundings while we are in high hills and mountains. Cold, low humidity, increased UV radiation, and lower air pressure are all stressors of the high-altitude environment, all of which can pose issues for travellers. Hypoxia, on the other hand, is the major worry. The severity of hypoxic stress is determined by altitude, rate of climb, and exposure time. The greatest hypoxia is produced when sleeping at high altitudes; day visits to high altitudes followed by a return to low altitudes are far less taxing on the body.
The human body adapts to mild hypoxia extremely effectively, but it takes time(Box 2-02). Acute acclimation to high altitude takes 3 to 5 days to complete. It is essential to acclimate for a few days at 8,000–9,000 feet (2,500–2,750 meters) before moving to a higher elevation. Acclimatization reduces the risk of altitude sickness, improves sleep quality, and enhances overall comfort and well-being. Exercise performance should be reduced slightly at high altitude compared to low altitude. The most important element in acute acclimatization is increased ventilation; therefore, respiratory depressants must be avoided at all costs. In extreme acclimation, increased red-cell production has little effect.
Risk for travellers
Any tourist travelling to altitudes of 8,000 feet (2,500 meters) or above may get altitude sickness due to insufficient acclimatization. Altitude sickness susceptibility and resistance are inherited characteristics, and there are no easy screening methods to identify risk. Training and physical fitness have little effect on risk. Children and adults are both vulnerable, however individuals over the age of 50 are at a somewhat reduced risk.
The most trustworthy indicator for future expeditions is how a tourist has responded to high altitude in the past, although it is not infallible. However, assuming a certain level of sensitivity, the rate of climb and effort have a significant impact on the risk (see Table 2-07).Because of differences in individual sensitivity, as well as starting places and topography, determining a route that will prevent any occurrence of altitude disease is challenging. The traveler’s objective may not be to prevent all symptoms of altitude sickness, but to keep any symptoms to a minimum.
Clinical Presentation
Acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE) are the three types of altitude illness.
- Acute mountain sickness:
The most frequent type of altitude sickness is acute mountain sickness (AMS). For example, In Colorado, 25% of all tourists sleep over 8,000 feet (2,500 meters). The symptoms are similar to those of an alcohol hangover: the most common symptom is a headache, which is sometimes followed by exhaustion, lack of appetite, nausea, and vomiting.
- Headaches generally start 2–12 hours after arriving at a higher elevation, and they usually happen during or after the first night. Loss of appetite, irritability, and pallor are common in preverbal children. After 24–72 hours of acclimatization, AMS usually goes away.
- High-altitude cerebral edema:
HACE (High-Altitude Cerebral Edema) is a rare severe development of AMS (Acute Mountain Sickness); it is most commonly linked with HAPE (High-Altitude Pulmonary Edema). Lethargy becomes severe, with sleepiness, disorientation, and ataxia on tandem gait tests, in addition to AMS symptoms. If a person with HACE does not descend from a higher elevation within 24 hours of developing ataxia, they will die from HACE.
- High-altitude pulmonary edema:
HAPE can happen on its own or in combination with AMS or HACE. Increasing breathlessness with exercise is the first sign, followed by increased breathlessness during rest, with weakness and cough. In this circumstance, oxygen or descent is life-saving. HAPE is more likely to be deadly than HACE.
Pre-existing Medical Problems
Before undertaking high-altitude travel, travelers with medical conditions such as heart failure, myocardial ischemia (angina), sickle cell disease, or any form of pulmonary insufficiency should consult a physician familiar with high-altitude medical issues. At high elevations, the risk of developing new ischemic heart disease in previously healthy tourists does not appear to rise.People with diabetes can safely go to high elevations, but they must become used to activity and use a glucometer to closely check their blood glucose levels. Travelers having type 1 diabetes, diabetic ketoacidosis may be triggered by altitude illness and may also be arduous to treat those on acetazolamide. At high elevations, not all glucose meters are accurate.
Visual difficulties at higher altitudes are rare. However, some persons who have had a radial keratotomy may develop acute hypermetropia and have difficulties ascending at very high altitudes. At high elevations, LASIK and other modern treatments may cause relatively minimal vision problems.There have been no studies or case reports of a fetus being harmed if the mother goes to high elevations shortly during pregnancy. However, it may be prudent to advise pregnant women to avoid sleeping at elevations more than 12,000 feet (3,700 meters), if conceivable. It’s also important to talk about the risks of having a pregnancy problem in a remote, hilly area.
Tips for acclimatization:
•If at all feasible, ascend gently. Try not to move from a low altitude to a >9,000 feet (2,750 m) sleeping elevation in one day. Move sleeping altitude no higher than 1,600 ft (500 m) each day once at >9,000 feet (2,750 m), and schedule an extra day for acclimatization every 3,300 ft (2,750 m) (1,000 m).
•If a sudden ascent is inevitable, consider taking acetazolamide to accelerate acclimatization.
•For the first 48 hours, better avoid alcohol.
•Exercise just lightly during the first 48 hours.
•Having a high-altitude exposure of >9,000 feet (2,750 m) for two nights or more within 30 days after the trip is vital.
Table: Acute mountain sickness risk categories
Abbreviations: AMS, acute mountain sickness; HACE, high-altitude cerebral edema; HAPE, high-altitude pulmonary edema.
DIAGNOSIS AND TREATMENT
Acute Mountain Sickness/High-Altitude Cerebral Edema
The differential diagnosis of AMS/HACE includes dehydration, fatigue, hypoglycemia, hypothermia, or hyponatremia. Focal neurologic symptoms, or seizures, are infrequent in HACE and should lead to suspicion of an intracranial lesion or seizure disease. Patients with AMS can descend up to 1,000 feet (300 meters) and their symptoms will subside quickly. Supplemental oxygen at a rate of 2 liters per minute, on the other hand, will ease headaches rapidly and treat AMS over many hours, although it is rarely accessible. Acute Mountain Sickness can be treated with non-opiate analgesics and antiemetics such ondansetron while staying at their present altitude. They can also take acetazolamide, which aids acclimatization and successfully cures AMS, but is best used for prevention rather than therapy.
Dexamethasone is more efficient than acetazolamide at relieving the symptoms of mild to critical AMS rapidly. If the traveler’s symptoms increase while resting at the same altitude, they must descend to a safer place.
When neurologic symptoms, such as ataxia, confusion, or altered mental state, are present, HACE represents a continuation of AMS. In the presence of HAPE, HACE may arise. HACE can be treated at altitude with supplementary oxygen and dexamethasone in inhabited regions with access to medical care. Descent should be started in anybody suspected of having HACE in remote regions. If descent is not possible due to logistical problems, Supplemental oxygen or a portable hyperbaric chamber would be the best option if available to cure it.
High-Altitude Pulmonary Edema
Although the development of decreasing exercise tolerance, increasing breathlessness, and breathlessness at rest is nearly always identifiable as HAPE, the differential diagnosis includes pneumonia, bronchospasm, myocardial infarction, or pulmonary embolism. In this situation, descending is urgent and necessary, and it should be done with as little effort as possible for the patient.
Supplemental oxygen or a portable hyperbaric chamber to be used if descent takes time. Patients with moderate HAPE who have access to oxygen (for example, in a hospital or a high-altitude medical clinic) may not need to descend to a lower elevation and can be treated with oxygen at their current altitude. Nifedipine can be utilized as an accompaniment to descent, oxygen, or portable hyperbaric treatment in the field, when resources are limited and there is a reduced margin for error. If nifedipine is not available, a PDE inhibitor can be used instead, although several pulmonary vasodilators should not be taken at the same time.
Medications
Along with discussions below, Table 2-08 contains guidelines for the use and dosing of medicines to prevent and treat altitude sickness.
Acetazolamide
When taken before climbing, acetazolamide prevents AMS, and when given after symptoms have started, it helps accelerate recovery. The drugs work by increasing respiration and therefore assisting acclimation by acidifying the blood. 125 mg every 12 hours, starting the day before climb and continuing for the first two days at altitude, or longer if ascent continues, is an effective adult dosage that reduces the usual side effects of increased urine and paresthesia of the fingers and toes. Acetazolamide causes little allergic responses. It does not react with antimicrobial sulfonamides since it is a non-antimicrobial sulfonamide. People who have previously experienced anaphylaxis to any sulfa should avoid it. Acetazolamide has caused adverse responses in those who have had a severe penicillin allergy in the past. The pediatric dosage is 5 mg/kg/day, split into two doses of 125 mg each.
Dexamethasone
Dexamethasone is a medication that can be used to prevent and treat AMS, HACE, and perhaps HAPE. In contrast to acetazolamide, if the medication is stopped before acclimation, a rebound might develop. While ascending, acetazolamide is preferred for preventing AMS, with dexamethasone retained for therapy as an adjuvant to descending. Adults should take 4 mg every 6 hours. Dexamethasone is increasingly being used on “summit day” on high peaks like Kilimanjaro and Aconcagua to prevent altitude sickness.
Nifedipine
Nifedipine both prevents and improves HAPE. It is only given to those who are particularly vulnerable to the disease in order to avoid it. Adults should take 30 mg of extended-release every 12 hours or 20 mg every 8 hours for prevention or therapy.
Other medications
Phosphodiesterase-5 inhibitors can also reduce pulmonary artery pressure while having a minimal effect on systemic blood pressure. Taking 10 mg of tadalafil twice a day during ascent can help avoid HAPE and is being researched as a therapy. Ginkgo Biloba, administered 100–120 mg twice a day before ascent, was proven to decrease AMS in adults in some studies, but not in others, perhaps owing to differences in components. Recently, it was shown that taking 600 mg of ibuprofen every 8 hours might help prevent AMS, though it was not as efficient as acetazolamide. It is, however, non-prescription, low-cost, and well-tolerated.
Prevention of acute altitude sickness or death
The goal of providing altitude sickness information to visitors is not to remove the risk, but to avoid mortality or evacuation as a result of altitude sickness. Because the onset of symptoms and clinical courses are both delayed and predictable, there is no reason for someone to die from altitude sickness unless they are trapped by extreme weather or geographical conditions that make descending nearly impossible.Altitude sickness can be avoided by following three rules:
• Recognize the early signs of altitude sickness and be prepared to admit when they occur.
• Never sleep at a higher altitude if you’re suffering from altitude sickness, no matter how slight the symptoms appear to be.
•If the symptoms worsen while resting at the same altitude, descend as soon as possible.
A pressurization bag (such as the Gamow bag) might be useful for hiking parties and excursions travelling into isolated high-altitude locations where the descent to a lower level may be problematic. Depending on the initial height, a foot pump provides a 2 lb/in2 rise in pressure, simulating a drop of 5,000–6,000 ft (1,500–1,800 m). The backpack and pump weigh around 14 pounds when packed (6.5 kg).
Table: Medication doses recommended to prevent and cure altitude sickness
Abbreviations: AMS, Acute Mountain Sickness; HACE, High-Altitude Cerebral Edema; IV, intravenous; IM, intramuscular; HAPE, High-Altitude Pulmonary Edema; SR, Sustained Release.
1. Acetazolamide can be used as an adjuvant to dexamethasone in the treatment of HACE at this dosage, although dexamethasone is still the primary therapy for that disease.
2. Should only be used in combination with oral medicines and not as a stand-alone treatment.
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