What is Medicine – Altitude Illness
ESSENTIAL DESCRIPTION Ascent to greater elevations can cause a variety of brain and pulmonary symptoms, some of which can be fatal, as a direct result of insufficient acclimatisation. The following height ranges are classified as intermediate: 1,520 to 2,440 metres; high: 2,440 to 4,270 metres; very high: 4,270 to 5,490 metres; and extreme: >5,490 metres. Everyone, even seasoned travellers and physically strong people, can develop altitude sickness. The majority of people experience it as an unpleasant (self-limited) syndrome that doesn't need treatment. Acute mountain sickness (AMS) is a set of symptoms brought on by the body's reaction to a hypobaric, hypoxic environment. Onset often happens 6 to 12 hours after climbing more than 2,500 metres. The majority of the symptoms are neurological, ranging from mild to serious headache, malaise, and severe impairment. High-altitude pulmonary edoema (HAPE): noncardiogenic pulmonary edoema that occurs at elevations of 3,000 m or higher and is uncommon between 2,500 and 3,000 m. High-altitude cerebral edoema (HACE) is a potentially fatal neurologic disease that develops after at least two days at altitudes greater than 4,000 metres. System(s) impacted: pulmonary and nervous Mountain sickness is a possible synonym. Aspects of Geriatrics Age alone should not prevent travel to high altitude; provide extra time to acclimatise. Risk does not increase with age. Exacerbation of pre-existing medical disorders known as altitude-exacerbated conditions Child Safety Considerations Altitude sickness seems to affect children at the same rate as it does adults, however younger children may take longer to get diagnosed. Any youngster who exhibits behavioural signs following a recent ascent should be assumed to have an illness associated with high altitude. No data suggests that exposure to high altitudes (1,500 to 3,500 m) poses a harm to a pregnancy, hence the risk during pregnancy is uncertain. EPIDEMIOLOGY The majority of epidemiologic studies are only conducted on male groups that are comparatively homogeneous. Incidence AMS: 10–25% of unacclimatized climbers who reach 2,500 m; 50–85% at 4,500–5,500 m; and HAPE/HACE: 0.5%–1.0% of climbers who spend two or more days at elevations above 3,000 m. Above 2,500 m (8,200 feet), for every 1,000 m rise in altitude, the risk of acute mountain sickness (AMS) increases by 13%. PATHOPHYSIOLOGY AND AETIOLOGY People who have experienced AMS, HACE, or HAPE in the past are more likely to experience it again. Altitude illness's pathophysiologic predecessors include hypobaric hypoxia and hypoxemia. Other mechanisms include impaired cerebral autoregulation, release of vasogenic mediators, and alteration of the blood-brain barrier. HAPE is a noncardiogenic pulmonary edoema characterised by exaggerated pulmonary hypertension leading to vascular leakage through overperfusion, stress failure, or both. Symptoms of AMS may be caused by cerebral swelling, either through vasodilatation induced by hypoxia or through cerebral edoema. Genetics It is unclear what genetic factors contribute to AMS predisposition. RISK FACTORS include: inadequate acclimatisation at a lower altitude; ascent rates greater than 300 to 500 metres per day; extreme altitude; increased time spent at high altitude; higher altitude at night; previous history of altitude illness; cardiac congenital abnormalities; female gender; migraine history; younger age (46 years); and history of anxiety. GENERAL PREVENTION Fundamental principles - Preacclimatization, or being exposed to hypoxia before climbing, guards against altitude sickness. – Altitude sickness can also be avoided by making a staged ascent over six to seven days at 2,200 to 3,000 metres. - >2,500 m, don't climb more quickly than 500 m/day, and take breaks every 3 to 4 days (2). - Lower sleeping altitude: "Climb high and sleep low" is advised for everyone travelling above 3,500 m. - For the first 1 to 3 days at altitude, refrain from strenuous activity. - Steer clear of sedatives and alcohol, which inhibit breathing. – Physical conditioning before an event is not preventative. Acetazolamide, dexamethasone, and ibuprofen are examples of pharmacologic prophylaxis. Only if at risk, consider nifedipine, -agonists, and tadalafil for the prevention of HAPE. DIAGNOSIS HISTORY Symptoms of AMS include headache, anorexia, irritability, extreme exhaustion, nausea, vomiting, lightheadedness, dizziness, and insomnia. – The Lake Louise diagnostic criteria, which range from 0 (none) to 3 (severe), has been used to study severity. Headache, GI symptoms, weakness or exhaustion, lightheadedness or dizziness, and AMS Clinical Functional Score (symptom impact on activities) A headache score of at least 1 point and a total score of at least 3 points are required to diagnose AMS. Reduced capacity for activity, coughing after exertion followed by dyspnea at rest, cyanosis, and a productive cough that may produce pink frothy sputum are all indications of HAPE. HACE symptoms include altered mental status, which may lead to ataxia and disorientation. Other symptoms include illogical behaviour, lethargy, obtundation, and coma. Physical examination findings include HAPE, lupus-like symptoms, central cyanosis, tachycardia, and tachypnea. HACE - Abnormal mental status examination (coma, coma-like behaviour, lethargy, obtundation) Truncal ataxia, papilledema, retinal haemorrhage, and cranial nerve palsies are some of the less common symptoms. DIFFERENTIAL DIAGNOSIS AMS/HACE - Dehydration - Ingestion of toxins, drugs, or alcohol - Subarachnoid haemorrhage, CNS mass, cerebrovascular accident - Migraine headache - Carbon monoxide exposure - CNS infection - Acute psychosis - HAPE - Pneumonia - Cardiogenic pulmonary edoema - Spontaneous pneumothorax - Pulmon The absence of a headache, the onset of symptoms after more than three days at a certain altitude, or a slow reaction to oxygen or descent point to a different diagnosis. Initial tests (lab, imaging) Diagnostic tests and interpretation AMS: Diagnostic laboratory tests are infrequent and nonspecific. HAPE: Extremely low oxygen levels as shown by oximetry or blood gas analyses. Patchy infiltrates are frequently visible on chest radiographs. A different diagnosis is suggested by clear lung areas. ECG results could indicate right-sided cardiac strain or sinus tachycardia. UNSPECIFED MEASURES People who have never been exposed to high altitudes should follow the acclimatisation instructions. If symptoms do not go away within 24 hours, discontinue your ascent, acclimatise at the same altitude, and/or descend. Moving to a lower altitude is the only effective treatment. Even slight drops in altitude result in dramatic improvements. Oxygen aids in symptom relief. Give continuously using a cannula or mask and titrate until your SaO2 is above 90%. AMS symptoms are lessened to a slight to moderate extent by acetazolamide. - Dexamethasone may be useful in the management of mild AMS. Keep the patient warm and minimise effort with oxygen treatment (HAPE). Immediate descent or evacuation to a lower altitude. When a descent is impossible, portable hyperbaric therapy (2 to 15 psi using a Gamow bag or Chamberlite) is a useful and effective option. - Nifedidipine Immediate descent HACE - Extra oxygen (maximum flow possible; keep SaO2 over 90%) - Dexamethasone - If available and impractical, portable hyperbaric therapy. First Line: MEDICATION Oxygen: Maintain SaO2 >90% at 2 to 15 L/min until symptoms subside Acetazolamide: Take into account therapy for primary prevention if the patient has a history of issues at altitude and/or expects to ascend more than 500 m per day above 2,500 m. In those who have a sulfonamide allergy, avoid. Adults should take 125 mg PO BID commencing 24 hours prior to ascension and continuing for 2 to 4 days at a steady altitude. Children should take 2.5 mg/kg (up to 125 mg) every 12 hours. - For the treatment of AMS, take 250 mg PO BID till the symptoms go away; for children, take 2.5 mg/kg q12h. Dexamethasone may considerably lessen both the frequency and severity of AMS. Negative side effects are uncommon. - To prevent AMS, take 2 mg or 4 mg orally every six hours (PO), beginning the day before climb and phasing it out gradually after two days at the highest altitude. Use not advised for prevention in children. Treatment for AMS: 4 mg PO/IV/IM every six hours; for children, 0.15 mg/kg every six hours. - To treat HACE, provide 8 mg PO/IV/IM at first, followed by 4 mg every six hours. The drug nifedipine lowers pulmonary arterial pressure.- To prevent HAPE, provide 30 mg extended-release PO BID beginning the day before climb and continuing for two days at the highest altitude. - If oxygen is available, treating HAPE with 30 mg extended-release PO every 12 hours is probably unnecessary. Tadalafil: Take into account for HAPE prevention (1). - In HAPE-susceptible individuals, use 10 mg PO BID 1 day before to ascent. Adjunct therapy with salmeterol may be used to treat HAPE (unproven): 125 mg breathed BID beginning the day before climb and continuing for two days at the highest altitude. - NSAIDs may help prevent and relieve headaches associated with AMS. Aspirin: 325 mg PO every four hours for a total of three doses Prochlorperazine: 10 mg PO/IM q6-8h; Promethazine: 25 to 50 mg PO/IM/PR q6h; Antiemetics (Ibuprofen: 400 to 600 mg PO every eight hours); Other tested treatments - Gingko balboa does not reduce the risk of AMs any more than a placebo does. Coca-containing items have been consumed in the Andes, although little research has been done on them. - There is insufficient evidence to support the use of simulated altitude or remote ischemic preconditioning (RIPC), antioxidant supplements, medroxyprogesterone, iron, or Rhodiola crenulata. - Furosemide: 20 to 80 mg PO/IV q12h for a total of 2 doses; previously evaluated for the treatment of AMS or HACE. presently unpopular, not advised for prophylaxis, and not approved for usage in HAPE. CONSIDERATIONS FOR ADMISSION, THE INPATIENT, AND NURSING minor patients receive outpatient care. RECOMMENDATIONS OR CONTINUING CARE patient observation There is no requirement for follow-up in moderate cases. For more severe cases, keep an eye on the patient until the symptoms go away. EDUCATION OF PATIENTS Talk to patients about the dangers of travelling at high altitudes and how to spot high-altitude disease signs. PROGNOSIS The majority of mild to moderate AMS cases resolve on their own and don't need treatment. Ascent may be resumed by the patient after the symptoms pass. If detected early, HAPE and HACE respond favourably to descent, evacuation, and/or medication. COMPLICATIONS Although high-altitude retinal haemorrhage typically has no symptoms, it can alter vision
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