Wilderness Medical Society Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness: 2014 Update
高海拔定義, 2500 公尺以上, 但在海拔 2000 公尺就有發生 AMS 和 HAPE 的案例. 診斷和治療高海拔疾病不要完全依賴海拔高度
預防措施要考量海拔和個人體質, 之前是否曾發生過高海拔疾病, 上升速率, 高度適應休息天數. 要排除嚴重脫水, 低血鈉, 肺炎, 低血糖等等疾病.
Defining the Threshold for High Altitude and Where to Apply These Guidelines
There is a risk of high altitude illness when unacclimatized individuals ascend to more than 2500 m. Prior studies and extensive clinical experience, however, suggest that susceptible individuals can develop AMS, and potentially HAPE, at elevations as low as 2000 m.2–4 Part of the difficulty of defining a specific threshold at which altitude illness can develop is the fact that the symptoms and signs of AMS, the most common form of altitude illness, are highly nonspecific, as demonstrated in several studies in which subjects met criteria for the diagnosis of AMS despite no gain in altitude.5–7 As a result, studies assessing AMS incidence at modest elevations may label individuals as having altitude illness when, in fact, symptoms are related to some other process, thereby falsely elevating the incidence of the disease at that elevation. Recognizing the difficulty in defining a clear threshold, the expert panel recommends an approach to preventing and treating acute altitude illness that does not depend strictly on the altitude to which an individual is traveling. Altitude illness is more common above 2500 m but can be seen at lower elevations. As a result, preventive measures should be considered not only based on the altitude to which the individual is traveling but should also take into account factors such as the prior history of performance at high altitude, rate of ascent, and availability of rest days for acclimatization (described in greater detail below). Similarly, the diagnoses of AMS, HAPE, or HACE should not be excluded simply based on the fact that an individual is ill below 2500 m. They should be strongly considered in the presence of compatible clinical features with careful attempts to exclude other entities such as severe dehydration, hyponatremia, pneumonia, or hypoglycemia, which may present in a similar manner.
AMS 與 HACE
HACE 是 AMS 末期的表現. 基本上可以當成同一疾病的早期與晚期差異. 所以在預防與治療也一起說明
Acute Mountain Sickness and High Altitude Cerebral Edema
Information on the epidemiology, clinical presentation, and pathophysiology of AMS and HACE is provided in several extensive reviews.8–11 From a clinical standpoint, HACE represents an extreme form of AMS and, as a result, preventive and treatment measures for the 2 disorders can be addressed simultaneously.
PREVENTION 預防
緩慢上升
Prophylactic measures for AMS and HACE, the evidence supporting them, and their recommendation grades are described below. Further information about how to apply these measures is then provided as part of a suggested approach to prevention.
Gradual ascent 緩慢上升. 讓身體有時間做高度適應. 睡眠海拔影響比較大.
Controlling the rate of ascent, in terms of the number of meters gained per day, is a highly effective means of preventing acute altitude illness; however, aside from 2 recent prospective studies,12,13 this strategy has largely been evaluated retrospectively.14 In planning the rate of ascent, the altitude at which someone sleeps is considered more important than the altitude reached during waking hours. Recommendation Grade: 1B.
Acetazolamide 丹木斯每天吃到 750 mg 雖也有預防效果. 但效果並沒有優於早晚各 125mg. 而副作用會加大. 目前多數指引都建議早晚各 125mg.
Multiple trials have established a role for acetazolamide in prevention of AMS.15–18 The recommended adult dose for prophylaxis is 125 mg twice daily (Table 1). Although doses up to 750 mg daily are effective at preventing AMS compared with placebo, they are associated with more frequent or increased side effects, do not convey greater efficacy, and, therefore, are not recommended for prevention. Recommendation Grade: 1A.
The pediatric dose of acetazolamide is 2.5 mg/kg/dose (maximum 125 mg/dose) every 12 hours.19 Recommendation Grade: 1C.
Dexamethasone 類固醇地塞米松. 在極端情況可以加大劑量服用(例如軍隊行軍或搜救行動需立即上升至海拔 3500 公尺以上地區). 不建議使用超過 10 天. 兒童不建議服用類固醇.
Prospective trials have established a benefit for dexamethasone in AMS prevention.20,21 The recommended adult doses are 2 mg every 6 hours or 4 mg every 12 hours. Very high doses (4 mg every 6 hours) may be considered in very high-risk situations such as military or search and rescue personnel being airlifted to altitudes greater than 3500 m with immediate performance of physical activity but should not be used outside these limited circumstances. The duration of use should not exceed 10 daysto prevent glucocorticoid toxicity or adrenal suppression. Recommendation Grade: 1A.
Dexamethasone should not be used for prophylaxis in the pediatric population because of the potential for side effects unique to this population and the availability of other safe alternatives—specifically graded ascent and acetazolamide.
Ginkgo biloba 銀杏的效果有爭議. 有些研究說有用. 有些說無用.
Although several trials have demonstrated a benefit of ginkgo in AMS prevention,22,23 several negative trials have also been published.24,25 This discrepancy may result from differences in the source and composition of the ginkgo products.26 Acetazolamide is considered far superior prophylaxis for AMS prevention. Recommendation Grade: 2C.
Ibuprofen 止痛藥物, 台灣常見的劑量是一顆 400 mg.
Two trials have demonstrated that ibuprofen (600 mg 3 times a day) is more effective than placebo at preventing AMS27,28; however, these trials did not include a comparison with acetazolamide. That comparison has been made in only a single other trial, which found equal incidence of high altitude headache and AMS between the 2 groups.29 No studies have compared ibuprofen with dexamethasone. Clinical experience with ibuprofen to prevent AMS is not extensively documented, so at this time ibuprofen cannot be recommended over acetazolamide and dexamethasone for AMS prevention. Recommendation Grade: 2B.
Preacclimatization and staged ascent 高度適應分段上升. 發 6-7 天的時間先待在中海拔 2200-3000 公尺. 之後再上升至更高海拔. 可降低AMS 機率. 緩衝肺動脈對於高海拔的反應. 但實務上可能難以執行,. 且應該怎樣做高度適應並沒有統一的解答. 在低氧環境待 15-60 分鐘或數小時這種方式可能難以達成, 長時間暴露比較能產生效益.
Several studies have shown that repeated exposure to hypobaric or normobaric hypoxia in the time preceding a high altitude excursion (referred to as preacclimatization) or spending up to 6 to 7 days at a moderate altitude (approximately 2200–3000 m) before proceeding to higher altitudes (referred to as staged ascent) decreases the risk of AMS, improves ventilation and oxygenation, and blunts the pulmonary artery pressure response after subsequent ascent to higher altitudes.30–32 Implementation of such strategies may be logistically difficult. Because the optimal methods for preacclimatization and staged ascent have not been fully determined, the panel recommends consideration of these approaches, but cannot endorse a particular protocol regarding their implementation. In general, short-term exposures (eg, 15–60 minutes of exposure to hypoxia, or a few hours of hypoxia a few times before ascent) are unlikely to be of use, whereas longer exposures (eg, 48 h/d for 47 days) are more likely to yield benefit. Recommendation Grade: 1C.
Other options 印地安山脈有咀嚼古柯葉. 古柯茶 的習俗,
Chewed coca leaves, coca tea, and other coca-derived products are commonly recommended for travelers in the Andes for prophylaxis, and anecdotal reports suggest they are now being used by trekkers in Asia and Africa for similar purposes. Their utility in prevention of Table 1. Recommended dosages for medications used in the prevention and treatment of altitude illness
Medication Indication Route Dosage
Acetazolamide (AMS, HACE)
Prevention Oral 125 mg twice a day Pediatrics: 2.5 mg/kg every 12 hours AMS
Treatment Oral 250 mg twice a day Pediatrics: 2.5 mg/kg every 12 hours
Dexamethasone AMS, HACE
Prevention Oral 2 mg every 6 hours or 4 mg every 12 hours
Pediatrics: Should not be used for prophylaxis AMS, HACE
Treatment Oral, IV, IM AMS: 4 mg every 6 hours
HACE: 8 mg once then 4 mg every 6 hours
Pediatrics: 0.15 mg/kg/dose every 6 hours
Nifedipine HAPE
Prevention Oral 30 mg ER version every 12 hours HAPE
Treatment Oral 30 mg ER version every 12 hours
Tadalafil HAPE Prevention Oral 10 mg twice a day
Sildenafil HAPE Prevention Oral 50 mg every 8 hours
Salmeterol HAPE Prevention Inhaled 125 μg twice a day
AMS, acute mountain sickness; ER, extended release; HACE, high altitude cerebral edema; HAPE, high altitude pulmonary edema.
Acetazolamide can also be used at this dose as an adjunct to dexamethasone in HACE treatment, but dexamethasone remains the primary treatment for that disorder.
Should not be used as monotherapy and should only be used in conjunction with oral medications.
Luks et al altitude illness has never been studied, however, and they should not be substituted for other established preventive measures described in these guidelines.
Multiple studies have sought to determine whether other agents, including antioxidants, leukotriene receptor blockers, phosphodiesterase inhibitors, salicylic acid, spironolactone, and sumatriptan, can prevent AMS, but the current state of evidence does not support a role in AMS prevention for any of these agents.
強迫呼吸與過度補充水分從未被證實有效. 且過度補水可能導致低血鈉,. 但適當補充水分很重要.
“Forced” or overhydration has also never been shown to prevent altitude illness and may even increase the risk of hyponatremia; however, maintenance of adequate hydration is important because symptoms of dehydration can mimic those of AMS.
Suggested approach to AMS/HACE prevention
Because the physiologic responses to high altitude and rates of acclimatization vary considerably between individuals, clinicians must recognize that the recommendations that follow, although generally effective, will not guarantee successful prevention in all high altitude travelers. The approach to prevention of AMS and HACE should be a function of the risk profile of the individual traveling to high altitude (Table 2). In low-risk situations, prophylactic medications are not necessary and individuals should rely on a gradual ascent profile. Above an altitude of 3000 m, individuals should not increase the sleeping elevation by more than 500 m per day and should include a rest day (ie, no ascent to higher sleeping elevation) every 3 to 4 days. The increase in sleeping elevation should be less than 500 m for any given day of a trip. In many areas, terrain and other logistical factors often prevent strict adherence to this approach and mandate larger gains in sleeping elevation in a single day. In such cases, rest days should be strongly considered before or after such large gains in elevation and elsewhere in the itinerary to ensure that the overall ascent rate averaged over the entire trip (eg, total elevation gain divided by the number of days of ascent during the trip) falls below the 500 m/d threshold. Prophylactic medications should be considered in addition to gradual ascent for use in moderate-to-high risk situations. Acetazolamide is the preferred agent, but dexamethasone may be used as an alternative in individuals with prior history of intolerance of or allergic reaction to acetazolamide. In rare circumstances (eg, military or rescue teams who must ascend rapidly to and perform physical work 43500 m), consideration can be given to concurrent use of acetazolamide and dexamethasone. This strategy should be avoided except in these particular or other emergency circumstances that mandate a very rapid ascent. Acetazolamide carries a low risk of cross-reactivity in persons with sulfonamide allergy, but persons with known allergy to sulfonamide medications should consider a supervised trial of acetazolamide before the trip, particularly if planning travel into an area remote from medical resources.33 A history of anaphylaxis to sulfonamide medications should be considered a contraindication to acetazolamide. Acetazolamide and dexamethasone should be started the day before ascent (but will still have beneficial effects if started on the day of ascent). For individuals ascending to and staying at the same elevation for more than several days, prophylaxis may be stopped after 2 days at the target altitude. Individuals ascending faster than the recommended ascent rates should continue prophylaxis for a total of 4 days after arrival at the target altitude. Recommendation Grade: 2C. For individuals ascending to a high point and then descending toward the trailhead (eg, descending from the summit of Kilimanjaro), prophylactic medications should be stopped once descent is initiated.
TREATMENT
Potential therapeutic options for AMS and HACE include the following. Descent When feasible, descent remains the single best treatment for AMS and HACE. However, it is not necessary in all circumstances (discussed further below). Individuals should descend until symptoms resolve, unless impossible because of terrain. Symptoms typically resolve after descent of 300 to 1000 m, but the required descent will vary between persons. Individuals should not descend alone, particularly in cases of HACE. Recommendation Grade: 1A.
Supplemental oxygen 使用鼻導管給予氧氣將血氧濃度提升到 90% 可代替下降高度, 通常是用於無法下降的情況, 一般情況不建議這樣用.
Oxygen delivered by nasal cannula at flow rates suffi- cient to raise SpO2 to 90% provides a suitable alternative to descent. Use is not required in all circumstances and is generally reserved for severe cases when descent is not feasible. Unlike at hospitals or large clinics, the supply of oxygen may be limited at remote high altitude clinics or on expeditions, necessitating careful use of this therapy. Recommendation Grade: 1C.
Portable hyperbaric chambers 加壓艙. 可治療嚴重高海拔疾病, 但需有人一直在旁邊照護,. 對於嘔吐患者可能不適用. 出艙之後可能症狀再發. 在能下降的情況. 不要因為想使用加壓艙而耽誤下降.
These devices are effective for treating severe altitude illness34,35 but require constant tending by care providers and are difficult to use with claustrophobic or vomiting patients. Symptoms may recur when individuals are removed from the chamber.36 Use of a portable hyperbaric chamber should not delay descent in situations in which descent is feasible. Recommendation Grade: 1B.
Acetazolamide
Only 1 study has examined acetazolamide for treatment of AMS. The dose studied was 250 mg twice daily and whether a lower dose might suffice is unknown.37 Recommendation Grade: 1B. No studies have assessed treatment of AMS in pediatric patients, but anecdotal reports suggest it has utility in this regard. The pediatric treatment dose is 2.5 mg/kg/dose twice daily up to a maximum of 250 mg/dose. Recommendation Grade: 1C.
Dexamethasone
Dexamethasone is very effective in the treatment of AMS.38–40 The medication does not facilitate acclimatization, and further ascent should be delayed until the patient is asymptomatic while off the medication. Recommendation Grade 1B.
Extensive clinical experience supports the use of dexamethasone in patients with HACE. It is administered as an 8-mg dose (IM, IV, or PO) followed by 4 mg every 6 hours until symptoms resolve. The pediatric dose is 0.15 mg/kg/dose every 6 hours.19 Recommendation Grade: 1C.
急性高山病/高海拔腦水腫建議事項 Suggested approach to AMS/HACE treatment
罹患AMS的人應停止上升.
服用非嗎啡類止痛藥物.
服用止吐藥物緩解腸道症狀.
可以在原地海拔待著.
丹木斯對於預防高海拔疾病的效果優於治療疾病,
丹木斯可加速高度適應,.
但類固醇對於治療已經出現的中度至重度高海拔症狀療效更快速.
但通常也需要配合下降高度.
當AMS 症狀緩解之後可再次上升.
但當症狀尚未緩解不可上升至發病高度.
Care should be taken to exclude disorders whose symptoms and signs may resemble those seen in AMS and HACE, such as dehydration, exhaustion, hypoglycemia, hypothermia, or hyponatremia.8 Persons with altitude illness of any severity should stop ascending and may need to consider descent depending on the clinical circumstances and severity of illness (Table 3).8 Patients with AMS can remain at their current altitude and use nonopiate analgesics for headache and antiemetics for gastrointestinal symptom relief; that may be all that is required. Acetazolamide will help treat AMS by facilitating acclimatization through increased ventilation and diuresis, but these physiologic effects may work better for prevention than for treatment. Although acetazolamide is good for treating mild illness, experienced clinicians have found dexamethasone a more reliably effective treatment for moderate-to-severe disease, which often requires descent as well. Individuals with AMS may resume their ascent once symptoms resolve, but further ascent or reascent to a previously attained altitude should never be undertaken in the face of ongoing symptoms.
After resolution of AMS, reascent with acetazolamide is prudent.
HACE與嚴重AMS的差異在於是否出現運動失調或神智改變, HACE與HAPE可同時發生. 發生HACE建議送醫, 同時開始氧氣治療與使用類固醇. 偏遠地區如果無醫療設備, 懷疑罹患HACE的時候應立即下降高度. 如果無法下降則考慮給予氧氣或使用加壓艙. 同時給予類固醇.
HACE is differentiated from severe AMS by neurological signs such as ataxia, confusion, or altered mental status in the setting of acute ascent to high altitude and may follow AMS or occur concurrently with HAPE. Individuals developing HACE in populated areas with access to hospitals or specialized clinics should be started on supplemental oxygen and dexamethasone. In remote areas away from medical resources, descent should be initiated in any suspected HACE victim or if symptoms of AMS are not responding to conservative measures or treatment with acetazolamide or dexamethasone. If descent is not feasible owing to logistical issues, supplemental oxygen or a portable hyperbaric chamber should be considered. Persons with HACE should also be started on dexamethasone. No further ascent should be attempted until the victim is asymptomatic and no longer taking dexamethasone.
Care should be taken to exclude disorders whose symptoms and signs may resemble those seen in AMS and HACE, such as dehydration, exhaustion, hypoglycemia, hypothermia, or hyponatremia.8 Persons with altitude illness of any severity should stop ascending and may need to consider descent depending on the clinical circumstances and severity of illness (Table 3).8 Patients with AMS can remain at their current altitude and use nonopiate analgesics for headache and antiemetics for gastrointestinal symptom relief; that may be all that is required. Acetazolamide will help treat AMS by facilitating acclimatization through increased ventilation and diuresis, but these physiologic effects may work better for prevention than for treatment. Although acetazolamide is good for treating mild illness, experienced clinicians have found dexamethasone a more reliably effective treatment for moderate-to-severe disease, which often requires descent as well. Individuals with AMS may resume their ascent once symptoms resolve, but further ascent or reascent to a previously attained altitude should never be undertaken in the face of ongoing symptoms.
After resolution of AMS, reascent with acetazolamide is prudent.
當AMS緩解之後, 再次上升建議預防性服用丹木斯.
HACE與嚴重AMS的差異在於是否出現運動失調或神智改變, HACE與HAPE可同時發生. 發生HACE建議送醫, 同時開始氧氣治療與使用類固醇. 偏遠地區如果無醫療設備, 懷疑罹患HACE的時候應立即下降高度. 如果無法下降則考慮給予氧氣或使用加壓艙. 同時給予類固醇.
仍在服用類固醇的HACE患者不可以再次上升. 症狀沒改善也不可以再次上升
HACE is differentiated from severe AMS by neurological signs such as ataxia, confusion, or altered mental status in the setting of acute ascent to high altitude and may follow AMS or occur concurrently with HAPE. Individuals developing HACE in populated areas with access to hospitals or specialized clinics should be started on supplemental oxygen and dexamethasone. In remote areas away from medical resources, descent should be initiated in any suspected HACE victim or if symptoms of AMS are not responding to conservative measures or treatment with acetazolamide or dexamethasone. If descent is not feasible owing to logistical issues, supplemental oxygen or a portable hyperbaric chamber should be considered. Persons with HACE should also be started on dexamethasone. No further ascent should be attempted until the victim is asymptomatic and no longer taking dexamethasone.
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