HACE 是 AMS 末期表現, HACE 發生率不高, 但如果沒有適當診斷治療, 會在 24 小時內因腦疝脫 brain herniation 快速進展至死,
Introduction
High Altitude Cerebral Edema (HACE) is a severe and potentially fatal manifestation of high altitude illness and is often characterized by ataxia, fatigue, and altered mental status. HACE is often thought of as an extreme form/end-stage of Acute Mountain Sickness (AMS). Although HACE represents the least common form of altitude illness, it may progress rapidly to coma and death as a result of brain herniation within 24 hours, if not promptly diagnosed and treated.
High Altitude Cerebral Edema (HACE) is a severe and potentially fatal manifestation of high altitude illness and is often characterized by ataxia, fatigue, and altered mental status. HACE is often thought of as an extreme form/end-stage of Acute Mountain Sickness (AMS). Although HACE represents the least common form of altitude illness, it may progress rapidly to coma and death as a result of brain herniation within 24 hours, if not promptly diagnosed and treated.
HACE 通常發生於抵達海拔 4000 公尺以上兩天之後, 但在稍低海拔 2500m 也可能發生, 有些病患(非全部)會先有AMS症狀(頭痛,失眠,噁心,嘔吐). 有些罹患 HACE 患者也會同時罹患 HAPE. 單獨發生 HACE 狀況很少見, 但不能因為病患沒同時出現 HAPE 或 AMS 症狀而直接排除 HACE
Etiology
HACE generally occurs after 2 days above 4000m but can occur at lower elevations (2500m) and with faster onset. Some, but not all, individuals will suffer from symptoms of AMS such as headache, insomnia, anorexia, nausea prior to transitioning to HACE. Some may also have concomitant High Altitude Pulmonary Edema (HAPE). HACE in isolation is rare, but the absence of concomitant HAPE or symptoms of AMS prior to deterioration does not rule-out the presence of HACE.
HACE generally occurs after 2 days above 4000m but can occur at lower elevations (2500m) and with faster onset. Some, but not all, individuals will suffer from symptoms of AMS such as headache, insomnia, anorexia, nausea prior to transitioning to HACE. Some may also have concomitant High Altitude Pulmonary Edema (HAPE). HACE in isolation is rare, but the absence of concomitant HAPE or symptoms of AMS prior to deterioration does not rule-out the presence of HACE.
HACE 在海拔 4000-5000 公尺的發生率約 0.5-1%, HACE 會影響所有年齡層, 任何性別, 雖然年輕男性可能較具危險(帶著AMS症狀繼續上升. 爬升速率快)
危險因子包括 : 過去曾有高海拔疾病 HAI. 缺乏高度適應, 高強度體力活動, 上升速率快, 突然從低海拔直接到達高海拔
Epidemiology
Incidence of HACE is 0.5-1% at altitudes of 4000-5000 m. HACE affects those of all ages and genders, though younger males may be at higher risk due to continuation of ascent despite symptoms of AMS and faster rate of ascent. Risk factors include prior history of high altitude illness, lack of acclimatization, heavy physical exertion, rapid rate of ascent, and abrupt ascent from lower altitudes.
Incidence of HACE is 0.5-1% at altitudes of 4000-5000 m. HACE affects those of all ages and genders, though younger males may be at higher risk due to continuation of ascent despite symptoms of AMS and faster rate of ascent. Risk factors include prior history of high altitude illness, lack of acclimatization, heavy physical exertion, rapid rate of ascent, and abrupt ascent from lower altitudes.
HACE確實的病理機制不明, 但被視為AMS末期症狀, 缺氧導致神經荷爾蒙分泌, 血液循環對低氧引起腦血管擴張的反應, 可能會導致腦部微血管床過度灌注(流入組織的血量過多). 進而造成顱內高壓, 微血管床壓力上升, 微血管滲漏(液體從血管漏到血管外的組織間隙).
有個理論是這樣說的, 關於個體是否容易得到 AMS/HACE, 與其腦部空間代償水腫的能力有關.
另一個理論則說, 缺氧造成自由基生成, 引起 Na-K-ATP幫浦損壞/失效, 導致星狀細胞 astrocyte 因滲透性氧化性壓力引發水腫, 以及其後的細胞毒性水腫 (我覺得還是看英文比較好理解.中文照字面翻譯不好翻)
Pathophysiology
Although the exact mechanism of development of HACE is not fully understood, it is thought to be the extreme form/end-stage of AMS. Hypoxia at altitude elicits neuro-hormonal (VEG-F, Nitric Oxide, reactive cytokines, free radicals) and hemodynamic responses resulting in hypoxia-induced cerebral vasodilation leading to over perfusion of microvascular cerebral beds. This leads to intracranial hypertension with elevated capillary pressure and capillary leakage. The disruption of the blood-brain barrier from these stressors leads to subsequent cerebral edema. The “tight fit” hypothesis suggests that one’s susceptibility to AMS/HACE is dependent upon the individual’s intracranial space available to compensate for increasing edema. This theory would help to explain the seemingly random nature of AMS that can evolve into HACE. The “revised theory” to the development of HACE argues against volume overload and intracranial hypertension as the leading cause. In this model, hypoxia induces free radical formation causing damage/failure of the Na+/K+ ATPase Pump with resultant astrocyte swelling from osmotic-oxidative stress, with subsequent cytotoxic edema. Neither theory is considered the standard by which HACE is fully understood.
Although the exact mechanism of development of HACE is not fully understood, it is thought to be the extreme form/end-stage of AMS. Hypoxia at altitude elicits neuro-hormonal (VEG-F, Nitric Oxide, reactive cytokines, free radicals) and hemodynamic responses resulting in hypoxia-induced cerebral vasodilation leading to over perfusion of microvascular cerebral beds. This leads to intracranial hypertension with elevated capillary pressure and capillary leakage. The disruption of the blood-brain barrier from these stressors leads to subsequent cerebral edema. The “tight fit” hypothesis suggests that one’s susceptibility to AMS/HACE is dependent upon the individual’s intracranial space available to compensate for increasing edema. This theory would help to explain the seemingly random nature of AMS that can evolve into HACE. The “revised theory” to the development of HACE argues against volume overload and intracranial hypertension as the leading cause. In this model, hypoxia induces free radical formation causing damage/failure of the Na+/K+ ATPase Pump with resultant astrocyte swelling from osmotic-oxidative stress, with subsequent cytotoxic edema. Neither theory is considered the standard by which HACE is fully understood.
多數個案是由 AMS 持續惡化造成, 通常會有近期內海拔提升, 先前曾有AMS症狀(失眠在這裡還是算). 有些患者可能同時罹患 HAPE. 當出現腦病變徵象, 代表已經惡化成HACE了.
腦病變徵象包括: 運動失調 ataxia (通常較早出現), 及輕度至嚴重的神智改變
其他症狀包括: 嚴重頭痛, 無法正常說話, 極度困乏, 神智狀態變差, 局部神經學症狀, 癲癇
History and Physical
Most cases develop as a progression of AMS and will include a history of recent ascent to altitude and prior complaints/findings of AMS including a headache, fatigue, nausea, insomnia, and/or lightheadedness. Some may also have signs/symptoms of HAPE. Transition to HACE is heralded by signs of encephalopathy including ataxia (usually the earliest clinical finding) and altered mentation which may range from mild to severe. Other symptoms may include a more severe headache, difficulty speaking, lassitude, a decline in the level of consciousness, and/or focal neurological deficits or seizures.
Most cases develop as a progression of AMS and will include a history of recent ascent to altitude and prior complaints/findings of AMS including a headache, fatigue, nausea, insomnia, and/or lightheadedness. Some may also have signs/symptoms of HAPE. Transition to HACE is heralded by signs of encephalopathy including ataxia (usually the earliest clinical finding) and altered mentation which may range from mild to severe. Other symptoms may include a more severe headache, difficulty speaking, lassitude, a decline in the level of consciousness, and/or focal neurological deficits or seizures.
HACE 是臨床診斷, 所謂臨床診斷就是不需要依靠醫療儀器或抽血檢驗作診斷, 僅依靠病患症狀及醫師對病患的身體檢查就能診斷.
早期的HACE症狀可能被誤判為體力耗盡, 或其他情況: 脫水,低血糖,失溫, 低血鈉
抽血可能出現白血球上升(實在太多原因都可能導致白血球上升)
腰椎穿刺會發現CSF壓力上升但CSF鏡檢及生化正常.
腦部斷層可能發現腦水腫, 但 MRI 是更好的診斷工具., 可評估較輕微的腦水腫, 且MRI異常會持續出現在發病之後數天至數周.
目前仍無法找出腦水腫嚴重度與病患預後(恢復正常或死亡)的直接關連性.
Evaluation
HACE is a clinical diagnosis with the patient typically presenting with signs of encephalopathy, preceeded by signs and symptoms of Acute Mountain Sickness. The onset of neurological findings such as progressive decline in cognitive/mental function, declining level of consciousness, impaired coordination, slurred speech, and/or lassitude signify the transition from AMS to HACE. Typical evaluation consists of an abnormal neurological exam, with ataxia often being the earliest finding. Early symptoms may be misinterpreted as exhaustion and it is important to exclude these, as well as other disorders such as dehydration, hypoglycemia, hypothermia, or hyponatremia which all may have signs and symptoms that overlap with that of HACE. Though rarely available, laboratory testing may show an elevated white blood cell count in the setting of HACE, whereas any number of metabolic abnormalities may be present with the aforementioned others within the differential diagnosis. Lumbar puncture may have an increased opening pressure with otherwise normal laboratory findings. CT may show cerebral edema, but MRI is a better study to evaluate for more subtle signs of edema and can remain abnormal for days up to weeks. To date, there has been no direct correlation with the severity of edema with clinical outcome.
HACE is a clinical diagnosis with the patient typically presenting with signs of encephalopathy, preceeded by signs and symptoms of Acute Mountain Sickness. The onset of neurological findings such as progressive decline in cognitive/mental function, declining level of consciousness, impaired coordination, slurred speech, and/or lassitude signify the transition from AMS to HACE. Typical evaluation consists of an abnormal neurological exam, with ataxia often being the earliest finding. Early symptoms may be misinterpreted as exhaustion and it is important to exclude these, as well as other disorders such as dehydration, hypoglycemia, hypothermia, or hyponatremia which all may have signs and symptoms that overlap with that of HACE. Though rarely available, laboratory testing may show an elevated white blood cell count in the setting of HACE, whereas any number of metabolic abnormalities may be present with the aforementioned others within the differential diagnosis. Lumbar puncture may have an increased opening pressure with otherwise normal laboratory findings. CT may show cerebral edema, but MRI is a better study to evaluate for more subtle signs of edema and can remain abnormal for days up to weeks. To date, there has been no direct correlation with the severity of edema with clinical outcome.
治療通常是立即下降一千公尺或下撤到症狀改善. 不要讓腦水腫病患單獨下撤(可能隨時會摔死), 盡量讓腦水腫病患減輕體力負荷(不要背東西下撤,攙扶等等).
如果無法下撤, 可考慮加壓艙或給予氧氣暫時緩解症狀, 但這兩種都不能取代下降, 能下降還是要以下降為主要治療手段.
如果手邊有藥物, 可給予類固醇 dexamethasone 8mg. 之後每六小時給 4mg. 可口服給藥. 肌肉注射給藥. 靜脈注射給藥.
丹木斯僅在一篇臨床研究顯示有治療HACE效果, 建議劑量是每次 250mg. 每天吃兩次.
以上治療輔助手段都不可以取代下降. 下降是唯一確切的治療方式.
Treatment / Management
The mainstay of treatment is the immediate descent of at least 1000m or until symptoms improve. One should not descend alone and should have assistance to minimize physical exertion, which may worsen the patient’s condition. If descent is not an option, one may use a portable hyperbaric chamber and/or supplemental oxygen to temporize illness, but this should never replace or delay evaluation/descent when possible. If available, dexamethasone 8mg for one dose, followed by 4mg every 6 hours should be given to adults via PO, IM, or IV routes. Pediatric dosing is 0.15 mg/kg every 6 hours. Acetazolamide has proven to be beneficial in only a single clinical study. The suggested dosing regimen for Acetazolamide is 250 mg PO, given twice daily. Though effective in alleviating or temporizing symptoms, none of the adjunct treatment modalities are definitive or a replacement for an immediate descent.
The mainstay of treatment is the immediate descent of at least 1000m or until symptoms improve. One should not descend alone and should have assistance to minimize physical exertion, which may worsen the patient’s condition. If descent is not an option, one may use a portable hyperbaric chamber and/or supplemental oxygen to temporize illness, but this should never replace or delay evaluation/descent when possible. If available, dexamethasone 8mg for one dose, followed by 4mg every 6 hours should be given to adults via PO, IM, or IV routes. Pediatric dosing is 0.15 mg/kg every 6 hours. Acetazolamide has proven to be beneficial in only a single clinical study. The suggested dosing regimen for Acetazolamide is 250 mg PO, given twice daily. Though effective in alleviating or temporizing symptoms, none of the adjunct treatment modalities are definitive or a replacement for an immediate descent.
Pearls and Other Issues
Acclimatization is the best means by which to prevent HACE and all other forms of AMS. Considerations for prevention of AMS and subsequent HACE is to have a slow rate of ascent with the altitude one sleeps at being more important than the altitude reached. Final ascent rates of 300-500m per day are recommended for safe and preventative acclimatization. If signs of AMS develop, stop ascent and if debilitating or severe, descend immediately. Prophylaxis for HACE/AMS includes both Acetazolamide and Dexamethasone. Ibuprofen is recommended for those with a history of altitude illness. There is less evidence for natural remedies such as ginkgo balboa and coca leaves. Most advocate training regimens and slow rate of ascent to optimize acclimatization. This often requires an intense time commitment and is difficult for many to achieve, particularly for those engaged in recreational climbing. Some studies have shown benefit to sleeping in specialized tents at home that provide normobaric hypoxia before departure to higher altitudes, although this has not been validated as a primary preventative measure of AMS or HACE. Even with robust training regimens, acclimatization, and prophylactic medications, HACE can strike any individual at any altitude, at any time. Even those with considerable experience at altitude may fall prey to the wares of HACE. Thus careful attention to the signs and symptoms of AMS and HACE should always be given proper consideration and respect.
Acclimatization is the best means by which to prevent HACE and all other forms of AMS. Considerations for prevention of AMS and subsequent HACE is to have a slow rate of ascent with the altitude one sleeps at being more important than the altitude reached. Final ascent rates of 300-500m per day are recommended for safe and preventative acclimatization. If signs of AMS develop, stop ascent and if debilitating or severe, descend immediately. Prophylaxis for HACE/AMS includes both Acetazolamide and Dexamethasone. Ibuprofen is recommended for those with a history of altitude illness. There is less evidence for natural remedies such as ginkgo balboa and coca leaves. Most advocate training regimens and slow rate of ascent to optimize acclimatization. This often requires an intense time commitment and is difficult for many to achieve, particularly for those engaged in recreational climbing. Some studies have shown benefit to sleeping in specialized tents at home that provide normobaric hypoxia before departure to higher altitudes, although this has not been validated as a primary preventative measure of AMS or HACE. Even with robust training regimens, acclimatization, and prophylactic medications, HACE can strike any individual at any altitude, at any time. Even those with considerable experience at altitude may fall prey to the wares of HACE. Thus careful attention to the signs and symptoms of AMS and HACE should always be given proper consideration and respect.
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