2018-12-16 edit. from uptodate
Heat syncope and exercise associated collapse
Definitions, clinical presentation, and pathophysiology — Heat syncope is among the more confusing diagnoses identified by the International Classification of Diseases. Like heat cramps, heat syncope is a misnomer as heat does not directly cause the syncopal event (ie, core body temperature is not significantly elevated). The treatment of heat-related syncope is discussed separately.
The syncopal event that occurs in the exercising athlete is more appropriately termed "exercise associated collapse" (EAC) [15]. EAC occurs when an athlete is unable to stand or walk as a result of lightheadedness or syncope. EAC usually occurs immediately after completing a race or workout and is commonly observed at endurance events (eg, marathon). The mechanism for collapse is an abrupt decrease in venous return once that athlete completes the event. Given the typical degree of vasodilatation seen with prolonged exertion, the sudden loss of the pressure exerted by the skeletal muscles on the vasculature leads to a precipitous decline in venous return, as well as postural tone, causing the athlete to collapse.
典型的EAC. 病患核心體溫可能正常或稍微上升. 而且經過適當處置之後神智狀態很快恢復正常 (約15-20分鐘). 藉此可與熱中暑(HEAT STROKE)區別
Heat is an indirect contributor to EAC as the body is dually tasked to provide blood to exercising muscle and the periphery, to assist in thermoregulation. In typical EAC, the athlete's core temperature is either normal or only marginally elevated and any alterations in mental status quickly resolve (within approximately 15 to 20 minutes) with appropriate treatment. These features help to distinguish EAC from heat stroke.
非運動造成的熱暈厥. 可由高溫環境間接影響導致. 通常是發生在環境變熱的前幾天. 身體尚未適應. 有兩種常見型態.
1. 久站於熱環境. 身體缺乏活動.
2. 在熱的環境突然站起來.
這類的熱暈厥症狀包括. 頭重腳輕. 隧道性視野. 臉色蒼白. 皮膚發汗. 脈搏變慢. 通常核心體溫是正常或輕微上升. 病患通常在適當治療之後很快恢復.
Heat syncope in those who are not exercising can be described as a transient loss or near-loss of consciousness due to the indirect effects of high ambient temperature. Heat syncope occurs most often during the first few days that someone is exposed to high environmental temperatures, before acclimatization is complete. Two common scenarios for heat syncope are:
●Prolonged standing in the heat with little movement
●Sudden standing after prolonged sitting in the heat
The signs and symptoms associated with these forms of heat syncope include light-headedness, tunnel vision, pale and sweaty skin, and decreased pulse rate. Most often the core temperature is normal or only mildly elevated. Patients generally recover rapidly with appropriate treatment.
非運動性熱暈厥的病生理反應與身體對於熱調節和維持直立姿勢的血壓調節機轉有關. 熱調節需要藉由血管擴張增加周邊血流, 增加排汗. 而周邊血管擴張可導致血液滯留在周邊組織. 造成姿勢性低血壓. 身體的適應最後會讓循環血量增加. 有利於在熱的環境排汗與活動. 在這些不同情境. 熱急症的嚴重度與身體體溫上升和脫水程度成正比.
The pathophysiology for each of these nonexertional events is related to the body's competing needs for thermoregulation and maintaining adequate blood pressure for an upright posture [41,57]. Thermoregulation requires increasing blood flow to the periphery through vasodilation in order to facilitate sweating. This increase in peripheral vasodilation can lead to peripheral pooling of blood, causing postural hypotension. Acclimatization eventually results in an increased circulating blood volume capable of accommodating both sweating and activity in the heat. In each scenario, the severity of illness is proportional to the rise in body temperature and the degree of dehydration.
2016-04-21 修改
中暑定義：體溫超過 40 度C 以上，合併下列症狀
無汗
皮膚乾熱
中樞神經異常（反應遲鈍、失憶、瞻妄、抽搐、神智不清、昏迷、癲癇）
沒有治療的中暑，死亡率高達 50％, 退燒藥物沒有作用.
Heat stroke is diagnosed by an elevated core body temperature (40°C or higher) accompanied by anhidrosis, hot dry skin, and central nervous system abnormalities such as attention deficit, impaired memory, drowsiness, delirium, convulsions, and coma.[4-6] It is sometimes fatal even if the body temperature is adequately reduced because the exaggerated acute-phase response, the altered expression of heat-shock protein released when cells are exposed to high temperatures, and immune system dysfunction often lead to inflammatory responses, intravascular coagulation, and multiorgan injury
熱急症
最輕微的是 heat cramps, 中度是 heat exhaustion, 最嚴重的是 heat stroke.
Definition By Mayo Clinic Staff
誘發原因主要是暴露在過熱環境，尤其是加上高濕度和高強度活動更易造成，如果沒有積極處理，可能惡化成中暑
Heat exhaustion is a condition whose symptoms may include heavy sweating and a rapid pulse, a result of your body overheating. It's one of three heat-related syndromes, with heat cramps being the mildest and heatstroke being the most severe.
Causes of heat exhaustion include exposure to high temperatures, particularly when combined with high humidity, and strenuous physical activity. Without prompt treatment, heat exhaustion can lead to heatstroke, a life-threatening condition. Fortunately, heat exhaustion is preventable.
熱衰竭, 身體因為高溫造成水分電解質大量流失. 通常是流太多汗, 在高熱環境工作的人還有老人容易發生
Heat Exhaustion
Heat exhaustion is the body's response to an excessive loss of the water and salt, usually through excessive sweating. Workers most prone to heat exhaustion are those that are elderly, have high blood pressure, and those working in a hot environment.
Symptoms
Symptoms of heat exhaustion include:
- Heavy sweating 大量流汗
- Extreme weakness or fatigue 極度疲憊
- Dizziness, confusion 頭暈 神智混亂
- Nausea 噁心
- Clammy, moist skin 皮膚濕冷
- Pale or flushed complexion 臉色發白或潮紅
- Muscle cramps 肌肉抽筋
- Slightly elevated body temperature 體溫輕微上升
- Fast and shallow breathing 呼吸淺快
First Aid
Treat a worker suffering from heat exhaustion with the following:
- Have them rest in a cool, shaded or air-conditioned area. 在陰涼處休息
- Have them drink plenty of water or other cool, nonalcoholic beverages. 補充大量水分或其他不含酒精的飲料
- Have them take a cool shower, bath, or sponge bath. 沖冷水澡，泡澡或用海綿擦澡
熱暈厥. 或熱昏厥. 有運動性和非運動性的. 運動性的機轉在上面有描述了. 非運動性的可能是站太久, 或久坐(躺著)突然站起, 造成昏厥. 脫水和身體不適應可能會增加發生機率
Heat Syncope
Heat syncope is a fainting (syncope) episode or dizziness that usually occurs with prolonged standing or sudden rising from a sitting or lying position. Factors that may contribute to heat syncope include dehydration and lack of acclimatization.
Symptoms
Symptoms of heat syncope include:
- Light-headedness 頭重腳輕
- Dizziness 頭暈
- Fainting 昏厥
First Aid
Workers with heat syncope should: 非大量脫水，補水不需太快
- Sit or lie down in a cool place when they begin to feel symptoms. 在陰涼處坐下或躺下休息，以病患舒服為原則
- Slowly drink water, clear juice, or a sports beverage. 慢慢補充水分，包括果汁或運動飲料
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