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基本外科：電解質（醫學英語）
脫水：脫水與電解質失衡（醫學英語）
脫水：病理生理學、實驗室檢測和數值-等滲性脫水（醫學英語）
脫水：病理生理學、實驗室檢測和數值-高滲性脫水（醫學英語）
脫水：病理生理學、實驗室檢測和數值-低滲性脫水（醫學英語）
鈉，低鈉血症（醫學英語）
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視頻
Potassium is the main intracellular ion; sodium, the main extracellular ion. The normal potassium concentration in serum is 4.5 mmol/liter. Small changes in serum reflect large intracellular changes that may cause significant morbidity and mortality. The daily average intake of potassium is 50 to 100 mmol/day. The kidneys control the daily excretion, which ranges widely from 20 to 400 mmol. The renin-angiotensin-aldosterone hormone axis is the key regulator of potassium clearance. As aldosterone increases in plasma, so does potassium excretion.
The primary functions of potassium in the body include regulating fluid balance and controlling the electrical activity of the heart and other muscles.
Hypokalemia
Patients with hypokalemia have a [K+] lower than 3.5 mmol/liter. Hypokalemia is commonly a result of hyperpolarization of the resting potential of the cell. Hyperpolarization interferes with neuromuscular function. Hypokalemia is associated with generalized fatigue and weakness, ileus, atrial arrhythmia, and acute renal insufficiency.
Hypokalemia is caused by renal losses, extrarenal losses, or intracellular shifts from medications or hyperthyroidism. Extrarenal losses can be caused by persistent vomiting, gastric tubes, diarrhea, alkalosis, catecholamine secretion, insulin administration, or high-output enteric or pancreatic fistulas. Hypokalemia is a common problem in patients with congestive heart failure who are receiving multiple drugs. It can also develop in patients treated with diuretics that force renal function to excrete urine with an elevated potassium concentration. Long-term diuretic therapy can produce a sustained negative potassium balance.
Patients with a chronic potassium deficiency can develop a cardiac rhythm disturbance. The electrocardiogram of patients with hypokalemia will show depressed T waves and U waves. Hypokalemia leads to cardiac arrhythmia, particularly atrial tachycardia with or without block, atrioventricular dissociation, ventricular tachycardia, and ventricular fibrillation. The risk for hypokalemia associated arrhythmia is higher inpatients treated with digoxin, even when potassium concentrations are in the low-normal range. Hypokalemia not caused by diuretics may be due to a rare endocrine disorder, including primary hyperaldosteronism and renin secreting tumors. Hypokalemia is also frequently associated with hypomagnesemia and acidemia.
Treatment of acute hypokalemia. Hypokalemic patients require potassium replacement, which can be achieved by oral or IV routes.
In patients with renal dysfunction, whose potassium excretion is reduced, both the IV rate of potassium replacement and the total dose should be lower. After treatment, frequent monitoring of potassium levels is necessary. Because hypokalemia represents large intracellular deficits, replenishing total body levels may take days. Potassium therapy is given as the chloride salt because hypokalemia is commonly associated with a contraction in the extracellular water, in which chloride is the predominant anion.
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鉀
鉀是主要的細胞內離子；鈉是主要的細胞外離子。血鉀正常濃度為4.5mmol/L。血清中小的變化反映了細胞內大的變化，可能導致顯著的發病率和死亡率。鉀的日平均攝入量為50至100 mmol/天。腎臟控制著每天的排洩量，範圍從20到400mmol不等。腎素血管緊張素醛固酮激素軸是鉀清除的關鍵調節因素。隨著血漿中醛固酮的增加，鉀的排洩也隨之增加。
鉀在體內的主要功能包括調節體液平衡和控制心臟和其他肌肉的電活動。
低鉀血症
低鉀血症患者的[K+]低於3.5 mmol/L。低鉀血症通常是細胞靜息電位超極化的結果。超極化幹擾神經肌肉功能。低鉀血症與全身乏力、腸梗阻、房性心律失常和急性腎功能不全有關。
低鉀血症是由腎臟損失、腎外損失或藥物或甲亢引起的細胞內轉移引起的。持續性嘔吐、胃管、腹瀉、鹼中毒、兒茶酚胺分泌、胰島素注射或高輸出量腸瘻或胰瘻可引起腎外損失。在接受多種藥物治療的充血性心力衰竭患者中，低鉀血症是一個常見問題。低鉀血症也可以在使用利尿劑的患者中發生，利尿劑迫使腎功能以高鉀濃度排洩尿液。長期的利尿治療可以產生持續的負鉀平衡。
慢性鉀缺乏症患者會出現心律失常。低鉀血症患者心電圖表現為T波和U波壓低。低鉀血症導致心律失常，特別是房性心動過速伴或不伴傳導阻滯、房室分離、室性心動過速和室顫。使用地高辛治療的患者發生低鉀相關心律失常的風險更高，即使鉀濃度在正常低範圍內。非利尿劑引起的低鉀血症可能是由於一種罕見的內分泌紊亂，包括原發性醛固酮增多症和腎素分泌腫瘤。低鉀血症也常伴有低鎂血症和酸血症。
急性低鉀血症的治療。低鉀血症患者需要補充鉀，這可以通過口服或靜脈途徑實現。
腎功能不全患者，其鉀排洩量減少，靜脈補鉀率和總劑量均應降低。治療後，需要經常監測鉀的水平。因為低鉀血症代表著細胞內的巨大缺陷，補充全身水平可能需要幾天的時間。鉀治療應以氯鹽給予，因為低鉀血症通常與細胞外水的收縮有關，其中氯是主要的陰離子。
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重要詞彙
potassium [pəˈtæsiəm] 鉀
intracellular 細胞內的
morbidity [mɔrˈbɪdəti] 發病率
mortality [mɔːrˈtæləti] 死亡率
renin-angiotensin-aldosterone hormone axis腎素血管緊張素醛固酮激素軸
regulator [ˈreɡjuleɪtər] 調節因子
aldosterone [æl'dɒstəroʊn] 醛固酮
excretion [ɪkˈskriʃən] 排洩
hypokalemia [ˌhaɪpoʊkeɪ'limiə] 低鉀血症
hyperpolarization [ˌhaɪpəˌpɒləraɪ'zeɪʃən] 超極化
atrial['eɪtriəl] arrhythmia [əˈrɪðmiə] 房性心律失常
acute renal insufficiency 急性腎功能不全
extrarenal 腎外的
hyperthyroidism [ˌhaɪpərˈθaɪrɔɪdɪzəm] 甲狀腺機能亢進
alkalosis [ˌælkə'loʊsɪs] 鹼中毒
catecholamine [ˌkætə'tʃoʊləˌmɪn] 兒茶酚胺
insulin [ˈɪnsəlɪn] 胰島素
electrocardiogram [ɪˌlektroʊˈkɑːrdioʊɡræm] 心電圖
depressed T waves 凹陷T波
cardiac [ˈkɑːrdiæk] arrhythmia 心律失常
atrial tachycardia [ˌtækɪ'kɑdɪr] 房性心動過速
atrioventricular dissociation 房室分離
ventricular [vɛnˈtrɪkjulər] tachycardia 室性心動過速
ventricular [vɛnˈtrɪkjulər] fibrillation [ˌfɪbrə'leɪʃən] 心室顫動
digoxin [daɪ'gɒksɪn] 地高辛
hyperaldosteronism ['haɪpəræl'dɒstəroʊnɪzəm] 醛固酮增多症
renin ['rinɪn] 腎素
hypomagnesemia ['haɪpəmægnə'simɪr] 低鎂血症
acidemia [ˌæsɪ'dimiə] 酸血症
oral or IV routes 口服或靜脈注射
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