閱讀本文之前,您得先知道,人體內的正常鈉離子濃度為 135-145 mEq/L。如果透析液用的鈉濃度,比體內的鈉濃度低,那麼洗腎過程中,體內的鈉離子會減少;如果相反的話,則透析液的鈉離子會跑進體內,增加身體裡的鈉。另外,為了閱讀方便,文中的鈉離子濃度單位皆為 mEq/L。
歷史:
1940年代,在血液透析還不普及的時候,為了控制血壓以及口渴的問題,透析液的鈉離子濃度是設定在 126.5,當時製作人工腎臟的技術剛起步,透析膜無法承受很高的壓力,血中的水沒辦法用壓的壓出去,所以,透析液中含有高濃度的糖,用來把血中的水拉出去,到底有多濃?當時用的糖濃度為 1360-2720 mg/dL!人體的血糖正常值在 100-140 mg/dL 以下,這個透析液濃度是人體的10-20倍!(這樣子的脫水方式,和腹膜透析所用的透析藥水原理相同,是以濃度差來脫水),也因為這麼高濃度的糖,平衡了低濃度的鈉所可能帶來的問題。
到了1960年代,透析治療真正普及之後,發生“透析不平衡症候群(dialysis disequilibrium syndrome)”的案例很多,雖然原因是體內其他毒素下降太快所導致,鈉離子濃度的角色並不很確定,不過,使用鈉離子 <120透析液的患者,常看到這樣的併發症。另一方面,製作人工腎臟的技術進步了,透析膜可以承受壓力,改成使用壓力差來脫水,糖濃度就不需要那麼高了 (降低到182 mg/dL,仍比人體高一些),所以,鈉離子濃度升高到 130,一方面是為了減少“不平衡症候群”的發生,一方面是糖濃度降下來了,就不能用那麼低的鈉離子濃度了。
隨著醫學的進步,透析時間也逐漸縮短
從“一周兩次,一次洗12-20小時”,
變為“一周三次,一次8-10小時”,
再變成“一周三次,一次4小時”,也就是現在大家能接受的模式,可以看出來透析是越來越有效率,用更短的時間來完成脫水以及清除毒素,可是,用更短的時間,也表示脫水的速度更快,患者的體內的變化更快速,透析中的不適變得更頻繁了,因此,為了透析之中的穩定,透析液鈉離子濃度逐漸調升,1990年代之後,大部分腎友所用的濃度是 140。
回顧歷史,你可以知道鈉離子濃度的幾個重點,幫你整理如下:
1. 歷史是一開始使用超低濃度的鈉,理由是控制血壓以及口渴症狀。
2. 鈉離子濃度太低,容易產生透析時不適。
3. 脫水速度越快,鈉離子濃度可能得要調高一點,才能減少透析時的不舒服。
那麼,該怎麼設定鈉離子濃度,對腎友才是最好的?請見下篇,會有更詳細的介紹。
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