Hypernatremia

1. 血中Osmolality算法：1.95(PNa+PK)+BUN/2.8+Glucose/18。若實測＞計算的超過10mOsm，要考慮由其他高滲物質：manitol, alcohol, ethylene glycol
2. Urine/Plasma Osmalality＞0.7：TBNa+ 不足，表free water deficit
3. Hypercatabolic state：如嚴重燒傷。因為urea太多而產生osmotic diuresis。吃含protein hydrolysate的高蛋白溶液的病人也會
4. Urine/Plasma Osmolality variable：若 UNa > 20 mEq/L，TBNa可能正常過過高
5. Cushing's disease, hyperaldosteronism：Na+會稍高
6. Urine/Plasma Osmolality ＜0.7：TBNa 可能正常或過高
7. polydipsia：較常低血鈉。要跟尿崩症的多尿鑑別診斷。病人可能也有psychi或是腦部lesion
8. CDI (central diabetes insipidus) ：pituitary gland製造ADH能力受損，有一半是secondary，原因如 trauma, sellar area primary tumor (ex. pinealoma, craniopharyngioma, metastatisis, esp. breast, lung), infection (GBS, syphilis), granulomatous disease (sarcoidosis, TB, Wegener's granulomatosis), histiocytic diseases, vascular events (sickle cell, aneurysm, CVA), postpartum necrosis (Sheehan's syndrome)
9. osmoreceptor ablation：hypothalamus lesion
10. 先天 NDI：distal tubule對ADH無反應
11. 後天NDI：最常見：PCKD, chronic pyelonephritis, ureteral obstruction，drug(alcohol, Li, demeclocycline, sulfonylurea, amphotericin, iodinated dyes, colchicine, flurene類麻醉藥, 抗生素), sickle cell, multiple myeloma, amyloidosis, sarcoidosis, Sjogren's disease, 飲食不良等。跟 hypercalcemia, hypokalemia, hypothyroidism也有關
12. paroxysmal atrial tachycardia：primary suppression of ADH → water diuresis