Hypertonic saline infusion test

Document polyuria (urine volume >2.5L/day) and exclude glycosuria. If desired, creatinine excretion can be measured as an estimate of completeness of urine collections snbstances that inflnence ADH secretion should be avoided (e.g., nicotine, alcohol, and caffeine). If plasma osmolality is >295 mOsm/kg or if serum sodium concentration >145mmol/L, primary polydipsia is unlikely proceed with the overnight water deprivation test (Box 50-9) or the hypertonic saline infusion test (Box 50-10). 

Hypertonic saline infusion test (Box 50-10) Plot plasma osmolality versus plasma ADH concentration. 

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