What is the role of furosemide in the treatment of acute syndrome of inappropriate antidiuretic hormone secretion (SIADH)?

Updated: Aug 16, 2019
  • Author: Christie P Thomas, MBBS, FRCP, FASN, FAHA; Chief Editor: Vecihi Batuman, MD, FASN  more...
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Answer

Furosemide and other loop diuretics can be used to increase the excretion of free water. Excess water that must be removed to correct the hyponatremia can be calculated using total body water (TBW). TBW equals body weight in kg multiplied by 0.6, assuming that the total body solute or water has not changed. The diuresis induced by furosemide has a urine solute concentration roughly equivalent to half-normal saline; thus, excretion of free water occurs. The excreted Na+ is replaced with 3% hypertonic saline or with normal saline (NaCl 154 mEq/L), thus avoiding a net Na+ loss while effecting a loss of free water.

Other sources of free water intake should be restricted as well. If the measured sum of urinary potassium and Na+ with furosemide is greater than the plasma Na, then hypertonic saline rather than normal saline should be used to replace excreted Na. Serum Na+ and osmolality and urine osmolality should be checked frequently to monitor the change in serum Na+ and the rate of correction.


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