The Joint Annual Scientific Meetings of the Endocrine Society of Australia and the Society for Reproductive Biology 2018

Urea improves hyponatraemia in fluid restriction refractory SIADH (#247)

Jack Lockett 1 2 , Kathryn E Berkman 1 , Goce Dimeski 2 3 , Anthony W Russell 1 2 , Warrick J Inder 1 2
  1. Department of Diabetes and Endocrinology, Princess Alexandra Hospital, Metro South Health, Brisbane, QLD, Australia
  2. Faculty of Medicine, The University of Queensland, Brisbane, QLD, Australia
  3. Department of Chemical Pathology, Pathology Queensland, Brisbane, QLD, Australia


Hyponatraemia in hospitalised patients has been associated with increased mortality. The syndrome of inappropriate anti-diuretic hormone (SIADH) is a common cause of hyponatraemia. Recent European and American guidelines gave conflicting advice regarding the role of urea in the treatment of SIADH. We hypothesised that urea would be a more effective treatment of hyponatraemia than fluid restriction in this setting. 



Review of urea use for the treatment of hyponatraemia in patients admitted to a tertiary hospital during 2016-17. Primary endpoint: Proportion of patients achieving a serum sodium ≥130mmol/L at 72h.



Urea was used on 75 occasions in 66 patients. The median age was 67 (IQR 52-76), 41% were female. Sixty-seven (89.3%) had hyponatraemia due to SIADH of which CNS pathology (62.7%) was the most common underlying cause. The median nadir serum sodium was 122mmol/L (IQR 118-126). Fluid restriction was first line treatment in 62.2%. Urea was first line treatment in 23% and second line in 77%. In fifty three patients who received other treatment prior to commencement of urea, the mean sodium change in the 72h following urea initiation (7.0±4.9mmol/L) was significantly greater than with the preceding treatments (-1.0±4.8mmol/L; p<0.001). Thirty-two (62.7%) achieved serum sodium ≥130mmol/L at 72h post-initiation of urea, and 13 (25.5%) ≥135mmol/L. The initial urea dose range was 15-90g daily (mode 30g, 54.7%), and median treatment duration 6 days (IQR 4-8).  Seventeen patients (22.7%) had side effects, distaste the most common (7), followed by nausea (6) and hypokalaemia (4). None were severe. No patients developed hypernatraemia, over-correction (>10mmol/L in 24h or >18mmol/L in 48h), or died.



Urea is a safe, effective treatment for moderate-severe hyponatraemia in patients who failed or were unable to have fluid restriction with a tolerable side effect profile.