Urea treatment in fluid restriction‐refractory hyponatraemia

Summary

Objective

Hyponatraemia in hospitalised patients is common and associated with increased mortality. International guidelines give conflicting advice regarding the role of urea in the treatment of SIADH. We hypothesised that urea is a safe, effective treatment for fluid‐restriction refractory hyponatraemia.

Design

Review of urea 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.

Patients

Urea was used on 78 occasions in 69 patients. The median age was 67 (IQR 52‐76), 41% were female. Seventy (89.7%) had hyponatraemia due to SIADH – CNS pathology (64.3%) was the most common cause. The duration was acute in 32 (41%), chronic in 35 (44.9%) and unknown in the rest.

Results

The median nadir serum sodium was 122mmol/L (IQR 118‐126). Fluid restriction was first line treatment in 65.4%. Urea was used first line in 21.8% and second line in 78.2%. Fifty treatment episodes (64.1%) resulted in serum sodium ≥130mmol/L at 72h. In 56 patients who received other prior treatment, the mean sodium change at 72h (6.9±4.8mmol/L) was greater than with the preceding treatments (‐1.0±4.7mmol/L; p<0.001). Seventeen patients (22.7%) had side effects (principally distaste), none were severe. No patients developed hypernatraemia, over‐correction (>10mmol/L in 24h or >18mmol/L in 48h), or died.

Conclusions

Urea is safe and effective in fluid restriction refractory hyponatraemia. We recommend urea with a starting dose of ≥30g/day, in patients with SIADH and moderate to profound hyponatraemia who are unable to undergo, or have failed fluid restriction.

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