Endocrine Abstracts

Introduction: Excess mortality due to hyponatraemia is well documented but it is not clear whether the mortality associated with SIADH is different to that associated with non-SIADH hyponatraemia (NSH).

Methods/design: Prospective evaluation of all patients admitted with or developing hyponatraemia in a tertiary hospital (pNa <130 mmol/l) in January 2015. Diagnosis of SIADH was based on standard clinical and biochemical criteria (pNa, spot urine sodium, urine osmolarity, 0900 h cortisol and TFTs). Statistics were by Mann–Whitney U, Student’s t, or χ² tests, as appropriate.

Results (SIADH VS NSH): 180 patients were included. 89 (45 females) were classified as SIADH vs 91 (45 females) as NSH. Clinical data: mean age was similar; SIADH 68 years (S.D.: 15) vs NSH 72 years (S.D.: 15), P=0.09. Premorbid history of hypertension, diabetes, COPD, liver disease, and cognitive impairment were similar (P>0.05) but CCF (6.7% vs 30.7%, P<0.0001) and ischemic heart disease (17.9% vs 31.8%, P=0.02) were commoner in NSH. Laboratory data: admission pNa was similar; SIADH 126 mmol/l (S.D.: 5) vs NSH 126 mmol/l (S.D.: 3), P=0.68. Other laboratory results (median (IQR), SIADH first): pK: 4 mmol/l (3.6, 4.3) vs 4.1 mmol/l (3.7, 4.9), P=0.003. pUrea: 5.3 mmol/l (4, 6.9) vs 11.6 mmol/l (7.4, 18.8), P<0.0001, pCreatinine 64 μmol/l (53.5, 74) vs 128 μmol/l (85, 213), P<0.0001, and spot uNa: 53.5 mmol/l (32, 89) vs 30 mmol/l (18, 59), P=0.005. In SIADH, 0900-h cortisol: 482 nmol/l (IQR: 412, 578), 21% were receiving therapeutic glucocorticoids. One patient with COPD had a subnormal post Synacthen peak cortisol of 363 mmol/l due to recent oral prednisolone course. No patient had hypothyroidism. Duration of hospital admission was similar: SIADH 13 days (11) vs 11 days (10), P=0.55 and mortality was similar in SIADH, 5.6% compared to NSH 9.8% (P=0.34).

Conclusion: Preliminary results show similar mortality rate in patients with SIADH compared to non-SIADH, although larger number of patients will confirm these observations.