Endocrine Abstracts

Introduction: Acute severe hyponatraemia is a medical emergency. Three percent hypertonic saline is recommended to increase sodium by 4–6mmol/l to reduce cerebral oedema. Many UK centres, including our own, use 1.8% saline, although there is no evidence to support this. Overcorrection may cause osmotic demyelination syndrome (ODS), particularly when sodium increases by >10 mmol/l in 24 hours, or >8 mmol/l in those with additional risk factors.

Aims: To assess the use of 1.8% saline, including indication, monitoring, correction rates, ODS episodes, and 30-day mortality.

Method: Retrospective review of patients admitted to a single-centre medical high dependency unit with hyponatraemia as the primary diagnosis between July 2019 and November 2024.

Results: Thirty-seven patients were identified (median age 64 (IQR 18)); median admission sodium was 110 (IQR 8) mmol/l. Risk factors for ODS were present in 65%. Biochemical investigations were performed in almost all cases: urine osmolality 100%, urine sodium 97%, serum osmolality 95%. Monitoring included urinary catheterisation in 68%, arterial access in 41%, and central venous access in 24%. Twenty-nine patients received hypertonic saline, appropriately indicated in 27. Median 24-hour sodium rise was 10 (IQR 7) mmol/l; 48% had an increase >10 mmol/l, and 83% of patients with risk factors (n = 18) rose >8 mmol/l. Fourteen patients (58%) required multiple boluses. The rate of sodium rise >10 mmol/l was lower in those given multiple boluses compared with a single bolus (35% vs 63%). Sodium increased by <4 mmol/l in four patients (14%), all receiving multiple boluses. ODS was not suspected in any cases, and there was no 30-day mortality.

Conclusion: Despite close monitoring, the rate of overcorrection with 1.8% saline was high, though lower in patients given multiple boluses. Further studies are needed to compare outcomes using 1.8% and 3% saline for severe symptomatic hyponatraemia.