Acid-base / electrolytes / nephrolithiasis

Extract

Abstract

Introduction and Aims: Osmotic demyelination syndrome (ODS) is a rare but dramatic complication that occurs in chronic hyponatraemia when sodium concentrations ([Na]) are corrected too rapidly. During the past ten years, researchers have advocated lowering the traditional limits of 12 and 18 mmol/L in 24 and 48h to minimize the risk of ODS. ERBP aimed to identify the evidence for stricter limits.

Methods: We searched MEDLINE from 1997 to September 2012 without language restriction and included all observational studies reporting cases of ODS and corresponding [Na] correction speeds. Two authors assessed studies for eligibility, extracted all data, and judged whether it was reasonable to assume the ODS was caused by the speed of increase in [Na]. Data are presented descriptively as percentages and absolute numbers for count data and medians with interquartile ranges (IQR) for continuous data. Sparse and heterogeneous data precluded informative formal meta-analysis.

Results: We identified 54 cases of ODS (45 case-reports and 3 case-series including a total of 9 patients); 63% were female with a median age of 45 years (IQR 45-58 years). In 96% (52/54), the diagnosis of ODS was based on MRI. Important details such as onset and cause of hyponatraemia, initial symptoms and their evolution, presence of other risk factors for ODS, and timing of ODS symptoms to the increase in sodium concentration were generally poorly reported. In 6% (3/54), data were insufficient to allow estimation of the 24h and/or 48h correction speed. In 87% (47/54) of cases, [Na] increased ≥12 mmol/L during the first 24h or ≥20 mmol/L during the first 48h. Only 7% (4/54) developed ODS at lower correction speeds: 2 of these patients developed ODS with [Na] increases of 10 to <12 mmol/L (24h) and <18 mmol/L (48h). Both men had a history of heavy drinking as a risk factor for ODS, but it was unclear whether the neurologic condition was caused by the speed of [Na] correction. One woman, with a history of alcohol abuse and hypokalaemia, developed ODS with a [Na] increase limited to even 2 mmol/L (24 h) and 4 mmol/L (48h). Finally, One woman developed ODS after [Na] increased with 15 mmol/L during the first 48 h; the 24h limit could not be calculated and reporting was too vague to allow a reasonable assumption of causality.