Hyponatraemia in Guillain-Barré syndrome revisited

Objectives: The objective of this study was to determine the relevance of hyponatraemia in the prognosis of Guillain-Barré syndrome (GBS). Materials and methods: We retrospectively analysed records of 48 consecutive patients with GBS and performed a systematic literature review on frequency/correlates of hyponatraemia in GBS. Results: Hyponatraemia <133 mmol/l was detected in 18/48 of our patients with GBS (37.5%). In 10/18 (55.5%), hyponatraemia occurred post-immunoglobulin therapy. Hyponatraemia correlated with age >50 years (P = 0.011), concurrent malignancy (P = 0.039), diuretic use (P < 0.001), preceding diarrhoea (P = 0.042) and Medical Research Council (MRC) sum score at discharge (MRCSSD) (P = 0.026). Only concurrent malignancy (P < 0.001) and diuretic use (P < 0.001) were independently associated with hyponatraemia. MRCSSD also correlated with MRC sum score on admission (MRCSSA) (P < 0.001), length of hospital stay (P < 0.001), summated compound muscle action potential (P = 0.034) and lowest forced vital capacity (P = 0.001). Only MRCSSA (P = 0.004) and length of hospital stay (P < 0.001) independently predicted MRCSSD. Combining our findings with previous literature indicates comparable frequencies of hyponatraemia in GBS in four of five studies and association with mortality in three of four studies, with an independent link in one. Independent association of hyponatraemia with muscle strength is not demonstrated. Conclusion: Hyponatraemia appears of comparable frequency in GBS to that in other diseased cohorts suggesting it is common but non-specific. Hyponatraemia has otherwise been shown to be an independent predictor of death in other disorders and available data indicate the same is also likely in GBS, although this may vary in patient subgroups. Hyponatraemia is, however, not an independent prognostic indicator of neuromuscular weakness severity in GBS.