Background: Hyponatraemia in adults with bacterial meningitis has been described as a common complication, but its true prevalence and clinical importance are unknown.
Aim: To investigate the prevalence, clinical characteristics and consequences of hyponatraemia in bacterial meningitis in adults.
Design: Nationwide observational cohort study.
Methods: We prospectively assessed the prevalence and clinical characteristics of hyponatraemia among 696 adults with community-acquired bacterial meningitis. Symptoms and signs on admission, blood and CSF test results, radiological examinations and complications during admission were recorded.
Results: Sodium levels were determined at admission in 685/696 episodes of bacterial meningitis (98%). Hyponatraemia (<135 mmol/l) was seen in 208/685 (30%) and was classified as severe (<130 mmol/l) in 38 (6%). Hyponatraemia developed during admission in an additional 53 episodes. Hyponatraemia was not associated with an increase in symptoms, with complications or with unfavourable outcome. Treatment for hyponatraemia was initiated in 16% of episodes, but did not influence its duration.
Discussion: Hyponatraemia appears both common and benign in adults with bacterial meningitis. In cases of severe hyponatraemia, we suggest the use of fluid maintenance therapy.