Clinical characteristics and outcomes of hyponatraemia associated with oral water intake in adults: a systematic review

Abstract

Introduction: Excessive water intake is rarely associated with life-threatening hyponatraemia. The aim of this study was to determine the clinical characteristics and outcomes of hyponatraemia associated with excess water intake.

Methods: This review was conducted using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. All studies (case reports, observational or interventional studies) reporting excess water intake and hyponatraemia in adults (1946-2019) were included.

Results: A total of 2970 articles were identified and 177 were included (88.7% case reports), consisting of 590 patients. The mean age was 46±16 years (95% CI 44 to 48 years), 47% female, 52% had a chronic psychiatric disorder and 31% had no underlying condition. The median volume of water consumed and serum sodium at presentation was 8 L/day (95% CI 8.9 to 12.2 L/day) and 118 mmol/L (95% CI 116 to 118 mmol/L), respectively. The motivator for increased water consumption was psychogenic polydipsia (55%); iatrogenic (13%); exercise (12%); habitual/dipsogenic polydipsia (7%) and other reasons (13%). The clinical features on presentation were severe in 53% (seizures, coma); moderate in 35% (confusion, vomiting, agitation) and mild in 5% (dizziness, lethargy, cognitive deficit) and not reported in 5% of studies. Treatment was supportive in 41% of studies (fluid restriction, treatment of the underlying cause, emergency care), and isotonic and hypertonic saline was used in 18% and 28% of cases, respectively. Treatment-related complications included osmotic demyelination (3%) and rhabdomyolysis (7%), and death occurred in 13% of cases.

Conclusion: Water intoxication is associated with significant morbidity and mortality and requires daily intake to substantially exceed population-based recommendations. The limitations of this analysis are the low quality and high risk of bias of the included studies.

Prospero registration number: A pre-existing protocol in the international prospective register of systematic reviews was updated to incorporate any new amendments and reregistered at http://www.crd.york.ac.uk/PROSPERO (registration no. CRD42019129809).

Keywords: adult psychiatry; general endocrinology; genitourinary medicine; nephrology; nutrition & dietetics.

Figure 1

PRISMA flow diagram outlining the literature selection process.

Figure 2

Categorisation of cases according to underlying comorbidities, main reason for water intake and use of concomitant drugs associated with hyponatraemia (low Na+).

Figure 3

3D scatterplot box to group cases according to water intake (A: litres per day; B: litres over 4 hours), comorbidity and serum sodium. Dots are coloured according to comorbidity group (psychiatric condition, pink; no underlying health condition or none, orange; multiple conditions, blue; medical condition, green). 3D, three dimensions.

Figure 4

3D scatterplot box to group cases according to serum sodium, treatment type and severity of clinical presentation. Dots are coloured according to treatment type (hypertonic saline, red; isotonic saline, orange; other, pink or not reported, blue). 3D, three dimensions.

Figure 5

Categorisation of cases according to underlying comorbidities, water intake (litres per day) and outcomes.