Are patients admitted to hospitals from care homes dehydrated? A retrospective analysis of hypernatraemia and in-hospital mortality.

OBJECTIVES To compare risks of hypernatraemia on admission to hospital in persons who were with those who were not identified as care home residents and evaluate the association of hypernatraemia with in-hospital mortality. DESIGN Retrospective observational study. SETTING A National Health Service Trust in London. PARTICIPANTS A total of 21,610 patients aged over 65 years whose first admission to the Trust was between 1 January 2011 and 31 December 2013. MAIN OUTCOME MEASURES Hypernatraemia on admission (plasma Na > 145 mmol/L) and in-hospital death. RESULTS Patients admitted from care homes had 10-fold higher prevalence of hypernatraemia than those from their own homes (12.0% versus 1.3%, respectively; odds ratio [OR]: 10.5, 95% confidence interval [CI]: 8.43-13.0). Of those with hypernatraemia, nine in 10 cases were associated with nursing home ECOHOST residency (attributable fraction exposure: 90.5%), and the population attributable fraction of hypernatraemia on admission associated with care homes was 36.0%. After correcting for age, gender, mode of admission and dementia, care home residents were significantly more likely to be admitted with hypernatraemia than were own-home residents (adjusted odds ratio [AOR]: 5.32, 95% CI: 3.85-7.37). Compared with own-home residents, care home residents were also at about a two-fold higher risk of in-hospital mortality compared with non-care home residents (AOR: 1.97, 95% CI: 1.59-2.45). Consistent with evidence that hypernatraemia is implicated in higher mortality, the association of nursing homes with in-hospital mortality was attenuated after adjustment for it (AOR: 1.61, 95% CI: 1.26-2.06). CONCLUSIONS Patients admitted to hospital from care homes are commonly dehydrated on admission and, as a result, appear to experience significantly greater risks of in-hospital mortality.