Impact of ICU-acquired hyperchloraemia on all-cause in-hospital mortality in adult patients who were critically ill: a retrospective cohort study in a tertiary grade A hospital.

Abstract

This study aims to investigate the association between acquired blood chloride abnormalities and all-cause in-hospital mortality in adult patients who were critically ill with normal blood chloride at admission to the intensive care unit (ICU). A retrospective cohort study. Serum chloride concentration was measured by an indirect potentiometric method. This study encompassed adult patients who were critically ill and admitted to the ICU, and who exhibited normal blood chloride levels (99-110 mmol/L) at Xiangyang Central Hospital between 1 April 2020 and 30 April 2022. The primary outcome was in-hospital mortality, defined as death from any cause during hospitalisation. The secondary outcomes included 30-day mortality, the length of ICU stay and the total length of stay in the hospital. This study included 1131 patients. The baseline characteristics were comparable among the three groups of patients (all p>0.05). The all-cause in-hospital mortality rate was 11.4% (n=129). The incidence of acquired hyperchloraemia 48 hours after admission was 16.53% (n=187), with a mortality rate of 17.6% (n=33). The incidence of acquired hypochloraemia was 9.37% (n=106), with a mortality rate of 12.3% (n=13). The proportion of patients with persistently normal blood chloride was 74.09% (n=838), with a mortality rate of 9.9% (n=83). ICU-acquired hyperchloraemia was associated with a higher in-hospital mortality rate than patients with persistently normal blood chloride (OR 1.83, 95% CI 1.09 to 3.05, p=0.022). Furthermore, for every 1 mmol/L increase in blood chloride levels, there was an 11% increase in the risk of all-cause in-hospital mortality (OR 1.11, 95% CI 1.02 to 1.20, p=0.014). Acquired hyperchloraemia 48 hours after ICU admission is independently associated with a higher risk of all-cause in-hospital mortality in adult patients who were critically ill.