Association of Hypocalcemia and Mean Arterial Pressure With Patient Outcome in ICU

OBJECTIVES: We aimed to verify the relationship between hypocalcemia in the first 24 hours of ICU admission and mortality, we also hypothesized that blood pressure and blood pressure reactivity are associated with ionized calcium (iCa) and might have mediation effects in the iCa-mortality association. DESIGN: Retrospective, observational study. SETTING: ICUs in a general hospital. PATIENTS: Nonhypercalcemia adult patients were divided into two groups based on mean iCa within the first 24 hours after ICU admission using a cutoff of 1.1 mmol/L. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A total of 4947 patients from Peking Union Medical College Hospital between January 2013 and December 2022 were included in the study, with 2160 (43.7%) suffering from hypocalcemia. Overall, the median (interquartile range) age was 61 years (49-71 yr), with 2824 (57.1%) being female. Time-weighted average mean arterial pressure (TWA-MAP) above 0 and 65 mm Hg, respectively, during the first 24 hours were used to analyze the MAP of each patient and TWA-MAP/norepinephrine (TWA-MAP/NE) dose was calculated to examine blood pressure reactivity. Among 4091 patients eligible for multivariate analysis, iCa was independently associated with ICU mortality (odds ratio, 0.17; 95% CI, 0.04-0.79; p < 0.05). Both the blood pressure parameter (TWA-MAP above 0 mm Hg [TWA-MAP-0]) and pressure reactivity parameter (TWA-MAP-0/weight-adjusted dose of norepinephrine infusion in the first 24 hr after ICU admission [TWA-MAP-0/NE]) mediated the outcome of ICU mortality with a proportion of 4.55% (95% CI, 0.16-17%; p < 0.05) and 2.6% (95% CI, 0.02-11%; p < 0.05), respectively. TWA-MAP-0 correlated positively with iCa (Spearman rank test, ρ = 0.17; p < 0.01) while no significant association was found between iCa and TWA-MAP-0/NE (Spearman rank test, ρ = -0.07; p < 0.01). CONCLUSIONS: In this retrospective study on nonhypercalcemia patients, iCa of the first 24 hours after admission was independently associated with ICU mortality, which was potentially mediated by TWA-MAP and blood pressure reactivity (TWA-MAP/NE). iCa was also positively associated with TWA-MAP, while no general relationship was found between iCa and TWA-MAP/NE.