Serum ionised calcium and the risk of acute respiratory failure in hospitalised patients: a single-centre cohort study in the USA

Abstract

ObjectivesThe objective of this study was to evaluate the risk of acute respiratory failure in all hospitalised patients based on admission serum ionised calcium.DesignA retrospective cohort study.SettingA tertiary referral hospital in Rochester, Minnesota, USA.ParticipantsAll hospitalised patients who had serum ionised calcium measurement within 24 hours of hospital admission from January 2009 to December 2013. Patients who were mechanically ventilated at admission were excluded.PredictorsAdmission serum ionised calcium levels was stratified into six groups: ≤4.39, 4.40–4.59, 4.60–4.79, 4.80–4.99, 5.00–5.19 and ≥5.20 mg/dL.Primary outcome measureThe primary outcome was the development of acute respiratory failure requiring mechanical ventilation during hospitalisation. Logistic regression analysis was fit to assess the independent risk of acute respiratory failure based on various admission serum ionised calcium, using serum ionised calcium of 5.00–5.19 mg/dL as the reference group.ResultsOf 25 709 eligible patients, with the mean serum ionised calcium of 4.8±0.4 mg/dL, acute respiratory failure requiring mechanical ventilation occurred in 2563 patients (10%). The incidence of acute respiratory failure was lowest when admission serum ionised calcium was 5.00–5.19 mg/dL, with the progressively increased risk of acute respiratory failure with decreased serum ionised calcium. In multivariate analysis with adjustment for potential confounders, the increased risk of acute respiratory failure requiring mechanical ventilation was significantly associated with admission serum ionised calcium of ≤4.39 (OR 2.52; 95% CI 2.12 to 3.00), 4.40–4.59 (OR 1.76; 95% CI 1.49 to 2.07) and 4.60–4.79 mg/dL (OR 1.48; 95% CI 1.27 to 1.72), compared with serum ionised calcium of 5.00–5.19 mg/dL. The risk of acute respiratory failure was not significantly increased when serum ionised calcium was at least 4.80 mg/dL.ConclusionThe increased risk of acute respiratory failure requiring mechanical ventilation was observed when admission serum ionised calcium was lower than 4.80 mg/dL in hospitalised patients.

Hypocalcemia is a distinctive biochemical feature of hospitalized COVID-19 patients

“…Hypocalcemia was an already reported finding in patients hospitalized in Internal Medicine departments [ 9 ] and was found quite consistently to be associated with increased risk of acute respiratory failure and mortality [ 10 , 11 ]. Therefore, it is currently unclear if hypocalcemia in COVID-19 is only a marker of disease severity rather than a specific feature of the disease.…”

The Association Between Hypocalcemia and Outcome in COVID-19 Patients: a Retrospective Study

“…Calcium levels should be monitored in all cases of acute and recovered COVID-19 patients [29]. Hospitalized patients with serum ionised calcium level below 4.80 mg/dl have increased risk of acute respiratory failure and had more requirement of mechanical ventilation [30]. Timely supplementation of calcium has been suggested in severe COVID-19 patients to prevent organ failure as an early diagnosis and treatment of hypocalcemia may alleviate organ injury [31].…”

Hospital-Acquired Serum Ionized Calcium Derangements and Their Associations with In-Hospital Mortality

“…The remaining total body calcium (approximately 10 in adults) exists outside of the skeletal system and participates in a myriad of essential functions, including neurotransmitter release, muscle contraction, and cellular signaling. Approximately 50% of circulating calcium ions are bound to protein, such as albumin or globulin, whereas the rest exists as unbound ionized (free) calcium [ 4 , 5 , 6 , 7 , 8 ]. Measuring ionized calcium is important, as Payne’s formula [ 6 ] for corrected total calcium level tends to overestimate ionized calcium, especially in patients with hypoalbuminemia [ 7 , 8 ].…”

“…Both reduced and elevated admission serum ionized calcium were associated with increased 1 year mortality with a U-shape relationship [ 19 ]. While the effects of calcium disturbances at hospital admission on poor outcomes among hospitalized patients have been demonstrated [ 4 , 5 , 19 ], the incidence of in-hospital calcium disturbances and their association with mortality are currently unknown.…”