Predictive Value of Ionized Calcium in Critically Ill Patients: An Analysis of a Large Clinical Database MIMIC II

Abstract

Background and Objectiveionized calcium (iCa) has been investigated for its association with mortality in intensive care unit (ICU) patients in many studies. However, these studies are small in sample size and the results are conflicting. The present study aimed to establish the association of iCa with mortality by using a large clinical database.MethodsMultiparameter Intelligent Monitoring in Intensive Care II (MIMIC II) database was used for analysis. Patients older than 15 years were eligible, and patients without iCa measured during their ICU stay were excluded. Demographic data and clinical characteristics were extracted and compared between survivors and non-survivors. iCa measure on ICU admission was defined as Ca0; Camax was the maximum iCa during ICU stay; Camin was the minimum value of iCa during the ICU stay; Camean was the arithmetic mean iCa during ICU stay.Main resultsA total of 15409 ICU admissions satisfied our inclusion criteria and were included in our analysis. The prevalence of hypocalcemia on ICU entry was 62.06%. Ca0 was significantly lower in non-survivors than in survivors (1.11±0.14 vs 1.13±0.10 mmol/l, p<0.001). In multivariate analysis, moderate hypocalcemia in Ca0 was significantly associated with increased risk of death (OR: 1.943; 95% CI: 1.340–2.817), and mild hypercalcemia was associated with lower mortality (OR: 0.553, 95% CI: 0.400–0.767). While moderate and mild hypocalcemia in Camean is associated with increased risk of death (OR: 1.153, 95% CI: 1.006–1.322 and OR: 2.520, 95% CI: 1.485–4.278), hypercalcemia in Camean is not significantly associated with ICU mortality.ConclusionThe relationship between Ca0 and clinical outcome follows an “U” shaped curve with the nadir at the normal range, extending slightly to hypercalcemia. Mild hypercalcemia in Ca0 is protective, whereas moderate and mild hypocalcemia in Camean is associated with increased risk of death.

Predictive accuracy of serum total calcium for both critically high and critically low ionized calcium in critical illness

“…Our findings are supported by a previous study, which reported that the incidence rates of moderate hypocalcemia (ionized calcium less than 0.9 mmol/L) and hypercalcemia (ionized calcium more than 1.35 mmol/L) were 10.8% and 6.7%, respectively . The increased rate of abnormal ionized calcium in critical illness may be due to the following: (i) increased urine or fecal calcium excretion; (ii) decreased intake of dietary calcium and vitamin D, a promoter of calcium absorption in the intestine; (iii) underlying diseases or comorbidities affecting calcium homeostasis, such as sepsis and renal failure; and (iv) medication side effects, such as parathyroid surgery, catecholamine administration, and transfusion of citrated blood.…”

“…Among these three states, only ionized calcium is physiologically relevant, and critically high or low ionized calcium is life‐threatening . Indeed, previous studies concluded that extremely low or high ionized calcium is independently associated with hospital mortality in adult patients admitted to the intensive care unit (ICU) …”

Refractory Hypocalcemia Effectively Treated with Steroids in Prostate Cancer Metastatic to Bone

“…The aim of the acute management isn't only to return the serum calcium to the normal level but rather to ameliorate the acute manifestations of hypocalcemia [16] which have a direct impact on patient's daily life. Some studies concluded that moderate hypocalcemia has an increased incidence of mortality compared to mild hypocalcemia [17]. Moreover, a large retrospective study showed that calcium supplementation during the ICU stay improved 28-day survival in critically ill adult patients [18].…”

Hypocalcemia in the Critically Ill: A Mini-Review

“…In contrast other studies have concluded thath both mild and moderate hypocalcemia are associated with increased mortality. One large retrospective study showed that callcium supplementation improved 28 day survival in the ICU in critically ill patients [45,46].…”