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A direct relationship between ionized calcium and arterial pressure among patients in an intensive care unit
T K Desai1, R W Carlson, M Thill-Baharozian
1Department of Internal Medicine, Wayne State University, Detroit, MI 48201.
Insights
Hypotension in the medical intensive care unit (MICU) is linked to lower serum ionized calcium (Ca+2) levels. This hypocalcemia may require vasopressor support and is associated with increased need for vasodilator therapy.
Area of Science:
- Critical Care Medicine
- Clinical Chemistry
- Nephrology
Background:
- Serum electrolyte and acid-base balance are crucial in critically ill patients.
- Abnormalities in calcium, creatinine, and pH are common in the medical intensive care unit (MICU).
- The relationship between these parameters and hemodynamic status requires further elucidation.
Purpose of the Study:
- To investigate the association between serum ionized calcium (Ca+2) levels and hemodynamic status (hypotensive, hypertensive, normotensive) in medical ICU patients.
- To determine if Ca+2 levels correlate with mean arterial pressure.
- To examine the relationship between Ca+2 levels and the requirement for vasopressor or vasodilator therapy.
Main Methods:
- Serum ionized calcium (Ca+2), creatinine, magnesium, phosphate, and arterial pH were measured in 112 patients on admission to the MICU.
- Patients were categorized into hypotensive, hypertensive, and normotensive groups based on vasopressor or vasodilator use.
- Analysis of variance was used to compare groups, with adjustments for creatinine as a covariate.
Main Results:
- Serum Ca+2, creatinine, and arterial pH differed significantly among the three hemodynamic groups.
- Hypotensive patients exhibited significantly lower mean Ca+2 levels compared to normotensive and hypertensive patients.
- Serum Ca+2 showed a significant positive correlation with mean arterial pressure, independent of other variables.
- Hypocalcemic patients required vasopressor support more frequently (41%) than normocalcemic patients (14%).
- Normocalcemic patients required vasodilator therapy more frequently (34%) than hypocalcemic patients (7.5%).
Conclusions:
- A clinically significant association exists between hypotension and hypocalcemia in medical ICU patients.
- Lower serum ionized calcium levels are linked to a higher likelihood of requiring vasopressor support.
- The findings suggest a potential role for calcium monitoring and management in hypotensive ICU patients, though causality is not established.
Abstract:
Serum ionized calcium (Ca+2), creatinine, magnesium, phosphate, and arterial pH were measured in patients on admission to the medical ICU (MICU). Patients were classified into three groups: a) hypotensive (n = 38), those who received vasopressor support for frank hypotension; b) hypertensive (n = 21), those who required vasodilator therapy; and c) normotensive (n = 53), those who required neither vasopressor nor vasodilator therapy. Analysis of variance revealed that only Ca+2, creatinine, and arterial pH differed among the three groups. The difference in Ca+2 persisted when analysis of variance was repeated with creatinine as a covariate. Hypotensive patients had a significantly (p less than .05) lower mean Ca+2 (1.04 +/- 0.13 mmol/L) than normotensive patients (1.13 +/- 0.10 mmol/L), who in turn had a significantly (p less than .05) lower Ca+2 than hypertensive patients (1.18 +/- 0.09 mmol/L). Ca+2 correlated with mean arterial pressure at the time of serum collection (n = 118; r = .43; p less than .01), independent of any other variable. Vasopressor support was required in 41% of hypocalcemic patients in comparison to 14% of normocalcemic patients (p less than .01). Vasodilator therapy was required for 34% of normocalcemic patients, compared to 7.5% of hypocalcemic patients (p less than .01). There appears to be a clinically significant association between hypotension and hypocalcemia. This association may or may not be causal.