Low serum total calcium concentration as a marker of low serum ionized calcium concentration in critically ill patients receiving specialized nutrition support.
BACKGROUND
The intent of this study was to ascertain to what extent serum total calcium concentration (tCa) <7 mg/dL reflects hypocalcemia (defined by ionized calcium concentration [iCa] of < or = 1.12 mmol/L) in critically ill patients receiving specialized nutrition support.


METHODS
Adult patients (> or = 18 years) admitted to the trauma, surgical, medical, burn, or neurosurgical intensive care units, trauma stepdown unit, or progressive care unit and referred to the nutrition support service were retrospectively identified for potential inclusion into the study. Serum chemistries, arterial blood gas measurements, nutrition markers, and serum iCa were simultaneously obtained from each patient approximately 1 day after initiation of specialized nutrition support. Patients with a serum creatinine > or = 2 mg/dL, hyperphosphatemia (> or = 6 mg/dL), severe hypomagnesemia (< or = 1.12 mg/dL), history of metabolic bone disease, or parathyroid disease were excluded from the analysis.


RESULTS
One hundred ninety-five patients (91% who had multiple trauma, with a mean Injury Severity Score 31 +/- 13) were enrolled into the study. Specialized nutrition support was initiated 2.8 +/- 1.8 days and calcium status was studied 4.2 +/- 3.1 days after hospital admission, respectively. The majority (28 of 33, or 85%) of patients with a tCa <7 mg/dL were hypocalcemic compared with 33% (22 out of 66) of patients with a tCa of 7-7.4 mg/dL, and 11% (11 of 96) of those with a tCa of 7.5-7.9 mg/dL (p < .001).


CONCLUSIONS
Critically ill patients with a serum total calcium concentration of <7 mg/dL have a high rate of hypocalcemia (iCa < or = 1.12 mmol/L). Hypocalcemia, defined as a serum iCa of < or = 1.12 mmol/L, occurs in 85% of acutely ill patients with a serum tCa <7 mg/dL.
Dickerson
Roland N
RN
Department of Clinical Pharmacy, University of Tennessee Health Science Center, Memphis, TN 38163, USA. rdickerson@utmem.edu
Henry
Natohya Y
NY
Miller
Patrice L
PL
Minard
Gayle
G
Brown
Rex O
RO
D000208:Acute Disease; D000328:Adult; D015415:Biomarkers / Q000097:blood; D001774:Blood Chemical Analysis; D001784:Blood Gas Analysis; D002118:Calcium / Q000097:blood*; D016638:Critical Illness / Q000628:therapy; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D006996:Hypocalcemia / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D018529:Nutritional Support; D012189:Retrospective Studies; D012720:Severity of Illness Index
D015415:Biomarkers; D002118:Calcium