Calcium, Blood, Total and Ionized

Calcium, Blood, Total and Ionized is a topic covered in the Davis's Lab & Diagnostic Tests.

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Synonym/Acronym:
Total and free calcium, Ca (total), unbound calcium (ionized), Ca++ (ionized), Ca2+ (ionized).

Rationale
To investigate various conditions, such as hypercalcemia and hypocalcemia, related to abnormally increased or decreased calcium levels.

Patient Preparation
There are no food, fluid, activity, or medication restrictions unless by medical direction.

Normal Findings
Method: Spectrophotometry for total calcium; ion-selective electrode for ionized calcium.


Calcium, Total
AgeConventional UnitsSI Units (Conventional Units × 0.25)
Cord8.2–11.2 mg/dL2.1–2.8 mmol/L
0–10 days7.6–10.4 mg/dL1.9–2.6 mmol/L
11 d–2 yr9–11 mg/dL2.2–2.8 mmol/L
3–12 yr8.8–10.8 mg/dL2.2–2.7 mmol/L
13 yr–adult8.4–10.2 mg/dL2.1–2.6 mmol/L
Adult older than 90 yr8.2–9.6 mg/dL2.1–2.4 mmol/L

Calcium, Ionized
AgeConventional UnitsSI Units (Conventional Units × 0.25)
Whole blood
 0–11 mo4.2–5.84 mg/dL1.05–1.46 mmol/L
 1 yr–adult4.6–5.08 mg/dL1.15–1.27 mmol/L
Plasma
 Adult4.12–4.92 mg/dL1.03–1.23 mmol/L
Serum
 1–18 yr4.8–5.52 mg/dL1.2–1.38 mmol/L
 Adult and older adult4.64–5.28 mg/dL1.16–1.32 mmol/L

Critical Findings and Potential Interventions

Calcium, Total

  • Less than 7 mg/dL (SI: Less than 1.8 mmol/L)
  • Greater than 12 mg/dL (SI: Greater than 3 mmol/L) (some patients can tolerate higher concentrations)

Calcium, Ionized

  • Less than 3.2 mg/dL (SI: Less than 0.8 mmol/L)
  • Greater than 6.2 mg/dL (SI: Greater than 1.6 mmol/L)

Timely notification to the requesting health-care provider (HCP) of any critical findings and related symptoms is a role expectation of the professional nurse. A listing of these findings varies among facilities.

Consideration may be given to verification of critical findings before action is taken. Policies vary among facilities and may include requesting immediate recollection and retesting by the laboratory or retesting using a rapid point-of-care testing instrument at the bedside, if available.

Observe the patient for symptoms of critically decreased or elevated calcium levels. Hypocalcemia is evidenced by convulsions, nervousness, dysrhythmias, changes in electrocardiogram (ECG) in the form of prolonged ST segment and Q-T interval, facial spasms (positive Chvostek sign), tetany, lethargy, muscle cramps, tetany, numbness in extremities, tingling, and muscle twitching (positive Trousseau sign). Possible interventions include seizure precautions, increased frequency of ECG monitoring, and administration of calcium or magnesium.

Severe hypercalcemia is manifested by excessive thirst, polyuria, constipation, changes in ECG (shortened QT interval due to shortening of the ST segment and prolonged PR interval), lethargy, confusion, muscle weakness, joint aches, apathy, anorexia, headache, nausea, and vomiting; ultimately, severe hypercalcemia may result in coma. Possible interventions include the administration of normal saline and diuretics to speed up dilution and excretion or administration of calcitonin or steroids to force the circulating calcium into the cells.

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