Calcium: Total or Ionized?

Schenck, Patricia A.; Chew, Dennis J.

doi:10.1016/j.cvsm.2008.01.010

Cited by 34 publications

(48 citation statements)

References 19 publications

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“…Careful attention to technique is important; the process of collecting a sample for ionized calcium should be as ‘anaerobic' as possible. Blood should be collected directly into a serum heparinized Vacutainer tube as those containing oxalate, citrate or ethylenediaminetetraacetic acid (EDTA) can decrease the calcium available for analysis due to these chemicals binding to it [6]. If a syringe is used, a premeasured quantity of dry heparin is preferable to manually coating the syringe with liquid heparin, which can dilute the sample and falsely decrease the measured ionized calcium.…”

Section: Measurement Of Calciummentioning

confidence: 99%

What Is Hypercalcemia? The Importance of Fasting Samples

Siyam

Klachko

2013

Cardiorenal Med

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The differentiation between primary or tertiary (both hypercalcemic) and secondary (normocalcemic) hyperparathyroidism requires the identification of hypercalcemia. Calcium in the blood exists as bound, complexed and ionized fractions. Calcium sensors on parathyroid cells interact only with the ionized fraction (about 50% of the total calcium concentration). Many formulas using albumin, total protein or phosphate to correct or adjust total calcium to reflect the level of ionized calcium may be accurate only within a limited range. In addition, they can introduce errors based on inaccuracies in the measurement of these other metabolites. Clinical conditions, mainly those illnesses affecting acid-base balance, can alter the proportions of bound and free calcium. How and when the blood samples are drawn can alter the level of total calcium. Prolonged standing or prolonged venous stasis causes hemoconcentration, increasing the bound fraction. Preceding exercise can also affect blood calcium levels. Ingestion of calcium supplements or calcium-containing nutrients can cause transient elevations in blood calcium levels lasting several hours, leading to unnecessary further testing. Fasting total calcium levels may be sufficient for monitoring progress. However, for diagnostic purposes, fasting ionized calcium levels should be used. Therefore, for an isolated high total calcium level, we recommend obtaining a repeat fasting total and ionized calcium measurement before further investigations. Hypercalcemia may be diagnosed if there are persistent or frequent total or, preferably, ionized calcium levels >3 SD above the mean of the normal range or if there are progressively rising levels.

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Section: Measurement Of Calciummentioning

confidence: 99%

What Is Hypercalcemia? The Importance of Fasting Samples

Siyam

Klachko

2013

Cardiorenal Med

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“…Overall, however, electrolyte analysis should be performed on serum samples that are col lected anaerobically. 3,4,[8][9][10][11] Anaerobic conditions are most important for ionized calcium and magnesium analysis. 4,10-12 Whole blood, anticoagulated whole blood, and plasma can also be used, but one must consider various possible artifacts and the risk of clot formation prior to the completion of analysis when using whole blood.…”

Section: Methods Of Electrolyte Quantificationmentioning

confidence: 99%

“…11,37 These formulas have since been shown to cause spurious interpretation of calcium levels in the face of hypoproteinemia. 11,37 Total calcium measurements correlate poorly with ionized calcium in situations of renal insufficiency and acidbase imbal ance. 4,12 Total calcium measurement can also be spuri ously affected by hemolysis, hyperbilirubinemia, and lipemia.…”

Section: Calcium Concentration Measurementmentioning

confidence: 99%

“…4,12 Total calcium measurement can also be spuri ously affected by hemolysis, hyperbilirubinemia, and lipemia. 11 Ionized calcium assessed by ISE, which mini mizes interference by other ions, protein, hemolysis, and Clinical signs of hyperphosphatemia include weak ness, tetany, seizures, tachycardia, and torsades de pointes, a potentially fatal cardiac dysrhythmia. 34 Initial treatment should directly address severe sequelae of hyperphosphatemia such as seizures and torsades de pointes.…”

Section: Calcium Concentration Measurementmentioning

confidence: 99%

“…Calcium exists in three forms in plasma or serum: ionized or "free" calcium (iCa ++ ), complexed or chelated calcium bound to other substances such as phosphate and sulfate, and proteinbound calcium. 11 Ionized calcium is the biologically active form of calcium and has a role in many physiologic functions including intra and extra cellular messaging, cardiac conduction, and muscle contraction. 36 The most common cause of hypercalcemia in veteri nary patients is neoplasia, specifically lymphoma.…”

Section: Calciummentioning

confidence: 99%

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