Calcium, Ionized, Whole Blood

Calcium, Ionized

Alternate Test Name

Ionized Calcium

Epic Mnemonic
Sunquest Mnemonic

LAB3227
CAIO

Category

Chemistry

Test Performance Schedule

Sunday - Saturday

Result Availability

Within 24 hours – STAT upon request

Container

Green top (lithium heparin) tube

Volume

Pref. Vol.: 3.0 mL
Min. Vol.: 0.5 mL

Collection Instructions

• Peripheral draw only
• Draw waste tube before collection tube
• Immediately after collection, gently invert tube 5-10 times
• Transport whole blood

Transportation Instructions

Transport on ice

Stability

• Room Temperature: 30 minutes
• Refrigerated: 4 hours
• Frozen: Unacceptable

Causes for Rejection

• QNS
• Syringe, capillary or microtainer specimen
• De-capped specimens
• Centrifuged specimens
• Gel barrier tubes

CPT Codes

82330

Effective/Revised

8/31/21

Ionized calcium (Ca++) is the physiologically active form of calcium and comprises approximately 45% of the total calcium in plasma. Calcium is essential for the contractility of smooth vascular muscle, and it plays a vital part in cardiovascular function. It is one of the most tightly controlled analytes in the body.

In critical care situations, especially when the patient receives large amounts of blood, the patient’s ionized calcium levels should be monitored closely. Transfused blood typically contains citrate as an anticoagulant that can bind ionized calcium and reduce its level in the blood. Decreased ionized calcium levels can lead to cardiac and neuromuscular malfunction.

Because hydrogen ions compete with calcium for calcium binding sites, a change in sample pH can have a direct effect on ionized calcium levels. For this reason, when blood pH is between 7.2 and 7.7 with be adjusted to a normalized pH of 7.4. If pH is <7.2 or >7.7, an Ionized Calcium result cannot be generated