Test Code CAION Calcium, Ionized LAB54
Test Method
Ion-Selective Electrode Potentiometry; iSTAT
Specimen Requirement
Venous lithium heparin whole blood is required.
Additional Specimen Collection Information
Collect blood in a lithium heparin, green-top
tube. Plasma gel tubes are NOT acceptable. Collection
tubes
must be filled to capacity. Samples must be run within 10
minutes
of collection; avoid exposing samples to air. Venous whole blood
is
the only acceptable sample type.
Note: Full heparin microtainers are acceptable. (DO NOT
overfill
or underfill)
Reference Values
1.12-1.32 mmol/L
-
Critical Value:
- Low: < 0.80 mmol/L
- High: > 1.60 mmol/L
Venous stasis (prolonged tourniquet application) and forearm
exercise may increase ionized calcium due to a decrease in pH
caused by localized production of lactic acid. Exposing the
sample
to air will cause an increase in pH due to the loss of
CO2, which will decrease ionized calcium.
Heparin binds calcium. Each unit of heparin added per ml of
blood will decrease ionized calcium by 0.01 mmol/L. Therefore,
the
correct ratio of heparin anticoagulant to blood must be
achieved
during sample collection. Intravenous injection of 10,000 units
of
heparin has been shown in adults to cause a significant decrease
of
ionized calcium of about 0.03 mmol/L.
Hemodilution of the plasma by more than 20% associated with
priming cardiopulmonary bypass pumps, plasma volume expansion
or
other fluid administration therapies using certain solutions
may
cause clinically significant error on ionized calcium results.
These errors are associated with solutions that do not match
the
ionic characteristics of plasma. To avoid these errors when
hemodiluting by more than 20%, use physiologically balanced
multi-electrolyte solutions containing low-mobility anions
(e.g.
Gluconate) such as Normosol-R (Abbott Laboratories),
Plasma-Lyte-A
(Baxter Healthcare oCrporation), and Isolyte-S (B Braun
Medical)
rather than solutions such as normal saline or ringer’s
lactate.
Performance
Testing is performed Monday through Sunday.
Typically completed within 30 minutes after the
specimen
arrives at the testing site.
Useful For
Assessing calcium states during liver transplantation
surgery,
cardiopulmonary bypass, or any procedure requiring rapid
transfusion of whole blood in neonates and in critically ill
patients.
LOINC Code Information
17864-0 Calcium.Ionized [Mass/Volume] In Serum Or Plasma By
Ion-Selective Membrane Electrode (ISE)
CPT Code Information
82330 Chemistry: Calcium, ionized