Blood Gases / Ionized Calcium Testing

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Clinical Pathology

Blood Gases

Blood gases provide more accurate information about acid-base and oxygen status than the chemistry panel. Blood for blood gas samples should be collected directly into heparinized syringes, kept anaerobic (capped) and assayed as soon as possible. Changes in pH occur rapidly in blood stored after sample collection, therefore samples should be submitted promptly to the laboratory. For this reason, blood gases should always be performed in the clinic or hospital and should not be sent out to a referral diagnostic laboratory.

We perform blood-gases, using a dedicated blood-gas analyzer, the Radiometer ABL-800. This machine also measures electrolytes, including ionized calcium, using ion-selective electrodes on undiluted samples (direct potentiometry). When an ionized calcium is measured with a blood gas (blood gas/lytes plus panel), the ionized calcium is corrected for the pH. This is because ionized calcium values are altered by pH (increase in states of acidosis). Furthermore, an anion gap is calculated from the results. We have reference intervals for dogs, cats, horses and cattle for venous blood only. In general, arterial blood gases are preferred for blood gas measurement, especially if you are concerned about the oxygen status of the animal. Venous blood gas results differ from arterial blood gas results, because the sample is affected by tissue metabolism. Therefore, the blood is more acidic and the oxygen content lower in the venous circulation.

Click on the highlighted panel below to obtain more information about the test components. For more information about blood gases and interpretation of acid base abnormalities, refer to Bicarbonate under our Chemistry section of eClinPath.

Test Components Specimen Requirements Comments
Arterial blood gas pO2, pCO2, pH, bicarb., Tot. CO2, base excess 1-3 ml heparinized blood (syringe sealed with a black cap (no needles) or vacutainer) NO MICROTAINERS!
Bring to lab immediately after collection.
Remove needles from syringes!!
DO NOT leave the sample without notifying someone in the lab that the sample has arrived.
Venous blood gas pO2, pCO2, pH, bicarb., Tot. CO2, base excess. see above see above
Blood gas/lytes plus panel pO2, pCO2, pH, bicarb., Tot. CO2, base excess, Na, K, Cl, ICa, ICa @ pH 7.4, anion gap Heparinized blood, ideally collected into a calcium titrated dedicated syringe see above