Arterial blood gas

Arterial blood gas measurement is a blood testthat is performed to determine the concentration of oxygen, carbon dioxideand bicarbonate, as well as the pH, in the blood. Its main use is in pulmonology, as many lung diseases feature poor gas exchange, but it is also used in nephrology(kidney diseases) and electrolyte disturbances. As its name implies, the sample is taken from an artery, which is more uncomfortable and difficult than venipuncture.

Obtaining and processing the sample

Arterial blood is taken from any easily accessible artery (typically either radial, brachialor femoral) or out of an arterial line. The syringe is prepacked and contains a small amount of heparin, to prevent coagulationor needs to be heparinised, by drawing up a small amount of heparin and squirting it out again.

The sealed syringe is taken to a blood gas machine. The machine aspirates this blood from the syringe and measures the pHand the partial pressuresof oxygenand carbon dioxideand the bicarbonateconcentration, as well as the oxygen saturationof hemoglobin. Some machines can also measure glucose, lactate, hemoglobinand limited electrolytes(sodiumand potassium).

The results are usually available within five minutes, and are now ready for interpretation.

Interpretation

The pHwill indicate if a patient is acidotic(pH <7.35) or alkalotic(pH > 7.45), while the oxygen and carbon dioxide partial pressure readings will indicate whether the cause is respiratoryproblems (increased/decreased CO₂), or metabolic(such as ketoacidosis), and whether or not there has been any compensation by the body.

Other results can determine oxygen saturation, blood sugarstatus, and other metabolites in the blood. Various analyzers may also test hemoglobin, electrolyte, lactateand others metabolites (urea, creat, gluc) levels.

Reference ranges

These are typical reference ranges, although various analysers and laboratories may employ different ranges.

Lactate levels are often included on blood gas machines in neonatalwards; infants often have elevated lactic acid.de:Blutgasanalyse fr:Gaz du sang

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It uses material from the http://en.wikipedia.org/wiki/Arterial+blood+gas Wikipedia article Arterial blood gas.