Wednesday July 15, 2009

Case: You are performing 'code blue' on a patient. You do not have an arterial line. What would be the best way to determine the efficacy of resuscitation?


Answer: Venous Blood Gas (VBG)

Arterial blood gas (ABG) analysis is useful in evaluation of the clinical condition of critically ill patients; however, arterial puncture or insertion of an arterial catheter may not be feasible or available in many situations. The VBG is easier, quicker, and safer to obtain and is associated with significantly less pain for the patient. It would be convenient for physician and patient to be able to replace the ABG with the VBG for analysis of base excess(acidosis). Actually, in code situation VBG would be a better indicator of overall acidosis. If VBG results are normal, ABG analysis should not be necessary. Conversely, abnormal venous levels predicted abnormal arterial values. A venous pH of 7 or lower, for example, predicted an arterial pH of 7.2 or lower.

In cardiac arrest victims, the disparity between arterial and venous values is even greater. During cardiac arrest, tissue hypoxia is all but a certainty and is reflected by the lower pH and higher PCO2 on the venous side.