The nurse is collecting a blood sample for a mixed venous oxygen saturation (SVO2) level from the distal lumen of a pulmonary artery (PA) catheter of a client in cardiogenic shock. Which action should the nurse implement?

A. Expel the excess air and heparin from the syringe. While removing excess air prevents gas exchange alterations, this is not the priority when obtaining an SVO₂ sample. Excess heparin could dilute the sample, but proper blood volume collection is the first concern. B. Place sample in arterial blood gas syringe. SVO₂ measures venous oxygen saturation, which is different from arterial blood gases (ABGs). Using an ABG syringe is incorrect because it is heparinized for arterial sampling, and arterial blood does not reflect mixed venous oxygenation. C. Obtain a minimum of 1 mL of blood. SVO₂ is measured from the distal lumen of a pulmonary artery (PA) catheter to assess oxygen delivery and consumption. At least 1 mL of blood is required for an accurate reading, ensuring sufficient sample volume for laboratory analysis. D. Aspirate the blood sample slowly. While slow aspiration can help prevent hemolysis, it is not the primary concern when collecting an SVO₂ sample. The priority is obtaining a sufficient volume (≥1 mL) for an accurate measurement.