Open stopcock to syringe and aspirate 5 ml to clear catheter of flush solution. Add blood gas syringe to stopcock and gently aspirate blood sample over one minute. Place immediately on ice. Flush stopcock port and replace deadhead cap. Mixed venous blood gases are frequently analyzed along with arterial blood in order to calculate the shunt fraction or the degree to which blood is bypassing unoxygenated from the lungs to the left side of the hear.
Ice ensures that results are accurate.
Close pressurized flush system to patient. Disconnect from monitor. Position patient in flat or slight Trendelenberg. Obtain vital signs. Monitor for dysrhythmias while physician removes catheter.