Pulses During CPR are Venous
The purpose of this investigation was to compare the use of real-time ultrasound guidance with the standard landmark-oriented approach for obtaining femoral vein catheterization during CPR. Twenty patients were studied, each receiving bilateral femoral lines, one by ultrasound guidance and one by the landmark approach (control). Real-time ultrasound-guided catheterization had a higher success rate (90% versus 65%), a lower number of needle passes (2.3 versus 5.0), and a lower rate of arterial catheterization (0% versus 20%) than the standard landmark-oriented approach. An incidental finding of interest was that real-time ultrasound demonstrated the presence of femoral vein pulsations during CPR.
The stated purpose of this study was to demonstrated the efficacy of real-time ultrasound to guide femoral vein catheterization during CPR. As an aside, the authors came across a most interesting (though not new) finding -- palpable femoral pulsations during CPR were venous rather than arterial. Despite the fact that the authors consider this to be an incidental finding, I believe it is the most significant discovery of the entire study. This is the first paper in quite a while that has mentioned arterial versus venous pulsations and the only one I am aware of to demonstrate the difference using real-time ultrasound. The implications of this finding are significant. We have traditionally used the palpable femoral "pulse" as a way to monitor CPR. Moreover, it is a common site from which to draw blood gases. Because there is a good chance the "femoral pulse" is actually a venous pulsation, it is relatively easy to assume that a gas is arterial when, in fact, it is really venous.