For vascular access, you still hear the old “We don’t have time for using ultrasound – this is an emergency!”. In many settings, the old landmark techniques are quick and good in experienced hands. But when going for the femoral vessels in cardiac arrest, you would want to use ultrasound.
CPR + femoral = ultrasound
It depends on what you’re going for. The jugular will often be ballooning, and the subclavian should be just as easy as in a circulated patient. But the femoral can be tricky. As found by Emerman in 1990 with higher success for the subclavian 94% vs the femoral 77% in cardiac arrest.
One reason is that feeling the femoral artery pulse is a central part of landmark femoral vein cannulation. And in arrest, and ongoing CPR, the pulsation will usually be most palpable in the vein, due to retrograde pulsation and good compliance of the vein. Or pulses can be difficult to feel altogether.
Cardiac arrest cannulation
I’ve seen this in cardiac arrest, often in the cath lab, where ultrasound cannulation has still to make its appearance. The hit and (mostly) miss approach is prevalent in femoral cannulation. This delays cannulation, but even worse: it creates multiple small tissue traumas and bleeding that frequently makes the vessels very difficult, or even impossible, to visualise afterwards. Ultrasound must be used from the get-go.
In this 1997 study by Hilty & Hudson in the Annals of Emerg Med is a few years old, but illustrates the point quite nicely, showing ultrasound outperforms landmark femoral cannulation in arrest by a large margin: Success rate 90% vs 65%, Needle passes 2.3 +/-3 vs 5 +/-5, and accidental arterial cannulation 0% vs 20%. Time to blood flash and catheterisation was also shorter in the ultrasound group, probably due to fewer needle passes.
Keep in mind that this is also a small study of only 20 patients, and basically a buddy study done by two emerg residents, all caths placed by them. But the good part of the design was that each patient received two central lines, one in each femoral vein. On one side, by landmark technique and on the other side by ultrasound guidance. Both by the same doctor, and randomisation dictated which technique to apply first.
The two buddies had fairly basic ultrasound experience, but still made a big win for ultrasound, both by placement success, needle passes and time used.
In no setting is correct vessel identification and cannulation more important than in an ECPR setting. I’ve seen several emergency ECMO initiations accidently turning out to be VV ECMO or even AA ECMO, thus giving no circulatory support. This loses time to return of circulation for the patient, as well as more big holes the patient can bleed from in the following ECMO run. Use ultrasound.
In a patient deteriorating in the cath lab with some flow, and the artery already cannulated, the situation can be different. An experienced invasive cardiologist with arterial access and contrast available, can usually cannulate well without ultrasound.
But with extreme low-flow or arrest, and no big lines in, ultrasound is the way to go. The invasive cardiologists either need to learn that, are pass the needle on to someone (usually an anaesthesiologist, intensivist or emergency physician) experienced in emergency ultrasound cannulation for the actual cannulation and guidewire procedure.
CPR vein pulsation
In this study, they could also verify the more pronounced pulsation of the femoral vein compared to the femoral artery. This is an important thing to keep in mind both for landmark cannulation and ultrasound cannulation during CPR, for identifying the right vessel to cannulate. In this study, they could only palpate a pulse in 40% of the patients, and often arising from the vein:
Eight of the 20 patients had no palpable pulse with CPR. Nine patients catheterized by one author (WH), two of whom had no palpable pulses, were observed to have ultrasonographically visible femoral venous pulsation without visible femoral artery pulsation during CPR.
In a CPR setting, cannulation of femoral vessels will be both quicker and more successful if you have ultrasound readily available. Multiple landmark attempts can screw up your ultrasound view, so if possible, wait for the machine, and let someeone with ultrasound cannulation experience do the cannulation. Especially if you’re going for ECPR VA ECMO.