Welcome to ICU Primary PrepQuest. Hi, I'm Maddy. Hi, I'm Swapnil. And this time we're going to dive into some of the anatomic questions that are quite challenging for candidates.
So Maddy, can you please describe the anatomy of the femoral vein as it relates to central venous scantilation? Sure. So this is something we commonly encounter in clinical practice, but thinking about the anatomy, I think it's important to structure your response. So the way I've structured this response is looking at the origin, course, and tributaries of the femoral vein, its location, important anatomical relations, and then the surface anatomy. So from the origin, course, and tributaries, the femoral vein begins at the adductor hiatus of the adductor magnus muscle as a continuation of the popliteal vein and it then extends into the anterior thigh.
It travels through the adductor canal into the femoral triangle, traverses the femoral sheath just lateral to the femoral canal and terminates posterior to the inguinal ligament as the external iliac vein which is retroperitoneal. So that's why it's important you might hear when you're learning to cannulate the femoral vein, it's important to cannulate below the inguinal ligament because we're able to then put pressure on the area if there is any injury to the vessel or if by mistake you hit the femoral artery. Whereas once the femoral vein extends past the inguinal ligament as the external iliac vein, it's retroperitoneal. So it's difficult or impossible to apply pressure to that area. In terms of the tributaries, there's several tributaries.
So the deep femoral vein, which empties into the femoral vein posteriorly, just distal to the inguinal ligament, and it's formed by perforating veins. The great saphenous vein, which is... also called the long saphenous vein sometimes, which joins the femoral vein anteriorly infralateral to the pubic tubercle and receives tributaries from the deep veins of the thigh and leg.
Approximately, it receives the external dendral superficial circumflex iliac superficial epigastric and accessory saphenous before joining the femoral vein and then the lateral and medial circumflex veins. So in terms of the location, the femoral vein lies within the femoral triangle and the borders of the femoral triangle, the inguinal ligament, which is a superior border. which runs from the ASIS to the pubic tubercle.
The medial border of the adductor longus muscle, which is the medial border of the femoral triangle. Laterally, it's the medial border of the sartorius muscle. The apex of this triangle is the sartorius crossing the adductor longus, and the roof of the triangle is skin, subcutaneous tissue, preperformed fascia, and the fascia lata. The floor is the adductor longus, the adductor brevis, the pectineus, and the iliopsoas muscle.
And the femoral triangle contains the femoral sheath, which is a fascial component divided into three compartments by two vertical septae. It contains the femoral canal, which is in the medial compartment. And the femoral canal contains the lymphatic vessels, fat, and the deep lymph node.
The femoral vein, which is in the intermediate compartment, and the femoral artery, which is within the lateral compartment. The femoral nerve is lateral to the femoral sheath and lateral to the artery as a result. The important anatomical relations, like when you're canulating, the main thing is the femoral artery. And I think we've all heard maybe some of the different acronyms to try and remember the way that you order from medial to lateral. So I don't know what you've heard.
Do you have any acronyms that you use, Swapnil, for that? No, I'm very bad in remembering the acronyms, to be honest. So what I was taught was NAVY. So that's going from lateral to medial.
And that's nerve, artery, vein. And then it's... Y-fronts, which is another word for undies, I guess. So that was what we were taught. But interestingly, the artery isn't always lateral.
It depends to the vein. It depends on the position of where you're actually cannulating the vein and where the vein is. So distally, the femoral vein lies postural lateral to the artery, but within the femoral sheath, it lies medial to the artery.
Usually we say that the vein is medial, but that will depend on how far you are, whether you're distal or proximal for your cannulation. In terms of the surface anatomy, we all use ultrasound guidance now, but generally from a surface anatomy point of view, the femoral artery pulsation is generally located midway between the ASIS and the pubic symphysis along the inguinal ligament. And the femoral vein is generally one to two centimeters inferior and medial to this. So traditionally, people would say...
Help out the artery and then try and insert your needle about one to two centimeters inferior and medial to that pulsation where you feel the femoral artery. And then the layers that you pass on the insertion of the needle are the skin, the subcutaneous tissue, the fascia, and then hopefully the femoral vein. There is a reference in the show notes if you want further information or diagrams.
Thanks, Maddy. So I guess these anatomic questions are always challenging. And as you said, Mnemonic, I was just hoping that you guys remember the lateral to medial sequence rather than medial to lateral sequence, because if you get that wrong, I guess even in real life, you're going to puncture the artery. So just remember which side we are going from. So thanks, Maddy.
Thanks for another comprehensive snippet. We'll be back. with another snippet in a week's time. Till then, goodbye.
Have a nice time. Thanks for listening and see you next time.