A ‘central line’ can actually mean many different things.
‘triple lumen’, ‘quad lumen’, ‘cordis’, ‘MAC’, ‘introducer sheath’,’trialysis’. Let’s decode all this a bit, shall we?
For the purposes of this discussion, we are going to split the central venous catheters into 3 different groups:
Note: Peripherally inserted central catheters (PICCs), midlines and tunneled catheters/ports will be covered in a separate post.
Standard Catheters
Standard catheters are central lines that are just regular old central lines. They provide multiple lumens for medications to be delivered reliably into a central vein. They can be used to draw central venous blood samples and can be hooked up to a transducer kit (more on this to come in a separate post) to measure central venous pressure (CVP), and that’s it. That’s all they’re for.
Their main advantage over the other two types of catheters is that they generally provide more usable lumens and are of a smaller diameter so they pose less theoretical risk of clot and of serious vascular complications if accidentally placed in the artery instead of the vein. However, based on the 2008 study by Guilbert et al, even catheters 7Fr in size that are accidentally inserted into the artery result in morbid complications and should be treated with surgical/endovascular repair, not just pulling it and compression. A whopping 47% of patients treated by the simple pull+compress method resulted in major complications, compared to 0% in those treated surgically. (https://www.jvascsurg.org/article/S0741-5214(08)00658-7/fulltext)
Triple lumen catheters tend to be the most common, although, I would make an argument that we should be stocking quad lumen catheters instead. Quad lumen catheters are generally 8.5 French, whereas triple lumen catheters range from 7-8.5 French. 1 French = 1/3 mm.
Why is it called French?
Because “Charrière” was too hard for English speakers to say. Joseph-Frédéric-Benoît Charrière invented the system in 1842 to standardize medical catheter and probe sizes.
Thus, the difference in diameter between these two catheters is only 0.5mm (2.33mm vs. 2.83mm) which is negligible when considering the diameter of the vein that you are catheterizing (***). What is not a negligible difference, however, is that in addition to the two 18g and one 16g lumens you get with the triple lumen, you get a fourth 14g lumen.
If you are looking to give massive amounts of volume very quickly, however, even the quad lumen’s 14g lumen isn’t going to cut it. For that, you should use an introduction catheter.
Introducer Catheters
AKA: Cordis (brand name), percutaneous sheath introducer (PSI), large bore line, resus line, MAC
Introducer catheters were originally designed and intended for introducing other types of catheters or instruments into the body, such as a transvenous pacing wire, Swan-Ganz catheter, cardiac stent, etc. The white hub on the proximal end of the catheter is a one-way valve that allows other instruments to be passed through it but prevents blood from coming out.
There are two very important things to note about this valve:
1 – The dilator MUST be preloaded through this valve in order to insert the catheter. The dilation and catheter insertion occurs in one step, this is distinct from standard and dialysis catheters where the dilation and catheter steps occur separately. If you do not preload the dilator through the valve, the wire will not come through it.
Images coming soon!
2 – The sterile sheath must be attached BEFORE passing your pacing wire, swan-ganz catheter or any other indwelling equipment through the intro catheter. The sterile sheath is what allows the indwelling equipment’s position to be adjusted in a sterile manner after the initial placement is complete.
Intro catheters are generally shorter and fatter than standard central line catheters, both of which increase the flow rate. (Flow through a cylinder is equal to pressure times pi times radius to the fourth divided by 8 times viscosity times length).
This endows them with ridiculously high flow rates and are thus used in scenarios where large volumes need to be infused quickly, i.e. hemorrhagic shock. If you are faced with a situation where you are unsure if the patient is in hemorrhagic shock or some other form of shock, I would strongly advocate for placing an introducer catheter. In the case where you place the intro catheter and you end up ultimately needing more lumens and are not needing to do a massive transfusion, you have two options: you can remove and replace the catheter with a quad lumen, or the more slick move, in my opinion, would be to place a triple or quad lumen through the valve of the intro catheter. [*** video of this coming soon***] If you choose to put a standard line through the intro catheter, remember that the proximal port of the standard line MUST NOT be used because it is still within the lumen of the intro catheter (ie incompatible meds will interact within the lumen of the intro catheter and render them inert, create blood clots, or precipitate out into crystals, all of which is very bad).
Flow rates for Teleflex Arrowg+ard Blue® MAC™ Two-Lumen 9Fr, 11.5cm long introducer catheter. Image Source: https://teleflexvascular.com/products/na-11242-cdc
You might be thinking, well what if I put in the intro catheter and then need to initiate the patient on dialysis, can I put a dialysis cath through the intro cath? No. No you cannot.
Dialysis Catheters
AKA: vascath, trialysis (dialysis cath with extra lumen for meds)
Dialysis catheters are generally larger in diameter than intro catheters, but their longer length and equal distribution of lumen size drops the flow rate to less than that of an intro catheter. The two lumens on a typical dialysis catheter are blue and red. If you pretend the dialysis machine is the actual kidney, the arterial, red, blood would be travelling toward it, and the venous, blue, blood would be travelling away from it back toward the heart. Hence, the red lumen is for drawing blood, blue is for return.
BD Power-Trialysis Dialysis Catheter Flow Rates. Image source: https://www.bd.com/en-us/products-and-solutions/products/product-families/power-trialysis-short-term-dialysis-catheter
‘Trialysis’ catheters, pictured above, which are dialysis catheters with an additional lumen that is not used for dialysis, are really the only ones we should be placing in the emergency department, in my opinion. Most of our patients are in acute renal failure and are critically ill so they need at least one central lumen that can be used for medications, blood draw, etc. without compromising the dialysis ports.
BD Power-Trialysis Dialysis Catheter. Image source: https://www.bd.com/en-us/products-and-solutions/products/product-families/power-trialysis-short-term-dialysis-catheter
Next up: