Central Line Basics
From a MAC introducer to a single-lumen trauma catheter, there are countless varieties of central venous catheters available to the Emergency Physician. Prior to insertion of a central line, providers should carefully consider the indication for the procedure. Whether it is administration of medications that cannot be given peripherally or rapid fluid resuscitation, the indication for this procedure can help dictate the type of line that should be placed.
One important factor that must be considered when selecting an appropriate line is the size of the lumen(s). Traditionally, catheters are sized based on their outer luminal diameter. By convention, multi-lumen and very large catheters are measured with the French system, whereas single lumen catheters are generally measured by gauge. The French unit is the outer diameter of the catheter in millimeters multiplied by three. For example, a one millimeter catheter would be a 3 French. Consequently, increasing the French corresponds to an increase in the size of the catheter. In contrary, the gauge of a catheter is inversely proportional to the catheter size, making a 16 gauge larger than a 24 gauge for instance. The exact difference between each catheter gauge was derived from wire manufacturing in the 19th century with no true mathematical formula to predict the difference in each gauge.
While sizing is based on the outer diameter of the catheter, the thickness of each catheter can differ, making the inner diameter variable. This leads to difficulty in predicting reliable flow rates for each line. Nonetheless, there are a few basic principles that can help guide providers. First, flow is faster through larger diameter catheters. Second, shorter catheter lengths correspond to higher flow rates. Finally, flow through a catheter is quickest if the lumen is parallel to the direction of flow (in contrast, for example, to the 90-degree angle seen in the Cordis).
Ultimately, selection of the appropriate line varies based upon the clinical presentation of the patient and the indication for the procedure. An understanding of the available options in the Emergency Department will assist providers in selecting the optimal catheter for the desired function.
Triple Lumen CVC
Available in the PAR units along the supply wall in the SRU, this is a triple lumen catheter (TLC). The central port projects to the distal end of the catheter and is a 16-gauge lumen. It also has two smaller 18-gauge lumens which each project as side ports just proximal to the end of the eight-inch-long catheter. Ideal for patients requiring multiple medications, this is the most commonly placed catheter in the Emergency Department. It is the smallest external diameter (7 French), anecdotally making it the least painful to insert. This particular catheter has an external antimicrobial layer of chlorhexidine acetate and silver sulfadiazine in addition to internal chlorhexidine, which has shown antimicrobial activity against several line-related infectious organisms. Because of this however, its placement is relatively contraindicated in patients with sulfa allergies as it can result in an adverse reaction to the sulfadiazine in these compounds.
This single-lumen catheter can be found in the shelves at the foot of the beds in SRU 1 and 3. This 8.5 French catheter is only 3.5 inches long, making it an ideal lumen for patients requiring rapid administration of large volumes of fluids or blood.
Multi-Lumen Access Catheter
Also known as the MAC catheter, this double-lumen catheter has an introducer sheath in addition to a 9 French and 12-gauge line. The 9 French lumen allows for rapid infusion and aggressive volume resuscitation while the additional 12-gauge side port allows for co-administration of other medications. It is an ideal line for unstable cardiac patients, as another catheter-a Swan-Ganz, a transvenous pacer, a SLIC or even a TLC-can be placed through the introducer while maintaining the two other infusion ports. It has the largest external diameter at 14 French, so generous administration of lidocaine prior to placement is often beneficial. The kit can be found at the bottom of the PAR unit in SRU 1. This line also has the chlorhexidine antimicrobial properties of the TLC, so use caution in patients with hypersensitivities to sulfa drugs.
An introducer sheath (e.g., a Cordis) is a single-lumen catheter with a hub on the proximal end that is covered by a one-way valve. This hub allows for the insertion of various other catheters or invasive monitoring devices such as Swan-Ganz catheters, transvenous pacemakers and central venous pressure monitors. Most introducers also contain an 8 French side port through which large volume infusions can be administered. These can be found in the PAR unit in SRUs 1 and 3.
Single Lumen Introducer Catheters
Known as a SLIC catheter, this is a single 7 French lumen which has been designed to be inserted in an introducer sheath. It allows for the addition of an extra infusion site in patients with an introducer in place. Traditionally, these catheters also have the capability to monitor central venous pressure as well. They can be found in the OR or in the cath lab.
Authored by Jessica Baez, MD Posted by Grace Lagasse, MD
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