Modification of intravenous cannula for arterial line insertion: Simple yet effective technique.

Sir,

Arterial cannulation is an important procedure for continuous arterial pressure monitoring and repeated blood gas sampling in perioperative and critical care settings. The success rate for radial artery cannulation is good in experienced hands using the palpation technique[1] but often there are occasions when the procedure becomes technically challenging. Commercially available dedicated arterial cannulae help in easing the procedure but are expensive and not available at all places. Widely available and cheaper peripheral intravenous (IV) cannula which comes with a Luer Lock plug is a common alternative for arterial cannulation at many institutes. With use of IV cannula the entry of stylet in artery is confirmed with the presence of blood in flashback chamber. Since the length of flashback chamber is very small, it fills rapidly and adds to limitation of its use as an arterial cannula. To confirm the presence of cannula inside the artery, the stylet is withdrawn slightly to see the existence of pulsatile blood in cannula, and then the catheter is introduced in to the artery. Catheter displacement during stylet withdrawal is a common reason for failure to negotiate the catheter inside the artery. Removal of the Luer Lock plug to check continuous arterial backflow leads to bleeding and soiling and also exposes the cannula to the environment making the procedure prone to infection. Repeated withdrawal and reinsertion of the stylet during cannulation may lead to shearing of the catheter resulting in failure of procedure as well as embolism and ischemic damage.[2] Hence, the major drawback of the IV cannula to be used as arterial catheter is the short length of flashback chamber which does not allow visualisation of continuous backflow of blood; hence catheter negotiation inside artery becomes blind. To overcome this problem, we suggest a simple modification in 20 G IV cannula (Primaflon IV Cannula, La-Med Healthcare Pvt. Ltd.) by extension of the length of flashback chamber. The distal part of the cover of needle and catheter has inbuilt holes. This distal part of the cover can be snugly fitted to proximal part of cannula after removal of flashback chamber and Luer Lock Plug. The open proximal part of cover is closed with Luer Lock Plug of the same cannula to make a new assembly [Figure 1]. We attempted right radial artery cannulation in a patient with this modified cannula [Figure 1]. After artery puncture, the backflow of blood was seen in the needle cover. Now, the stylet can be withdrawn slightly confirming continuous blood backflow in needle cover and the catheter can be negotiated inside the artery. Herein, one need not to wait for the entire chamber to fill up and the cannula can be advanced as soon as a flash of arterial blood is observed. In addition, the increased length at the distal end acts as a buffer lessening the chances of blood spillage on the health-care worker. An additional advantage is that the anaesthesiologist can see backflow of blood for relatively longer period while inserting cannula in an artery. This avoids repeated withdrawal of the needle to see continuous flow of blood from artery and also prevents potential catheter shearing during reintroduction of stylet. Since this is a closed assembly, sterility can also be maintained.

Figure 1

Modification of intravenous cannula and radial artery cannulation

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Conflicts of interest

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