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Air Emboli: Risks Associated With Catheter Exchanges

May 7, 2009
Written by: , Filed in: Emergency Radiology
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Air embolization (AE) is a potentially fatal complication of central venous catheter placement, manipulation, removal, or exchange.

There are a variety of protective devices or techniques that are used to limit the incidence of air emboli during catheter procedures, but the effectiveness of these has not been evaluated by objective experimental means until now.

An air embolism can occur during this frequently used technique under physiologic pressure differential in vitro; therefore, care should be taken not just during catheter placement, but especially during exchange of a catheter.

The Study
To use the in vitro method of Kolbeck to measure the effectiveness of these protective techniques and devices in reducing the occurrence of air emboli.

Methodology
The experimenters used the common practice of exchanging a 28-cm, 14-F dialysis catheter over a wire. Placement of the clamp over a wire leaves a small gap through which AE can occur.

Other things that were tested were a sliding clamp (FloSwitch) and a valve device (H-flow valve). The valve device is marketed to be aerostatic.

The procedure was as follows. The catheter was placed into the device horizontally and tested for 60 seconds with the catheter clamp closed.

Next, a 0.038-inch wire was inserted and the catheter clamped again around the wire. This was tested for 30 seconds, and then the wire was removed. This was repeated 10 times.

For a positive control, the catheter was left open for 30 seconds in between.

Then the sliding clamp was tested in the open and closed position, and then the valve was tested, with 10 iterations of each condition tested. With the catheter clamp on over the wire, a mean of 32 mL of air was introduced into the system.

With the catheter clamp open, there was a mean of 43 mL of air introduced into the system.

With the sliding clamp closed, no air was introduced into the system after 30 seconds, and with it open, 44 mm of air was introduced over 30 seconds.

Next, the hemostatic valve was tested for 30 seconds and no air was introduced.

Conclusions and Reviewer’s Comments
This paper suggests that a commonly used method of catheter exchange can predispose the patient to having an AE.

The catheter clamp method of line exchange allows a large AE to occur in these experimental conditions, one almost as large as using no clamp at all. Using either a hemostatic valve or a sliding clamp decreases that risk to zero in vitro.

Significant limits to this experimental study are present and the literature on the subject suggests that, despite these experimental findings, the occurrence of a clinically significant AE is very low when a monorail technique is being used in vivo.

In conclusion, this study demonstrates that an AE can occur during this frequently used technique under physiologic pressure differential in vitro; therefore, care should be taken during exchange.

Author: Sharon Gonzales, MD

Reference:
Kolbeck KJ, Stavropoulos SW, Trerotola SO. Over-the-Wire Catheter Exchanges: Reduction of the Risk of Air Emboli. J Vasc Interv Radiol; 2008; 19 (August): 1222-1226

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