Air-bubble method of locking central-vein catheters for prevention of hub colonization: a pilot study

The major source of catheter-associated bacteremia is contamination of the catheter hub during connection-disconnection procedures. A new method of catheter locking has been developed wherein anticoagulant is injected first, followed by a 0.1-mL air bubble and 0.9 mL of bactericidal solution. The anticoagulant is then located at the catheter tip and the bactericidal solution is located at the catheter hub. The air bubble prevents mixing of the two solutions. The bactericidal solution was acidified concentrated saline (ACS). The 27% saline solution has a pH of 2.0. ACS was chosen because it is theoretically harmless if injected in the amount used to lock the catheter lumens. The goals of this pilot study were to determine whether the new method of catheter locking is easy to perform with available syringes and whether eventual injection of the experimental solution is well tolerated.

Ten patients were randomly assigned, either to heparin lock (5 patients, 62 treatments) or air-bubble method (5 patients, 56 treatments). In the control group, the catheters were locked with heparin, 5000 U/mL. In the experimental group, the catheters were locked with heparin, air bubble, and ACS. Altogether, the lumens were overfilled by 0.2 mL.

Compared to the routine method, the experimental method required a 1- to 2-min-longer procedure time. There were no errors in proper sequence of injections into the lumina. There were no episodes of bacteremia related to hub contamination in either group. In the air-bubble group, there was one case of bacteremia associated with purulent drainage from the exit and the same organism in both cultures. In three instances in each group, the locking solution could not be aspirated and was injected without any subjective symptoms or objective signs.

We conclude that the air-bubble method of locking central-vein catheters is easy to perform. In three instances of air-bubble and ACS injection, there were no adverse effects. A full-scale prospective randomized study is feasible and warranted.