Abstract: Objective To observe the in vitro leakage of catheter lock solution from the clinically used central venous catheters after lock with the solution for 1 min to 96 hrs. Methods The side holes of the catheter were horizontally placed in advance. The catheter was flushed and locked with distilled water. The tip of the catheter was placed in a beaker containing 100ml distilled water. The volume of lock solution (50% dextrose solution) injected into the catheter (artery access) equaled the catheter nominal capacity. The leak ratio was calculated from the concentration of dextrose in the beaker. The experiment was repeated for 15 times, and the average data were then calculated. Results After injection of lock solution into the artery access, the leak ratio was 26.6%～46.0% after 1min, 39.2%～67.2% after 2 hrs, 56.5%～71.5% after 24 hrs, 63.7%～ 82.1% after 48 hrs, and 71.4%～87.9% after 96 hrs. Hence, there were a rapid early leak and a slower later
leak of the lock solution. Conclusion After injection of the lock solution a large quantity of lock solution leaked into the beaker, indicating that a great deal of lock solution may infiltrate into body circulation and interfere with blood coagulation. Therefore, heparin concentration in lock solution should be individualized based on clinical status of the patients.

Key words: Central venous catheter, leak ratio, lock solution