Measurement of air emboli during central venous access: Do "protective" sheaths or insertion techniques matter?

PURPOSE: Clinically significant air emboli during placement of central venous catheters are rare yet potentially fatal events. An in vitro model was developed to measure the volume of air emboli during catheter placement under a variety of experimental conditions. MATERIALS AND METHODS: The volume of air emboli during catheter insertion with use of a standard sheath was measured using "open," "finger-pinch," and "hemostat" techniques. Corresponding experiments were performed with newly designed protective sheaths. Additional experiments evaluated the air emboli related to specific steps of catheter insertion, a sheathless insertion technique, and two commonly used dialysis catheters. RESULTS: Under physiologic conditions, the volumes of air emboli were 9.1 mL ± 3.6, 8.6 mL ± 3.9, and 10.0 mL ± 4.1 for dialysis catheter insertions with open, finger-pinch, and hemostat techniques, respectively. In the open and closed positions, the sliding-valve protective sheath yielded 5.8 mL ± 2.3 and 4.4 mL ± 2.3 of air emboli, respectively, and the slide-clamp protective sheath yielded 5.6 mL ± 2.0 and 5.4 mL ± 2.1 of air emboli, respectively. The standard sheath demonstrated air emboli volumes of 14.4 mL ± 12.8, 17.3 mL ± 3.9, and 32.3 mL ± 10.9 during cumulative steps of catheter insertion. The sliding-valve and slide-clamp protective sheaths yielded air emboli measuring 4.4 mL ± 2.0, 10.9 mL ± 5.2, and 8.6 mL ± 1.5, and 4.4 mL ± 1.8, 10.9 mL ± 1.4, and 9.4 mL ± 4.0, respectively. The sheathless insertion technique resulted in air emboli measuring 12.2 mL ± 5.4. Split-tip and step-tip catheters resulted in air emboli volumes of 16.1 mL ± 4.5 and 15.3 mL ± 7.6, respectively, in the open position and 11.3 mL ± 3.1 and 12.9 mL ± 5.0, respectively, in the closed position. CONCLUSIONS: The newly designed protective sheaths result in smaller volumes of air emboli compared with standard sheaths in most situations evaluated. There was no significant difference in the volume of air emboli with use of protective clinical maneuvers. In some cases, the volume of the air emboli continued to increase during catheter insertion and sheath removal. There was no statistically significant difference between the use of protective sheaths and the use of the sheathless insertion technique.