Use of a Large Bore Syringe Creates Significantly Fewer High Intensity Transient Signals (HITS) Into a Cardiopulmonary Bypass System Than a Small Bore Syringe

Introduction: High intensity transient signals (HITS) have been reported to occur following perfusionist intervention during cardiac surgery. This study investigates the relationship of the syringe bore, injection rate, and HITS created.

Methods: Syringes (10 mL) with a male luer-lock connection (Large Bore) and Abboject ‘jet syringes’ with a 20 GA needle and male luer-lock connector (Small Bore) were filled with 10 mL of 0.9 N saline. A perfusionist was randomly assigned a set of four similar syringes followed by the other syringe bore. Each of the four syringes was injected into an in vitro saline-primed cardiopulmonary bypass (CPB) system over 5, 10, 15, or 20 sec. Sixteen randomizations of small and large bore syringes were completed at the four injection times (128 injections). HITS in the CPB arterial line were detected with transcranial Doppler (TCD) probes, were recorded for the 2 min following the injection, and were counted independently off-line by two reviewers.

Results: The use of a large bore syringe compared to a small bore syringe created significantly fewer HITS (29±6 versus 145±17 [mean ± SEM], p <0.001) introduced into the CPB arterial line. Injection over a longer time produced significantly fewer HITS than shorter injection times (p <0.001).

Conclusion: Significantly fewer HITS are introduced into the CPB system by using standard syringes and slower injection time.