Ten plus ten equals twenty: a prospective crossover study evaluating syringe size and speed of epidural injection

Background: For emergent intrapartum cesarean delivery, epidural catheters are dosed as quickly as possible with ∼20 mL of local anesthetic. At our institution, emergency local anesthetics are drawn into two 10 mL syringes, as opposed to a single 20 mL syringe, due to the belief that it is faster to inject medication via two 10 mL syringes. However, it is unclear if using two 10 mL syringes is actually faster. Our hypothesis was that injecting 20 mL through an epidural catheter using one 20 mL syringe is faster than injecting 20 mL using two 10 mL syringes. Methods: In this study, 20 anesthesia professionals were timed while injecting 20 mL of water (simulating a local anesthetic solution) through an epidural catheter using each method, a 20 mL syringe and two 10 mL syringes. Participants were instructed to inject as if they were dosing an epidural for an emergent cesarean delivery. Analysis was by paired-t-test. Results: The mean time of injection was 41.77 seconds ± 11.16 with the 20 mL syringe and 43.32 seconds ± 7.40 with the two 10 mL syringes (P = 0.338). There was, however, a statistically significant difference among men injecting through one 20 mL vs. two 10 mL syringes (37.81 seconds ± 11.22 vs. 41.52 seconds ± 8.10, respectively; P = 0.028), but not among women. Conclusions: There was no difference in injection speed between one 20 mL syringe and two 10 mL syringes, suggesting that anesthesiologists can use whatever size is most comfortable for them.