Administration of anesthetics using metal syringes. An ex vivo study

The aim of the present study was to assess injection flow rates of metal syringes, with an emphasis on injection speed and the generation of flow pulsations. A cohort of 64 operators (32 practitioners and 32 students) performed 3 consecutive ex vivo simulated injections (SIs) of 1.8-mL cartridges of anesthetic solution. Two needle diameters were tested (27-gauge and 30-gauge). Each SI was filmed and analyzed using a computer. In most cases, the SI lasted longer than 60 seconds with the 30-gauge needle (75%) but not with the 27-gauge needle (47.9%) (P < .0001). Practitioners and men delivered a full cartridge significantly faster than students and women, respectively (P  =  .0007 in both cases). All operators generated 1 pulse in at least 1 of the 3 SIs with both types of needles, especially during the first 3 seconds (254/384; 66.1%). Pulses occurred more frequently with practitioners (P  =  .0176) and with the 27-gauge needle (P  =  .005). Within its methodological limits, the present study showed how difficult it is to control injection pressure when using a metal syringe, especially at the beginning of the injection. Computerized systems may help overcome this problem.