Evaluation of a needle-free injection system for local anaesthesia prior to venous cannulation

We evaluated a single-use, disposable, carbon-dioxide-powered, needleless injector (J-Tip, National Medical Products Inc., CA, USA), which is claimed to deliver a virtually painless, subcutaneous injection. Seventy-two patients undergoing various types of surgery had a large-bore intravenous cannula inserted prior to induction of general anaesthesia. Three minutes beforehand, a subcutaneous injection of 0.3 mi of 1% plain lidocaine was administered. Subjects were randomly allocated to receive the lidocaine either by the needleless injector or from a conventional syringe and a 25G needle. Pain scores were recorded on injection of the lidocaine and on insertion of the cannula. There was significantly less pain on injection with the needleless injector than with the 25G needle (p < 0.001) but, surprisingly, there was more pain on cannulation (p < 0.001). We conclude that the device certainly delivers a less painful subcutaneous injection than a 25G needle, but perhaps provides less effective skin anaesthesia for venous cannulation at sites where the subcutaneous space is small; its use might be better suited to areas where the subcutaneous space is deeper.