A New Technique for Halving Dental Local Anesthetic Cartridges and Diluting Adrenaline

When using dental local anesthetics containing adrenaline as a vasoconstrictor, it is essential to exercise sufficient caution regarding hemodynamic fluctuations, particularly in patients with cardiovascular disease. In this report, we introduce a safe and simple method to halve the adrenaline concentration in anesthetic cartridges. The equipment used includes a syringe (1-3 mL), an IV catheter (22- or 24-G), and a metal needle, which are typically available in dental clinics for IV sedation or emergency use. By connecting the inner needle (24- or 27-G) of the IV catheter to the syringe and puncturing the edge of the rubber stopper at the head of the cartridge, 0.9 mL of anesthetic solution can be accurately aspirated while reducing the risk of coring. Furthermore, by injecting an equal volume of 2% lidocaine without adrenaline into the cartridge, the adrenaline concentration can be effectively halved. This method is quick, broadly applicable, and does not require any special equipment, making it feasible even for dentists who are not specialists in dental anesthesia. In Japan, four types of dental local anesthetics are commonly used. However, dental treatment cannot always be completed with a preparation that does not contain adrenaline, and there are many situations where the excellent anesthetic and hemostatic effects of adrenaline are required. Dentists must accurately assess these situations and confidently select and administer the appropriate anesthetic. It should be noted that articaine alone is not commercially available in Japan; therefore, this method can only be applied to cartridges containing 2% lidocaine with 1:80,000 adrenaline. Although local anesthetics containing 1:80,000 adrenaline are generally considered safe for patients with cardiovascular disease, the use of the lowest possible adrenaline concentration is desirable. Therefore, this method provides a practical approach to minimize cardiovascular risk while maintaining anesthetic efficacy and hemostasis, especially in procedures requiring large amounts of local anesthetic. Given the increasing number of patients with cardiovascular disease due to aging, this technique is considered a practical approach to ensuring safer dental treatment.