How to minimize the pain of local anesthetic administration

This solution can be easily prepared, as standard syringes hold an additional milliliter (ie, 10-mL syringes hold 11 mL) and, thus, can accommodate the additional volume of bicarbonate.²¹

Warming the solution helps, too

Warming the solution to body temperature prior to injection decreases pain on injection.²² This may be done in a variety of ways depending on available in-office equipment. Water baths, incubators, fluid warmers, heating pads, or specific syringe warmers may be used. Multiple studies have shown improvement in patient satisfaction with warming.²³ Moreover, warming and buffering solution provide a synergistic effect on pain reduction.²³

Equipment: Size matters

Smaller diameter needles. Reducing the outer diameter of the needle used for injection improves pain by reducing activation of nociceptors.^24-26 Reduced inner diameter restricts injection speed, which further reduces pain.²⁵ We recommend 27- to 30-gauge needles for subcutaneous injection and 25- to 27-gauge needles for intra-articular or tendon sheath injections.

Appropriate syringe size. Filling a syringe to capacity results in maximal deployment of the plunger. This requires greater handspan, which can lead to fatigue and loss of control during injection.^26,27 Using a syringe filled to approximately half its capacity results in improved dexterity. We recommend 10-mL syringes with 5 mL to 6 mL of local anesthetic for small procedures and 20-mL syringes filled with 10 mL to 12 mL for larger procedures.

Topical local anesthetics may be used either as an adjunct to decrease pain during injection or as the primary anesthetic.²⁸ A variety of agents are available for clinical use, including eutectic mixture of local anesthetics (EMLA), lidocaine-epinephrine-tetracaine (LET), lidocaine, benzocaine, and tetracaine. FPs should be familiar with their different pharmacokinetic profiles.

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