How to minimize the pain of local anesthetic administration

Injection technique: Consider these helpful tips

Site of needle entry. Prior to injecting local anesthesia, assess the area where the procedure is planned (FIGURE 1). The initial injection site should be proximal along the path of innervation. If regional nerves are anesthetized proximally and infiltration of local anesthesia proceeds distally, the initial puncture will be painful; however, further injections will be through anesthetized skin. Additionally, consider and avoid regional vascular anatomy.^41,42

Counter-stimulation. Applying firm pressure, massaging, or stroking the site prior to or during the injection decreases pain.^43,44 This technique may be performed by firmly pinching the area of planned injection between the thumb and index fingers, inserting the needle into the pinched skin, and maintaining pressure on the area until the anesthetic effect is achieved.

Angle of needle insertion. Perpendicular entry of the needle into the skin appears to reduce injection site pain (FIGURE 1). Anecdotal reports are supported by a randomized, controlled crossover trial that demonstrated significantly reduced pain with perpendicular injection compared to delivery at 45°.⁴⁵

Depth of injection. Subcutaneous needle placement is associated with significantly less pain than injection into superficial dermis.^2,46 Dermal wheals cause distention of the dermis, increased intradermal pressure, and greater activation of pain afferents in comparison to injection in the subcutaneous space.⁴⁶ One important exception is the shave biopsy in which dermal distention is, in fact, desirable to ensure adequate specimen collection.

Other methods of pain reduction should still be employed. In the setting of traumatic wounds when a laceration is present, injection into the subcutaneous fat through the wound is easy and associated with less pain than injection through intact skin.⁴⁷

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