How to minimize the pain of local anesthetic administration
Expertise in the delivery of effective local analgesia is critical to the success of in-office procedures. Here’s how to optimize patient outcomes and satisfaction.
PRACTICE RECOMMENDATIONS
› Add epinephrine and sodium bicarbonate buffer to local anesthetic solution to reduce pain and procedural blood loss. A
› Use such techniques as counter-stimulation, a perpendicular angle of injection, a subcutaneous depth of injection, and a slow rate of injection to minimize patient discomfort. A
Strength of recommendation (SOR)
A Good-quality patient-oriented evidence
B Inconsistent or limited-quality patient-oriented evidence
C Consensus, usual practice, opinion, disease-oriented evidence, case series
The advantages (and misconceptions) of epinephrine
The advantage of adding epinephrine is that it prolongs the effect of the anesthesia and it decreases bleeding. Epinephrine is commonly available as a premixed solution with lidocaine or bupivacaine at a concentration of 1:100,000 and is generally differentiated from “plain” local anesthetic by a red label and cap. Although maximum vasoconstriction may occur as long as 30 minutes after injection,10 adequate vasoconstriction is achieved in 7 to 10 minutes for excision of skin lesions.11
Traditional teaching recommends against using epinephrine in the “fingers, toes, penis, ears, or nose” because of potential arterial spasm, ischemia, and gangrene distal to the injection site.12 These concerns were based on experiences with procaine and cocaine mixed with epinephrine. Studies suffered from multiple confounders, including tourniquets and nonstandardized epinephrine concentrations.13-15
No association of distal ischemia with epinephrine use was identified in a recent Cochrane Review or in another multicenter prospective study.16,17 Phentolamine, a non-selective alpha-adrenergic receptor antagonist and vasodilator, can be administered to reverse vasoconstriction following inadvertent administration of high-dose epinephrine (1:1000) via anaphylaxis autoinjector kits.
Dosing of phentolamine is 1 mL of 1 mg/mL solution delivered subcutaneously to the affected area; reversal decreases the duration of vasoconstriction from 320 minutes to approximately 85 minutes.18 As always, when applying literature to clinical practice, one must keep in mind the risks and benefits of any intervention. As such, in patients with pre-existing vascular disease, vaso-occlusive or vasospastic disease, or compromised perfusion due to trauma, one must weigh the benefits of the hemostatic effect against potential ischemia of already susceptible tissues. In such instances, omitting epinephrine from the solution is reasonable.
The benefits of sodium bicarbonate
The acidity of the solution contributes to the level of pain associated with administration of local anesthesia. Previously opened containers become more acidic.19 Addition of 8.4% sodium bicarbonate, at a ratio of 1 mL per 10 mL of 1% lidocaine with 1:100,000 epinephrine, neutralizes the pH to 7.4.19 A Cochrane Review showed that correction of pH to physiologic levels results in a significant reduction in pain.20
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