The effect of buffering on pain and duration of local anesthetic in the face: A double-blind, randomized controlled trial

Abstract

Background: The acidity of lidocaine preparations is believed to contribute to the pain of local anesthetic injection.

Objective: To investigate the effect of buffering lidocaine on the pain of injection and duration of anesthetic effect.

Methods: A double-blind, randomized trial involving 44 healthy volunteers was conducted. The upper lip was injected with a solution of: lidocaine 1% (Xylocaine, AstraZeneca, Canada, Inc) with epinephrine; and lidocaine 1% with epinephrine and 8.4% sodium bicarbonate. Volunteers reported pain of injection and duration of anesthetic effect.

Results: Twenty-six participants found the unbuffered solution to be more painful. Fifteen participants found the buffered solution to be more painful; the difference was not statistically significant. Twenty-one volunteers reported duration of anesthetic effect. The buffered solution provided longer anesthetic effect than the unbuffered solution (P=0.004).

Conclusion: Although buffering increased the duration of lidocaine's anesthetic effect in this particular model, a decrease in the pain of the injection was not demonstrated, likely due to limitations of the study.

Keywords: Lidocaine; Local anesthesia; Pain; Sodium bicarbonate.

Figures

Figure 1)

Drugs that were used: 1% lidocaine (Xylocaine, AstaZeneca Canada, Inc) 1% with 1:100,000 epinephrine (left) and 8.4% sodium bicarbonate (right)

Figure 2)

Injection site of each solution in the upper lip is indicated by ‘x’

Figure 3)

Study questionnaire

Figure 4)

CONSORT flow diagram

Figure 5)

Effect of buffering on pain sensation of lidocaine injection (P=0.23)

Figure 6)

Duration of anesthetic effect for buffered lidocaine (red diamond) and nonbuffered lidocaine (black square) (P=0.004)