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Onset and Duration of Intradermal Mixtures of Bupivacaine and Lidocaine with Epinephrine
James Bartow Collins, Juhee Song and Raman C. Mahabir
Division of Plastic Surgery, Scott and White Memorial Hospital, Temple, TX
Background: Bupivacaine and lidocaine are often used concordantly, in theory, to combine the quicker onset of lidocaine and the longer duration of bupivacaine. The purpose of this study was to evaluate this concept. Methods: Twenty-five subjects were enrolled in a double blind, randomized block design study to evaluate the onset and duration of four different mixtures of lidocaine and bupivacaine with epinephrine. The study was designed to achieve an 80% power to detect an effect size of 0.37 at 5% overall significance. The four mixtures tested were 0.25% bupivacaine with epinephrine (1:200,000), 1% lidocaine with epinephrine (1:100,000), 0.125% bupivacaine and 0.5% lidocaine with epinephrine (1:150,000), and 0.25% bupivacaine and 1% lidocaine with epinephrine (1:150,000). Four intradermal injections were made in the volar forearms of each participant. Time to effect and duration were measured by sensation of sharp to skin prick. Results: Mean time to onset ranged from 12 seconds to 29 seconds without statistical significance across all tested solutions (p-value = 0.891). Mean duration ranged from 6 hours 38 minutes to 7 hours 25 minutes with a statistically significant difference across tested solutions (p-value = 0.036). Conclusions: No statistical benefit was measured when comparing lidocaine with epinephrine, bupivicaine with epinephrine, and mixtures of these local anesthetics with regard to onset of action. While a statistical difference was observed in duration of effect, the clinical benefit measured was narrow.
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