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Comparison of the Sensory Modality Effects of Bupivacaine Digital Nerve Blocks with and without Epinephrine: A Level One Study
Kevin A. Calder, BSc, MD1; Bryan Chung, MD, PhD1; CM O'Brien, BSc1; Donald H. Lalonde, BSc, MSc, MD2
1Division of Plastic Surgery, Dalhousie University, Halifax, NS, Canada; 2Plastic Surgery Dept, Dalhousie University, Saint John, NB, Canada

Introduction: There are no published reports to indicate the duration of action of bupivacaine with epinephrine in digital nerve blocks. In addition, the effect of bupivacaine with epinephrine on the various sensory modalities as compared to bupivacaine alone has not been studied. Furthermore, the duration and magnitude of bupivacaine-induced vasodilation has not been quantified. The goals of this double-blind randomized control trial are:

1.) To determine the duration of bupivacaine anesthesia on digital nerve blocks +/- epinephrine.
2.) To assess the duration of action of bupivacaine +/- epinephrine on the digital sensory modalities of pain, touch and pressure.
3.) To assess the skin temperature changes that result from bupivacaine finger injection +/- epinephrine.

Methods: A sample size calculation revealed that forty-three subjects were required for this study. Ring fingers were randomized to receive 2ml of 0.5% bupivacaine injection with (+) or without (-) 1:200,000 epinephrine. All injections were performed using the single volar subcutaneous technique by one injector blinded to the injectate. Pain was elicited using diabetic lancets and measured on a numeric rating scale (0-10). Touch was assessed using a Semmes-Weinstein monofilament. The duration of time for digits to return to normal pain, touch and pressure sensations were recorded. Temperature was measured using a digital infrared thermometer to quantify the vasoactive effects of bupivacaine injection. All measurements were recorded at 1h, 6h, 12h, 14h and each subsequent hour from injection until the subjectís finger regained normal sensation. 

Results: None of the subjects experienced any adverse reaction or ischemic injury with bupivacaine +/- epinephrine injection. Return to normal sensation was 29.25h (+s=10.29) and 28h (-s=10.29). Pressure sensation returned at 16h (+s=2.76) and 14h (-s=3.95) with touch returning at 17h (+s=3.88) and 15h (-s=5.16). Onset of pain return began at 16.5h (+s=2.62) and 15h (-s=3.25) but was not complete until 20h (+s=3.53) and 19.5h (-s=4.51). Temperature change [>1°C difference compared to the index finger] began within 1h of administration and lasted 16h (+s=6.91) and 15h (-s=6.65). Peak effect occurred at 12h (+s=7.22; -s=6.82) with an absolute temperature measurement of 33.6°C (+s=3.03) versus 34°C (-s=2.26) and a relative temperature difference of 6.8°C (+s=3.33) and 7.35°C (-s=3.71).

Conclusion: Bupivacaine with epinephrine is safe for use in digital nerve blockade. It does not affect the sensory modalities as compared to bupivacaine alone. Bupivacaine with or without epinephrine may be used clinically to induce digital temperature elevation through its inherent vasodilatory properties.


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