Background and Objectives. Skin blood flow changes after intradermal injection of ropivacaine in various concentrations with or without epinephrine were investigated using laser Doppler flowmetry.
Methods. Twenty-three non-smoking, healthy, young male volunteers participated. Four test sites were used on each forearm (volar surface) in a randomized, double-blind study. Recordings were made at 20, 40, 60, and 90 minutes after intradermal injection (0.1 ml, 30-gauge needle). Injections of saline and 1% lidocaine and an untreated area served as controls. In Series 1, various concentrations of ropivacaine (1%, 0.5%, 0.375%, 0.125%, and 0.063%) were injected.
Results. The data from this series showed a doseresponse relationship: 1% ropivacaine provoked an increase in skin blood flow similar to saline; 0.5% and weaker concentrations of ropivacaine showed a reduction in flow compared to saline, this being more pronounced with the weakest solutions (0.125% and 0.063%). In Series 2, injection of 1:200,000 (5 μg/ml) epinephrine alone and injections of ropivacaine in various concentrations (1%, 0.5%, and 0.25%) with addition of epinephrine were carried out. Injection of epinephrine alone showed a flow almost as low as at the untreated control sites. Ropivacaine epinephrine injections were followed by a lower skin blood flow compared to saline, but the flow was significantly larger compared to the effect of epinephrine itself at the 20-minute recording.
Conclusion. The combination of ropivacaine and adrenaline did not accentuate but instead diminished the vasoconstrictive effect of epinephrine.
- intradermal injection
- laser Doppler flowmetry
- local anesthetic agents
- skin blood flow.
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The authors thank Anna Torrång, B.S., for advice and contribution to the statistical evaluation; Jan Sjövall, Ph.D., associate professor and head of the Department of Clinical Pharmacology, Astra Pain Control for suggestions; Mats Bengtsson, M.D., Ph.D., associate professor and head of the Department of Anaesthesiology, University Hospital, Linköping, Sweden, for advice and criticism; and Ingemar Ideholm, Astra Reklam, for help with the graphic presentations.