Hypoperfusion in response to epinephrine in local anaesthetics: Investigation of dependence on epinephrine concentration, spread of hypoperfusion and time to maximal cutaneous vasoconstriction

Objectives: The present study aimed to examine hypoperfusion in response to epinephrine following the administration of a local anaesthetic. The . concentration of epinephrine that causes maximal hypoperfusion, the . spread of hypoperfusion in the tissue and the . time to the stabilization of hypoperfusion were investigated. Methods: Blood perfusion was monitored using laser Doppler velocimetry and laser speckle contrast imaging of random-pattern advancement flaps (1 × 4 cm) or intact skin on the pig flank. Epinephrine was either injected cumulatively (0.1, 1.0, 10 or 100 μg/ml) after injecting 20 mg/ml lidocaine, to determine the concentration response, or given as a single dose (12.5 μg/ml epinephrine. +. 20 mg/ml lidocaine). Control experiments were performed with saline or lidocaine (without epinephrine). Results: Increasing concentrations of epinephrine resulted in a gradual decrease in skin perfusion, approaching a minimum after injecting 10 μg/ml. The area of hypoperfusion was 12 mm in radius, and the time from the injection to the stabilization of hypoperfusion was approximately 120 s. After the administration of 10 μg/ml epinephrine in flaps with small pedicle, 25% blood perfusion still remained. Conclusions: Local anaesthetic with an epinephrine concentration of approximately 10 μg/ml appears to be adequate for vasoconstriction before surgery. Incisions were required to be delayed only for 2 min following local anaesthetic with epinephrine in pigs. The remaining 25% blood perfusion observed after the administration of epinephrine supports the use of epinephrine in flaps with a small pedicle. Obviously, these experimental findings must be clinically assessed before being considered for infiltration anaesthesia during plastic surgery procedures.