Effects of epidural anesthesia on microcirculatory blood flow in free medial saphenous fasciocutaneous flaps in dogs

Objective— To assess the effects of epidural anesthesia using lidocaine on microcirculatory blood flow, volume, and velocity in free fasciocutaneous flaps in dogs. Study Design— In vivo experimental investigation. Animal Population— Ten adult dogs weighing 20 to 25 kg. Methods— A medial saphenous fasciocutaneous free flap was removed and an orthotopic transfer was performed by anastomosing the primary flap vessels back to the medial saphenous vessels. Blood flow (mLLD/min/100 g), volume (%volume or tissue hematocrit) and velocity (mm/s) in the flap were recorded throughout the procedure. After epidural anesthesia, blood flow, volume, and velocity values were again recorded. Results— Microcirculatory blood flow, volume, and velocity, as measured by a laser-Doppler flowmeter, failed to reveal any significant changes over time. Immediately after epidural anesthesia, mean arterial pressure was significantly reduced and remained depressed throughout the experimental procedure. Conclusions— Epidural anesthesia combined with general anesthesia does not improve microcirculatory flow in free flaps in the pelvic limbs of dogs. No significant change in blood flow to the medial saphenous fasciocutaneous free flap occurred after division and anastomosis of the vascular pedicle. Clinical Relevance— We recommend that epidural anesthesia with 2% lidocaine be used with caution in dogs undergoing microvascular free-flap transfer.