Minimum Effective Dose of Lidocaine Needed to Block Evoked Potentials in the Sciatic Nerve of the Rat

摘要

Local anesthetics are used daily by anesthesia providers to perform spinal, epidural, and peripheral nerve blocks. Large volumes of local anesthetic are used for peripheral nerve blocks especially if more than one block is performed on a patient. These local anesthetics can have side effects such as nerve compression, nerve damage, or even toxic plasma levels that can lead to seizures. Using less volumes and concentrations of these anesthetics would reduce the chances of these complications. To discover the minimum amount of local anesthetic needed intraneurally, an in vivo model of the rat sciatic nerve was used. In the anesthetized rat, the sciatic nerve was surgically exposed and then injected in the subperineural space with either 10 or 20 ml of 2% lidocaine or a control solution. The proximal end of the nerve (at the greater sciatic notch) was electrically stimulated and the tibial division of the nerve (near the ankle) was used for recording the compound action potential (CAP). The averaged CAPs were recorded periodically for up to an hour. The data displayed a trend of 20ml of 2% lidocaine blocking the CAPs and that 10ml of 2% lidocaine did not consistently block the CAPs. The data suggests that 20ml is the minimum dose of 2% lidocaine needed intraneurally to block evoked potentials in muscle and rapidly conducting sensory signals, including fast pain.