Towards a real time pediatric regional anesthesia titration device.

When possible, regional anesthesia is generally preferred over general anesthesia. Although this is especially true with respect to pediatric care, pediatric regional anesthesia dosing guidelines are mostly unknown and based only on expert conjecture (Suresh et al., 2015). Further complicating this problem, systemic toxic reactions can present vastly differently in children than adults. In addition, pediatric regional anesthesia is mostly performed under deep sedation, making it yet more difficult to qualify and quantify dosage efficacy. To address these pediatric-specific problems, we propose to change common practice by introducing a tool that can measure the effectiveness of local anesthetic dosage in children. Our solution will involve a computer-controlled electromechanical system designed to administer anesthetic solution, in real time, based on monitoring the compound action potential of the target nerve. The majority of the work establishing the relationship between compound action potential shape and anesthetic agents has been performed in-vitro, based on the seminal work of Gasser and Erlanger (Gasser & Erlanger, 1929). In order to translate this work to pediatrics, we need to show that the shape of the compound action potential can be controlled by anesthetic agents in-vivo. In the intact anesthetized cat (Northwestern University IACUC approved) we closely followed the protocol described by Gissen and colleagues who studied the differential sensitivities of mammalian nerve fibers to local anesthetic agents (Gissen et. al., 1980). In short, after exposing the major branch of the sciatic nerve in the cat, we implanted a custom drug delivery cuff which allows for the control of both volume and concentration of the anesthetic agent on the nerve. At each end of the cuff we installed cuff electrodes, one to deliver an electrical stimulus and one to record compound action potential from the nerve. After surgery, we proceeded to measure a control period of action potentials followed by series of drug exposure and washout following an increase of concentration and volume. We can report thus far on the construction and implementation of the drug delivery cuff and gathering pilot data. A qualitative analysis suggests that we are poised to replicate the methods developed by Gissen and colleagues in-vivo. Secondly, and perhaps more importantly, we are close to showing that it is possible to precisely control the shape of the compound action potential by delivering a controlled volume and concentration of an anesthetic agent around a peripheral nerve in-vivo and in real-time. The work presented is preliminary and ongoing. We expect to refine our results with further experimentation and refinement of both the protocol and drug delivery cuff. Ultimately, we expect that this work will lead to more precise and safer anesthesia dosing, increasing patient safety and improving outcomes for pediatric patients.