A Single-center, Randomized, Double-blind Clinical Study to Evaluate the Effect of pH on Pain Upon Local Anesthetic Administration.

When one receives a local anesthetic, such as novocaine for a dental procedure, there is a burning painful sensation experienced upon injection of the local anesthetic. We are trying to understand the role of pH (how acidic a solution is) in the production of pain during local anesthetic administration. We hypothesize that less acidic solutions produce less burning. We also want to determine whether or not the pH of the solution affects the rate of onset of the local anesthesia. We will recruit subjects from patients who have a clinical indication for lumbar medial branch (LMB) nerve blocks, procedures frequently performed at the Massachusetts General Hospital Center for Pain Medicine. For each patient, three nerve blocks are administered at adjacent spinal levels, typically using either lidocaine or bicarbonate-buffered lidocaine as the local anesthetic. We will add a saline control as part of the research procedure and then provide lidocaine at the control location before continuing with the nerve blocks. This clinical procedure offers an ideal opportunity to compare the effects of the three solutions. There will be almost no deviation from the standard clinical procedure. After the injection of each solution, the pain score on administration of the medication will be recorded immediately. We will also provide a continuous stimulation (pin taps) after the local anesthetic injection and record when the patient experiences hypoesthesia (reduced sensation) and anesthesia (absent sensation). Finally, we will record the pain score upon reinsertion of a needle to mark the precise location (part of the clinical procedure) one minute after the local anesthetic injection. All data will be collected during the a single clinical visit.

The study will conclude when 60 subjects have successfully been tested. Data will be reviewed annually.