Intraductal Liposomal Bupivacaine as a Therapeutic Trial to Determine the Contribution of Peripheral Versus Central Sensitization in the Pathogenesis of Pain in Chronic Pancreatitis- a Pilot and Feasibility Study

The major clinical features of chronic pancreatitis include glandular (exocrine and endocrine) failure and pain. The former can usually be managed satisfactorily by replacement strategies (enzymes or insulin) to restore nutritional and metabolic stability. However, pain has remained a major clinical challenge and is present in up to 90% of patients and is the primary cause of hospitalization in most patients. Unfortunately, pain in chronic pancreatitis has been very difficult to treat, and the investigators' lack of understanding about the underlying biology has led to various empirical approaches that are often based on purely anatomical grounds, and are generally highly invasive. Significant tissue injury such as that observed in chronic pancreatitis not only triggers nociceptor activation but over time, can also increase the pain in the whole system, a process called sensitization.

Determination of the contribution of peripheral versus central factors to nociceptive sensitization has significant clinical implications in an individual patient. Thus, if pain is caused primarily by signals emanating in the peripheral nerves, then perhaps invasive procedures directed against the pancreas (including pancreatectomy) are justified and can be expected to have a high probability of success. On the other hand, if central sensitization is the dominant pathophysiological factor, then these procedures may cause more harm than good and the patient may be best served using aggressive neuromodulator therapies.

The most direct way to address this question is to interrupt peripheral nerve signaling and determine how much of the pain, if any, is taken away. Unfortunately, there are no satisfactory methods to do this currently. Although celiac or splanchnic nerve blocks have been used for the treatment of pain in chronic pancreatitis, the treatments have had limited success for a variety of reasons, including the fact that the technique may not always be accurate in terms of the site of injection.

The investigators hypothesize that the best method to reliably abolish peripheral nerve signaling is the use of a local anesthetic within the target organ (i.e. pancreas). This can best be done during endoscopic retrograde cholangiopancreatography (ERCP), a technique in which the main pancreatic duct is cannulated with the help of a duodenoscope and contrast material injected. This technique is routinely done to assess pancreatic duct anatomy prior to consideration of a therapeutic intervention such as a stent, stricture dilation, or stone removal/lithotripsy.

Since ERCP is done under deep sedation or general anesthesia, it is critical to select a local anesthetic whose effect persists well after recovery from the procedure; if not, the assessment of the effect of the local anesthetic on pain will be impossible to assess. The investigators have therefore chosen liposomal bupivacaine (Exparel, Pacira Pharmaceuticals), which is an FDA approved product for local infiltration that has a longer duration of action (up to 72 hours) and a slower absorption into the systemic circulation, avoiding high plasma concentrations.