Ultrasound Guided Transversus Abdominis Plane (TAP) vs. Trigger Point Injection (TPI) for Abdominal Wall Pain

Ultrasound Guided Transversus Abdominis Plane (TAP) vs. Trigger Point Injection (TPI) for Abdominal Wall Pain

Ultrasound Guided Transversus Abdominis Plane Block vs. Trigger Point Injection for Abdominal Wall Pain: A Randomized Comparative Trial

Patients with chronic abdominal pain- with a component of abdominal wall pain- are often treated with trigger point injections. This study will help to determine if a block within the transversus abdominis plane (TAP) will provide superior analgesic benefit to a trigger point injection as therapy for these patients.

Only patients referred to the Pain Clinic for abdominal trigger point injections for abdominal wall pain will be considered for study recruitment. Following informed consent, patients will complete a baseline questionnaire in the Pain Clinic which gathers basic demographic data, pain scores and functional scores. Patients will be randomized to receive either a TAP injection or a TPI. Because the TAP injection involves a larger area to be anesthetized, a larger volume of medication will be used. Thirty minutes after the injection, a sensory exam will be performed on the patient to determine the level of block. At one week, one month, three months and six months after the injection, a staff member will telephone the patient to assess how they are doing. The call will take approximately 10 minutes and will consist of relaying a pain score as well as daily functioning and sleep questions. Subjects are responsible for all clinical costs associated with the injection. There is no remuneration offered for study participation.

Trigger point injection under ultrasound guidance into the fascial layer above the external oblique or rectus muscle, whichever corresponds to patient's identifiable trigger point. The injectate will include 5 ml of bupivacaine 0.25% mixed with triamcinolone 20 mg.

Injection into transversus abdominis plane layer under ultrasound guidance on the affected side along the mid-axillary line. The injectate will include 10 ml of bupivacaine 0.25% mixed with triamcinolone 20 mg.

Pain intensity will be assessed using the 11-point Numerical Pain Score questionnaire where "0" denotes no pain and "10" signifies the most intense pain imaginable.

Inclusion Criteria: Only patients referred to Pain Clinic for a trigger point injection. Non-cancer pain greater than 3 months duration. Unilateral abdominal pain. Positive Carnett's sign (A test in which acute abdominal pain remains unchanged or increases when the muscles of the abdominal wall are tensed.) An identifiable abdominal trigger point. Exclusion Criteria: History of chronic psychotic disorder. History of dementing illness. Active abdominal visceral disease as a known contributor of the pain. Abdominal surgery in the past 6 months. More than one trigger point. Abdominal wall hernias. BMI>40.

Moeschler SM, Pollard EM, Pingree MJ, Pittelkow TP, Bendel MA, Mauck WD, Watson JC, Eldrige JS, Loftus CG, Hooten WM. Ultrasound-guided transversus abdominis plane block vs trigger point injections for chronic abdominal wall pain: a randomized clinical trial. Pain. 2021 Jun 1;162(6):1800-1805. doi: 10.1097/j.pain.0000000000002181.