Title: Characterization of rebound pain following peripheral nerve block and its association with gut microbiome diversity.

Investigating team: David Brenner, Siobhain O’Mahony, Ihsan Butt, Timothy Switzer, Niall O’Brien, Brian McNamara, Gabriella Iohom, George Shorten

Background: Although rebound pain occurs in as many as 40% of patients following resolution of peripheral nerve blockade, its pathophysiology is undetermined. Gut microbiota are likely to influence somatic pain. We aim to determine if there is an association between gut microbiota and postoperative pain, including rebound pain in patients undergoing upper limb trauma surgery. 

Objective: Our objectives were to quantitatively characterise rebound pain (RP) in patients undergoing upper limb trauma surgery, and its associations with patient factors, preoperative stress and gut microbiome (GMB) diversity.

Preliminary Results: Seventeen patients experienced rebound pain (NRS 5.4/10), pain level was acceptable for 8/20 patients during the first 24 hours. Equivalent morphine consumption was 253 mg during the first postoperative week. Patients with and without RP were similar in terms of PPT and PTT. RP was primarily nociceptive with contributory hypersensitivity due to neuronal changes. Salivary cortisol and faecal sample analyses are in progress.

Current status: Under manuscript preparation.