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Chronic neuropathic pain occurring after an operation is a common problem, however little data is available describing the nature or prevalence of acute neuropathic pain following surgery. In this thesis, I explore the measurement scale properties of a commonly used neuropathic pain screening tool, and use this tool to describe the prevalence of acute and chronic neuropathic pain following thoracic surgery. I also explore how best to diagnose acute neuropathic pain with a Delphi survey of expert opinion and confirmatory observational cohort study. The results show that the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) neuropathic pain screening tool demonstrates acceptable fit to the Rasch measurement model in the chronic postoperative pain population, but only has reliability consistent with use at a group level. Using this tool, I demonstrate that 8% of thoracic surgery patients experience acute neuropathic pain an average of 3 days after surgery, with 22% developing neuropathic pain by 3 months. Experiencing acute neuropathic pain significantly increased the odds of developing chronic neuropathic pain (odds ratio 7.7 [95% confidence interval 1.5-39.7]). A Delphi survey of specialists identified 9 items considered important in the diagnosis of acute neuropathic pain, and suggests that unlike diagnosis in the chronic pain population, a poor response to opioid medications was an important indicator of neuropathic pain. Preliminary results from a matched cohort study confirm this, by demonstrating that verbal descriptors of neuropathic pain are significantly more common in patients with poorly controlled postoperative pain despite strong opioid use. |
