Acute pain is taken to be of recent onset with the expectation of limited duration although evidence is accumulating that a significant number of patients experience protracted po pain (duration of more than 1 year) after a range of surgical procedures (vide infra). Acute pain usually has an identifiable temporal and causal relationship injury disease. It although t to or commonly, not invariably, follows surgery or trauma and be associated with a may other conditions such as renal calculi. pancreatitis and acute low back pain. Acute post-surgical pain has been regarded as noci- ceptive in nature, that is the result of activation of specialized peripheral neurones (nociceptors) in response to injury, but it is now recognized that there may also be a neuropathic component