Preventing the development of complex regional pain syndrome after surgery.

COMPLEX regional pain syndrome (CRPS), previously known as reflex sympathetic dystrophy (RSD), is used to describe a syndrome of pain and sudomotor or vasomotor instability. This pain syndrome usually has an initiating noxious event in the periphery, is not limited to the distribution of a single nerve, and is disproportionate to the inciting event. The Consensus Conference of the International Association for the Study of Pain has subclassified CRPS into two forms: CRPS I (formerly RSD) and CRPS II (formerly causalgia). According to the International Association for the Study of Pain, the diagnosis of CRPS I requires (1) continuing pain, allodynia, or hyperalgesia disproportionate to the injury; (2) evidence at some time of edema, changes in skin blood flow, or abnormal sudomotor activity in the region of pain; and (3) no other conditions that would otherwise account for the degree of pain and dysfunction. Motor disturbances and trophic changes, such as altered nail and hair growth, may be observed in some cases. CRPS II is a pain syndrome that starts after a nerve injury and is not necessarily limited to the distribution of the injured nerve. The diagnostic criteria are the same as those of CRPS I. Patients with CRPS I or CRPS II can have sympathetically maintained pain or sympathetically independent pain. Sympathetically maintained pain, a term introduced in 1986 by Roberts, is pathologic pain that is supported by sympathetic efferent activity, circulating catecholamines, and/or increased sensitivity of -adrenergic receptors. Sympathetically maintained pain is identified by the ability to lessen the pain by sympatholytic blocks or interventions. Sympathetically independent pain has components of pain from sources other than sympathetic innervation and is believed to be most commonly observed in advanced cases of CRPS that do not respond to sympathetic blocks. Patients with CRPS may present with components of only sympathetically maintained pain or sympathetically independent pain or, more commonly, a combination of pain from each. Despite increasing research interest, little is known regarding which patients are at increased risk for development of postoperative CRPS and what the optimal perioperative treatment strategy is for those patients undergoing surgery who have a previous history of CRPS. This review outlines the surgical procedures that are believed to increase risk for development of CRPS and describes pharmacologic and regional analgesic techniques that may be of benefit for preventing the development of CRPS after surgery.