Chronic Pain as an Outcome of Surgery : A Review of Predictive Factors

Long-term pain is a common sequela of thoracotomy, occurring in approximately 50% of patients 2 years after thoracic surgery. Despite this alarming statistic, little is known about the factors responsible for the transition of acute to chronic pain. The aim of the present study is to identify predictors of long-term post-thoracotomy pain. Follow-up was for 1.5 years for patients who had participated in a prospective, randomized, controlled trial of preemptive, multimodal analgesia. Subjects were recruited from a tertiary care center. Thirty patients who had undergone lateral thoracotomy were followed up by telephone, administered a structured interview, and classified according to long-term pain status. Present pain status was measured by a verbal rating scale (VAS). Measures obtained within the first 48 h after surgery were compared between patients with and without pain 1.5 years later. These include VAS pain scores at rest and after movement, McGill Pain Questionnaire data, patient-controlled morphine consumption (mg), and pain thresholds to pressure applied to a rib contralateral to the thoracotomy incision. Fifty-two percent of patients reported long-term pain. Early postoperative pain was the only factor that significantly predicted long-term pain. Pain intensity 24 h after surgery, at rest, and after movement was significantly greater among patients who developed long-term pain compared with pain-free patients. A significant predictive relationship was also found at 24 and 48 h using the McGill Pain Questionnaire. Cumulative morphine was comparable for the two groups. Pain thresholds to pressure applied to a rib contralateral to the incision did not differ significantly between the groups. Aggressive management of early postoperative pain may reduce the likelihood of long-term post-thoracotomy pain.

The phenomenon of a phantom limb is a common experience after a limb has been amputated or its sensory roots have been destroyed. A complete break of the spinal cord also often leads to a phantom body below the level of the break. Furthermore, a phantom of the breast, the penis, or of other innervated body parts is reported after surgical removal of the structure. A substantial number of children who are born without a limb feel a phantom of the missing part, suggesting that the neural network, or 'neuromatrix', that subserves body sensation has a genetically determined substrate that is modified by sensory experience.

In a prospective study 58 patients undergoing limb amputation were interviewed the day before operation about their pre-amputation limb pain and 8 days, 6 months and 2 years after limb loss about their stump and phantom limb pain. All but one patient had experienced pain in the limb prior to amputation. Pre-amputation limb pain lasted less than 1 month in 25% of patients and more than 1 month in the remaining 75% of patients. At the first examination the day before amputation 29% had no limb pain. The incidence of phantom pain 8 days, 6 months and 2 years after amputation was 72, 65 and 59%, respectively. Within the first half year after limb loss phantom pain was significantly more frequent in patients with long-lasting pre-amputation limb pain and in patients with pain in the limb immediately prior to amputation. Phantom pain and pre-amputation pain were similar in both localization and character in 36% of patients immediately after amputation but in only 10% of patients later in the course. Both the localization and character of phantom pain changed within the first half year; no further change occurred later in the course. The incidence of stump pain 8 days, 6 months and 2 years after limb loss was 57, 22 and 21%, respectively. It is suggested that preoperative limb pain plays a role in phantom pain immediately after amputation, but probably not in late persistent phantom pain.