[High pain expectation and impairment from pre-existing pain are risk factors for severe postoperative pain : Results of a study using the Lübeck Pain Risk Questionnaire].

BACKGROUND: The intensity of postoperative pain is characterized by large interindividual variability. Furthermore, strong postoperative pain is known to influence physical recovery after surgery. High (preoperative) pain expectation and pre-existing pain, which are associated with pain-related disability (impairing pain) are risk factors for strong postoperative pain. They can be determined with the Lübeck Pain Risk Questionnaire used for the first time in this study. The aim of this study was to explore the hypothesis that patients with a combination of the characteristics (1) preoperative impairing pain and (2) high pain expectation are more likely to have strong postoperative pain. Patients with these characteristics represent a unique group of patients and are more likely to develop distinct postoperative pain and can therefore be characterized as a risk group.

MATERIAL AND METHODS: A total of 501 patients at the departments of general surgery, plastic surgery, trauma surgery and orthopedic surgery of the UKSH Campus Lübeck were included in this study. All underwent elective surgery. Study patients were 18 years and older. Those needing postoperative treatment in an intensive care unit were excluded from this study (n = 18). The characteristics "preoperative pain" and "pain expectation" were measured with the Lübeck Pain Risk Questionnaire the day before surgery. The primary outcome variable was the average postoperative pain intensity, which was measured with a numeric rating scale (NRS 0-10) and scores > 4 were defined as severe pain.

RESULTS: The NRS range for "preoperative pain" was subdivided as follows: "no pain" (NRS = 0), "functional pain" (NRS = 1-3), and "impairing pain" (NRS = 4-10); that for "pain expectation" as: "low expectation" (NRS = 0-4) and "high expectation" (NRS = 5-10). To determine these cut-off points, they were varied from > 1 to > 8 and those with highest effect size for strong postoperative pain were chosen. Patients with a high pain expectation had significantly stronger postoperative pain (p < 0.001) and significantly more often higher pain intensity than patients with a low expectation (53.3% vs. 20.6%, respectively, p < 0.001). Patients with pre-existing impairing pain had significantly stronger and more frequently higher postoperative pain than patients with pre-existing functional pain (43.4% vs. 18.4%, p < 0.05). Patients with a combination of the factors "preoperative impairing pain" and "high pain expectation" showed distinct postoperative pain with NRS > 4 significantly more often (59.4%, p < 0.001). These findings could be demonstrated for the departments general surgery, plastic surgery and trauma surgery.

CONCLUSION: The combination of both risk factors results in a unique risk group for the appearance of strong postoperative pain. This group can be economically determined in the daily clinical routine using the Lübeck Pain Risk Questionnaire. Further studies must be carried out to show if additional perioperative procedures can be profitable for the risk group identified with the Lübeck Pain Risk Questionnaire; however, patients falling outside the risk group must not be neglected because they too can develop severe postoperative pain.