A major limitations in postoperative pain management has been the fact that a patient’s personal perception of pain may not always be taken into account during preoperative pain counseling. Acute postoperative pain is a subjective and multidimensional experience that is extremely hard to measure and manage optimally. The results of this study demonstrated that female patients, younger patients, patients took regular benzodiazepine at bedtime, and patients scheduled for laparotomic/orthopedic surgery or long procedures are especially concerned about inadequate pain control after surgery.
Gender is commonly considered as a strong predictor for pain perception and analgesic requirements after surgery [27 ,28]. However, some systematic reviews have not found gender to be an independent predictor for postoperative pain levels or analgesic requirements . The results of our survey suggest that female patients anticipated significantly higher pain levels preoperatively than male patients, the difference remained statistically significant following a multivariate regression analysis with an odds ratio of 1.710 (95% CI 1.254-2.331). These results support the findings of numerous previous studies [29-31]. Our study also indicated that older patients (>40 years) anticipated a lesser degree of surgery-related pain during their preoperative assessments as compared to those who were younger. We suggest that this observation may be due to the elderly being associated with less preoperative anxiety and that they do not request for as much information concerning their operations [32-34]. Our results are also consistent with a previous prospective observational study which showed that older patients reported lower anxiety scores and expected pain scores before operations . Since a history of previous surgery is usually associated with decreased preoperative anxiety [36 ,37], it was not surprising to find that previous surgery had a diminishing effect on preoperative anticipated pain levels.
Previous studies have suggested that patients with psychosomatic and behavioral disorders (e.g. major depression, insomnia, and catastrophizing pain) can have a decreased tolerances for postoperative pain [18, 38-40]. Our study has found that regular benzodiazepine use at bedtime is an independent risk factor for high anticipated postoperative pain intensity during preoperative assessments. However, no differences were found in preoperative pain anticipation between surgical patients with and without depression.
Several perioperative factors were surveyed for their effects on anticipated pain levels. Consistent with other clinical studies, our analysis identified that patients scheduled for laparotomies, spinal, and orthopedic surgeries anticipated higher pain scores than those receiving laparoscopic procedures [41-43]. On the other hand, patients receiving uroscopies and hysteroscopies anticipated less surgical pain. Compared with general anesthesia, univariate analysis showed that regional blocks significantly reduced patient concerns regarding postoperative pain. Prolonged operation times was also an independent risk factor for increased anticipated pain. These findings support the general concept that the invasiveness and duration of an operation can affect patients’ anticipated perception of surgical-related pain in the preoperative period . Nevertheless, this study did not find significant effects of other patient characteristic variables, such as educational levels, marital and socioeconomic status on the anticipation of surgical pain intensity.
Preoperative anticipated pain intensity was compared with the highest postoperative pain intensity recorded in PACU, and the total equivalent dose of opioids prescribed perioperatively. Our analysis found that patients anticipated significantly more pain preoperatively than they actually experienced after surgery. This was particularly evident in patients who anticipated severe pain (NRS³ 7) preoperatively, these patients were actually more likely to report a lower pain intensity in PACU. Although there was a positive relationship between preoperative anticipated pain intensity and perioperative total equivalent dose of opioid administered (during surgery and in PACU), the correlation coefficient was extremely low. These observations suggest that patients tend to overestimate surgery-related pain levels. However, anesthesiologists are still more likely to prescribe postoperative analgesics based on the type and duration of the operation rather than the patient’s subjective perception of pain [43 ,44].
After extensively reviewing 48 studies, Ip et al. identified several independent perioperative factors for predicting actual levels of postoperative pain and analgesic usage . These predictive factors include the presence of preoperative pain, anxiety, age, and type of surgery (i.e. major joint, thoracic, and open abdominal surgery) and are associated with higher postoperative pain scores. Surgery type, age, and psychological distress were found to be significant predictors of analgesic usage. Ip and colleagues’ systematic review found that gender had a neutral effect on postoperative pain levels and analgesic requirements, but the results of our study indicated that females anticipated more postoperative pain preoperatively. This major discrepancy could be due to the general understanding that female patients can react more emotionally to physical distress, but the distress is no less authentic and they are not less ill than the male patients [45-47].
The results of this study must be interpreted in light of several limitations. Firstly, patients were invited to voluntarily rate the anticipated pain intensity during their preoperative anesthesia assessment. Therefore, the knowledge and motives of the individual patient might impact the response to the quantitative question. Secondly, patients’ preoperative psychological conditions are routinely assessed using a culturally relevant depression screening questionnaire, the Taiwanese Depression Questionnaire (TDQ) in our hospital. This short questionnaire were designed to be simple and practical so that it could be applied to the general population in a time-efficient manner. The comprehensive versions for diagnosing depression and chronic insomnia were not used in this study. Therefore, this study may have been underpowered to isolate depression as an independent risk factor for the anticipation of severe postoperative pain. Lastly, our results were not generalized to critically ill patients who were scheduled for postoperative intensive care or emergent surgery.