It remains common clinical practice to prescribe perioperative pain management based primarily on the type and invasiveness of surgery. One of the limitations in postoperative pain management has been the fact that the patient’s personal perception of pain may not always be taken into account during preoperative pain counseling, as 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 with sleep disorders, and patients scheduled for laparotomic/orthopedic surgery or long procedures are especially concerned about inadequate pain control after surgery. Although it was not identified as an independent factor in multivariate analysis, the use of regional anesthetic techniques has a potential role in relieving patient concerns on postoperative pain.
Gender is commonly considered as a strong predictor for pain perception and analgesic requirements after surgery [19 ,20]. However, other systematic reviews have not found gender to be an independent predictor for postoperative pain levels or analgesic requirements [11]. The results of our survey suggests 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 are congruent with the findings of numerous previous studies [21-23]. Our study also indicated that older patients (>40 years) anticipated a lesser degree of surgery-related pain during their preoperative assessments as compared to younger patients. We suggest that this may be due to the elderly having less preoperative anxiety and requesting for less information concerning the operation [24-26]. Since a history of previous surgery is usually associated with decreased preoperative anxiety [27 ,28], it was expected to find that previous surgery had a diminishing effect on preoperative anticipated pain levels. Our findings were also consistent with the observation that preoperative anxiety is negatively correlated with preoperative pain expectations [29].
Previous studies have suggested that patients with psychosomatic and behavioral disorders (e.g. major depression, insomnia, and pain catastrophization) can have decreased tolerances for postoperative pain [30-33]. Our study has found that regular benzodiazepines for sleep disorder management is an independent risk factor for high anticipated NRS scores 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 [34-36]. On the other hand, patients receiving uroscopies and hysteroscopies anticipated less surgical pain. Compared with general anesthesia, regional blocks significantly attenuated 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 [11].
The preoperative anticipating NRS were correlated to the highest postoperative VAS quantified by the PACU nurses, and the total equivalent dose of opioids prescribed perioperatively. Since patient’s anticipating pain scale was not recorded in the clinical notes and the clinical anesthesia team did not aware of the preoperative NRS, the establishment of relationships between preoperative anticipating NRS and the actual postoperative pain levels could be clinically valuable. 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 VAS in PACU. Although there was a positive relationship between preoperative NRS scores and perioperative total equivalent dose of opioid administered (during surgery and in PACU), the correlation coefficient was extremely low. These observations suggests 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.
After extensively reviewing 48 studies, Ip et al. identified several independent perioperative factors for predicting actual levels of postoperative pain and analgesic usage [11]. 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 or ill than the male patients [37].
The results of this study must be interpreted in light of several limitations. Firstly, this study aimed to determine patients’ subjective anticipation of pain preoperatively and to identify the predictive factors for anticipating severe postoperative pain. The results of our study may not be generalizable to actual postoperative pain levels and analgesic requirements. Secondly, perioperative pain was managed based on clinical practice guidelines in this study [38 ,39], rather than being based on preoperative anticipated pain. Therefore, we did not find any significant relationships between preoperative anticipated NRS scores and postoperative VAS scores or analgesic requirements. Thirdly, the preoperative questionnaires used to evaluate psychological conditions 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 anticipating severe postoperative pain. Lastly, our results were not generalized to critically ill patients who were scheduled for postoperative intensive care.
By identifying the predictive factors for anticipating severe postoperative pain, our study demonstrated that factors such as female gender, younger age (< 40 years), regular benzodiazepine use, prolonged operation times (> 2 h), operation type (e.g. laparotomy and orthopedic surgery) are significant risk factors for higher anticipated postoperative pain. Therefore, these patients may require additional assessments and pain management counseling during their pre-anesthesia consultation. Appropriate preoperative counseling for analgesic control (especially the introduction of multimodal analgesia) and the elimination of unnecessary anticipated pain levels could improve the quality of anesthesia service and patient perioperative satisfaction.