Investigating the Effect of Perioperative Chlorzoxazone on Acute Postoperative Pain After Total Hip and Knee Replacement Surgery

Use of Muscle Relaxants for Acute Postoperative Pain: A Practical Review

Background

Skeletal muscle relaxants have emerged as a broad category of analgesic adjuncts, aiming to improve pain relief and reduce opioid reliance. These drugs induce muscle relaxation and reduce muscle spasms, and therefore, they are commonly used in surgical procedures involving muscle manipulation, such as abdominal surgery, breast surgery, and spine surgery. However, their analgesic efficacy and opioid-sparing effects are poorly explored.

Methods

A scoping review of literature was performed with several electronic databases. We used a search string with a sequence of text words and word variants related to central muscle relaxants, pain management, postoperative pain, and specific muscle relaxants.

Results

Review of literature shows significant heterogeneity among the studies in terms of surgical procedures, patient populations, choice of muscle relaxant, and timing and duration of administration, potentially limiting the generalizability of the findings and the ability for pooled analysis.

Conclusions

Given the lack of evidence, we recommend that the use of skeletal muscle relaxants be reserved for patients in whom an optimal multimodal analgesic technique is not adequate. Also, there may be a limited role for these drugs in patients at high risk of postoperative pain undergoing surgical procedures with expected high opioid requirements. Due to the concerns of potential adverse effects, the decision to use muscle relaxants in vulnerable populations should be made carefully, weighing the benefits against the risks.

The association between sleep quality, preoperative risk factors for chronic postoperative pain and postoperative pain intensity 12 months after knee and hip arthroplasty

BACKGROUND

Chronic postoperative pain following total joint replacement (TJA) is a substantial clinical problem, and poor sleep may affect predictive factors for postoperative pain, such as pain catastrophizing. However, the magnitude of these associations is currently unknown. This exploratory study investigated (1) the relationship between preoperative sleep quality, clinical pain intensity, pain catastrophizing, anxiety, and depression and (2) their associations with chronic postoperative pain following TJA.

METHODS

This secondary analysis from a larger randomized controlled trial included rest pain intensity (preoperative and 12 months postoperative; visual analogue scale, VAS), preoperative Pittsburgh Sleep Quality Index (PSQI), Pain Catastrophizing Scale (PCS), Hospital Anxiety and Depression Scale (HADS) data from 74 knee and 89 hip osteoarthritis (OA) patients scheduled for TJA. Poor sleepers were identified based on preoperative PSQI scores higher than 5.

RESULTS

Poor sleepers demonstrated higher preoperative VAS, pain catastrophizing, anxiety, and depression compared with good sleepers (all p < 0.003). Preoperative PSQI (β = 0.23, p = 0.006), PCS (β = 0.44, p < 0.005), and anxiety (β = 0.18, p = 0.036) were independent factors for preoperative VAS. Preoperative VAS (β = 0.32, p < 0.005), but not preoperative sleep quality (β = -0.06, p = 0.5), was an independent factor for postoperative VAS.

CONCLUSION

The OA patients reporting poor preoperative sleep quality show higher preoperative pain, pain catastrophizing, anxiety, and depression. High preoperative pain intensity, but not poor sleep quality, was associated with higher chronic postoperative pain intensity. Future studies are encouraged to explore associations between sleep and chronic postoperative pain.

The Combination of Preoperative Pain, Conditioned Pain Modulation, and Pain Catastrophizing Predicts Postoperative Pain 12 Months After Total Knee Arthroplasty

OBJECTIVES

Approximately 20% of knee osteoarthritis patients undergoing total knee arthroplasty (TKA) report chronic postoperative pain. Studies suggest that preoperative variables such as impaired descending pain control, catastrophizing, function, and neuropathic pain-like symptoms may predict postoperative pain 12 months after TKA, but the combined prediction value of these factors has not been tested. The current prospective cohort study aimed to combine preoperative risk factors to investigate the predictive value for postoperative pain 12 months after TKA.

DESIGN

Prospective cohort with follow-up 12 months after surgery.

PATIENTS

A consecutive sample of 131 knee osteoarthritis patients undergoing TKA.

METHODS

Pain intensity, Pain Catastrophizing Scale (PCS) scores, PainDETECT Questionnaire scores, conditioned pain modulation (CPM), and Oxford Knee Score (OKS) were obtained before and 12 months after TKA.

RESULTS

TKA improved pain (P < 0.001), PCS scores (P < 0.001), PainDETECT Questionnaire scores (P < 0.001), and OKSs (P < 0.001). Preoperative pain correlated with preoperative PCS scores (r = 0.38, P  <  0.001), PainDETECT scores (r = 0.53, P  <  0.001), and OKSs (r = -0.25, P  =  0.001). Preoperative PainDETECT scores were associated with preoperative PCS scores (r = 0.53, P  <  0.001) and OKSs (r = -0.25, P  =  0.002). Higher postoperative pain was correlated with high preoperative pain (r = 0.424, P  <  0.001), PCS scores (r = 0.33, P  <  0.001), PainDETECT scores (r = 0.298, P  =  0.001), and lower CPM (r = -0.18, P  =  0.04). The combination of preoperative pain, PCS score, and CPM explained 20.5% of variance in follow-up pain. PCS scores had a significant effect on pain trajectory when accounting for patient variance (t  =  14.41, P  <  0.0005).

CONCLUSION

The combination of high preoperative clinical pain intensity, high levels of pain catastrophizing thoughts, and impaired CPM may predict long-term postoperative pain 12 months after surgery.