Acute pain Factors predictive of post-operative pain and opioid requirement in multimodal analgesia following knee replacement

• Published in: European journal of pain Vol. 20; no. 5; pp. 822 - 832
• Main Authors: Thomazeau, J., Rouquette, A., Martinez, V., Rabuel, C., Prince, N., Laplanche, J.L., Nizard, R., Bergmann, J.F., Perrot, S., Lloret-Linares, C.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01-05-2016; Wiley
• Subjects: Acute Pain - physiopathology; Acute Pain - psychology; Aged; Amides - therapeutic use; Analgesics - therapeutic use; Analgesics, Opioid - therapeutic use; Anesthetics, Local - therapeutic use; Anxiety - psychology; Arthroplasty, Replacement, Knee; Catechol O-Methyltransferase - genetics; Celecoxib - therapeutic use; Cyclooxygenase 2 Inhibitors - therapeutic use; Depression - psychology; Female; Humans; Life Sciences; Linear Models; Male; Middle Aged; Morphine - therapeutic use; Multivariate Analysis; Nerve Block; Pain Management; Pain Threshold; Pain, Postoperative - drug therapy; Pain, Postoperative - genetics; Polymorphism, Single Nucleotide; Pregabalin - therapeutic use; Preoperative Period; Prospective Studies; Receptors, Opioid, mu - genetics; Severity of Illness Index
• ISSN: 1090-3801; 1532-2149
• DOI: 10.1002/ejp.808

Background
Despite the development of multimodal analgesia for postoperative pain management, opioids are still required for effective pain relief after knee arthroplasty. We aimed to identify the determinants of post‐operative pain intensity and post‐operative opioid requirement in this context.
Methods
In this observational prospective study, we recorded patient characteristics, pre‐operative pain intensity, anxiety and depression levels, sensitivity and pain thresholds in response to an electrical stimulus, and mu‐opioid receptor (OPRM1) and catechol‐O‐methyltransferase (COMT) single‐nucleotide polymorphisms. Multivariate linear regression models were used to identify predictors of post‐operative pain at rest and opioid requirement.
Results
We included 109 patients. Pre‐operative pain at rest (p = 0.047), anxiety level (p = 0.001) and neuropathic pain symptoms (p = 0.030) were independently and positively associated with mean post‐operative pain intensity adjusted for mean post‐operative morphine equivalent dose (MED). Mean post‐operative pain intensity at rest was lower (p = 0.006) in patients receiving celecoxib and pregabalin in the post‐operative period, with all other variables constant. Mean post‐operative MED over 5 days was low, but highly variable (78.2 ± 32.1 mg, from 9.9 to 170 mg). Following adjustment for mean post‐operative pain intensity, it was independently negatively correlated with age (p = 0.004), and positively correlated with associated paracetamol treatment (p = 0.031). No genetic effect was detected in our sample.
Conclusions
Our findings suggest that clinicians could use the pre‐operative pain profile, in terms of anxiety levels, neuropathic pain symptoms, and chronic pre‐operative pain intensity, to improve the efficacy of pain management after knee surgery.