Higher doses of intraoperative analgesia are associated with lower levels of persistent pain and less analgesic consumption six months after total hip arthroplasty.

BACKGROUND: Persistent postoperative pain is a major health problem affecting nearly 30% of all patients undergoing total hip arthroplasty. Previous studies have demonstrated an association between the intensity of acute postoperative pain and persistent pain, but this association might be an epiphenomenon of insufficient intraoperative analgesia. In this study, we investigated the association between the intraoperative level of analgesia and the persistent postoperative pain 6 months after surgery.

METHODS: We investigated 110 patients undergoing primary total hip arthroplasty under total intravenous general anaesthesia in a prospective cohort study. A highly standardized surgical and a standardized anaesthetic procedure were performed to reduce variability and psychosocial influences were investigated to adjust for confounders. Acute postoperative pain was controlled using patient-controlled analgesia pumps. Postoperative pain intensities and analgesic requirements were monitored for 6 months following surgery.

RESULTS: Of 105 patients included in the analysis, 32% continued using daily pain medication 6 months after surgery and reported a median pain level of 4/10. Multivariate analyses confirmed that the amount of intraoperative analgesia is a significant predictor of regular analgesic use and pain intensity 6 months after surgery.

CONCLUSIONS: Higher levels of intraoperative analgesia are associated with lower levels of persistent pain and less analgesic consumption 6 months after total hip arthroplasty. Persistent pain may be attributable to intraoperative nociception, which is likely not adequately assessed and suppressed using current clinical measures.

SIGNIFICANCE: Our study suggests that lower doses of intraoperative analgesia are associated with higher levels of persistent postoperative pain. Persistent pain may be caused by intraoperative nociception, which is likely not adequately suppressed using current clinical standard analgesic measures.