Analgesic effect of ropivacaine combined with methylene blue in fascia Iliaca block for patients undergoing hip arthroplasty.

Abstract

Background: The duration of a single fascia iliaca compartment block (FICB) with ropivacaine is limited. This study investigated whether methylene blue as an adjuvant anesthetic in FICB can enhance the postoperative analgesic effect following total hip arthroplasty (THA).

Methods: Patients who planned to undergo THA were recruited for this randomized clinical trial from June 2023 to February 2024. Ninety elderly patients undergoing THA were randomly divided into two groups that received ultrasound-guided FICB with either ropivacaine and methylene blue (MB + R group, n = 45) or ropivacaine only (R group, n = 45) before induction of general anesthesia. The primary outcomes were postoperative Visual Analog Scale (VAS) scores. Secondary outcomes included inflammatory factor levels, heart rate (HR), mean arterial pressure (MAP), postoperative analgesic use, postoperative activity, and adverse events.

Results: The MB + R group had significantly lower VAS scores at both rest and with activity at 24 and 48 h postoperatively than the R group (P < 0.001). Additionally, the hypersensitive C-reactive protein, procalcitonin, and neutrophil-to-lymphocyte ratio values were significantly lower in the MB + R group than in the R group on the first and second days after surgery (P < 0.05). The number of patients requiring supplemental analgesia postoperatively was significantly lower in the MB + R group (P = 0.020). Additionally, the MB + R group had a significantly longer walking distance on the first time out of bed and a higher number of out-of-bed activities within 48 h postoperatively (P < 0.001).

Conclusion: Compared to ropivacaine alone, the combination of ropivacaine and methylene blue in FICB provided better analgesic effects over a longer duration. Additionally, the addition of methylene blue reduced the postoperative production of inflammatory markers and promoted patients' functional recovery.

Trial registration: ClinicalTrials.gov, Registration number: NCT06284941, Retrospectively registered, Date of registration: February 04, 2024.