Postoperative analgesia for total knee replacement: comparing between pre-and postoperative "3-in-1" femoral nerve block.

Background: Total Knee Replacement (TKR) produces severe postoperative pain. Pre- and postoperative single-shot "3-in-1" Femoral Nerve Block (FNB) were reported to improve analgesia and reduce morphine consumption post TKR.

Objective: To find out the most beneficial time for injection of single shot "3-in-1" FNB for TKR between preoperative and postoperative in a prospective controlled trial.

Methods: In a Randomized, double-blind Controlled Trial (RCT), 48 patients undergoing TKR received either pre- or postoperative "3-in-1" FNB using 30 mL of bupivacaine 0.25% after a standardized general anesthesia. Morphine consumption, Numeric Pain-Rating Scale (NPRS) at rest and during movement, tension in the back of the knee, nausea/vomiting, pruritus, sedation, and respiratory depression at 1, 4, 24 and 48 hr after TKR were compared

Results: There were no significant differences in 48-hr morphine consumption [46.5 (20.0) vs 45.0 (23.6) mg, p = 0.809], NPRS both at rest and during movement, tension in the back of knee, nausea/vomiting, pruritus, sedation, and respiratory depression at any time during 48-hr postoperative TKR between groups.

Conclusions: Preoperative single-shot "3-in-1" FNB using 30 mL of bupivacaine 0.25% is not better than postoperative single-shot "3-in-1" FNB using the same drug in postoperative pain and morphine reduction in patients undergoing elective TKR under general anesthesia.