In-plane three-step needle insertion technique for ultrasound-guided continuous femoral nerve block after total knee arthroplasty: a retrospective review of 488 cases.

BACKGROUND: Continuous femoral nerve block (CFNB) improves postoperative analgesia after total knee arthroplasty (TKA). The aim of this study was to investigate the clinical efficacy and complications of our in-plane three-step needle insertion technique that was devised to reduce the risk of direct femoral nerve injury during CFNB in anesthetized patients. METHODS: This retrospective study included 488 patients who had undergone TKA. Ultrasound (US)-guided CFNB was performed under general or spinal anesthesia using an in-plane, three-step needle insertion technique. The success rate and difficulties of catheter placement, clinical efficacy of analgesia, and complications were recorded. RESULTS: Femoral catheters were placed with a 100% success rate. In 488 patients, real-time US imaging revealed easy separation of the fascia iliaca and the femoral nerve following injection of local anesthetic through a Tuohy needle. Verbal numerical rating scale pain scores (0-10) were 2.0 ± 1.2, 3.5 ± 1.9, 3.2 ± 1.7, 2.9 ± 1.3, and 2.5 ± 1.1 at 1, 6, 12, 24 and 48 h postoperatively. No femoral hematoma, femoral abscess, or neurologic complications, including paresthesia or neurologic deficits, were observed during the 8-week follow-up period. CONCLUSIONS: This retrospective study suggests that an in-plane three-step needle insertion technique for CFNB may reduce the risk of femoral nerve injury in anesthetized patients.

Epidural dexamethasone decreased inflammatory hyperalgesia and spinal cPLA2 expression in a rat formalin test.

PURPOSE: The aim of this study was to investigate the effect of epidural dexamethasone on analgesia and cytosolic phospholipase A2 (cPLA2) expression in the spinal cord in a rat formalin test. MATERIALS AND METHODS: Epidural dexamethasone injection was performed to Sprague-Dawley rats with a 25 gauge needle under fluoroscopy. Following the epidural injection, a formalin induced pain behavior test was performed. Next, the spinal cords corresponding to L4 dorsal root ganglion was extracted to observe the cPLA2 expression. RESULTS: There were no differences in pain response during phase I among the groups. The phase II pain response in 300 µg of epidural dexamethasone group decreased as compared to control, 30 µg of epidural dexamethasone, 100 µg of epidural dexamethasone, and 300 µg of systemic dexamethasone groups. The expression of cPLA2 decreased in Rexed laminae I-II in 300 µg of the epidural dexamethasone group compared with the ones in the control group. CONCLUSION: Taken together, these results suggest that 300 µg of epidural dexamethasone has an attenuating effect on the peripheral inflammatory tissue injury induced hyperalgesia and this effect is mediated through the inhibition of intraspinal cPLA2 expression and the primary site of action is the laminae I-II of the spinal cord.