Femoral nerve inguinal approach versus proximal femoral triangle ap proach for continuous regional analgesia in active rehabilitation after total knee arthroplasty: A prospective, randomised study.

BACKGROUND: A catheter in femoral nerve block (F-Cath) is an effective regional analgesia technique in total knee arthroplasty (TKA) but results in significant quadriceps weakness. The femoral triangle catheter (FTB-Cath) seems to be an interesting alternative. In this study, we aim to demonstrate that the nerve block administration for analgesic purposes via an FTB-Cath results in less quadriceps weakness than via an F-Cath. METHODS: This study included patients scheduled for TKA performed under general anaesthesia. The patients were randomised to receive either an F-Cath or an FTB-Cath. A unique regimen of 0.2% ropivacaine was administrated for 72 h. The primary endpoint was quadriceps strength assessed clinically on postoperative day (POD) 2 by the Manual Muscle Test (MMT) using a motor grading scores (0-5). The secondary endpoints were quadriceps strength measured by a dynamometer, the Timed Up and Go (TUG) test, the 30-m walk test (30MWT) and pain scores. RESULTS: Forty-four patients were analysed (22 in each group). On POD 2, 77.3% of the patients in the FTB-Cath group had MMT scores ≥ 4 and 13.6% in the F-Cath group (p < 0.001). During the first four POD assessments, quadriceps strength evaluated with a dynamometer was less diminished in the FTB-Cath group (p < 0,001). There was no difference between groups regarding pain scores, TUG test results and 30MWT assessment. CONCLUSION: The FTB-Cath provided a better preservation of quadriceps strength than the F-Cath in TKA, with a similar pain relief.

Effect on neurostimulation of injectates used for perineural space expansion before placement of a stimulating catheter: normal saline versus dextrose 5% in water.

BACKGROUND AND OBJECTIVES: We clinically assessed the electrophysiologic effect of dextrose 5% in water (D5W) and of normal saline (NS) used for expansion of the perineural space before placing a stimulating catheter. We questioned if higher current was required with NS but not with D5W, as has been observed experimentally. METHODS: This was a prospective randomized double-blind study of ASA I to II patients scheduled for total knee replacement. Patients from 2 hospitals were randomly assigned to receive unidentified injectate D5W (n = 25) or NS (n = 25). The primary outcome was the minimal intensity of stimulation (MIS) recorded before and after 2 and 5 mL of study injectates were flushed through the needle before placing a stimulating catheter for continuous femoral and sciatic nerve blocks. Secondary outcomes included, among other parameters, MIS recorded during placement of stimulating catheters. RESULTS: No difference between groups was found with MIS before injection. However, MIS recorded during neurostimulation via the needle in all blocks was significantly higher after 2 and 5 mL of NS than after D5W. In femoral blocks, MIS recorded during placement of catheters was higher during insertion after NS than after D5W but was not different after reaching the final site, regardless of injectate used. In sciatic blocks, MIS was not different during insertion regardless of injectate but was higher after NS than after D5W after reaching the final site. CONCLUSIONS: The current needed to electrostimulate the femoral or sciatic nerve was higher after injection of NS than after D5W.

Various possible positions of conventional catheters around the femoral nerve revealed by neurostimulation.

BACKGROUND AND OBJECTIVES: In continuous femoral nerve blocks, the various perineural positions of the tip of a conventional catheter and their clinical implication are not completely known.We used stimulating catheters to explore the relationship of catheter tip to nerve. METHODS: American Society of Anesthesiologists physical status IYII patients scheduled for total knee arthroplasty were administered effective single-shot blocks of the obturator and sciatic nerves using ropivacaine 0.5% 10 and 20 mL, respectively. Continuous femoral blocks were performed using stimulating catheters, which were advanced blindly. Neurostimulation via catheter was performed but was masked from the investigators' sight. Before general anesthesia was induced for surgery, 5 mL of ropivacaine 0.2% was administered through the femoral nerve catheter, followed by infusion (5 mL/hr). Visual analog scale (VAS) score at rest was recorded on admission to the postanesthesia care unit. Characteristics of neurostimulation via the catheters were analyzed. RESULTS: Thirty-three patients were studied. Motor responses to stimulation via the catheters were obtained at 1 mA or less in 55% of patients and at greater than 1 mA in 45%. Various motor responses involved twitches of the pectineus (12%), sartorius (18%), or quadriceps (48%) muscles, or no muscular twitch up to 5 mA (22%). Catheter-induced motor response at 1 mA or less was associated with median values of VAS scores lower than those at greater than 1 mA (0 vs 30 mm; P = 0.008). CONCLUSION: The effectiveness of a continuous femoral block depends on neurostimulation characteristics, which likely correspond to various possible catheter tip positions. Conventional catheters provide no information on this issue. These results suggest that better VAS scores are attainable by placing catheters with neurostimulation guidance.

Is there any need for expanding the perineural space before catheter placement in continuous femoral nerve blocks?

BACKGROUND AND OBJECTIVE: There is debate regarding the benefit of perineural space expansion before catheter placement in continuous femoral nerve block. This question is addressed in this prospective, comparative, and randomized study. METHODS: Sixty patients scheduled for total knee replacement were randomly assigned to receive continuous femoral nerve block with or without perineural space expansion using 10 mL dextrose 5% in water (D5W) flush before stimulation-guided catheter placement. Femoral block was initiated with a 5-mL bolus followed by an infusion of 5 mL/h ropivacaine 0.2% during the 2-hour surgery. The number of attempts before successful placement of the stimulating catheter and the resistance during its insertion were assessed. Patients also received obturator nerve blocks by using ropivacaine 0.75% (10 mL) and sciatic nerve blocks (20 mL). The number of boluses of ropivacaine 0.2% needed to achieve zero VAS scoring was recorded in the postanesthesia care unit during the 2-hour stay. Images of the contrast spread were also studied. RESULTS: There were 30 patients in each group. The number of successful catheter placements at the first attempt was higher with expansion than without (22 vs. 8, P = .007). The resistance felt during insertion was lower with than without expansion (P = .01). More boluses of ropivacaine were required postoperatively without expansion (P = .03). No difference between groups was found regarding the images of the contrast spread. CONCLUSION: Expansion of the perineural space with D5W is useful for catheter placement in continuous femoral nerve block.

The value of adding sciatic block to continuous femoral block for analgesia after total knee replacement.

BACKGROUND AND OBJECTIVES: The benefit of adding a sciatic nerve block to the femoral block to improve analgesia after total knee replacement is controversial. The aim of this study is to address this controversy in a prospective, comparative, and randomized study. METHODS: Patients were allocated randomly to receive a continuous femoral nerve block or continuous blocks of both the femoral and sciatic nerves. Stimulating catheters were used in all cases. A loading dose of 15 mL ropivacaine 0.75% was injected into each catheter, followed by administration of ropivacaine 0.2% (2-5 mL/h infusion via the femoral catheter; bolus 10 mL repeated every 12 hours in the sciatic catheter). The primary outcome was visual analog scale (VAS) scores (0 = no pain, 100 mm = worst pain) in postanesthesia care unit and in the 48-hour period after surgery. The secondary outcomes were amplitude of knee flexion, morphine consumption, and occurrence of postoperative nausea and vomiting (PONV). RESULTS: The VAS scores at rest were significantly higher when there was only continuous femoral nerve block than when there was both continuous femoral and sciatic nerve blocks. This difference progressively decreased and disappeared at 36 hours after surgery. The combined femoral and sciatic blocks decreased the morphine consumption by 81% and significantly decreased the occurrence of PONV. CONCLUSION: During the 36 hours immediately after total knee replacement, the combination of continuous femoral and sciatic nerve blocks improves analgesia while decreasing morphine consumption and PONV.