Adductor Canal Block With Continuous Infusion Versus Intermittent Boluses and Morphine Consumption: A Randomized, Blinded, Controlled Clinical Trial.

BACKGROUND: Based on the assumption that relatively large volumes of local anesthetic optimize an adductor canal block (ACB), we theorized that an ACB administered as repeated boluses would improve analgesia without compromising mobility, compared with a continuous infusion. METHODS: We performed a randomized, blinded, controlled study, including patients scheduled for total knee arthroplasty with spinal anesthesia. Patients received 0.2% ropivacaine via a catheter in the adductor canal administered as either repeated intermittent boluses (21 mL/3 h) or continuous infusion (7 mL/h). The primary outcome was total (postoperative day [POD], 0-2) opioid consumption (mg), administered as patient-controlled analgesia. Pain, ambulation, and quadriceps muscle strength were secondary outcomes. RESULTS: We randomized 110 patients, of whom 107 were analyzed. Total opioid consumption (POD, 0-2) was a median (range) of 23 mg (0-139) in the bolus group and 26 mg (3-120) in the infusion group (estimated median difference, 4 mg; 95% confidence interval [CI], -13 to 5; P = .29). Linear mixed-model analyses revealed no difference in pain during knee flexion (mean difference, 2.6 mm; 95% CI, -2.9 to 8.0) or at rest (mean difference, 1.7 mm; 95% CI, -1.5 to 4.9). Patients in the bolus group had improved quadriceps sparing on POD 2 (median difference, 7.4%; 95% CI, 0.5%-15.5%). However, this difference was not present on POD 1 or reflected in the ambulation tests (P > .05). CONCLUSIONS: Changing the mode of administration for an ACB from continuous infusion to repeated intermittent boluses did not decrease opioid consumption, pain, nor mobility.

The Effect of Local Anesthetic Volume Within the Adductor Canal on Quadriceps Femoris Function Evaluated by Electromyography: A Randomized, Observer- and Subject-Blinded, Placebo-Controlled Study in Volunteers.

BACKGROUND: Single-injection adductor canal block (ACB) provides analgesia after knee surgery. Which nerves that are blocked by an ACB and what influence-if any-local anesthetic volume has on the effects remain undetermined. We hypothesized that effects on the nerve to the vastus medialis muscle (which besides being a motor nerve innervates portions of the knee) are volume-dependent. METHODS: In this assessor- and subject-blinded randomized trial, 20 volunteers were included. On 3 separate days, subjects received an ACB with different volumes (10, 20, and 30 mL) of lidocaine 1%. In addition, they received a femoral nerve block and a placebo ACB. The effect on the vastus medialis (primary endpoint) and the vastus lateralis was evaluated using noninvasive electromyography (EMG). Quadriceps femoris muscle strength was evaluated using a dynamometer. RESULTS: There was a statistically significant difference in EMG response from the vastus medialis, dependent on volume. Thirty-five percent (95% confidence interval [CI], 18-57) of the subjects had an affected vastus medialis after an ACB with 10 mL compared with 84% (95% CI, 62-94) following 20 mL (P = 0.03) and 100% (95% CI, 84-100) when 30 mL was used (P = 0.0001). No statistically significant differences were found between volume and effect on the vastus lateralis (P = 0.81) or in muscle strength (P = 0.15). CONCLUSIONS: For ACB, there is a positive correlation between local anesthetic volume and effect on the vastus medialis muscle. Despite the rather large differences in EMG recordings, there were no statistically significant differences in quadriceps femoris muscle strength. Subsequent clinical studies comparing different volumes in a surgical setting, powered to show differences not only in analgesic efficacy, but also in adverse events, are required.

The Isolated Effect of Adductor Canal Block on Quadriceps Femoris Muscle Strength After Total Knee Arthroplasty: A Triple-Blinded, Randomized, Placebo-Controlled Trial with Individual Patient Analysis.

BACKGROUND: Using peripheral nerve block after total knee arthroplasty (TKA), without impeding mobility, is challenging. We hypothesized that the analgesic effect of adductor canal block (ACB) could increase the maximum voluntary isometric contraction (MVIC) of the quadriceps femoris muscle after TKA. METHODS: We included 64 patients on the first postoperative day. Group A received an ACB with 30 mL ropivacaine 0.75% at t0 and with 30 mL saline 60 minutes later (t60). Group B received the treatment in the opposite order. The primary end point was the difference between groups in MVIC at t60, expressed as a percentage of postoperative preblock values. In this manner, the effect of the ACB could be isolated from the detrimental effect on muscle strength caused by the surgery. Secondary end points were differences between groups in mobility and pain scores. We planned a subgroup analysis dividing patients according to preblock pain scores during knee flexion. RESULTS: At t60, MVIC was higher in group A, with a median of 170% (95% confidence interval [CI], 147-231) of preblock values compared with 93% (95% CI, 82-98) in group B (P < 0.0001). No statistically significant differences were found in the Timed Up and Go (TUG) test. Three patients lost the ability to perform the TUG test in group A. At t60, differences in visual analog scale pain were in favor of group A; 12 mm (95% CI, 6-18) at rest, 14 mm (95% CI, 5-22) during knee flexion, and 18 mm (95% CI, 10-26) during the TUG test. CONCLUSIONS: ACB improves quadriceps femoris muscle strength, but whether this translates into enhanced mobility is not clearly supported by this study.

Limited knowledge of lipid rescue therapy in local anaesthetic systemic toxicity.

INTRODUCTION: There is increasing evidence to support the use of intravenous lipid emulsion (ILE) in the management of local anaesthetic systemic toxicity (LAST) and non-local anaesthetic lipophilic-drug poisoning. This trend is supported by the Association of Anaesthetists of Great Britain and Ireland's latest guidelines on LAST treatment. Similar national guidelines have yet to be introduced in Denmark. The aim of the present study was to study the adoption of lipid rescue therapy in Denmark. MATERIAL AND METHODS: All Danish hospitals with an attending anaesthesiologist (no. 38) were contacted by phone. A total of 34 attending anaesthesiologists (AAs) participated in the systematic telephone survey. RESULTS: A total of 22 (65%) of the AAs were aware of use of ILE in the management of LAST. One (3%) had knowledge of ILE treatment for non-local anaesthetic-drug poisoning. Eight (24%) had access to local guidelines on lipid rescue therapy. The same eight AAs also knew where to find ILE. None of the hospitals lacking guidelines had taken an active stand against the treatment. CONCLUSION: Patients with toxic reactions who could potentially benefit from ILE will not be offered lipid rescue therapy in 26 of 34 hospitals (76%)--either because the AA is not aware of this treatment modality, or due to absence of either guidelines or ILE. To improve the availability of lipid rescue therapy, more hospitals need to develop emergency packs containing ILE and guidelines. Introduction of national guidelines on lipid rescue therapy would probably accelerate this process.

[Intravenous administration of lipids in poisoning caused by local analgesics]. / Intravenøs administration af lipid ved forgiftning med lipofilt laegemiddel.

OBJECTIVE: To draw attention to the use of intravenous lipids in the treatment of cardiac arrests caused by overdosage of lipophilic drugs. Case reports and animal studies have shown beneficial use of lipids in severe intoxication. The literature is reviewed. CONCLUSION: Lipids have a place in the treatment of severe cardiac events caused by local analgesics for regional anaesthesia. Lipids should be readily available when regional anaesthesia is performed. National guidelines should be prepared. Lipids may also be an option in the treatment of intoxication with other lipophilic drugs.