Combined Dexamethasone and Dexmedetomidine as Adjuncts to Popliteal and Saphenous Nerve Blocks in Patients Undergoing Surgery of the Foot or Ankle: A Randomized, Blinded, Placebo-controlled Clinical Trial.

BACKGROUND: Both dexamethasone and dexmedetomidine increase the duration of analgesia of peripheral nerve blocks. The authors hypothesized that combined intravenous dexamethasone and intravenous dexmedetomidine would result in a greater duration of analgesia when compared with intravenous dexamethasone alone and placebo. METHODS: The authors randomly allocated participants undergoing surgery of the foot or ankle under general anesthesia and with a combined popliteal (sciatic) and saphenous nerve block to a combination of 12 mg dexamethasone and 1 µg/kg dexmedetomidine, 12 mg dexamethasone, or placebo (saline). The primary outcome was the duration of analgesia measured as the time from block performance until the first sensation of pain in the surgical area as reported by the participant. The authors predefined a 33% difference in the duration of analgesia as clinically relevant. RESULTS: A total of 120 participants from two centers were randomized and 119 analyzed for the primary outcome. The median [interquartile range] duration of analgesia was 1,572 min [1,259 to 1,715] with combined dexamethasone and dexmedetomidine, 1,400 min [1,133 to 1,750] with dexamethasone alone, and 870 min [748 to 1,138] with placebo. Compared with placebo, the duration was greater with combined dexamethasone and dexmedetomidine (difference, 564 min; 98.33% CI, 301 to 794; P < 0.001) and with dexamethasone (difference, 489 min; 98.33% CI, 265 to 706; P < 0.001). The prolongations exceeded the authors' predefined clinically relevant difference. The duration was similar when combined dexamethasone and dexmedetomidine was compared with dexamethasone alone (difference, 61 min; 98.33% CI, -222 to 331; P = 0.614). CONCLUSIONS: Dexamethasone with or without dexmedetomidine increased the duration of analgesia in patients undergoing surgery of the foot or ankle with a popliteal (sciatic) and saphenous nerve block. Combined dexamethasone and dexmedetomidine did not increase the duration of analgesia when compared with dexamethasone.

Risk factors for multimodal conservative approach failure before bariatric surgery.

BACKGROUND: A multimodal conservative approach (MCA) is internationally recommended prior to bariatric surgery for the majority of patients. This research aimed to identify risk factors for therapy failure within the MCA. METHODS: This study was conducted in a German bariatric obesity centre. Patients who underwent a 3- to 6-month preoperative MCA from November 2019 to October 2020 were prospectively recorded and analysed. MCA included dietary and movement therapy, psychological and endocrinological referral and connection to a patient support group. The change in BMI was considered the main parameter for therapeutic success. Explanatory factors were evaluated for this outcome of interest and included physical and mental well-being (SF-36), perceived stress (DASS-21), social and economic situation and educational background (SOEP). RESULTS: Out of 413 eligible patients, 209 were analysed. Overall, patients gained BMI (average gain 0.23 kg/m² (s.d. 1.44 kg/m²)) during the preoperative MCA. Diverse social, demographic and economic and health properties did not influence the course of the therapy. There was a significant positive correlation between successful loss of BMI and physical well-being (ß = 0.03, 95% c.i. 0.01 to 0.04, P < 0.0001) and a negative correlation between mental well-being (ß = -0.02, 95% c.i. -0.004 to -0.001, P = 0.001) as well as self-perceived stress (ß = -0.05, 95% c.i. -0.09 to -0.01, P = 0.019), although these effects were small and did not affect the overall trend of gaining BMI during MCA. CONCLUSION: The current therapeutic approach of preoperative conservative treatment within the multimodal concept of bariatric treatment fails to achieve its intended outcome. A different conservative weight loss programme from the pre-bariatric setting, which should focus on a surgical preparation, is therefore recommended.

Effects of combined dexamethasone and dexmedetomidine as adjuncts to peripheral nerve blocks: a systematic review with meta-analysis and trial sequential analysis.

BACKGROUND/IMPORTANCE: The effects of combining dexamethasone and dexmedetomidine on block duration are unclear. OBJECTIVE: To investigate the effects of combining dexamethasone and dexmedetomidine on block duration. EVIDENCE REVIEW: Systematic review of randomized controlled trials (RCTs) from Medline, Embase, CENTRAL, CINAHL, the Web of Science, and BIOSIS until June 8, 2023. RCTs with adults undergoing surgery with a peripheral nerve block randomized to combined dexamethasone and dexmedetomidine versus placebo or other adjuncts were eligible. Primary outcome was duration of analgesia. We performed meta-analysis, trial sequential analysis, risk of bias-2, and Grading Recommendations Assessment, Development, and Evaluation assessment. FINDINGS: We included 9 RCTs with 14 eligible comparisons. The combination of dexamethasone and dexmedetomidine was compared with placebo in three RCTs (173 participants), dexamethasone in seven (569 participants), and dexmedetomidine in four (281 participants). The duration of analgesia was likely increased with the combination versus placebo (mean difference 460 min, 95% CI 249 to 671) and versus dexmedetomidine (mean difference 388 min, 95% CI 211 to 565). The duration was likely similar with the combination versus dexamethasone (mean difference 50 min, 95% CI -140 to 239). The certainty of the evidence was moderate because most trials were at high risk of bias. CONCLUSIONS: Combined dexamethasone and dexmedetomidine likely increased the duration of analgesia when compared with placebo and dexmedetomidine. The combination likely provided a similar duration of analgesia as dexamethasone. Based on this systematic review, it seems reasonable to use dexamethasone as the sole adjunct if the goal is to increase the duration of analgesia.

Perineural and Systemic Dexamethasone and Ulnar Nerve Block Duration: A Randomized, Blinded, Placebo-controlled Trial in Healthy Volunteers.

BACKGROUND: The authors hypothesized that both perineural and systemic dexamethasone as adjuncts to bupivacaine increase the duration of an ulnar nerve block compared with bupivacaine alone, and that systemic dexamethasone is noninferior to perineural dexamethasone. METHODS: The authors performed bilateral ulnar nerve blocks with 3 ml bupivacaine 5 mg/ml in 16 healthy volunteers on two trial days. According to randomization, subjects received adjunct treatment with 1 ml dexamethasone 4 mg/ml + 1 ml of saline (perineural condition) in one arm and 2 ml saline in the other arm (systemic condition, through absorption and redistribution of the contralaterally administered perineural dexamethasone) on one trial day; and 2 ml saline in one arm (placebo condition) and 2 ml of lidocaine in the other arm (lidocaine condition) on the other trial day. The primary outcome was the duration of the sensory nerve block assessed by temperature discrimination. RESULTS: Mean sensory block duration was 706 ± 94 min for the perineural condition, 677 ± 112 min for the systemic condition, and 640 ± 121 min for the placebo condition. The duration of the sensory nerve block was greater with perineural dexamethasone versus placebo (mean difference 66 min (95% CI, 23 to 108). Block duration was similar between systemic dexamethasone and placebo (mean difference 36 min; 95% CI, -30 to 103). CONCLUSIONS: Perineural dexamethasone as an adjunct to bupivacaine in healthy volunteers resulted in a greater duration of an ulnar nerve block when compared with placebo. Systemic dexamethasone resulted in a similar duration as placebo.

Alpha2 -receptor agonists as adjuvants for brachial plexus nerve blocks-A systematic review with meta-analyses.

BACKGROUND: We review the efficacy and safety of dexmedetomidine and clonidine as perineural or systemic adjuvants for brachial plexus blocks (BPB). METHODS: We included randomised controlled trials on upper limb surgery with BPBs in adults, comparing dexmedetomidine with clonidine or either drug with placebo. The primary outcome was duration of analgesia. Secondary outcomes included adverse and serious adverse events. The review was conducted using Cochrane standards, trial sequential analyses (TSA) and Grading of Recommendations Assessment, Development and Evaluation (GRADE). RESULTS: We included 101 trials with 6248 patients. Overall, duration of analgesia was prolonged with both clonidine (176 min [TSA adj. 95% CI: 118, 205, p < .00001; 33 trials]) and dexmedetomidine (292 min [TSA adj. 95% CI: 245 329, p < .00001; 53 trials]), but was longer for dexmedetomidine than clonidine (205 min [TSA adj. 95% CI: 157, 254, p < .00001; 19 trials]). Compared with placebo, dexmedetomidine was associated with bradycardia (RR 4.2 [95% CI 2.2, 8.3]), and both clonidine (RR 4.5 [95% CI 1.1, 18.3]) and dexmedetomidine (RR 3.9 [95% CI 2.0, 7.5]) were associated with hypotension. Serious adverse events were mostly related to block technique. GRADE-rated quality of evidence was low or very low. CONCLUSION: Alpha2-receptor agonists used as adjuvants for BPBs lead to a prolonged duration of analgesia, with dexmedetomidine as the most efficient. Alpha2-receptor agonists were associated with increased risk of cardiovascular adverse events. The quality of evidence was low to very low.

Sphenopalatine ganglion block for the treatment of postdural puncture headache: a randomised, blinded, clinical trial.

BACKGROUND: Current treatment of postdural puncture headache includes epidural blood patch (EBP), which is invasive and may result in rare but severe complications. Sphenopalatine ganglion block is suggested as a simple, minimally invasive treatment for postdural puncture headache. We aimed to investigate the analgesic effect of a transnasal sphenopalatine ganglion block with local anaesthetic vs saline. METHODS: We conducted a blinded, randomised clinical trial including adults fulfilling the criteria for EBP. Participants received a sphenopalatine ganglion block bilaterally with 1 ml of either local anaesthetic (lidocaine 4% and ropivacaine 0.5%) or placebo (saline). Primary outcome was pain in upright position 30 min post-block, measured on a 0-100 mm VAS. RESULTS: We randomised 40 patients with an upright median pain intensity of 74 and 84 mm in the local anaesthetic and placebo groups at baseline, respectively. At 30 min after sphenopalatine ganglion block, the median pain intensity in upright position was 26 mm in the local anaesthetic group vs 37 mm in the placebo group (estimated median difference: 5 mm; 95% confidence interval: -14 to 21; P=0.53). In the local anaesthetic group, 50% required an EBP compared with 45% in the placebo group (P=0.76). CONCLUSIONS: Administration of a sphenopalatine ganglion block with local anaesthetic had no statistically significant effect on pain intensity after 30 min compared with placebo. However, pain was reduced and EBP was avoided in half the patients of both groups, which suggests a major effect not necessarily attributable to local anaesthetics. CLINICAL TRIAL REGISTRATION: NCT03652714.

[Sphenopalatine ganglion block for treatment of post-dural puncture headache].

In this review, we discuss transnasal sphenopalatine ganglion (SPG) block: a new, simple and minimally invasive procedure for the treatment of post-dural puncture headache (PDPH) by applying local anaesthesia through the patient's nose to the nasopharynx. PDPH is a severe and disabling complication sometimes caused by lumbar puncture or unintentional dural puncture. Current treatment includes epidural blood patch, which is an invasive and resource-demanding procedure with the potential of causing severe complications such as infection and paralysis. SPG block seems to be effective and may ease and improve the treatment of PDPH.

Ultrasound-guided percutaneous peripheral nerve stimulation: neuromodulation of the suprascapular nerve and brachial plexus for postoperative analgesia following ambulatory rotator cuff repair. A proof-of-concept study.

BACKGROUND AND OBJECTIVES: Percutaneous peripheral nerve stimulation (PNS) is an analgesic modality involving the insertion of a lead through an introducing needle followed by the delivery of electric current. This modality has been reported to treat chronic pain as well as postoperative pain following knee and foot surgery. However, it remains unknown if this analgesic technique may be used in ambulatory patients following upper extremity surgery. The purpose of this proof-of-concept study was to investigate various lead implantation locations and evaluate the feasibility of using percutaneous brachial plexus PNS to treat surgical pain following ambulatory rotator cuff repair in the immediate postoperative period. METHODS: Preoperatively, an electrical lead (SPR Therapeutics, Cleveland, Ohio) was percutaneously implanted to target the suprascapular nerve or brachial plexus roots or trunks using ultrasound guidance. Postoperatively, subjects received 5 min of either stimulation or sham in a randomized, double-masked fashion followed by a 5 min crossover period, and then continuous stimulation until lead removal postoperative days 14-28. RESULTS: Leads (n=2) implanted at the suprascapular notch did not appear to provide analgesia, and subsequent leads (n=14) were inserted through the middle scalene muscle and placed to target the brachial plexus. Three subjects withdrew prior to data collection. Within the recovery room, stimulation did not decrease pain scores during the first 40 min of the remaining subjects with brachial plexus leads, regardless of which treatment subjects were randomized to initially. Seven of these 11 subjects required a single-injection interscalene nerve block for rescue analgesia prior to discharge. However, subsequent average resting and dynamic pain scores postoperative days 1-14 had a median of 1 or less on the Numeric Rating Scale, and opioid requirements averaged less than 1 tablet daily with active stimulation. Two leads dislodged during use and four fractured on withdrawal, but no infections, nerve injuries, or adverse sequelae were reported. CONCLUSIONS: This proof-of-concept study demonstrates that ultrasound-guided percutaneous PNS of the brachial plexus is feasible for ambulatory shoulder surgery, and although analgesia immediately following surgery does not appear to be as potent as local anesthetic-based peripheral nerve blocks, the study suggests that this modality may provide analgesia and decrease opioid requirements in the days following rotator cuff repair. Therefore, it suggests that a subsequent, large, randomized clinical trial with an adequate control group is warranted to further investigate this therapy in the management of surgical pain in the immediate postoperative period. However, multiple technical issues remain to be resolved, such as the optimal lead location, insertion technique, and stimulating protocol, as well as preventing lead dislodgment and fracture. TRIAL REGISTRATION NUMBER: NCT02898103.

Systemic dexmedetomidine is not as efficient as perineural dexmedetomidine in prolonging an ulnar nerve block.

BACKGROUND: We tested the joint hypotheses that both perineural and systemic dexmedetomidine prolong the duration of an ulnar nerve block (UNB) compared with ropivacaine alone and that systemic dexmedetomidine is noninferior compared with perineural dexmedetomidine in block prolongation. METHODS: We performed bilateral UNBs in 22 healthy volunteers on two separate days. On the first day, each arm was randomized to either 4 mL ropivacaine 5 mg/mL+1 mL dexmedetomidine 100 µg/mL (Perineural) or 4 mL ropivacaine 5 mg/mL+1 mL saline (Systemic). On the subsequent treatment day, each arm was randomized to 1 mL of saline plus 4 mL of ropivacaine at either 7.5 mg/mL(HiRopi) or 5 mg/mL (NoDex). The primary outcome measure was the duration of sensory block assessed by mechanical discrimination. RESULTS: Mean sensory block duration was longer in both the Perineural (14.4 hours, 95% CI 13.1 to 15.6) and Systemic treatments (9.2 hours, 95% CI 8.6 to 9.8) compared with the NoDex treatment (7.1 hours, 95% CI 6.6 to 7.6) (p<0.0001 for both). Systemic dexmedetomidine was inferior (not noninferior) compared with perineural dexmedetomidine, as the 95% CI of the difference (mean difference 5.2 hour, 95% CI 4.2 to 6.1) exceeded the noninferiority limit of 3.6 hour. Onset time did not differ among the groups. The other test modalities demonstrated similar block durations as the primary outcome. CONCLUSIONS: Adding dexmedetomidine perineurally to ropivacaine doubles the duration of an UNB. Systemic dexmedetomidine also prolongs the duration of UNB, but has less of an effect compared with the perineural route. TRIAL REGISTRATION NUMBER: NCT03222323.

Ultrasound-Guided Percutaneous Peripheral Nerve Stimulation: Neuromodulation of the Femoral Nerve for Postoperative Analgesia Following Ambulatory Anterior Cruciate Ligament Reconstruction: A Proof of Concept Study.

OBJECTIVES: The purpose of this prospective proof of concept study was to investigate the feasibility of using percutaneous peripheral nerve stimulation of the femoral nerve to treat pain in the immediate postoperative period following ambulatory anterior cruciate ligament reconstruction with a patellar autograft. MATERIALS AND METHODS: Preoperatively, an electrical lead (SPRINT, SPR Therapeutics, Inc., Cleveland, OH, USA) was percutaneously implanted with ultrasound guidance anterior to the femoral nerve caudad to the inguinal crease. Within the recovery room, subjects received 5 min of either stimulation or sham in a randomized, double-masked fashion followed by a 5-min crossover period, and then continuous active stimulation until lead removal postoperative Day 14-28. Statistics were not applied to the data due to the small sample size of this feasibility study. RESULTS: During the initial 5-min treatment period, subjects randomized to stimulation (n = 5) experienced a slight downward trajectory (decrease of 7%) in their pain over the 5 min of treatment, while those receiving sham (n = 5) reported a slight upward trajectory (increase of 4%) until their subsequent 5-min stimulation crossover, during which time they also experienced a slight downward trajectory (decrease of 11% from baseline). A majority of subjects (80%) used a continuous adductor canal nerve block for rescue analgesia (in addition to stimulation) during postoperative Days 1-3, after which the median resting and dynamic pain scores remained equal or less than 1.5 on the numeric rating scale, respectively, and the median daily opioid consumption was less than 1.0 tablet. CONCLUSIONS: This proof of concept study demonstrates that percutaneous femoral nerve stimulation is feasible for ambulatory knee surgery; and suggests that this modality may be effective in providing analgesia and decreasing opioid requirements following anterior cruciate ligament reconstruction. clinicaltrials.gov: NCT02898103.

Ultrasound-Guided Percutaneous Peripheral Nerve Stimulation: Neuromodulation of the Sciatic Nerve for Postoperative Analgesia Following Ambulatory Foot Surgery, a Proof-of-Concept Study.

BACKGROUND AND OBJECTIVES: Percutaneous peripheral nerve stimulation (PNS) is an analgesic modality involving the insertion of a lead through an introducing needle followed by the delivery of electric current. This modality has been reported to treat chronic pain as well as postoperative pain the day following knee surgery. However, it remains unknown if this analgesic technique may be used in ambulatory subjects following foot procedures beginning within the recovery room immediately following surgery, and with only short series of patients reported to date, the only available data are derived from strictly observational studies. The purposes of this proof-of-concept study were to demonstrate the feasibility of using percutaneous sciatic nerve PNS to treat postoperative pain following ambulatory foot surgery in the immediate postoperative period and provide the first available data from a randomized controlled study design to provide evidence of analgesic effect. METHODS: Preoperatively, an electrical lead (SPRINT; SPR Therapeutics, Inc, Cleveland, Ohio) was percutaneously inserted posterior to the sciatic nerve between the subgluteal region and bifurcation with ultrasound guidance. Following hallux valgus osteotomy, subjects received 5 minutes of either stimulation or sham in a randomized, double-masked fashion followed by a 5-minute crossover period and then continuous stimulation until lead removal on postoperative days 14 to 28. RESULTS: During the initial 5-minute treatment period, subjects randomized to stimulation (n = 4) experienced a downward trajectory in their pain over the 5 minutes of treatment, whereas those receiving sham (n = 3) reported no such change until their subsequent 5-minute stimulation crossover. During the subsequent 30 minutes of stimulation, pain scores decreased to 52% of baseline (n = 7). Three subjects (43%) used a continuous popliteal nerve block for rescue analgesia during postoperative days 0 to 3. Overall, resting and dynamic pain scores averaged less than 1 on the numeric rating scale, and opioid use averaged less than 1 tablet daily with active stimulation. One lead dislodged, 2 fractured during use, and 1 fractured during intentional withdrawal. CONCLUSIONS: This proof-of-concept study demonstrates that percutaneous sciatic nerve PNS is feasible for ambulatory foot surgery and suggests that this modality provides analgesia and decreases opioid requirements following hallux valgus procedures. However, lead dislodgement and fracture are concerns. CLINICAL TRIAL REGISTRATION: This study was registered at Clinicaltrials.gov, identifier NCT02898103.

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.

Clonidine used as a perineural adjuvant to ropivacaine, does not prolong the duration of sensory block when controlling for systemic effects: A paired, blinded, randomized trial in healthy volunteers.

BACKGROUND: Clonidine used as an adjuvant to ropivacaine have been shown to prolong the duration of peripheral nerve blocks. The mechanism of action remains unclear. We hypothesized, that clonidine used as an adjuvant to ropivacaine extends the duration of an adductor canal block (ACB) by a peripheral mechanism, compared to ropivacaine alone when controlling for systemic effects. METHODS: We conducted a paired, blinded, randomized trial in healthy volunteers. Participants received bilateral ACBs containing 20 ml ropivacaine 0.5% + 1 ml clonidine 150µg/ml in one leg and 20 ml ropivacaine 0.5% + 1 ml saline in the other leg. The primary outcome measure was duration of sensory block assessed by temperature sensation (alcohol swab). Secondary outcome measures were duration of sensory block assessed by: pinprick, maximum pain during tonic heat stimulation, warmth detection threshold and heat pain detection threshold. RESULTS: We enrolled 21 volunteers and all completed the trial. There was no difference in duration of sensory block assessed with an alcohol swab: Mean duration in the leg receiving ropivacaine + clonidine was 19.4h (SD 2.7) compared to 19.3h (SD 2.4) in the leg receiving ropivacaine + placebo with a mean difference of 0.1h (95% CI: -1.0 to 1.3), P = 0.83. No differences in block duration were detected when assessed by: Pinprick, mean difference 0.0 h (95% CI: -1.3 to 1.3), maximum pain during tonic heat stimulation, mean difference -0.7 h (95% CI: -2.1 to 0.8), warmth detection threshold, mean difference -0.1 h (95% CI: -1.8 to 1.6) or heat pain detection threshold, mean difference -0.2 h (95% CI: -1.7 to 1.4). CONCLUSIONS: Administering clonidine perineurally as an adjuvant to ropivacaine in an ACB did not prolong the duration of sensory block in a setup controlling for systemic effects of clonidine.

Does Dexmedetomidine Have a Perineural Mechanism of Action When Used as an Adjuvant to Ropivacaine?: A Paired, Blinded, Randomized Trial in Healthy Volunteers.

BACKGROUND: Dexmedetomidine used as an adjuvant to local anesthetics may prolong the duration of peripheral nerve blocks. Whether this is mediated by a perineural or systemic mechanism remains unknown. The authors hypothesized that dexmedetomidine has a peripheral mechanism of action. METHODS: The authors conducted a randomized, paired, triple-blind trial in healthy volunteers. All received bilateral saphenous nerve blocks with 20 ml ropivacaine, 0.5%, plus 1 ml dexmedetomidine, 100 µg/ml, in one thigh and 20 ml ropivacaine 0.5% plus 1 ml saline in the other thigh. The primary outcome measure was the duration of block assessed by temperature sensation (alcohol swab). The secondary outcome measure was the duration of block assessed by pinprick, pain during tonic heat stimulation, warmth detection threshold, and heat pain detection threshold. RESULTS: All 21 enrolled volunteers completed the trial. The mean duration of block assessed by temperature sensation in the leg receiving ropivacaine plus dexmedetomidine was 22 h (95% CI, 21 to 24) compared to 20 h (95% CI, 19 to 21) in the leg receiving ropivacaine plus placebo with a mean difference of 2 h (95% CI, 1 to 3; P = 0.001). The duration of block was also significantly longer in the leg receiving dexmedetomidine when assessed by pinprick, pain during tonic heat stimulation, and warmth detection threshold but not heat pain detection threshold. One participant experienced numbness in an area in the leg receiving dexmedetomidine. CONCLUSIONS: Dexmedetomidine prolongs the duration of a saphenous nerve block by a peripheral mechanism when controlling for systemic effects but not necessarily to a clinically relevant extent.

Effect of Total Dose of Lidocaine on Duration of Adductor Canal Block, Assessed by Different Test Methods: A Report of Two Blinded, Randomized, Crossover Studies in Healthy Volunteers.

BACKGROUND: The binary aims of this study were to investigate the effect of total dose of lidocaine on duration of an adductor canal block (ACB) and to validate different methods used to assess nerve blocks. METHODS: We performed 2 blinded, randomized, controlled crossover trials, including healthy, young men. In study 1, 14 subjects received 4 ACBs with saline and 40, 80, and 160 mg lidocaine. In study 2, 14 new subjects received 2 ACBs with 100 and 300 mg lidocaine. We kept volume constant at 20 mL for all blocks, only altering concentration. ACB duration was assessed every hour postblock using mechanical (primary outcome) and temperature discrimination; warmth and heat pain detection thresholds; pain during heat stimulation; and tolerance to electrical current in the saphenous distribution. Finally, we measured quadriceps femoris muscle strength (clinical trial registration: NCT02172729). RESULTS: In study 1, block duration assessed by mechanical discrimination differed significantly when comparing the 40-mg dose with the 80-mg dose (mean difference, 1.15 hours; 99% confidence interval [CI], 0.38-2.09 hours) and with the 160-mg dose (mean difference, 0.92 ours; 99% CI, 0.17-1.62). However, there was no difference between the 80-mg and 160-mg doses (mean difference, -0.23 hour; 99% CI, -1.12 to 0.46 hours). Neither for the secondary outcomes were there any differences between the 80- and 160-mg doses (99% CI including 0). Because of 38% (5/13) failed blocks in the 40-mg group, we decided to perform study 2. In study 2, all but 1 test showed no difference in duration despite a 3-fold increase in dose. The temperature discrimination test showed 100% sensitivity and specificity for differentiating between the presence and absence of block and was the only test with scores >90% for both parameters. CONCLUSIONS: We did not find evidence that increasing the total dose of lidocaine may prolong duration of an ACB. The temperature discrimination test was the only test with scores >90% for both specificity and sensitivity.

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.

Continuous Adductor Canal Blocks: Does Varying Local Anesthetic Delivery Method (Automatic Repeated Bolus Doses Versus Continuous Basal Infusion) Influence Cutaneous Analgesia and Quadriceps Femoris Strength? A Randomized, Double-Masked, Controlled, Split-Body Volunteer Study.

BACKGROUND: It remains unknown whether continuous or scheduled intermittent bolus local anesthetic administration is preferable for adductor canal perineural catheters. Therefore, we tested the hypothesis that scheduled bolus administration is superior or noninferior to a continuous infusion on cutaneous knee sensation in volunteers. METHODS: Bilateral adductor canal catheters were inserted in 24 volunteers followed by ropivacaine 0.2% administration for 8 hours. One limb of each subject was assigned randomly to a continuous infusion (8 mL/h) or automated hourly boluses (8 mL/bolus), with the alternate treatment in the contralateral limb. The primary end point was the tolerance to electrical current applied through cutaneous electrodes in the distribution of the anterior branch of the medial femoral cutaneous nerve after 8 hours (noninferiority delta: -10 mA). Secondary end points included tolerance of electrical current and quadriceps femoris maximum voluntary isometric contraction strength at baseline, hourly for 14 hours, and again after 22 hours. RESULTS: The 2 administration techniques provided equivalent cutaneous analgesia at 8 hours because noninferiority was found in both directions, with estimated difference on tolerance to cutaneous current of -0.6 mA (95% confidence interval, -5.4 to 4.3). Equivalence also was found on all but 2 secondary time points. CONCLUSIONS: No evidence was found to support the hypothesis that changing the local anesthetic administration technique (continuous basal versus hourly bolus) when using an adductor canal perineural catheter at 8 mL/h decreases cutaneous sensation in the distribution of the anterior branch of the medial femoral cutaneous nerve.

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.

Adductor Canal Block With 10 mL Versus 30 mL Local Anesthetics and Quadriceps Strength: A Paired, Blinded, Randomized Study in Healthy Volunteers.

BACKGROUND AND OBJECTIVES: Adductor canal block (ACB) is predominantly a sensory nerve block, but excess volume may spread to the femoral triangle and reduce quadriceps strength. We hypothesized that reducing the local anesthetic volume from 30 to 10 mL may lead to fewer subjects with quadriceps weakness. METHODS: We performed a paired, blinded, randomized trial including healthy men. All subjects received bilateral ACBs with ropivacaine 0.1%; 10 mL in 1 leg and 30 mL in the other leg. The primary outcome was the difference in number of subjects with quadriceps strength reduced by more than 25% from baseline in 2 consecutive assessments. Secondary outcomes were quadriceps strength as a percentage of baseline at predefined time points, functional outcome assessed by the 30-Second Chair Stand Test (1 leg at a time), and sensory block. Clinicaltrials.gov Identifier: NCT01981746. RESULTS: We included and analyzed 26 subjects. For either volume, 2 subjects had a reduction in quadriceps strength by more than 25% from baseline (difference, 0%; 95% confidence interval, -13 to 13; P > 0.999). Similarly, we found no significant differences between volumes in quadriceps strength at any of the predefined time points or in sensory block. The only statistically significant difference between volumes was found in the 30-Second Chair Stand Test at 2 hours (P = 0.02), but this difference had disappeared at 4 hours (P = 0.06). CONCLUSIONS: Varying the volume of ropivacaine 0.1% used for ACB between 10 and 30 mL did not have a statistically significant or clinically relevant impact on quadriceps strength.

Effect of adductor canal block versus femoral nerve block on quadriceps strength, mobilization, and pain after total knee arthroplasty: a randomized, blinded study.

BACKGROUND AND OBJECTIVES: Total knee arthroplasty (TKA) is often associated with severe pain. Different regional anesthetic techniques exist, all with varying degrees of motor blockade. We hypothesized that pain relief provided by the adductor canal block (ACB) could increase functional muscle strength. METHODS: We included 50 TKA patients with severe movement-related pain; defined as having visual analog scale pain score of greater than 60 mm during active flexion of the knee. The ACB group received an ACB with ropivacaine 0.2% 30 mL and a femoral nerve block (FNB) with 30 mL saline. The FNB group received an ACB with 30 mL saline and an FNB with ropivacaine 0.2% 30 mL. We compared the effect of the ACB versus FNB on maximum voluntary isometric contraction of the quadriceps muscle relative to a postoperative baseline value. Secondary end points were differences between groups in ability to ambulate and changes in pain scores (Clinicaltrials.gov identifier NCT01922596). RESULTS: After block, the quadriceps maximum voluntary isometric contraction increased to 193% (95% confidence interval [CI], 143-288) of the baseline value in the ACB group and decreased to 16% (95% CI, 3-33) in the FNB group with an estimated difference of 178% (95% CI, 136-226), P < 0.0001. Pain scores were similar between groups. Before block, 2 of 25 patients in each group were unable to perform the Timed-Up-and-Go test; after block, this number increased to 7 of 25 in the FNB group and decreased to 0 of 25 in the ACB group. CONCLUSION: Adductor canal block provides a clinically relevant and statistically significant increase in quadriceps muscle strength for patients in severe pain after TKA.