Perineural Local Anesthetic and Adjuvant Action: The Meaning of an Ex Vivo Data Set for Efficacy and Safety

Efficacy of multimodal analgesia with perineural buprenorphine or dexmedetomidine for surgeries performed under ultrasound-guided infraclavicular brachial plexus block

Background and Aims:

Perineural adjuvants when used as a part of multimodal analgesia (MMA) will maximize the quality and duration of analgesia of the nerve blocks. In the present study, we compared the duration of postoperative analgesia and other block characteristics of two groups of MMA comprising either perineural buprenorphine or dexmedetomidine in the upper limb surgeries performed under ultrasound-guided (US-guided) infraclavicular brachial plexus blocks.

Material and Methods:

A total of 100 adult patients undergoing elective upper limb orthopedic surgery under US-guided infraclavicular brachial plexus block were randomly divided into two groups. Group I received 150 μg buprenorphine and Group II received 50 μg dexmedetomidine, perineurally added to 30 ml of 0.375% bupivacaine. Both groups also received tramadol 50 mg IV, dexamethasone 4 mg IV, and diclofenac 75 mg infusion as part of MMA. Both groups were compared for the duration of postoperative analgesia, block characteristics, and incidence of adverse effects.

Results:

The duration of postoperative analgesia was significantly prolonged in Group II (937.6 ± 179.1 min vs 1280.4 ± 288.8 min). The onset of sensory and motor blocks was shorter in Group II (P < 0.05). The duration of sensory and motor blocks was significantly prolonged in Group II (P < 0.05). The number of rescue analgesics required in the first 24 hours was less in Group II (1.98 ± 0.62 vs 0.8 ± 0.64). Although heart rate and blood pressure levels were lower in Group II, all patients were hemodynamically stable.

Conclusion:

For surgeries under brachial plexus block, perineural dexmedetomidine when used as a part of MMA provided a prolonged duration of postoperative analgesia and improved block characteristics than perineural buprenorphine.

Comparison of the effect of three different adjuvants on the analgesic duration of single injection interscalene brachial plexus block: a prospective, randomized, triple blinded clinical trial

BACKGROUND AND OBJECTIVES

Use of regional anesthesia can result in faster recovery and better patient satisfaction. Addition of perineural adjuncts to local anesthetics may improve the duration of analgesia, but there is a paucity of data comparing them in a single randomized trial. We compared the effects of three adjuncts clonidine, dexamethasone, and buprenorphine, on the duration of analgesia of interscalene brachial plexus block.

METHODS

160 patients, undergoing elective shoulder surgery, were randomized to four groups to receive an interscalene block with one of the following solutions: ropivacaine alone, ropivacaine with clonidine 75 µg, ropivacaine with dexamethasone 8 mg, or ropivacaine with buprenorphine 300 µg. The primary outcome variable was the duration of analgesia; secondary outcome measures were time to onset of the block, and the duration of sensory and motor blocks.

RESULTS

There was no statistically significant difference in the total analgesia time among the four groups; p=0.11. The pairwise comparison in analgesic time and 99% CI were: control versus clonidine (-1.94 hours (-7.33 to 3.12)), control versus dexamethasone (-4.16 hours (-9.50 to 0.58)) and control versus buprenorphine (-1.1 hours (-5.34 to 3.23)). There was no differences in block set-up time, or total sensory and motor block duration among the groups.

CONCLUSION

There was no significant improvement in the duration of analgesia with addition of any of the three adjuncts to interscalene blocks. However, there was a larger than expected variability in patient response, hence the study may have been underpowered for the primary outcome.

IV and Perineural Dexmedetomidine Similarly Prolong the Duration of Analgesia after Interscalene Brachial Plexus Block

Background

Perineural and IV dexmedetomidine have each been suggested to prolong the duration of analgesia when administered in conjunction with peripheral nerve blocks. In the first randomized, triple-masked, placebo-controlled trial to date, the authors aimed to define and compare the efficacy of perineural and IV dexmedetomidine in prolonging the analgesic duration of single-injection interscalene brachial plexus block (ISB) for outpatient shoulder surgery.

Methods

Ninety-nine patients were randomized to receive ISB using 15 ml ropivacaine, 0.5%, with 0.5 μg/kg dexmedetomidine administered perineurally (DexP group), intravenously (DexIV group), or none (control group). The authors sequentially tested the joint hypothesis that dexmedetomidine prolongs the duration of analgesia and reduces the 24-h cumulative postoperative morphine consumption. Motor blockade, pain severity, hemodynamic variations, opioid-related side effects, postoperative neurologic symptoms, and patient satisfaction were also evaluated.

Results

Ninety-nine patients were analyzed. The duration of analgesia was 10.9 h (10.0 to 11.8 h) and 9.8 h (9.0 to 10.6 h) for the DexP and DexIV groups, respectively, compared with 6.7 h (5.6 to 7.8) for the control group (P &lt; 0.001). Dexmedetomidine also reduced the 24-h cumulative morphine consumption to 63.9 mg (58.8 to 69.0 mg) and 66.2 mg (60.6 to 71.8 mg) for the DexP and DexIV groups, respectively, compared with 81.9 mg (75.0 to 88.9 mg) for the control group (P &lt; 0.001). DexIV was noninferior to DexP for these outcomes. Both dexmedetomidine routes reduced the pain and opioid consumption up to 8 h postoperatively and did not prolong the duration of motor blockade.

Conclusion

Both perineural and IV dexmedetomidine can effectively prolong the ISB analgesic duration and reduce the opioid consumption without prolonging motor blockade.

Additives to local anesthetics for peripheral nerve blocks or local anesthesia: a review of the literature

SUMMARY 

A multitude of studies have focused on individual additives to local anesthetics and their effect on quality, onset, duration, spread and selectivity, as well as the potential toxic effects of their use. This review aims to give a broad overview of the current evidence in this developing field, based on beneficial and adverse effects of these drugs. We discuss the limitations of the available data and hope to convey implications and future perspectives for clinicians and researchers alike.

Facilitatory effects of perineural dexmedetomidine on neuraxial and peripheral nerve block: a systematic review and meta-analysis

Nerve blocks improve postoperative analgesia, but their benefits may be short-lived. This quantitative review examines whether perineural dexmedetomidine as a local anaesthetic (LA) adjuvant for neuraxial and peripheral nerve blocks can prolong the duration of analgesia compared with LA alone. All randomized controlled trials (RCTs) comparing the effect of dexmedetomidine as an LA adjuvant to LA alone on neuraxial and peripheral nerve blocks were reviewed. Sensory block duration, motor block duration, block onset times, analgesic consumption, time to first analgesic request, and side-effects were analysed.

RESULTS

were combined using random-effects modelling. A total of 516 patients were analysed from nine RCTs. Five trials investigated dexmedetomidine as part of spinal anaesthesia and four as part of a brachial plexus (BP) block. Sensory block duration was prolonged by 150 min [95% confidence interval (CI): 96, 205, P<0.00001] with intrathecal dexmedetomidine. Perineural dexmedetomidine used in BP block may prolong the mean duration of sensory block by 284 min (95% CI: 1, 566, P=0.05), but this difference did not reach statistical significance. Motor block duration and time to first analgesic request were prolonged for both intrathecal and BP block. Dexmedetomidine produced reversible bradycardia in 7% of BP block patients, but no effect on the incidence of hypotension. No patients experienced respiratory depression. Dexmedetomidine is a potential LA adjuvant that can exhibit a facilitatory effect when administered intrathecally as part of spinal anaesthesia or peripherally as part of a BP block. However, there are presently insufficient safety data to support perineural dexmedetomidine use in the clinical setting.