Optimal dose of perineural dexmedetomidine to prolong analgesia after brachial plexus blockade: a systematic review and Meta-analysis of 57 randomized clinical trials

What Is the Role of Dexmedetomidine in Modern Anesthesia and Critical Care?

Dexmedetomidine's unique sedative properties have led to its widespread use. Dexmedetomidine has a beneficial pharmacologic profile including analgesic sparing effects, anxiolysis, sympatholysis, organ-protective effects against ischemic and hypoxic injury, and sedation which parallels natural sleep. An understanding of predictable side effects, effects of age-related physiologic changes, and pharmacokinetic and pharmacodynamic effects of dexmedetomidine is crucial to maximize its safe administration in adults and children. This review focuses on the growing body of literature examining advances in applications of dexmedetomidine in children and adults.

Low-dose dexmedetomidine as a perineural adjuvant for postoperative analgesia: a randomized controlled trial

Purpose

Dexmedetomidine has been proposed as an additive to local anesthetics to prolong peripheral nerve block duration; however, perineural dexmedetomidine has been associated with an increased risk of bradycardia and hypotension This randomized controlled study investigated the effects of low-dose dexmedetomidine as a perineural adjuvant for postoperative analgesia.

Methods

Fifty-five patients who had undergone elective upper extremity surgery were randomized to receive an ultrasound-guided supraclavicular brachial plexus block with 20 mL 0.5% ropivacaine with or without 30 μg dexmedetomidine. The primary outcome was the duration of analgesia. Secondary outcomes included the onset time and duration of the motor and sensory blocks, incidence of hypotension and bradycardia, total postoperative analgesics, and safety assessment during the 24 h after surgery.

Results

Dexmedetomidine significantly prolonged the duration of analgesia (887 ± 92 min vs 661 ± 83 min, P < 0.0001). The onset time and the duration of motor and sensory block were significantly different between the groups (all P < 0.001). No episodes of hypotension or bradycardia were detected in the dexmedetomidine group. The total postoperative analgesic use and side effect profiles in the first 24 h postoperative period were similar for both groups.

Conclusions

Low-dose dexmedetomidine (30 μg) as a perineural adjuvant significantly prolonged the analgesic duration of a brachial plexus block without inducing hemodynamic instability.

Trial registration

This trial was registered at ClinicalTrial.gov (NCT02630290).

A New Potential Antidepressant: Dexmedetomidine Alleviates Neuropathic Pain-Induced Depression by Increasing Neurogenesis in the Hippocampus

INTRODUCTION

Studies have suggested dexmedetomidine (DEX) as a potential antidepressant. However, no relevant research exists on its effects and mechanisms in curing depression caused by chronic pain. Therefore, an understanding of DEX's role in depressive disorders proposes new approaches for antidepressant treatment.

METHODS

In this study, C57Bl/6 mice (n = 80) were divided into sham (n = 8) and chronic constrictive injury (CCI, n = 72) groups. The CCI group was further divided into six subgroups: CCI + normal saline (NS), CCI + DEX6.25, CCI + DEX12.5, CCI + DEX25, CCI + DEX50, and CCI + DEX100. Fourteen days after CCI, mice that did not develop a depressive phenotype were excluded through sucrose preference test (SPT), forced swimming test (FST), paw thermal withdrawal latency (PTWL), and serum corticosterone (CORT). Subsequently, mice in the sham group were administered 0.1 mL/10 g NS once daily. However, mice in the CCI subgroups were administered NS (0.1 mL/10 g), DEX (6.25 µg/kg), DEX (12.5 µg/kg), DEX (25 µg/kg), DEX (50 µg/kg), and DEX (100 µg/kg) intraperitoneally once daily for 1 week, respectively. Afterward, bromodeoxyuridine (BrdU) was injected intraperitoneally once daily as well for 3 consecutive days before sampling, following BrdU- and doublecortex (DCX)-positive cell detection in the hippocampus through immunofluorescence.

RESULTS

The success rate of the chronic pain-depression (CPD) model was 62.5%. As observed, DEX dose-dependently affected sucrose preferences during the SPT and immobility time during FST. Results also showed that 25 µg/kg DEX had the best promotion effect during increased sucrose preference and reduced immobility time. Moreover, although DEX improved PTWL and serum CORT, no improvement over the DEX 25 µg/kg treatment was observed. Compared to the sham group, the percentage of BrdU+ and DCX+ cells was also significantly lower in the CCI + NS group. Besides, DEX dose-dependently affected cell proliferation and neuronal differentiation. Additionally, the percentage of BrdU+ and DCX+ cells in the dentate gyrus (DG) region of the hippocampus was highest in the CCI + DEX25 group.

CONCLUSION

Therefore, DEX dose-dependently alleviates depression induced by chronic pain through neurogenesis promotion in the DG region of the hippocampus.

Does dexmedetomidine combined with levobupivacaine in inferior alveolar nerve blocks among patients undergoing impacted third molar surgery control postoperative morbidity?

Background

Postoperative analgesia (POA) is an important determinant of successful treatment. Dexmedetomidine (DEX) has recently gained attention as a promising adjuvant to local anesthetics (LA). The present study aimed to evaluate the efficacy and safety of levobupivacaine (LB) as an adjuvant during inferior alveolar nerve block (IANB) in the extraction of lower impacted third molars (LITM).

Methods

A prospective, randomized, placebo-controlled, triple-blind, parallel-arm, and clinical study was performed on 50 systemically healthy participants who required removal of an asymptomatic LITM. Using a 1:1 distribution, the participants were randomized into two groups (n = 25). Group L (control group) received 1.8 mL of 0.5% LB and 0.2 mL normal saline (placebo) and Group D (study group) received a blend of 1.8 mL of 0.5% LB and 0.2 mL (20 µg) DEX. The primary outcome variable was the duration of POA and hemodynamic stability, and the secondary variable was the total number of analgesics required postoperatively for up to 72 h. The participants were requested to record the time of rescue analgesic use and the total number of rescue analgesics taken. The area under the curve was plotted for the total number of analgesics administered. The pain was evaluated using the visual analog scale. Data analysis was performed using paired students and unpaired t-test, Mann–Whitney U test, Chi-square test, and receiver operating characteristic analysis. Statistical significance was set at P < 0.05.

Results

The latency, profoundness of anesthesia, and duration of POA were statistically significant (P < 0.05). The differences between mean pain scores at 6, 12, 24, 48, and 72 h were found to be significant (each P = 0.0001). Fewer analgesics were required by participants in group D (2.12 ± 0.33) than in L (4.04 ± 0.67), with a significant difference (P = 0.0001).

Conclusion

Perineurally administered LA with DEX is a safe, effective, and therapeutic approach for improving latency, providing profound POA, and reducing the need for postoperative analgesia.