Effect of Locally Administered Dexmedetomidine as Adjuvant to Levobupivacaine in Supraclavicular Brachial Plexus Block: Double-blind Controlled Study.

CONTEXT

Brachial plexus block is effective with good postoperative analgesia in upper limb surgery has gained importance as it safe, low cost, and maintains stable hemodynamics intraoperatively. To decrease the onset time and prolong the duration of nerve block bicarbonate, opioids (morphine, fentanyl, etc.), sympathomimetic agents (epinephrine, phenylephrine, etc.), α-2 agonists (clonidine and dexmedetomidine), calcium channel blocker (verapamil), magnesium sulfate, etc., were studied with local anesthetics and their isomers. For their sedative, analgesic, perioperative sympatholytic, and cardiovascular stabilizing effects with reduced anesthetic requirements, α-2 adrenergic receptor agonists, such as more potent and highly selective dexmedetomidine, have been the focus of interest for regional anesthesia. Intravenous dexmedetomidine infusion resulted in significant opioid-sparing effects as well as a decrease in inhalational anesthetic requirements. Animal studies proved that dexmedetomidine enhances sensory and motor blockade along with increased duration of analgesia. In humans, dexmedetomidine has also shown to prolong the duration of block and postoperative analgesia when added to local anesthetic in various regional blocks. Bupivacaine, the widely used local anesthetic in regional anesthesia, is available in a commercial preparation as a racemic mixture (50:50) of its two enantiomers: levobupivacaine, S (-) isomer and dextrobupivacaine, R (+) isomer. Severe central nervous system and cardiovascular adverse reactions reported in the literature after inadvertent intravascular injection or intravenous regional anesthesia have been linked to the R (+) isomer of bupivacaine. The levorotatory isomers were shown to have a safer pharmacological profile with less cardiac and neurotoxic adverse effects. The decreased toxicity of levobupivacaine is attributed to its faster protein binding rate. The pure S (-) enantiomers of bupivacaine, i.e., ropivacaine and levobupivacaine were thus introduced into the clinical anesthesia practice. Such an increased usage mandates the documentation of evidence-based literature with regard to risk and safety concerns as well as clinical issues related to levobupivacaine. This study is designed to assess the efficacy of adding dexmedetomidine to levobupivacaine during placement of supraclavicular brachial plexus blockade.

MATERIALS AND METHODS

This prospective observational double-blinded study was conducted over a 1-year period among randomly selected seventy ( = 35) American Society of Anesthesiologists Classes I and II patients of ages between 18 and 60 years of both sexes scheduled to undergo upper limb surgery. With nerve locator, levobupivacaine (0.5%) 28 ml and 2 ml normal saline for Group L and levobupivacaine (0.5%) 28 ml and 0.75 μg/kg dexmedetomidine made up a solution of 2 ml, for Group D, a total 30 ml will be injected locally, in both the groups. Onset and duration of sensory and motor block will be assessed.

RESULTS AND DISCUSSION

One patient in Group L and two patients in Group D failed to achieve block within 30 min. Those three patients were then excluded from the analysis. Hence, the analysis was done by taking 34 patients in Group L and 33 patients in Group D. Onset of sensory and motor block was earlier in Group D (12.03 ± 0.85 and 13.58 ± 0.97) than Group L (14.32 ± 1.15 and 15 ± 0.98), and the difference is statistically significant ( < 0.0001). Duration of sensory and motor block was longer in Group D (563.94 ± 15.60 and 495.15 ± 10.34) than Group L (368.53 ± 9.89 and 321.47 ± 7.84), and the difference is also statistically significant ( < 0.0001). Duration of analgesia was longer in Group D (672.12 ± 11.39) than Group L (506.47 ± 9.497), and the difference is statistically significant ( < 0.0001). Heart rate and mean arterial pressure were well maintained within the presumed range of significant variation, i.e., 20% from baseline, though at some point of time, intergroup comparison was statistically significant. Visual analog scale score compared at the time for administration of rescue analgesic between the groups come out to be statistically significant.

CONCLUSION

Addition of 0.75 μg/kg dexmedetomidine to 0.5% levobupivacaine for supraclavicular plexus block shortens sensory and motor block onset time and extends sensory block, motor block, and analgesia duration.