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

Abstract

BackgroundWe 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.MethodsWe 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.ResultsMean 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.ConclusionsAdding 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.

<p>The Effect of Different Doses of Intravenous Dexmedetomidine on the Properties of Subarachnoid Blockade: A Systematic Review and Meta-Analysis</p>

“…As an adjuvant medication, dexmedetomidine has been used by different routes to prolong the duration of local anaesthetics. It has been shown to prolong the duration of regional blocks when administered perineurally 25,26 and shown to prolong the duration of subarachnoid block when administered via the intrathecal route, 2,[27][28][29] suggesting both peripheral and central mechanisms of action for dexmedetomidine. It has high selectivity towards α2-adrenergic receptors 30 acting at the presynaptic C-fibers, postsynaptic dorsal horn neurons and locus ceruleus of the brain stem.…”

Perineural Dexmedetomidine Reduces the Median Effective Concentration of Ropivacaine for Adductor Canal Block

“…Brummett et al [ 8 ] showed that dexmedetomidine could increase the action time and improve the potency of ropivacaine in rats. Andersen et al [ 10 ] found that dexmedetomidine could increase the action time of ulnar nerve block. Andersen et al [ 14 ] also reported that dexmedetomidine could extend the duration of nerve block.…”

“…Perineural adjuvant of local anesthetics is a useful technique to address this problem [ 7 ]. Previous studies found that dexmedetomidine can improve the potency of local anesthetics, while sparing nerve injury [ 8 – 10 ]. However, whether the quantity of local anesthetic for adductor canal block can be reduced by dexmedetomidine has not been reported.…”

Adjuvants in pain medicine. Selection of the drug depending on the desired effect – so which drug to choose?

“…Метааналіз переглянув 14 клінічних досліджень із 848 пацієнтами для порівняння периневрального дексмедетомідину проти клонідину. Було встановлено, що дексмедетомідин подовжував тривалість сенсорного та моторного блоку [60,61]. Ефект дексмедетомідину в сім разів перевищує ефект клонідину [58,59].…”

“…порівняло периневральне введення з внутрішньовенним. Хоча було виявлено, що обидва шляхи дексмедетомідину подовжують тривалість ропівакаїну, периневральний шлях введення виявився ефективнішим, ніж при системному застосуванні [61].…”