Comparison Of Dexmedetomidine And Dexamethasone As An Adjuvant To Bupivacaine In Brachial Plexus Block
Condition: Brachial Plexus Block; Dexmedetomidine; Dexamethasone; Bupivacaine
Study type: Interventional

Summary: 
      Brachial plexus block is a regional anaesthesia technique employed as a safe and valuable
      alternative to general anaesthesia for upper limb surgery. In recent practices of day care
      surgeries, brachial plexus block seems to be a better alternative to general anesthesia with
      minimal hospital stay and better analgesic effect. Among several techniques of brachial
      plexus block, supraclavicular approach is considered as easiest, effective and can be
      performed much more quickly than other approaches. Various local anaesthetic agents and
      adjuvants are used for this purpose. Among them, bupivacaine has been the most widely used
      long-acting local anaesthetic agent. Combining local anesthetics with different adjuncts can
      prolong the duration of analgesia associated with brachial plexus block. Among various
      adjuncts, dexamethasone and dexmedetomidine have been identified as clinically effective
      adjuncts. Several metaanalyses have convincingly demonstrated their efficacy in prolonging
      the analgesic duration of brachial plexus block. However, there has been limited research
      conducted to compare the effects of dexamethasone and dexmedetomidine added as adjuvants to
      the local anesthetics for BPB. Studies have demonstrated benefits of one agent over other
      without any definitive conclusion as which is the best agent for this purpose. Therefore,
      there is a need of study to compare the onset and duration of bupivacaine when
      dexmedetomidine or dexamethasone is used as an adjuvant to bupivacaine for ultrasound-guided
      supraclavicular BPB
    

Detailed description: 
      Peripheral nerve block (PNB), as an integral part of regional anesthetic technique, remains a
      well-accepted component of comprehensive anaesthetic care. William Halstead (1852-1922) was
      first to perform Brachial Plexus Block (BPB) in 1884 by surgically exposing the roots of the
      brachial plexus and injecting each nerve directly. Kulenkampff described the first
      percutaneous supraclavicular approach in 1911. BPB provides both intraoperative anaesthesia
      as well as postoperative analgesia. Being a regional anaesthetic technique, it has many
      advantages over general anaesthesia like effective analgesia with good motor blockade, awake
      patient, extended postoperative analgesia, early mobilization, no airway manipulation,
      avoidance of polypharmacy and decreased incidence of postoperative nausea and vomiting.
      Advantages of supraclavicular approach include rapid onset and reliable blockade with a small
      volume of local anaesthetic and produced a more intense motor blockade and reduced the
      incidence of Horner's syndrome compared with Interscalene BPB. The clinical indications of
      supraclavicular BPB have been confined to upper limb surgeries below the midshaft of humerus
      because of concerns that it is performed too distally from the cervical nerve roots to block
      the suprascapular nerve which innervates 70% of the shoulder joint in addition to the
      subacromial bursa, coracoclavicular ligament, and acromioclavicular joint. There is evidence
      that peripheral nerve blocks performed by ultrasound guidance alone, or in combination with
      Peripheral Nerve Stimulator (PNS), are superior in terms of improved sensory and motor block,
      reduced need for supplementation and fewer minor complications reported. Using ultrasound
      alone shortens performance time when compared with nerve stimulation, but when used in
      combination with PNS it increases performance time. Many local anaesthetics have been used to
      produce brachial plexus block. Most common among them is bupivacaine, because of its higher
      potency and prolonged duration of action. Bupivacaine is an amide local anaesthetic. It
      prevents transmission of nerve impulses by inhibiting passage of sodium ions through
      selective ion channel in nerve membranes. This slows the rate of depolarization such that
      threshold potential is not reached and action potential not propagated. The half life of
      bupivacaine in adults is 3.5 hours. The commonly used concentrations in brachial plexus block
      are 0.25%, 0.375% and 0.5%. Studies have shown that mass of bupivacaine rather than
      concentration is the major determinant of the Effective Dose 50 (ED50) for achieving
      supraclavicular brachial plexus block. The concentration of bupivacaine that will be used in
      our study is 0.5% and volume is 20 ml. Adjuvants or additives are often used with local
      anaesthetics for its synergistic effect by prolonging the duration of sensory-motor block and
      limiting its cumulative dose requirement. Various drugs like opioids, epinephrine, alpha-2
      adrenergic antagonists, steroids, anti-inflammatory drugs, midazolam, ketamine, magnesium
      sulfate and neostigmine have been used to potentiate the effect of local anesthetics. Due to
      its potential adverse effects, current researches are exploring newer drugs and delivery
      mechanisms to prolong the duration of action of local anesthetics. Recently, dexamethasone
      and dexmedetomidine have been identified as clinically effective adjuncts; several
      metaanalyses have convincingly demonstrated their efficacy and prolonging the analgesic
      duration of PNB. Dexmedetomidine, a potent α2 adrenoceptor agonist, is approximately
      eight-times more selective towards the α2 adrenoceptor than clonidine. Dexmedetomidine is
      also reportedly safe and effective when administered with long-acting local anesthetics in
      PNBs. No significant histopathologic abnormalities were reported after intrathecal or
      perineural administration of dexmedetomidine. There have been four proposed mechanisms for
      the action of alpha 2 adrenergic agonists in peripheral nerve blocks. These mechanisms
      include centrally mediated analgesia, ∝2B-adrenoceptor mediated vasoconstrictive effects,
      attenuation of the inflammatory response, and direct action on the peripheral nerve. In this
      study we are adding 1mcg/kg dexmedetomidine as adjunct to bupivacaine as previous studies
      have shown that 1 mcg/kg dexmedetomidine added perineurally to levobupivacaine in
      Supraclavicular BPB is a safer dose than 2 mcg/kg with less sedation, bradycardia, and
      comparable analgesia. Dexamethasone is a very potent and highly selective glucocorticoid.
      Various studies have been done using dexamethasone as an adjuvant to local anaesthetics
      mixture in brachial plexus block resulting in variable effects on onset but prolonged
      duration of analgesia and motor block. Dexamethasone produces analgesia by blocking pain
      signal transmission in nociceptive c-fibers, suppressing ectopic neural discharge and by
      inhibiting the action of phospholipase A2. The block prolonging effect of peripherally
      applied dexamethasone could be due to alteration in the function of potassium channels in the
      excitable cells by dexamethasone via glucocorticoid receptors present in the brachial plexus.
      It may also be due to the local vasoconstrictive effect of dexamethasone via glucocorticoid
      receptors. In this study we are using 4 mg dexamethasone as articles have shown that
      perineural dexamethasone at a dose of 4 mg prolongs the duration of analgesia after local
      anaesthetic PNB with efficacy similar to a dose of 8 mg and without any reported serious
      adverse effects. However, each of these molecules is associated with undesirable side
      effects: increased glycemia, neurotoxicity and risk of precipitation may occur after use of
      dexamethasone but studies show that these toxicities are very unlikely with peripheral use
      and at the low dose of 4mg which will be used in this study; bradycardia, hypotension, and
      sedation for dexmedetomidine. Importantly, most published trials of dexamethasone and
      dexmedetomidine have compared these adjuncts to control, with very scant head-to-head
      comparison. Notably, literature is characterized by conflicting results and inconsistent
      reporting of side effects.
    

Intervention name(s): adding Dexmedetomidine and dexamethasone to bupivacaine in USG guided supraclavicular brachial plexus block.
Intervention type(s): Procedure
Intervention description(s): The linear transducer probe (frequency 4 -12 Hz) of USG machine will be used. A superficial skin wheal will be made by 2ml of 1% lignocaine subcutaneously at the point of needle insertion. USG guided Brachial plexus block will be performed by supraclavicular route via the subclavian perivascular approach in in-plane technique from lateral to medial using 22 gauge spinal needle. Study Drug will be administered via Pressure Monitoring line connected to syringe according to the allocated group with repeated aspiration and incremental dosing. • Intercostobrachial nerve block will be performed to alleviate the tourniquet pain. A 25 G needle will be inserted at the level of axillary fossa. The entire width of the medial aspect of arm, starting at the deltoid prominence and proceeding inferiorly, will be infiltrated with 5ml of 1% Lignocaine with Epinephrine (1:4,00,000) to raise a subcutaneous wheal. •
Intervention MeSH terms: Dexamethasone; Dexmedetomidine; Bupivacaine
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Triple (Participant, Care Provider, Investigator)
Primary purpose: Treatment
Keywords: Brachial Plexus Block; Dexmedetomidine; Dexamethasone; Bupivacaine