A COMPARATIVE STUDY OF DEXMEDITOMEDINE AND DEXAMETHASONE AS ADJUVANTS TO LOCAL ANESTHETICS IN BRACHIAL PLEXUS BLOCK FOR UPPER LIMB SURGERIES

Department of Anesthesiology, Santhiram Medical College, Nandyal. ................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History Received: 30 November 2019 Final Accepted: 31 December 2019 Published: January 2020


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Various adjuvants have been used to prolong regional blockade, shorten the onset of block, and prolong the duration of postoperative analgesia. Various adjuvants, including Opioids, Midazolam, Magnesium sulfate, Dexamethasone, and Neostigmine, have been added to local anesthetic to increase the duration of a block and postoperative analgesia with the risk of various adverse effects. The efficacy of alpha 2-adrenoceptor agonists has been established in a variety of regional anesthesia techniques.
Dexmedetomidine is a selective alpha2 adrenoceptor agonist and is approximately eight times more potent than Clonidine. Dexmedetomidine has been reported safe and effective when administered with long-acting local anesthetic in peripheral nerve blocks.
Various clinical studies have foundthat administration of dexmedetomidine as an adjuvant to local anesthetics prolonged duration of sensory and motor blockade.
Steroids have potent anti-inflammatory as well as analgesic properties. They suppress inflammation through inhibition of phospholipase A2. Local application of methylprednisolone has been found to block transmission in nociceptive C-fibers but not myelinated A-beta fibers. The effect was reversible, suggesting a direct membrane action of steroids. Corticosteroids also suppress ectopic neuronal discharge. Perineural injection of Glucocorticoid, along with local anesthetics, is reported to influence the onset and duration of sensory and motor blockade.
Dexamethasone is a very potent and highly selective glucocorticoid. Many studies were done using Dexamethasone 4mg as an adjuvant to the local anesthetic mixture in brachial plexus block resulted in variable effects on the onset but the prolonged duration of analgesia and motor block.
The present study is being undertaken to evaluate the onset time,duration of sensory and motor block,duration of postoperativeanalgesia,with dexmedetomidine and dexamethasone as adjuvants to local anesthetic in brachial plexus block by supraclavicular approach.

Exclusion criteria:
unwilling patients, infection at the site of injection, coagulopathy disorders, hyperthyroid patients, pregnancy, peripheral neuropathy, patients with known hypersensitivity to local anesthetics.

Procedure:
iv access obtained in the opposite limb with large bore iv cannula. Standard monitors-ecg, pulse oximeter, noninvasive blood pressure were connected and monitored in all patients and recorded at 5 minutes interval in the first 30mins and after that every 30mins. The patients were placed in a supine position with the head turned opposite side. Arm to be anesthetized adducted and extended towards the ipsilateral knee. The supraclavicular area is draped and subclavian artery pulsations palpated, and a 23g needle is inserted lateral to artery and directed backwardinwards-downward till paresthesia in forearm elicited. After negative aspiration for blood, 40ml of a respective drug was injected.
The onset of sensory block was assessed by spirit swab Assessment of motor block was done using a modified Bromage scale 0 -Normal power 1 -Paresis but able to move an arm 2 -Not able to move the arm but ready to move fingers 3 -Complete motor blockade 1000 Postoperative pain assessed using a visual analog scale [VAS] score of 0-10 Blood loss assessment was done, and fluid was administered as per need. The duration of surgery was noted. Side effects like nausea and vomiting, dryness of mouth complications like pneumothorax, hematoma, post block neuropathy, local anesthetic toxicity were monitored.

Results:-
Regarding the Age and sex distribution, there was no significant difference among both groups.    15mins  86  84  30min  78  80  60min  74  79  120min  75  78  180min 66 72 Table 4 shows that the pulse rates in both groups were found to have no statistical significance.

Discussion:-
Regional anesthesia with a brachial plexus block has been widely used alternative to general anesthesia in patients who are at high risk for general anesthesia. Single-shot Brachial plexus block usage is limited by early onset of postoperative pain, high opioid dose requirement, high incidence of PONV, which can be managed by adding an adjuvant to local anesthetics.We choose supraclavicular approach for brachial plexus block as the narrowest part of plexus is located there and anesthesia will be rapid, dense and predictable for entire upper limb. The advantages of adding an adjuvant to local anesthetics include prolongation of sensory and motor block, delayed onset of pain in the postoperative period. Low opioid analgesic dose requirement in the postoperative period.Addition of steroid to LA effectively and significantly prolongs the duration of analgesia as well as producing earlier onset of action. Dexamethasone, synthetic glucocorticoid derivative is preffered because of it is highly potent anti inflammatory property, about 25-30times more potent than hydrocortisone and without any mineralocoarticoid activity. Dexmeditomedine is a selective α-2 agonist, has been shown to improve the duration of analgesia when added as adjuvant to LA in nerve block. The analgesic effect is by blockade of hyper-polarisation activated cation currect as seen in animal study.
In our study, the surgeries varied from distal humerus fractures to radius ulna and hand surgeries. No significant complications were encountered in our research.

Conclusion:-
Dexmeditomedine and Dexamethasone, both are good adjuvants in nerve blocks. But the study conducted revealed that the onset of block was shorter when dexamethasone was added. whereas dexmeditomedine is better alternative having an added advantage of conscious sedation and hemodynamic stability with enhanced quality and duration of block.