The Optimal Dose Of Dexamethasone To Be Used As An Adjuvant To Low Volume Bupivacaine Ultrasound Guided Supraclavicular Brachial Plexus Block. A Randomized Controlled Double Blinded Dose Ranging Study

Brachial plexus nerve blocks (BPBs) for upper extremity surgery provide superior analgesia and reduce opioid consumption. Supraclavicular block anesthetizes the brachial plexus where it is in its most compact form, thus providing a complete and reliable block for upper extremity surgery. Ultrasound guided single injection (SI) and triple injection (TI) techniques were found to provide the same degree of surgical anesthesia at 30 minutes while the TI technique needed more time to perform.

Many studies were conducted to examine the effect of perineural Dexamethasone as a local anesthetic adjuvant in low volume peripheral nerve blocks were it was found to increase the mean duration of analgesia (sensory block) with short, medium and long acting local anesthetics as well as the duration of motor blockade, with a reduction in pain scores at rest during the intermediate (8-12 h) and late (24 h) postoperative periods and in movement at all times. At 24 postoperative hours, cumulative morphine consumption and the rate of nausea or vomiting were also reduced without any reported related serious adverse effects, also the value of its concomitant intravenous use in prolonging the duration of analgesia after regional blocks was studied with promising results that can sometimes be compared to the perineural route but more short-lived and associated with higher increase in blood glucose levels. Dexamethasone's mechanism of action may result from decreased nociceptive C-fibre activity via a direct effect on glucocorticoid receptors and inhibitory effect on potassium channels.(8) Other authors suggest a local vasoconstrictive effect, resulting in reduced local anaesthetic absorption or a systemic anti-inflammatory effect following vascular uptake of the drug.

A debate exists whether perineural corticosteroids are harmful or not, but reports of neurotoxicity seem to be related mainly to the preservative benzyl alcohol and the vehicle polyethylene glycol found in some preparations, also may be related to the presence of insoluble steroid particulate matter in the injectate. Dexamethasone is non-particulate and can be found in a preservative-free formulation. In addition, no significant long-term electrophysiological, behavioural or histological effects for corticosteroids were identified on rat sciatic nerve tissue even some data suggest dexamethasone may actually be neuroprotective. In reality, perineural corticosteroid injections with and without preservative are widely used throughout the world.

Various doses of Dexamethasone were used in local anaesthetic mixtures in regional blocks in various studies, including 4, 5, 8 and 10 mg. In a recent review & meta-analysis by E. Albrecht and his colleagues, sub-group analysis revealed no association between the total dose of perineural Dexamethasone and the mean increase in duration of analgesia showing that Dose-finding studies are needed to better define the optimal balance between dose, effects and side-effects, particularly at doses lower than 4 mg.