Dexmedetomidine versus Fentanyl as an Adjuvant to Bupivacaine in Ultrasound-guided Supraclavicular Brachial Plexus Block

Abstract

Poorly controlled acute pain after surgery is associated with a variety of unwanted postoperative consequences, including patient suffering, distress, myocardial ischemia, prolonged hospital stay and an increased likelihood of chronic pain. Systemic analgesics (opioids and non opioids) have long been used for postoperative pain. Then, neuroaxial or peripheral nerve blocks were employed. Local anesthetics alone were used , then various adjuvants were added to achieve quick, dense and prolonged block. Brachial plexus is a complex network of nerves supplying the whole upper limb, with both motor and sensory supply. It arises from the neck and passes through the axilla to the upper limb. Itis composed of 5 roots, 3 trunks, 6 divisions, 3 cords, and terminal branches. There is a growing importance of the application of the ultrasound in clinical practice of anesthesia and regional nerve block especially in supraclavicular brachial plexus block.The idea of pre-emptively scanning patient’s anatomy for neurovascular variations or abnormalities has been suggested as a means of improving patient safety by preventing block complications such as pneumothorax, hematoma formation, improper block or intravascular injection. Clinically, α2-adrenoceptor agonists such as dexmedetomidine are widely used as sedative agents, as adjuncts to anesthesia and have been noted to produce good analgesic effects. Dexmedetomidine is a potent analgesic but the accompanying sedation and hypotension produced by systemic administration has limited the widespread deployment of α2-agonists as analgesics and prompted investigations to separate these effects. Its systemic side effects directed the attention to its use as an adjuvant to local anesthetics. The aim of this study was to compare the effects of adding either 100 micrograms of dexmedetomidine or 75 micrograms of fentanyl to bupivacaine in ultrasound-guided supraclavicular nerve block. The comparison included the onset and the duration of the sensory and motor blocks,the duration of analgesia of the block, presence or absence of sedative effect as well as their effects on the postoperative analgesic requirements. The effect of the drugs on hemodynamics and monitoring the occurrence of any complication were also done. The study included 60 patients, aged 25-50 years, of either sex and of ASA class I. underwent elective orthopedic surgeries of elbow, forearm and hand with an average tourniquet time less than 2 hours. In the present study, patients were randomly divided into 3 equal groups, 20 patients each. Patients of group I (control group) received bupivacaine (0.375%) only. In group II (dexmedetomidine group) 100 micrograms of dexmedetomidine were added to bupivacaine. Patients of group III (fentanyl group) received 75 micrograms of fentanyl in addition to bupivacaine. All patients received equal volumes of 30 milliliters. The presentstudyshowed that addition of a 100 micrograms of dexmedetomidine to bupivacaine in ultrasound-guided supraclavicular nerve block shortened the onset times of sensory and motor blocks and significantly prolonged their durations. In addition, dexmedetomidine prolonged the duration of analgesia of the plexus block significantly, as proved by the time of request of first analgesia. Moreover, in dexmedetomidine group, postoperative analgesic requirements were greatly lesser than that in fentanyl and bupivacaine groups.Also, dexmedetomidine hadthe added effect of sedationwith minimal side effects. Dexmedetomidine did not affect the hemodynamics to a significant level. This makes dexmedetomidine more superior than fentanyl in the previously used doses.