Comparison of Dexmedetomidine with Clonidine as an adjuvant to Bupivacaine in Supraclavicular Brachial Plexus Block

INTRODUCTION: Brachial plexus blocks provides a useful alternative to general anaesthesia for upper limb surgeries. They achieve near ideal operating conditions by producing good muscular relaxation, maintaining stable haemodynamics and associated sympathetic block. The sympathetic block reduces the postoperative pain, vasospasm and edema. Although various anaesthetic agents have been used, bupivacaine is a better choice due to its longer duration of action of 3 to 8hrs. However it has certain disadvantages like delayed onset, patchy or incomplete analgesia etc, Various adjuvants like neostigmine, midazolam, opioids etc, have been tried to improve the onset of block, quality of block, prolong the duration of block and postop analgesia. But these were associated with side effects. Clonidine an alpha-2 agonist which had been used as antihypertensive initially has sedative, sympatholytic and analgesic properties. It is also known to have anti nociceptive action and enhances the effect of local anasthetics when given intrathecally, epidurally and in peripheral nerve blocks. This effect is produced by modulating pain pathways through presynaptic alpha-2 adrenergic receptors. It also produces sedation through its action on pontine locus ceruleus where highest number of alpha-2 receptors are present. Dexmedetomidine, the next recent highly potent alpha-2 agonist, is also a sedative, anxiolytic and analgesic similar to clonidine. The peculiar features of dexmedetomidine is its high selectivity for alpha-2 receptors and its ability to produce sedation and analgesia while still maintaining patient arousability and respiratory function. So the present study has been undertaken as randomized single blinded manner to compare the onset time, duration and analgesic efficacy of clonidine with dexmedetomidine when added as adjuvant to bupivacaine (0.25%) for brachial plexus block by supraclavicular approach. AIM OF THE STUDY: To compare the effectiveness of clonidine and dexmedetomidine as adjuvant in brachial plexus block by supraclavicular approach for prolongation of sensory and motor blockade and duration of analgesia. OBJECTIVES: 1. This study of adding clonidine (1μg/kg) or dexmedetomidine (1μg/kg) to bupivacaine (0.25%) in brachial plexus block for surgeries involving the upper limb has the following objectives: 2. To compare the • Onset of sensory and motor blockade, • Duration of sensory and motor blockade, • Sedation score intra and postoperatively, • Haemodynamic variables (HR, BP, SPO2), • No of rescue analgesics in postoperative 24hrs between clonidine and dexmeditomedine. METHODOLOGY: This study was conducted on 50 patients undergoing upper limb surgeries aged between 15 & 55 yrs under supraclavicular block in Annal Gandhi Memorial Government Hospital attached to K.A.P.Viswanatham Government Medical College, Trichy. Informed written consent was obtained from each patient. Values were recorded using a preset proforma. It was a bouble blinded study in which patients were divided into two groups BD & BC comprising 25 each. Surgery was done under supraclavicular approach of brachial plexus block. Inclusion criteria: 1. ASA grade – I & II, 2. Age between 15 & 55yrs. Exclusion criteria: 1. ASA grade – III & IV, 2. Patients with complications like severe anaemia, hypovolemia, septicemia, shock. 3. Known case of hypersensitivity reaction to clonidine or dexmedetomidine. 4. Bleeding disorders or on anticoagulant therapy. 5. Local infection at the site of puncture. RESULTS: 50 ASA I & II of either sex aged 15-55yrs, posted for upper limb surgeries under supraclavicular brachial plexus block were selected for the study. The study was undertaken to evaluate the efficacy of dexmedetomidine (1μ/kg) over clonidine (1μ/kg) as an adjuvant to bupivacaine (0.25%) for brachial plexus block. SUMMARY: This study, “A clinical comparison between dexmedetomidine and clonidine with bupivacaine in brachial plexus block by supraclavicular approach” was conducted in 50 patients of either sex, in the range of 15 – 55yrs. ASA grade I & II, admitted in K.A.P.Viswanatham Government Hospital, Trichy for upper limb surgeries from 2010 – 2013. They were randomly divided into two groups; Group BC : received 35ml of 0.25% bupivacaine with clonidine 1μg/kg. Group BD : received 35ml of o.25% bupivacaine with dexmedetomidine 1μg/kg. The following parameters were recorded and compared: • Onset of sensory block and motor block. • Duration of sensory block and motor block. • No of rescue analgesic doses in post-op 24hrs. • Sedation score. • Hemodynamic variables like pulse rate, systolic BP, diastolic BP and oxygen saturation. • Onset of sensory and motor block: The mean time for onset of sensory block was in group BC was 11.14±1.13min and in group BD was 8.8min. The mean time for onset of motor block in group BC was 13.6±1.11 and in group BD was 11.36±0.952min. Both differences were statistically significant (p<0.05). Duration of sensory and motor block: The mean duration of sensory block in group BC was 7.06±0.664 and in group BD was 9.3±0.667hrs. The mean duration of motor block in group BC was 6.66±0.657and in group BD was 8.5±0.692hrs. Both the differences were statistically significant (p<0.05). Rescue analgesic requirement in post-op 24hrs: In group BC 20% required one rescue analgesic dose and 80% required 2 analgesic doses, whereas in group BD, 56% required one analgesic dose and only 44% required 2 analgesic doses. The rescue analgesic doses required by group BD was significantly higher (p<0.05). Sedation score: In group BC, 20% of patients at 15min, 32% at 30min & 26% at 60min had sedation score of 2. In group BD, 66% at 15min, 100% at 30min, 80% at 60min and 16% at 2hrs had a sedation score of 2, both responding to verbal stimulus. Statistical analysis by Chi-square test showed that the difference in sedation score was significant (p<0.05). Hemodynamic variables: Both the groups were comparable with regard to pulse rate, systolic BP, diastolic BP and oxygen saturation. There was no statistically significant difference (P>0.05). CONCLUSION: To conclude, we would like to state that dexmedetomidine prolongs the duration of sensory and motor block as compared with clonidine when it is used as an adjuvant to Bupivacaine in peripheral nerve block. Hence it is seen that dexmedetomidine when added to bupivacaine compared to clonidine has 1. Faster onset of sensory block, 2. Faster onset of motor block, 3. Prolonged duration of sensory block, 4. Prolonged duration of motor block, 5. Less no of rescue analgesics in post-op 24hrs, 6. Comfortable sedation where the patient can be arousable at any time, 7. No significant difference in hemodynamic variables