INTRODUCTION

Upper limb surgeries are preferably done under regional anesthesia. Peripheral nerve blocks not only provide for intra operative anesthesia but also ensure analgesia in the post operative period without any systemic side effects. Levobupivacaine, is a new local anaesthetic having, similar pharmacological profile, but less cardiotoxicity when compared to Bupivacaine.

There has always been a search for ideal adjuvants in peripheral nerve blocks which prolong the duration of analgesia with lesser adverse effects. Various adjuvants used are clonidine, dexamethasone, tramadol etc. Lately dexmedetomidine highly selective α2 adrenergic agonist, has been used as an adjuvant to local anaesthetics. Very few clinical trials have studied the effect of dexmedetomidine as an adjuvant to levobupivicaine in supraclavicular brachial plexus block. Only a single dose of 100 ug has been studied which has been associated with hemodynamic changes.  We aim to compare the efficacy and adverse effect of 2 doses of dexmedetomidine (1ug/kg and 2ug/kg) added to levobupivicaine.

MATERIALS AND METHOD

After obtaining clearance from IEC, 90 ASA I and II patients between the age group 18 to 60 scheduled for upper limb orthopaedic surgeries under supraclavicular brachial plexus block will be included in the study.

INCLUSION CRITERIA

1.      Age : 18 to 60 years

2.       ASA I and II

3.      Posted for Forearm/ elbow surgeries

EXCLUSION CRITERIA

1.      ASA III or more

2.      Bleeding / coagulation disorder

3.      Uncontrolled diabetes/ HTN

4.      Patients with heart blocks/ cardiac disease

Computer based randomisation will be done and the patients will be randomised into either of the groups:

GRP I: 25 cc 0.5% levobupivicaine with 1ug/kg dexmed (volume=26 ml)

GRP II: 25 cc 0.5% levobupivicaine with 2 ug/kg dexmed (volume 26 ml)

All the drug preparations will be made by an anaesthesiologist not involved in the perioperative  management .

All the patients will be premedicated with 0.25 mg alprazolam a night before surgery. On arrival in the operation room, baseline heart rate, blood pressure and oxygen saturation will be recorded. An intravenous line will be secured in the unaffected limb and 10 ml/kg Ringer′s lactate given.

All the patients will receive brachial plexus block through the supraclavicular  perivascular approach ( USG guided) by an experienced anaesthesiologist blinded to the group allocation.

Sensory block will be assessed by the pin prick method. Assessment of sensory block will be done at every 2 minutes after completion of drug injection in the dermatomal areas corresponding to median nerve, radial nerve, ulnar nerve and musculocutaneous nerve till complete sensory blockade. Sensory onset will be considered when there will be a dull sensation to pin prick along the distribution of any of the above-mentioned nerves. Complete sensory block will be considered when there is complete loss of sensation to pin prick.

Sensory block will be graded as-

Grade 0: Sharp pin felt

Grade 1: Analgesia, dull sensation felt

Grade 2: Anaesthesia, no sensation felt.

Assessment of motor block will be carried out by the same observer at every 2 minutes till complete motor blockade after drug injection. Onset of motor blockade will be considered with Grade 1 motor blockade for any of the four nerves. Peak motor block was considered when there will be Grade 2 motor blockade for all the four nerves. Motor block will be determined according to a modified Bromage scale for upper extremities on a 3-point scale. 

Grade 0: Normal motor function

Grade 1: Decreased motor strength

Grade 2: Complete motor block

Motor blockade will be assessed for the 4 nerves as follows:  

1. thumb abduction (radial nerve),

2. thumb adduction (ulnar nerve),

3.  thumb opposition (median nerve),

4. flexion of elbow (musculocutaneous nerve)

The block will be considered incomplete when any of the segments supplied by median, radial, ulnar and musculocutaneous nerve will not have analgesia even after 30 min of drug injection. These patients will be supplemented with intravenous fentanyl (1 μg/ kg) and midazolam (0.02 mg/kg). If more than one nerve remains unaffected, it will be considered a failed block. In this case, general anaesthesia will be given intraoperatively.

ASSESSMENT

1.      Patients will be monitored for haemodynamic variables such as heart rate, blood pressure and oxygen saturation every 15 min after the block intraoperatively and every 30 min post-operatively.

2.      Sedation of patient was assessed by the Ramsay Sedation Score every 15 minutes after the block till the end of surgery and every 30 minutes post operatively till 6 hours.

3.      Postoperative pain assessment using visual analogue score every half an hour till  is >4. Once the pain reaches vas>4, Iv paracetamol 15 mg/kg will be administered for rescue analgesia and the time of administration will be noted.

4.      Adverse effects like nausea, vomiting, dryness of mouth and complications like pneumothorax, haematoma, local anaesthetic toxicity and post-block neuropathy in the intra- and post-operative periods.

5.      The duration of sensory block was defined as the time interval between the end of local anaesthetic administration and the complete resolution of anaesthesia on all nerves.