ABSTRACT

Background:

Postoperative analgesia is a sine qua non in current clinical practice. However, perineural catheters for extending analgesia offered by local anaesthetics for peripheral nerve blocks are not yet very popular. So we are in need for an adjuvant that can prolong the action of local anaesthetics after single- injection blocks. Dexmedetomidine and clonidine are two commonly used adjuvants. This study was undertaken to assess which among them proved to be a superior analgesic adjuvant in lower doses.

Materials and Methods:

After ethical committee approval and written informed consent this study was conducted on 60 patients , aged 18-55 years, posted for upper limb surgery under USG guided supraclavicular brachial plexus block at St.John‘s Hospital, Bangalore. The study was conducted from January 2015-January 2016- Prospective Randomised double blind study. Preoperative baseline values of heart rate, blood pressure and oxygen saturation was recorded. Brachial plexus block by supraclavicular approach was carried out under USG guidance using strict aseptic precautions. Patients were assigned randomly to one of the two groups using computer generated tables:-

Group C- Clonidine 0.5 μg /kg added to 25ml of 0.375% bupivacaine.

Group D - Dexmedetomidine 0.5 μg /kg and 25ml of 0.375% bupivacaine.

The onset of sensory block, onset of motor block, the duration of analgesia, duration of  

motor block and sedation scores were assessed. Complications were also noted.

Results:

In our study the mean onset of sensory and motor block were faster in clonidine group than dexmedetomidine group. The mean onset of sensory block was 11.6 +/-3.4 minutes in group C, 14.4 +/-4.5 minutes in group D. The mean onset of motor block was 17.6 +/-4.9 in group C, 20.6+/-5.9 in group D. The duration of sensory block in Group C was 9.7+/-1.6 hours, 13.3+/-1.9 hours in Group D. Duration of motor blockade (hrs) was 9.1+/-1.7 in Group C, 12.1+/-2.0 in Group D. Duration of sensory and motor blockade was longer in Dexmedetomidine group than Clonidine group. First rescue was required at 10.5 ± 1.7 hrs in Clonidine group and at 15 ± 2.2 hrs in Dexmedetomidine group. None of the subjects in Clonidine group had side effects, wereas 10% of subjects in Dexmedetomidine group had side effects (Most common side effect observed was Bradycardia).

Conclusions:

Dexmedetomidine proves to be better adjuvant compared to clonidine as it notably prolongs analgesia and is also lesser complications at lower doses. But the prolonged motor block is still a matter of concern and the search for an adjuvant that selectively prolongs analgesia without impairing motor function continues.

Keywords:

Bupivacaine, Dexmedetomidine, Clonidine, Ultrasound, Supraclavicular brachial plexus block.