Comparative study on the onset time and duration of brachial plexus block with addition of potassium chloride to bupivacaine versus plain bupivacaine

Abstract

Background: Peripheral nerve blockade remains a well accepted component of comprehensive anaesthetic care. The onset of brachial plexus block is slow because the anaesthetic is usually deposited at some distance from the nerve and must diffuse through various tissue barriers before reaching the nerve membrane. Aim: Comparative study on the onset time and duration of supraclavicular brachial plexus block with addition of potassium chloride to bupivacaine versus plain bupivacaine. Methodology: Sixty patients belonging to ASA class I and II were included in the study and were randomly divided into two groups with 30 patients in each group. Group – I: KCl group received 30 ml of 0.375% bupivacaine with 0.2 mmol of potassium chloride (prepared by adding 0.1 ml (0.2mmol) of potassium chloride and 7.5 ml of distilled water to 22.5 ml of 0.5% bupivacaine). Group – II: Non KCl group/ plain bupivacaine group received 30 ml of 0.375% bupivacaine. Results: The mean time for onset of sensory block in group I was 17.7 ± 2.80 min which was significantly faster when compared to group II with a mean time of 27.86 ± 2.55 min. The mean time for onset of motor block in group I was 14.86 ± 2.56 min which was significantly faster compared to group II with a mean time of 25.46 ± 3.04 mins. The mean duration of sensory block in group I was 357.8 ± 101.9 min which was significantly prolonged when compared to group II mean duration of 256.1 ± 71.48 min. The mean duration of motor block in group I was 429.1 ± 85.09 min which was significantly prolonged when compared to group II mean duration of 336.46 ± 81.88 min. The number of supplements used in group I were significantly less when compared to group II. There was no statistically significant difference found between the group’s in terms of duration of surgery Conclusion: On the basis of the study one can draw the conclusion that addition of potassium chloride to bupivacaine hastens the onset of blockade and improves the duration of analgesia and motor blockade. It also improves the quality of analgesia, whereas quality of motor blockade remains the same.