Recent research compared the use of a mixed injection of short-acting lignocaine and long-acting ropivacaine versus undiluted sequential injections for ultrasound-guided supraclavicular brachial plexus block in upper limb surgeries. The primary outcome was the percentage of participants with complete four-nerve sensory blocks at 10 minutes post block injection, and secondary outcomes included sensory and motor block characteristics at 30 minutes, total duration of analgesia, and complications. The study involved a double-blinded randomized trial on 64 adult patients and found that the percentage of participants with a complete four-nerve sensory block at 10 minutes was higher in the sequential injections group (69%) versus the mixed injections group (41%). However, complete sensory and motor block rates were similar at 30 minutes. The block procedure time, total duration of analgesia, and sensory and motor block were similar in both groups. There were no major complications.
Comparison of Drug Mixtures and Sequential Injections
The study investigated the use of mixtures of local anesthetic drugs, specifically short-acting lignocaine and long-acting ropivacaine, for nerve blocks. It compared the block characteristics of these drugs when administered as a mixture versus undiluted sequential injections for ultrasound-guided supraclavicular brachial plexus blocks in upper limb surgeries. The findings indicated that sequential lignocaine-ropivacaine, compared to the mixed injection technique, has a higher initial rate of sensory and motor block onset with a similar total block duration. The study discussed the influence of factors such as dose, pKa, drug deposition close to the nerve, and use of additives on the onset of nerve blocks and reviewed existing literature on the use of sequential injections in regional nerve blocks.
Analysis of Study Findings
It was noted that the percentage of patients with a complete four-nerve sensory block at 10 minutes post injection was significantly higher in the sequential injections group compared to the mixed injections group. However, the total duration of sensory and motor block, as well as the duration of analgesia, was similar in both groups. The study acknowledged a few limitations, such as the inability to extrapolate the findings to the technique of giving mixtures of local anesthetics versus single agent, and the small margins of the time requiring a high measurement frequency of multiple variables.
Conclusion
In conclusion, the study found that the sequential injection of lignocaine and ropivacaine has a higher rate of sensory and motor block onset initially, but the difference becomes minimal 30 minutes after block injection. Both groups demonstrated similar total durations of sensory and motor block and duration of analgesia. The findings from this research provide valuable insights into the comparative efficacy of mixed versus sequential injections of local anesthetics for nerve blocks in upper limb surgeries.
Key Points
1. The study compared the use of mixed injection of short-acting lignocaine and long-acting ropivacaine versus undiluted sequential injections for ultrasound-guided supraclavicular brachial plexus block in upper limb surgeries. It involved a double-blinded randomized trial on 64 adult patients, with the primary outcome being the percentage of participants with complete four-nerve sensory blocks at 10 minutes post block injection. Secondary outcomes included sensory and motor block characteristics at 30 minutes, total duration of analgesia, and complications.
2. The findings indicated that the sequential injections group had a higher percentage of participants with a complete four-nerve sensory block at 10 minutes compared to the mixed injections group. However, complete sensory and motor block rates were similar at 30 minutes. The study also compared the block characteristics of the local anesthetic drugs, highlighting that sequential lignocaine-ropivacaine had a higher initial rate of sensory and motor block onset with a similar total block duration when compared to the mixed injection technique.
3. The study concluded that while the sequential injection of lignocaine and ropivacaine had a higher rate of sensory and motor block onset initially, the difference became minimal 30 minutes after block injection. Both groups demonstrated similar total durations of sensory and motor block and duration of analgesia. The research provides valuable insights into the comparative efficacy of mixed versus sequential injections of local anesthetics for nerve blocks in upper limb surgeries.
Reference –
Dhar M, Talawar P, Sharma S, Tripathy DK, Gupta V, Varshney P. A randomised trial comparing block characteristics of a mixture versus sequential injections of lignocaine and ropivacaine for supraclavicular brachial plexus nerve block in patients undergoing upper limb surgery. Indian J Anaesth 2024;68:540-6.
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