Authors: Sheoran B et al.
Cureus 18(2): e104270, February 25, 2026
This prospective observational study evaluated whether adding low-dose clonidine (0.5 mcg/kg) to 0.2% ropivacaine prolongs postoperative analgesia in ultrasound-guided supraclavicular brachial plexus blocks for upper limb surgeries. Ninety adult patients were divided into two groups: ropivacaine alone (Group A, n=45) versus ropivacaine plus clonidine (Group B, n=45).
The primary outcomes included duration of analgesia, time to first pain complaint, time to rescue analgesia, and postoperative pain assessed via Visual Analog Scale (VAS) at 0, 6, 12, and 24–48 hours.
Group B demonstrated a markedly prolonged duration of analgesia (14.33 ± 0.91 hours) compared with Group A (6.96 ± 1.13 hours), with strong statistical significance (p < 0.001). VAS scores at 6 and 12 hours were also significantly lower in the clonidine group. The time to first pain complaint and need for rescue analgesia were correspondingly delayed when clonidine was used. Importantly, no significant hemodynamic instability or other adverse effects were observed in the clonidine group.
Mechanistically, clonidine acts as an alpha-2 adrenergic agonist, enhancing peripheral nerve block effects by hyperpolarizing neuronal membranes, decreasing norepinephrine release, and prolonging sensory block duration. When combined with a long-acting local anesthetic such as ropivacaine, this synergistic effect can extend analgesia without significantly increasing motor blockade or systemic side effects at low doses.
This study reinforces existing regional anesthesia literature showing alpha-2 agonists can meaningfully enhance block duration. The low dose used (0.5 mcg/kg) is clinically relevant, particularly for ambulatory upper limb surgery where prolonged analgesia without excessive sedation or bradycardia is desirable.
Limitations include the observational design, absence of blinding description, and lack of long-term follow-up beyond 48 hours. Nonetheless, the magnitude of analgesic prolongation is clinically meaningful.
Key Points
• Clonidine 0.5 mcg/kg nearly doubled the duration of analgesia (approximately 14 hours vs 7 hours).
• VAS scores were significantly lower at 6 and 12 hours when clonidine was added.
• No significant adverse hemodynamic events were reported.
• Low-dose alpha-2 agonist adjuvant appears to be an effective strategy in supraclavicular blocks.
• Observational design limits definitive causal conclusions, but results are consistent with prior regional anesthesia evidence.
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