Minimum Effective Concentration of Ropivacaine for Ultrasound-Guided RISS Block in VATS: A Biased Coin Design...

Area of Science:

• Anesthesiology
• Pain Management
• Thoracic Surgery

Background:

• Postoperative pain management is crucial after video-assisted thoracoscopic surgery (VATS).
• The rhomboid intercostal and sub-serratus (RISS) block is an effective analgesic technique for VATS.
• Optimizing local anesthetic concentration is key for effective RISS block analgesia.

Purpose of the Study:

• To determine the minimum effective concentration (MEC) of ropivacaine for ultrasound-guided RISS block in VATS patients.
• To establish the MEC90, MEC95, and MEC99 for ropivacaine in RISS blocks.
• To refine postoperative analgesia protocols for VATS.

Main Methods:

• Utilized a biased coin design sequential method and isotonic regression to determine MEC.
• Initiated ropivacaine concentration at 0.25% with 0.025% increments/decrements based on block success.
• Calculated MEC values with 95% confidence intervals (CI).

Main Results:

• The MEC90 of 40mL ropivacaine for RISS block was 0.220% (95% CI, 0.198-0.260%).
• MEC95 was 0.248% (95% CI, 0.223-0.338%) and MEC99 was 0.270% (95% CI, 0.261-0.351%).
• Negative correlation observed between ropivacaine concentration and pain scores at 0, 0.5, and 6 hours post-surgery.

Conclusions:

• The MEC90 of 40 mL ropivacaine for RISS block in VATS is 0.220%.
• MEC95 and MEC99 were determined to be 0.248% and 0.270%, respectively.
• These findings optimize ropivacaine dosage for effective RISS block analgesia in VATS patients.