Spinal ropivacaine for lower limb surgery: a dose response study.

Area of Science:

• Anesthesiology
• Pharmacology

Background:

• The optimal dosage of spinal ropivacaine for lower extremity surgery requires further investigation.
• Understanding dose-response relationships is key for safe and effective anesthesia.

Purpose of the Study:

• To determine the effective dose of intrathecal ropivacaine for lower limb surgery.
• To establish the ED50 and ED95 for spinal ropivacaine in this patient population.

Main Methods:

• A prospective, randomized, double-blind study involving 60 patients undergoing lower limb surgery.
• Patients received varying doses of intrathecal ropivacaine (2, 4, 7, 10, or 14 mg).
• Success was defined by sensory block to T12 and surgery duration without supplementation.

Main Results:

• Anesthesia success rates were 0%, 0%, 42%, 83%, and 100% for the respective ropivacaine doses.
• The estimated ED50 was 7.6 mg (95% CI: 6.2-8.7 mg).
• The estimated ED95 was 11.4 mg (95% CI: 9.7-18.3 mg), with higher doses correlating to greater sensory and motor block.

Conclusions:

• The ED50 and ED95 for spinal ropivacaine in lower limb surgery (≤50 min) are 7.6 mg and 11.4 mg, respectively.
• These findings offer valuable guidance for selecting appropriate spinal ropivacaine doses in clinical practice.