Minimum local anesthetic dose of ropivacaine in real-time ultrasound-guided intraspinal anesthesia for lower extremity surgery: a randomized controlled trial

Ting Zheng; Peng Ye; Weilan Wu; Bin Hu; Lifei Chen; Xiaochun Zheng; Mingxue Lin

doi:10.21037/atm-20-3805

Minimum local anesthetic dose of ropivacaine in real-time ultrasound-guided intraspinal anesthesia for lower extremity surgery: a randomized controlled trial

Ann Transl Med. 2020 Jul;8(14):861. doi: 10.21037/atm-20-3805.

Authors

Ting Zheng¹, Peng Ye¹, Weilan Wu¹, Bin Hu², Lifei Chen¹, Xiaochun Zheng^{1

3}, Mingxue Lin¹

Affiliations

¹ Department of Anaesthesiology, Shengli Clinical Medical College of Fujian Medical University, Fujian Provincial Hospital, Fuzhou, China.
² Department of Anaesthesiology, Beijing Friendship Hospital, Capital Medical University, Beijing, China.
³ Fujian Emergency Medical Center, Fuzhou, China.

Abstract

Background: Despite the many advantages real-time ultrasound-guided lumbar anesthesia has over traditional lumbar anesthesia, it seemingly involves a much higher dose of ropivacaine. This study aimed to determine the minimum local anesthetic dose (MLAD) and the 95% confidence interval of ropivacaine at different concentrations in real-time ultrasound-guided lumbar anesthesia for lower extremity surgery.

Methods: A total of 60 patients who were consecutively scheduled for selective lower extremity surgery were enrolled. The patients were randomly divided into two groups, which each received different concentrations of ropivacaine at different initial dosages when Dixon's up-and-down sequential method was applied. The high ropivacaine group and the low ropivacaine group received 0.75% and 0.5% ropivacaine, respectively. The patients' baseline characteristics, the MLAD, and the 95% confidence interval were assessed. The highest level of sensory block, time to reach the T10 sensory block, duration for sensory blocks higher than T10, highest plane for sensory block, and onset time and duration for motor block were recorded. Comparisons were also made between the patients' vital signs and adverse reactions.

Results: The minimum local anaesthetic dose (MLAD) and 95% confidence interval in the high ropivacaine group and the low ropivacaine group were 17.176 (16.276 to 18.124) and 20.192 (19.256 to 21.174) mg, respectively. Moreover, motor block maintenance was greatly reduced in the 0.5% ropivacaine compared to the 0.75% ropivacaine group (P=0.0309).

Conclusions: In real-time ultrasound-guided intraspinal anesthesia for lower extremity surgery, both 0.75% and 0.5% ropivacaine provide satisfactory anesthesia. Our results suggest that shortened motor block duration can hold benefits for patients including earlier mobilization and a quicker rehabilitation process.

Keywords: Lower extremity; minimum local anaesthetic dose (MLAD); ropivacaine; spinal anesthesia, ultrasound.