Related Experiment Video
Updated: Apr 5, 2026

Knee Arthrocentesis in Adults
Published on: February 25, 2022
Relative potency ratio between hyperbaric and isobaric solutions of ropivacaine in subarachnoid block for knee
Tao Xu1, Jia Wang1, Geng Wang1
1Department of Anesthesiology, Beijing Jishuitan Hospital Beijing 100035, China.
Objective:
To observe the potency ratio of hyperbaric to isobaric solutions of ropivacaine in subarachnoid block for knee arthroscopy.
Methods:
Fifty patients receiving knee arthroscopy under combined spinal-epidural anesthesia were randomly divided into isobaric ropivacaine group and hyperbaric ropivacaine group (0.5% ropivacaine, prepared with equal volume of 10% glucose and 1% isobaric ropivacaine). Successful criteria of spinal anesthesia were (1) a bilateral loss of pinprick sensation at or above the level of T12; (2) adequate motor block during knee arthroscopy (modified Bromage's score ≥2); and (3) no requirement of additional epidural administration at least within 60 min after intrathecal injection. Drug consumption was determined with up-and-down method, and then ED50 was calculated.
Results:
The ED50 of isobaric ropivacaine was 9.71 mg (95% CI 8.11-11.32), and the ED50 of hyperbaric ropivacaine was 6.55 mg (95% CI 6.07-7.04), and the relative potency ratio was 0.67 (95% CI 0.56-0.80) for hyperbaric/isobaric ropivacaine.
Conclusions:
The ED50 of hyperbaric ropivacaine is less than that of isobaric ropivacaine in subarachnoid block anesthesia for knee arthroscopy.
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