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. 2022 Jun 7:15:1647-1657.
doi: 10.2147/JPR.S357750. eCollection 2022.

Median Effective Concentration of Ropivacaine for Femoral Nerve Block Maintaining Motor Function During Knee Arthroscopy in Two Age Groups

Yan-Lei Tai  1 , Li Peng  1 , Ying Wang  2 , Zi-Jun Zhao  3 , Ya-Nan Li  1 , Chun-Ping Yin  1 , Zhi-Yong Hou  4 , De-Cheng Shao  5 , Ya-Hui Zhang  1 , Qiu-Jun Wang  1
Affiliations

Median Effective Concentration of Ropivacaine for Femoral Nerve Block Maintaining Motor Function During Knee Arthroscopy in Two Age Groups

Yan-Lei Tai et al. J Pain Res. .

Abstract

Background: Femoral nerve block combined with general anesthesia is commonly used for patients undergoing knee arthroscopy in ambulatory care centers. An ideal analgesic agent would selectively (differentially) block sensory fibers, with little or no effect on motor nerves. Ropivacaine is considered to cause less motor block than others. This study investigated the median effective concentration (EC50) of ropivacaine for differential femoral nerve block in adults either younger or older than 60 years.

Methods: Patients with American Society of Anesthesiologists physical status I-III and scheduled for knee arthroscopy were categorized as 18- to 60-years-old (Group 1), or older than 60 years (Group 2). Surgeries were performed under general anesthesia combined with femoral nerve block via 22 mL ropivacaine. The EC50 of ropivacaine for differential femoral nerve block was determined using the up-and-down method and probit regression. The primary outcome was the EC50 (95% confidence interval [CI]) of the 2 groups. Data on the sensory block, analgesic effect, complications, and hemodynamics during surgery were also recorded.

Results: The EC50 of 22 mL ropivacaine for differential femoral nerve block of Group 1 (0.124%, 95% CI 0.097-0.143%) was significantly higher than that of Group 2 (0.088%, 95% CI 0.076-0.103%). The sensory block and hemodynamic data of the 2 groups were comparable. None of the patients experienced neurological complications.

Conclusion: The EC50 of ropivacaine administered for differential femoral nerve block during knee arthroscopy was lower in patients older than 60 years, relative to younger adults.

Keywords: EC50; age groups; femoral nerve block; motor block; ropivacaine.

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Conflict of interest statement

The authors declare that they have no conflicts of interest in this work.

Figures

Figure 1
Figure 1
Femoral nerve blocking guided by ultrasound. Arrow indicates the femoral nerve, which is surrounded by injected ropivacaine.
Figure 2
Figure 2
Flow diagram for the up-and-down method.
Figure 3
Figure 3
Femoral nerve block responses to predetermined ropivacaine concentrations using the Dixon’s up-and-down method in consecutive Group 1 (in black) and Group 2 (in grey) patients. Only patients from the first negative to positive response crossover in the 2 respective age groups were included. These sequential arrays included seven crossovers from negative to positive responses in 2 groups (Group 1, aged 18–60 years; Group 2, >60 years). Solid circle, negative response concentration; open circle, positive response concentration.
See this image and copyright information in PMC

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