Lower-Dose Mepivacaine Plus Fentanyl May Improve Spinal Anesthesia for Knee Arthroscopy



Previous work indicates that 30 mg isobaric mepivacaine 1.5% plus 10 μg fentanyl produces reliable anesthesia for knee arthroscopy with a more rapid recovery profile than 45 mg mepivacaine.


This randomized controlled trial compared plain mepivacaine to three reduced doses of mepivacaine with 10 μg fentanyl for spinal anesthesia.


Following written informed consent, subjects undergoing outpatient knee arthroscopy were prospectively randomized into one of four groups: mepivacaine 37.5 mg (M37.5); mepivacaine 30 mg plus fentanyl 10 μg (M30/F10); mepivacaine 27 mg plus fentanyl 10 μg (M27/F10); and mepivacaine 24 mg plus fentanyl 10 μg (M24/F10). The spinal was evaluated by the blinded anesthetist and surgeon. In the post-anesthesia care unit, sensory and motor block resolution was assessed. Subjects rated their satisfaction with the overall experience.


Group M30/F10 (n = 6) had two “fair” anesthetics, and group M27/F10 (n = 10) had one “fair” and one “inadequate” anesthetic. Both groups were eliminated from further enrollment per study protocol. The recovery profiles showed little difference between groups M37.5 and M30/F10, except for motor block resolution (median (25th percentile, 75th percentile): 171 (135, 195) and 128 (120, 135), respectively). Groups M27/F10 and M24/F10 demonstrated recovery profiles that were faster than group M37.5. Patient satisfaction was 10/10 for all groups.


Adding fentanyl 10 μg to a lower dose of mepivacaine 1.5% can lead to quicker recovery profiles. However, this advantage of a quicker recovery must be weighed against the likelihood of an incomplete anesthetic.

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Conflict of Interest

Richard L. Kahn, MD, Jennifer Cheng, PhD, James J. Bae, MSc, Kara Fields, MS, John G. Muller, MD, John D. MacGillivray, MD, Howard A. Rose, MD, Riley J. Williams III, MD, and Jacques T. YaDeau, MD, PhD have declared that they have no conflict of interest.

Human/Animal Rights

All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008 (5).

Informed Consent

Informed consent was obtained from all patients for being included in the study.


This work was supported by the Department of Anesthesiology at Hospital for Special Surgery, and REDCap was funded by the National Institute of Health: Clinical and Translational Science Center (UL1-RR024996).

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Corresponding author

Correspondence to Richard L. Kahn MD.

Additional information

Level of Evidence: Level II: Therapeutic Study.

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Kahn, R.L., Cheng, J., Bae, J.J. et al. Lower-Dose Mepivacaine Plus Fentanyl May Improve Spinal Anesthesia for Knee Arthroscopy. HSS Jrnl 11, 236–242 (2015). https://doi.org/10.1007/s11420-015-9454-8

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  • fentanyl
  • mepivacaine
  • spinal anesthesia
  • arthroscopy