Effects of adding epinephrine plus fentanyl to low-dose lidocaine for spinal anesthesia in outpatient knee arthroscopy.

BACKGROUND: This study investigated whether addition of 15 microg epinephrine plus 25 microg fentanyl to lidocaine spinal anesthesia for outpatient knee arthroscopy makes it possible to use a subanesthetic lidocaine dose. The aim was to assess the quality of anesthesia and the suitability of this protocol for outpatient knee arthroscopy.

METHODS: Seventy-five outpatients scheduled for knee arthroscopy were randomly assigned to one of three spinal anesthetic protocols: Group L10F25 received 10 mg of lidocaine plus 25 micro g fentanyl; Group L10F25E15 received 10 mg of lidocaine plus 25 microg fentanyl plus 15 microg epinephrine; and Group L20F25 received 20 microg lidocaine plus 25 microg fentanyl. Tourniquet pain and surgical pain were assessed using a visual analog scale. If spinal anesthesia was inadequate despite supplementary intravenous analgesia and sedation, the patient was converted to general anesthesia. Recovery times and side-effects in the early postoperative period were recorded.

RESULTS: The highest level of sensory block was above the T12 dermatome in all patients. Compared with the other groups, significantly more patients in Group L10F25 converted to general anesthesia. Group L10F25 had a significantly higher mean surgical pain score than the other groups. The mean tourniquet pain score was significantly higher in Group L20F25 than Group L10F25E15. Group L10F25E15 had a significantly shorter time to discharge than the other groups. Post-operative nausea and vomiting and drowsiness were more frequent in Group L10F25 than in the other groups.

CONCLUSION: The combination of 10 mg lidocaine and 25 microg fentanyl plus 15 microg epinephrine provides adequate spinal anesthesia and has favorable recovery characteristics for outpatient knee arthroscopy.