Intrathecal hyperbaric 2% prilocaine versus 0.4% plain ropivacaine for same-day arthroscopic knee surgery: a prospective randomized double-blind controlled study

Background: Short-duration spinal anesthesia is a good option for ambulatory knee surgery. Hyperbaric 2% prilocaine has short onset and rapid recovery times and, therefore, may be well suited in this setting. The aim of this study was to compare the times to reach motor block, motor block resolution, and discharge from the postanesthesia care unit (PACU) between hyperbaric 2% prilocaine and 0.4% plain ropivacaine. Methods: In this prospective randomized double-blind study, 140 patients (ages 18-80 yr and American Society of Anesthesiologists physical status I-II) scheduled for elective unilateral arthroscopic knee surgery lasting < 45 min were allocated to either 3 mL of 2% prilocaine (60 mg) or 3 mL of 0.4% plain ropivacaine (12 mg). Time to reach complete recovery of motor block, time to reach criteria for discharge, as well as side effects up to 48 hr after discharge were recorded. Results: The median (interquartile range [IQR]) time to recovery from the motor block was faster in the 2% prilocaine group compared with the 0.4% ropivacaine group (180 [169-240] min vs 240 [180-300] min, respectively; median difference, 60 min, 95% confidence interval (CI), 23 to 97 min; P = 0.036). The median [IQR] time to reach discharge criteria was similar between the two groups (330 [295-365] min vs, 335 [290-395] min; median difference 5 min, 95% CI, −25 to 35 min; P = 0.330). The incidence of side effects was low and similar in both groups. No case of transient neurologic symptoms occurred in either group. Conclusion: The recovery of motor block was faster after intrathecal administration of hyperbaric 2% prilocaine compared with 0.4% plain ropivacaine; however, discharge time was similar between the two groups. Both drugs showed a similar risk profile