Intrathecal Anesthesia: Ropivacaine Versus Bupivacaine

We compared intrathecal ropivacaine to bupivacaine in patients scheduled for transurethral resection of bladder or prostate. Doses of ropivacaine and bupivacaine were chosen according to a 3:2 ratio found to be equipotent in orthopedic surgery. One hundred patients were randomly assigned to blindly receive either 10 mg of isobaric bupivacaine (0.2%, n = 50) or 15 mg of isobaric ropivacaine (0.3%, n = 50) over 30 s through a 27-gauge Quincke needle at the L2-3 level in the sitting position. Onset and offset times for sensory and motor blockades and mean arterial blood pressure were recorded. Pain at surgical site requiring supplemental analgesics was recorded. Cephalad spread of sensory blocks was higher with bupivacaine (median level, cold T4 and pinprick T7) than with ropivacaine (cold T6 and pinprick T9) (P <0.001). Eight patients in Group Ropivacaine received IV alfentanil (P <0.01). Onset time (mean ± sd) to T10 anesthesia and offset time at L2 were not different (bupivacaine = 13 ± 8 min, 127 ± 41 min; ropivacaine = 11 ± 7 min, 105 ± 29 min). Complete motor blockade occurred in 43 patients with bupivacaine and in 41 patients with ropivacaine (not significant). Total duration of motor blockade was not different. No difference in hemodynamic effects was detected between groups. No patient reported back pain. We conclude that 15 mg of intrathecal ropivacaine provided similar motor and hemodynamic effects but less potent anesthesia than 10 mg of bupivacaine for endoscopic urological surgery. Implications Inadequate intrathecal anesthesia was observed in 16% of patients with 15 mg of ropivacaine, whereas intensity and duration of motor blockade was not different in comparison to 10 mg of bupivacaine. Ropivacaine appears to be less potent than bupivacaine at doses used in spinal anesthesia.