Ropivacaine spinal anesthesia is not antagonized by ondansetron pretreatment.

BACKGROUND: We investigated a possible effect of ondansetron on the duration of sensory and motor block produced by ropivacaine. METHODS: Fifty male patients undergoing transurethral surgery received either 8 mg oral ondansetron the evening before surgery plus IV 8 mg ondansetron 15 min before subarachnoid anesthesia or placebo. All patients received 2.2 mL of 0.75% plain ropivacaine intrathecally. Sensory and motor block were assessed 30 min after the intrathecal injection and every 30 min thereafter until recovery from the motor block. RESULTS: Thirty minutes after spinal injection of ropivacaine, we first measured, in both groups, the time to maximum block for both sensory and motor modalities. The maximum level of the sensory block, defined as decreased sensation, was T8 in the control and T6 in the ondansetron group, and absence of sensation was defined as T11 and T9 for the control and the ondansetron groups, respectively. Regarding block duration, 180 min after spinal injection, sensory block was detected in 11 of 22 and 16 of 24 patients and motor block in 1 of 22 and 0 of 24 in the control and ondansetron groups, respectively. Sensory and motor block did not differ between groups at any measured time point. CONCLUSIONS: Ondansetron had no effect on the subarachnoid sensory or motor block produced by ropivacaine.

Preoperative gabapentin: the effect on ropivacaine subarachnoid block and hemodynamics.

BACKGROUND: Gabapentin is an adjuvant analgesic and may enhance the spread of subarachnoid block. We investigated the effects of pretreatment with gabapentin on subarachnoid block characteristics and hemodynamics. METHODS: Seventy patients undergoing transurethral procedures under subarachnoid anesthesia with 2.2 mL of 0.75% ropivacaine were randomly assigned to receive preoperatively 400 mg of gabapentin 6 hourly, up to a total dose of 1200 mg, or placebo. Sensory and motor blocks were assessed every 30 min until regression of sensory block to L4. At the same time intervals, systolic and diastolic arterial blood pressures and heart rate were recorded. RESULTS: There were no differences between groups in the sensory block levels or degree of motor block. Sensory block 150 min after the subarachnoid injection had regressed to L4 in 26 of 32 patients in the gabapentin group and in 25 of the 33 patients in the control group. Systolic arterial blood pressure was decreased in the gabapentin group (P = 0.002 for the main effect of group, and P = 0.03 at 60 min between the groups). The diastolic arterial blood pressure did not differ between the groups, but overall, the heart rate was more rapid in the gabapentin group (P = 0.002, but only for baseline values between the groups, P = 0.036). CONCLUSION: Pretreatment with gabapentin had no effect on the spread of sensory block or the regression of motor block but was associated with lower systolic arterial blood pressure values in patients undergoing subarachnoid anesthesia with ropivacaine.