[Randomized controlled trial comparing a low dose to a conventional dose of hyperbaric bupivacaine for scheduled...

Spinal anesthesia is the technique most often applied in cases of scheduled cesarean section. Many authors have tried decreasing the local anesthetic dose by adding opioids to achieve adequate analgesia with greater hemodynamic stability, although the ideal dose remains to be established. Our aim was to analyze hemodynamic stability and quality of analgesia with 2 different regimens for administering spinal hyperbaric bupivacaine.

We designed a controlled, double-blind trial comparing 2 doses of spinal hyperbaric bupivacaine with fentanyl in 42 patients undergoing elective cesarean section randomized to 2 groups to receive either the low dose or the conventional one. One group received an 11 mg dose of bupivacaine and the other group received a 6.5 mg dose, combined with 20 microg of fentanyl in both cases.

The hemodynamic profile and the level of maximum sensory block obtained were similar in the two groups. The motor block was less intense in patients receiving the lower dose and it was necessary to convert 2 patients (10%) to general anesthesia in that group.

Spinal anesthesia with low doses of bupivacaine and fentanyl provides acceptable intraoperative conditions for a high percentage of patients undergoing cesarean section, with a similar incidence of hypotension. The low dose generates a less intense intraoperative motor blockade with similar spread of the sensory block. The low dose was not efficacious for 10% of the patients who received it.