Single-shot spinal anesthesia with small doses of bupivacaine.

Background and objectives: The potential risks of spinal lidocaine have generated interest in an alternative local anesthetic solution. Features of anesthetic block were therefore assessed in a double-blind randomized prospective study following administration of spinal bupivacaine in small doses.

Methods: Ninety patients scheduled for lower limb saphenous vein stripping were randomized to receive a 4-mL hyperbaric solution containing 4, 6, or 8 mg bupivacaine in the subarachnoid space. Sensory and motor block and hemodynamic changes were assessed at regular intervals. Patients were also questioned regarding transient radicular irritation symptoms.

Results: The mean duration of sensory block increased with increasing dose (duration at L2: 56 +/- 27, 71 +/- 29, 79 +/- 25 minutes in groups 4, 6, and 8 mg, respectively, P < .05). Motor block was also dose dependent. The incidence of grade 3 motor block increased from 0%, to 21%, and to 53%. No patient had symptoms of transient radicular irritation. Arterial pressure and heart rate were stable throughout the study.

Conclusion: Hyperbaric bupivacaine 6-8 mg provides a suitable alternative to spinal lidocaine for surgical procedures of short duration.