50% enantiomeric excess hyperbaric bupivacaine (S75:R25) for infraumbilical surgeries. Study with different volumes

Hyperbaric bupivacaine is commercially available in its racemic form. In Brazil, 50% enantiomeric excess bupivacaine (S75:R25) was introduced as an isobaric presentation. The objective of this study was to evaluate different volumes of hyperbaric S75:R25 bupivacaine in spinal blocks for infraumbilical surgeries.

Forty patients, ages 20 to 60 years, physical status ASA I and II, scheduled for infraumbilical surgeries under spinal block participated in this study. Patients were randomly divided in four groups of 10 patients: Group 2.5--received 2.5 ml of the solution (10 mg), Group 3--3 ml (12 mg), Group 4--4 ml (16 mg), and Group 5--5 ml (20 mg). The following parameters were evaluated and compared: latency, cephalad dispersion, motor blockade, cardiovascular changes, and neurologic complications.

The study showed a latency of 1:33 +/- 0:26 (min:sec) without significant differences among the different doses. Motor blockade was dose-dependent. The incidence of bradycardia or hypotension was related with the increase in the dose. Anesthetic failures were not observed.

0.4% hyperbaric 50% enantiomeric excess bupivacaine (S75:R25) with D5W provided fast onset of the blockade and the level of sensitive and motor blockades as well as the duration of the blockade were dose-dependent.