[Evaluation of 0.5% hypobaric bupivacaine in spinal anesthesia]

Spinal anesthesia may cause hemodynamic changes due to factors related or not to the patient. The density of the anesthetic compared to the CSF, which interferes with the number of dermatomes blocked and, consequently, with the level of the sympathetic blockade and reduction in blood pressure (BP), is one of those factors. The objective of this study was to evaluate the dispersion of 0.5% hypobaric bupivacaine prepared aseptically in a laboratory, with controlled and uniform density.

Thirty patients, physical status ASA I, II, or III, ages ranging from 18 to 60 years, without cardiovascular comorbidities, who underwent orthopedic surgery of the lower limb, were enrolled in this study. They were sedated with diazepam, 0.03 mg.kg-1, placed in lateral decubitus, with the side to be operated on top. A lumbar puncture in the L3-L4 space was performed with a 27G Quincke needle, and the direction of the bevel and rate of injection were standardized. The sensitive and motor levels (modified Bromage scale) were evaluated.

At the end of the surgery, two patients (6.6%) did not present a level 3 motor blockade in the Bromage scale, and the sensitive blockade varied from T4 to T12. Only 12.9% of the patients presented a level of sensitive blockade considered 'high' for the proposed surgery (above T6). The reduction in blood pressure was statistically significant, but it did not fall below 20% of basal levels and, therefore, was not clinically significant. The change in heart rate was non-significant.

It was demonstrated that 0.5% hypobaric bupivacaine is a safe choice, with little hemodynamic repercussion in orthopedic surgeries of the lower limbs. The mean duration of the anesthesia, 250 minutes, allows the realization of minor and medium orthopedic procedures.