Comparison of hemodynamic and anesthetic effects of hyperbaric bupivacaine and tetracaine in spinal anesthesia.

Purpose: To compare the anesthetic and hemodynamic effects and the predictive factor of anesthesia level of commonly used preparations of hyperbaric bupivacaine and tetracaine in spinal anesthesia.

Methods: Two hundred patients aged 40 to 75 years with ASA physical status I or II were anesthetized spinally via the L4-5 interspace using 0.5% hyperbaric bupivacaine in 7.27% glucose (Bupivacaine group, n = 100) or 0.5% hyperbaric tetracaine dissolved in a 10% glucose solution (Tetracaine group, n = 100) in a lateral position. The volume of anesthetic used was decided by the resident according to the surgical procedure. Patients were returned to the supine position immediately after drug injection. Blood pressure, heart rate, and anesthesia level tested by cold sensation were measured for 30 min.

Results: Blood pressure and heart rate decreased significantly but without any differences between the groups. The volume of drug used was significantly larger in the Bupivacaine group (2.6 +/- 0.5 ml) than in the Tetracaine group (2.1 +/- 0.4 ml) to obtain the same maximum anesthesia level. The time to reach the maximum anesthesia level was significantly longer in the Bupivacaine group (18 +/- 7 min) than in the Tetracaine group (15 +/- 6 min). The volume of the drug was the only predictive factor of the maximum anesthesia level in both groups: Level (as expressed by the number of anesthetized segments from S5 to cephalad) = 1.55 x (volume in ml) + 13.06 in the Bupivacaine group, and 2.59 x (volume) + 11.46 in the Tetracaine group.

Conclusion: In spinal anesthesia, hyperbaric tetracaine in 10% glucose induced a faster and higher spread of anesthesia than hyperbaric bupivacaine in 7.27% glucose without any differences in hemodynamics.