Hemodynamic effects of continuous spinal anesthesia: a comparative study between low and high doses of bupivacaine

Arterial hypotension is a major side effect of spinal anesthesia. Continuous spinal anesthesia may allow titration of the amount of local anesthetic to obtain a level that is appropriate for the surgical procedure.

This study compared the hemodynamic effects and the quality of analgesia of spinal anesthesia performed with 3 ml of either 0.125% (n = 12) or 0.5% (n = 13) plain bupivacaine in 25 elderly patients undergoing orthopedic surgery.

The initial dose's duration of action (time elapsed between the end of injection and the first patient's complaint of pain during surgery) was shorter in the group receiving 3 ml of 0.125% plain bupivacaine than in the group receiving 0.5% plain bupivacaine: 80 +/- 31 minutes versus 114 +/- 37 minutes, respectively (mean +/- SD; p less than 0.05). In 6 (50%) of 12 patients of the 0.125% group and in 2 (15%) of 13 of the 0.5% group, analgesia became insufficient during the surgical procedure, necessitating injection of an additional 1 ml (top-up) of the previous solution. All subjects obtained good anesthesia for the entire procedure. The mean dose of bupivacaine necessary for the procedure was significantly lower in the 0.125% group (4.8 +/- 1.3 mg) compared with the 0.5% group (16.1 +/- 3 mg). For a similar maximal upper level of analgesia (T4-T12 in the 0.125% group versus T2-T10 in the 0.5% group), the decrease in systolic arterial pressure was more pronounced in the 0.5% group than in the 0.125% group during the period 15-40 minutes after induction of spinal anesthesia (p less than 0.05%). The mean dose of ephedrine was threefold larger in the 0.5% group than in the 0.125% group.

Continuous spinal anesthesia with small amounts of 0.125% plain bupivacaine produces effective anesthesia for orthopedic procedures in elderly patients with minimal hemodynamic changes.