[Bupivacaine in continuous epidural infusion using a portable mechanical devise for postoperative analgesia after surgery for hernia of the lumbar disk].

OBJECTIVES

To determine the optimum concentration of bupivacaine administered by continuous epidural infusion, using a Baxter Single Day elastomeric infusor at a rate of 2 ml/h, to treat pain during the first 24 h after lumbar laminectomy.

PATIENTS AND METHODS

Sixty patients undergoing elective repair of a herniated lumbar disk were randomly assigned to three homogeneous groups of 20 each. Group I received epidural infusion of 0.0625% bupivacaine, group II received 0.125% bupivacaine and group III received 0.25% bupivacaine. After surgery each patient was given a 4 mL solution of the local anesthetic being studied, followed by an infusion of the same through an elastomeric infusor at a rate of 2 ml/h throughout the first 24 h after surgery. Ketorolac was delivered through a device for patient controlled analgesia after surgery. Pain was assessed on a visual analog scale (VAS) at rest and during movement. Pain relief was assessed on a simple descriptive scale.

RESULTS

Significantly less ketorolac was required during epidural infusion of 0.125% and 0.25% bupivacaine than when the 0.0625% concentration was being infused (29 +/- 16 and 28 +/- 13 mg, respectively, versus 110 +/- 35 mg; p < 0.001). VAS scores were significantly lower during infusion of 0.125% and 0.25% bupivacaine than with 0.0625% bupivacaine. No instances of motor blockade or infection related to catheter insertion were observed in any of the patients.

CONCLUSIONS

Continuous epidural infusion of 0.125% and 0.25% bupivacaine through an elastomeric infusor gives excellent analgesia during the first 24 h after surgery. Administration of 0.25% bupivacaine is associated with a higher incidence of urinary retention. We therefore think that the most recommendable concentration of bupivacaine for infusion is 0.125%.