Back pain after epidural anesthesia with chloroprocaine.

Background: Chloroprocaine has been associated with severe back pain after epidural anesthesia. Factors proposed to contribute to this problem are: 1) the preservative disodium ethylenediaminetetraacetic acid (EDTA), 2) large volumes of chloroprocaine, 3) low pH of chloroprocaine, and 4) local infiltration with chloroprocaine.

Methods: Using a prospective, balanced, randomized study design, 100 patients aged 18-65 yr who were undergoing outpatient knee surgery during continuous epidural anesthesia received one of five local anesthetics (all containing epinephrine 1:200,000). Group I received a bolus of 30 ml 2% lidocaine, followed by 10 ml every 45 min. Group II received 15 ml of 3% chloroprocaine (containing EDTA), plus 5 ml every 45 min. Group III received 30 ml of 3% chloroprocaine plus 10 ml every 45 min. Group IV received 30 ml of 3% chloroprocaine (containing metabisulfite as the preservative but no EDTA) plus 10 ml every 45 min. Group V received 30 ml of 3% chloroprocaine with the pH adjusted to 7.3, plus 10 ml every 45 min. After the anesthesia dissipated and before any analgesic agents were given, the patients were asked to rank maximum knee and back pain on a visual analog scale (0-10) and to give a description of back pain. A telephone interview was conducted 24 h after surgery to determine if back pain returned. Back pain scoring was assessed using a verbal analog scale.

Results: After dissipation of anesthesia, the back pain reported by patients fell into two distinct categories. Type 1 pain was described commonly as superficial and localized to the site of needle insertion. There was no difference among groups in incidence of type 1 pain. Type 2 pain was described as deep, aching, burning, and poorly localized in the lumbar region (5% of the patients in group I, 10% in groups II and IV, 50% in group III, and 25% in group V). The incidence of type 2 pain was significantly greater in group III than in groups I, II, or IV. Group III also had a significantly greater mean visual analog scale pain score (types 1 and 2) than all other groups.

Conclusions: Large doses (> or = 40 ml) of chloroprocaine containing EDTA resulted in a greater incidence of deep burning lumbar back pain. Using 25 ml or less of the same solution resulted in an incidence of both types 1 and 2 postepidural anesthesia back pain similar to that in the lidocaine control group.