Reduction of pain and local complications when buffered lidocaine solution is used as a local anesthetic in conjunction with hyperthermia treatments: results of a randomized trial.

Unbuffered lidocaine (pH = 6.5) is commonly employed as a local anesthetic prior to transcutaneous placement of catheters for use in temperature monitoring during hyperthermia treatments. The most frequent complaint associated with this procedure is stinging or burning pain at the injection site. Tender firm subcutaneous nodules at sites of lidocaine infiltration for catheter placement have also been noted in fields treated with radiation and hyperthermia. A reduction in the pain associated with lidocaine infiltration has been reported by the use of alkalinized (buffered) local anesthetic solutions. To confirm this finding in patients treated with hyperthermia for superficially-located tumors, a randomized prospective double blind trial comparing unbuffered (pH 6.5) and buffered (pH 7.3) 2% lidocaine (without epinephrine) was undertaken. Between March and October 1990, a total of 54 hyperthermia treatment fields were each randomized to buffered or unbuffered lidocaine to be used at the time of all catheter placements (146 placements). Patients were scored both for the pain noted during the infiltration of lidocaine and the pain noted with subsequent catheter placement. In addition, the development of subcutaneous nodules at the sites of catheter placement was monitored at the time of 3-week follow-up. Follow-up was available for all but two fields. Treatment fields that received the buffered anesthetic had a statistically significant reduction in the pain associated with infiltration of lidocaine (p less than 0.05) without any compromise in its therapeutic efficacy as observed on a linear Visual Analog Scale. Furthermore, the incidence of subcutaneous nodules was lower in the fields treated with the buffered solution (1/23 vs 7/29, p = 0.05 for buffered and unbuffered solutions, respectively). The results of this trial support the use of buffered lidocaine prior to catheter placement for hyperthermia treatments as a method of reducing pain at infiltration and the subsequent development of subcutaneous nodules.