Stability of local anesthetics in heparinized blood, plasma and sulfuric acid

BACKGROUND: This study was undertaken to investigate the stability of local anesthetics in different media. METHODS: 60 patients with axillary plexus block, using prilocaine, mepivacaine or lidocaine 1%, or with lumbar epidural catheter-anesthesia, using bupivacaine 0.5%, were investigated. Stability was evaluated in heparinized whole blood for 24 h at +4 degrees C, in plasma for 8 week at -25 degrees C and in sulfuric acid for 6 months at -25 degrees C. RESULTS: Mean recovery rates were between 96.4% and 102.6% in all local anesthetics and media. No statistical significance became obvious for differences between recovery rates and initial values. CONCLUSION: Stability of prilocaine, mepivacaine, lidocaine and bupivacaine can be expected when samples are stored as heparinized whole blood for 24 h at +4 degrees C, plasma for 8 weeks at -25 degrees C, and after preparation into sulfuric acid for 6 months at -25 degrees C.