Monitoring Serum Bupivacaïne Levels During Arthroscopy

Arthroscopy was carried out after subcutaneous injection of lignocaïne to produce local anaesthesia, using controlled pressure-irrigation with bupivacaïne, followed by final rinsing with an isotonic solution. This procedure, which was painless for the patient and had no systemic toxic effects, gave very good distension of the joint and clear visualization of its structure. A sharp peak in the serum bupivacaïne level (Cmax: 76.2 ng/ml) was observed only 5 min after the start of the irrigation, which was attributed to synovial resorption. This was followed by a slight increase in blood concentration 4 to 5 h after the end of the arthroscopy, probably as a result of absorption by the peripheral soft tissues. Bupivacaïne concentrations never exceeded 350 ng/ml (much lower than the toxic level). The drug persisted in blood for 36 to 48 h (terminal half-life 12.1 h).