Distribution of local anesthetics injected into the interpleural space, studied by computerized tomography

Twenty-one patients were given interpleural analgesia for postoperative pain relief after cholecystectomy, or renal or breast surgery. The patients were classified randomly into two groups: an interpleural injection of 20 ml of 0.375% bupivacaine mixed with 10 ml contrast medium was given to 11 patients in the supine position, and 10 in the lateral position. The patients remained in this position for 1 h. There was no significant difference in the rostrocaudal distribution of the contrast on computerized tomography taken 20 min later: Th3-L1 in the supine group vs. Th5-L1 in the lateral group. In the supine group the mean level of contrast medium reached significantly higher medially along the mediastinum (51 +/- 11 mm) than laterally (27 +/- 11 mm).