A prospective study of analgesic quality after a thoracotomy: paravertebral block with ropivacaine before and after rib spreading☆

Abstract

Paravertebral block (PVB) is an effective alternative to epidural analgesia in the management of post-thoracotomy pain. Rib spreading (RS) is an important noxious stimulus considered a major cause of post-thoracotomy pain. Our hypothesis was that a bolus of ropivacaine 0.2% through a paravertebral catheter (PVC) inserted before RS could decrease pain during the first 72 postoperative hours. The methodology employed was to perform a prospective randomised study of 60 consecutive patients submitted to thoracotomy. Patients were divided in two independent groups (anterior thoracotomy (AT) and posterolateral thoracotomy (PT)). A catheter was inserted under direct vision in the thoracic paravertebral space at the level of incision. In each group, patients were randomised to receive a bolus of 20 ml of ropivacaine 0.2% before rib spreading (pre-RS) or after (post-RS), just before closing the thoracotomy. They postoperatively received 15 ml of ropivacaine 0.2% every 6 h combined with methamizol (every 6h). Subcutaneous meperidine was employed as a rescue drug. The level of pain was measured with the visual analogue scale (VAS) at 1, 6, 24, 48 and 72 h after surgery. The need of meperidine as a rescue drug and secondary effects were also recorded. We did not register secondary effects in relation to the PVC (paravertebral or cutaneous bleeding or haematoma, respiratory depression, cardiotoxicity, confusion, sedation, urinary retention, nausea, vomiting or pruritus). Seven patients (11.6%) needed meperidine as rescue drug (four pre-RS and three post-RS). The mean VAS values were the following: all cases (n=60): 4.7+/-2.0; AT (n=32): 4.0+/-2.1; PT (n=28): 5.6+/-1.8; pre-RS (n=30): 4.8+/-1.9; post-RS (n=30): 4.6+/-2.0; AT-pre-RS (n=16): 4.1+/-2.0; AT-post-RS (n=16): 3.9+/-2.1; PT-pre-RS (n=14): 5.6+/-1.6; PT-post-RS (n=14): 5.4+/-1.7. Post-thoracotomy analgesia combining PVC and a non-steroidal anti-inflammatory drug is a safe and effective practice. VAS values are acceptable (only 11.6% of patients required meperidine). It prevents the risk of side effects related to epidural analgesia. Patients submitted to AT experienced less pain than those with PT (4.0 vs 5.6; p<0.01). PVB with ropivacaine before RS got similar VAS values than the block after RS (4.8 vs 4.6; p>0.05). The moment of the insertion of the PVC does not seem to affect postoperative pain levels.