Comparative analysis of analgesic quality in the postoperative of thoracotomy: paravertebral block with bupivacaine 0.5% vs ropivacaine 0.2%.

OBJECTIVES

Paravertebral block is an effective alternative to epidural analgesia in the management of post-thoracotomy pain, however, there are no established guidelines regarding what is the most suitable strategy when varying drugs and dosages between different groups. Our objective was to evaluate the effectiveness of paravertebral block comparing the most frequently employed drugs in this procedure (bupivacaine vs ropivacaine).

METHODS

Prospective randomized study of 70 patients submitted to thoracotomy. Patients were divided in two independent groups (anterior thoracotomy (AT) and posterolateral thoracotomy (PT)). At the end of surgery a catheter was inserted under direct vision in the thoracic paravertebral space at the level of incision. In each group (AT or PT) patients were randomized to receive a bolus of 15 ml of bupivacaine 0.5% or 20 ml of ropivacaine 0.2% before closing the thoracotomy. They postoperatively received 10 ml of bupivacaine or 15 ml of ropivacaine every 6h combined with methamizol (every 6h). Subcutaneous meperidine was employed as rescue drug. The level of pain was measured with the visual analogic scale (VAS) at 1, 6, 24, 48 and 72 h after surgery. The need of meperidine as rescue drug and secondary effects was also recorded.

RESULTS

We did not register secondary effects in relation to the paravertebral catheter (paravertebral or cutaneous bleeding or hematoma, respiratory depression (respiratory rate <8 breaths per minute), cardiotoxicity, confusion, sedation, urinary retention, nausea, vomiting and pruritus). Eleven patients (16%) needed meperidine as rescue drug (six with ropivacaine and five with bupivacaine). Mean VAS values were the following: all the cases (n=70): 5.2+/-2.1, AT (n=38): 4.5+/-2.1, PT (n=32): 5.9+/-1.7, bupivacaine (n=35): 4.9+/-2.1, ropivacaine (n=35): 5.4+/-1.9, AT with bupivacaine (n=19): 4.2+/-2.2, AT with ropivacaine (n=19): 4.9+/-2.0, PT with bupivacaine (n=16): 5.7+/-1.6, PT with ropivacaine (n=16): 6.0+/-1.7.

CONCLUSIONS

Post-thoracotomy analgesia combining paravertebral catheter and a nonsteroidal anti-inflammatory drug is a safe and effective practice, VAS values are acceptable (only 16% of patients required meperidine as rescue). It prevents the risk of side effects related to epidural analgesia. Patients submitted to AT experienced less pain than those with PT (4.5 vs 5.9, p<0.01). Bupivacaine got slightly better VAS values than ropivacaine (4.9 vs 5.4 p<0.05). Higher doses and volumes of local anesthetic could be used to obtain better VAS values.