ANALGESIA AFTER THORACOTOMY USING CONTINUOUS EXTRAPLEURAL BUPIVACAINE

This study was aimed to assess the efficiency and the side effects of a continuous administration of bupivacaine into the paravertebral space. Twenty patients, ranked ASA 2 or 3, with a mean age of 57.9 years, and having had a posterolateral thoracotomy for resection of lung tissue. were randomly assigned to one of two groups, B or C. At the end of the surgical procedure, a 22 gauge catheter was inserted into the paravertebral extrapleural space. at T4 levels As soon as pain ocurred during recovery (T0), the patients were given two-hourly intravenous boluses of buprenorphine. The patients in group B were also given, through the paravertebral catheter. a 20 ml bolus of 0.25 % bupivacaine, followed by a continuous steady rate infusion (10 ml - h-1). Group C patients were given normal saline in the same way. All patients could improve their analgesia with 0.05 ml boluses of buprenorphine given by an auto-analgesia pump (Pharmacia). The following parameters were assessed during the 72 h which followed the first injection pain with a visual analogic scale, quality of sedation (5 grades), heart and breathing rate, systolic and diastolic blood pressure, arterial blood gases. In group B, plasma bupivacaine concentrations were measured throughout the infusion, and for an 8-hour period after its end. The statistical analysis included 15 patients only, as the catheter had moved into the chest cavity in the other 5. Analgesia was qualified to be adequate by all patients, but there was no statistically significant difference in the amounts of self-administered buprenorphine between groups B and C. The buprenorphine concentration reached a plateau of 1.6 mug . ml-1 at about the twelth hour. No signs of toxicity, arterial hypotension or respiratory depression were noticed. It was therefore impossible to conclude that paravertebral bupivacaine was more efficient than normal saline after thoracotomy for lung surgery. Patient controlled analgesia used both to achieve an optimal analgesia and to act as an objective method for assessing analgesia provided less optimistic results than those previously published by other authors.