Local anesthesia for pain relief after surgery

Abstract

Postoperative pain is a common problem in spite of increased awareness among patients and healthcare professionals. The prevailing practice is still to administer opiates, which have a good painrelieving potential but opiates also have a number of negative sideffects. In this Thesis 1 have analysed the use of local anesthetics in various forms as an alternate means of pain relief after surgery.

Paper I: Twentyone patients operated with an open cholecystectomy received an intrapleural catheter for administration of bupivacaine-adrenaline in various dose regimens. Pain relief and ventilatory parameters were recorded before and after administration. Plasma concentration of bupivacaine was assessed. A double-blind comparison was made in six of the patients. Five patients received an injection of local anesthesia with contrast to determine the distribution of the fluid within the pleura.The intrapleural treatment resulted in an effective pain relieving effect with an improved pulmonary function. The local anesthetic was distributed dorsally in the pleura from the base to the apex. No patient in the placebo group experienced pain relief or improved lungfunction, while the patients in the treatmentgroup were improved.

Paper II: Twenty patients operated with open cholecystectomy received an intrapleural catheter for postoperative painrelief. The studied parameters were: analgesic effect (n=20), temperature and pain sense (n7=20), cutaneous bloodflow (n=9) and phrenic nerve stimulation (n=4). All patients reported reduced pain scores after treatment with 20 nil 0.25% bupivacaine, eleven patients had a loss of their temperature sense on the right side and of these ten also lost their pain sense after treatment, but all had reduced VAS scores. A sligh t increase in blood flow was recorded without difference between the sides, the phrenic nerve was not affected by the local anesthetic.

Paper III: Twenty males undergoing inguinal hernia repair were subjected to treatment with infiltration of ropivacaine postoperatively. Ten patients received 300 mg and ten 375 mg in a double blind design. VAS scores and consumption of additional anIgesics were followed. Plasma concentrations were determined as well as blood samples and a close monitoring of adverse events was instituted. Both groups reported similar reduction of VAS scores and both groups required the same amount of additional analgesics. Plasma concentrations of ropivacaine were well below the estimated toxic levels and no patient reported any adverse events attributable to the local anesthetic.

Paper IV: In a multicenter trial the efficacy of 300 mg ropivacaine was compared to 100 mg bupivacaine given as infiltration anesthesia after inguinal hernia surgery. The study comprised 144 patients operated in four hospitals. VAS scores and request for additional anIgesics were recorded, and ability to perform activities of daily life were followed as well as safety parameters. Both drugs proved to be effective in reducing postoperative pain without any difference between the two tested drugs. No adverse events causally related to the local anesthetics were found.

Paper V: Ninety patients operated with breast conservative surgery and axillary clearance, for malign breast tumors were allocated to three groups. One received infiltration with 20 nil bupivacaine 0.5%, one topical application of 10 grams of Emla cream, and one group served as control. All patients received a PCA device for self administration of morphine in a pre programmed mode. Very little difference was found between the groups, only when analyzing the patients with highest pain scores could a beneficial effect be seen with the local anesthetic treatment. The clinical relevance of this finding is limited.