Sympatho-adrenal and pituitary hormone responses during and immediately after thoracic surgery--modulation by four different pain treatments.

Four different pain treatments (single intercostal block with bupivacaine, repeated intercostal block, epidural morphine and epidural bupivacaine infusions) were compared in 39 patients subjected to lung surgery under general anaesthesia. The patients' own estimate of the postoperative pain was not significantly different between the groups, but the epidurally treated patients required fewer doses of supplementary analgesic than those given just a single dose of intercostal bupivacaine. Bupivacaine levels in blood were below the toxic range in all groups. The concentration of antidiuretic hormone in blood was increased early during the operation, and had only partly returned to normal on the first postoperative morning. Growth hormone in plasma was increased only at the end of the operation. Catecholamine levels in blood increased gradually, reaching their peak postoperatively. There were only slight differences between the groups in these posterior and anterior pituitary and sympatho-adrenal responses to surgical stress. Thus, neither repeated intercostal blockade nor epidural administration of morphine or bupivacaine could prevent the endocrine responses to thoracic surgery, in spite of significant, albeit incomplete, pain relief. This was probably caused in part by residual pain, and also by poor access of the extradural medications to the autonomic afferent pathways mediating nociceptive signals from thoracic organs and tissues.