Pain scores and ventilatory and circulatory sequelae of epidural morphine in cancer patients with and without prior narcotic therapy.

Pain scores and respiratory and circulatory sequelae of epidural morphine were studied in 25 patients with cancer, classified into two groups: 15 with and 10 without a history of previous narcotic analgesic therapy. Morphine, 2.5 mg initially and 5.0 mg 12 hours later, was given through an indwelling lumbar epidural catheter. Pain scores, heart rate, blood pressure, respiratory rate and minute volume, arterial PO2 and PCO2, and arterial pH were measured for 24 hours. Both groups had the same degree of analgesia after each epidural dose, suggesting that local morphine concentrations seen with epidural administration may be sufficient to overcome any degree of tolerance that may have developed at the spinal level during previous systemic narcotic administration. Statistically significant dose-dependent hypoventilation and concomitant respiratory acidosis were seen in both groups, the changes being significantly greater in opiate-naive patients. These results demonstrate that the ventilatory depressant actions of opioids are attenuated but not eliminated in narcotic-familiar cancer patients and that epidural narcotics are as effective in relieving pain in narcotic-naive patients as in patients previously exposed to narcotics for relief of cancer pain.