Posthoracotomy pain and pulmonary function following epidural and systemic morphine

Abstract

Thirty patients undergoing thoracotomy for lung resection were entered in a randomized, double-blind trial comparing the effects of epidural (E) versus intravenous (iv) morphine on postoperative pain and pulmonary function. Postoperatively the patients were given repeated doses of either 5.0 mg of morphine epidurally or 0.05-0.07 mg/kg morphine intravenously until there were no further spontaneous complaints of pain. Two, 8, and 24 h postoperatively, the following indices were measured: linear analogue pain score, somnolence score, vital signs, arterial Pa(O2), Pa(CO2) and pH, forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), and peak expiratory flow rate (PEER). Patients receiving epidural morphine had significantly less pain at 2 h (P < 0.01) and 8 h (P < 0.004) postoperatively. There was no difference in vital signs except for significantly slower respiratory rates at 2 h (P < 0.04), 8 h (P < 0.02) and 24 h (P < 0.01) in the epidural group. No significant differences occurred in the somnolence scores or blood-gas measurements, which were within normal limits. The epidural morphine group has significantly less decrease in both FVC at 2 h (E -1.8 ± 2 l, iv -2.5 ± 0.2 l, P < 0.03), 8 h (E -1.4 ± 0.2 l, iv -2.1 ± 0.2 l. P < 0.01), and 24 h (E -1.2 ± 0.2 l, iv -2.0 ± 0.2 l, P < 0.02), and FEV1 at 2 h (E -1.3 ± 0.2 l, iv -1.9 ± 0.2 l, P < 0.04), 8 h (E -1.0 ± 0.2 l, iv -1.7 ± 0.2 l, P < 0.01), and 24 h (E -0.8 ± 0.1 l, iv -1.5 ± 0.2 l, P < 0.01). In addition, the epidural morphine group had significantly less decrease in PEFR at 24 h (E -134 ± 29 l·min·-1, iv -238 ± 30 l·min-1, P < 0.03). The authors conclude that lumbar epidural morphine is highly effective in alleviating pain and improving respiratory function in postthoracotomy patients.