[Comparative studies on the side effects of morphine after peridural, spinal and intravenous administration]

A prospective randomized study was carried out on 29 patients undergoing transurethral prostatectomy. In addition to the regional anaesthetic given for the operation, the patients received either: 1 mg morphine intrathecally (spinal group), 0.05 mg/kg body weight of morphine i.v. (i.v. group), or 0.05 mg/kg body weight epidurally (PDA group). Two of the intrathecal group patients had to be given an antagonist because of clinically relevant respiratory depression. In one of these cases, this depression could be documented by a continuous fall in respiratory minute volume, and an increase in PCO2. In the other, bradypnoea and vomiting developed within a few minutes of injection. The presence of a central action of intrathecal and epidural opiates was indicated by the significant increase in reaction time found. In the two instances of respiratory depression, the CSF morphine concentration 24 hrs after injection was markedly lower (0 and 18 ng/ml respectively) than in unaffected patients. It must therefore be assumed that the respiratory depression was caused by a more rapid cephelad transport than that occurring in normal cases.