[Post-operative analgesia with sub-arachnoid fentanyl: ventilatory effects in elderly patients].

Twenty eight elderly patients scheduled for urologic surgery were randomly assigned to receive in a double blind fashion subarachnoid hyperbaric bupivacaine 15 mg with the addition of 50 micrograms (group A, n = 7), 25 micrograms (group B, n = 7), 12.5 micrograms (group C, n = 7), of fentanyl or 1 ml of saline (group D, n = 7) for a total volume of 4 ml. The pattern of breathing and the ventilatory response to CO2 were studied before 90, 150, 480 minutes after the subarachnoid injection. In group A mild pruritus and sedation occurred in 5 patients, nausea, vomiting and periodic breathing occurred in 2 patients. In group B mild pruritus and sedation were observed in 4 patients, nausea, vomiting in 2 patients. No significant changes in VE, Vt/Ti and Ti/Ttot were observed between the groups. Patients receiving 50 micrograms of fentanyl showed a slope VE/PET CO2 significantly below baseline values at 90 and 150 minutes (p less than 0.05). In this group the baseline values were restored after 480 minutes. No side effects were observed in group C and D. 25 micrograms fo fentanyl is the only dose with a significant analgesic effect without any respiratory depression.