Prolonged and biphasic respiratory depression following epidural buprenorphine.

Ventilatory sensitivity to carbon dioxide was measured in six healthy volunteers before, and at various times up to 20 hours after, administration of epidural buprenorphine 0.15 mg with a modified Read rebreathing technique. The carbon dioxide response curves were depressed in a time-dependent, prolonged and biphasic manner. Significant depression was seen in the intercept values at an end tidal carbon dioxide of 7.2 kPa, for mouth occlusion pressure (p less than 0.01), tidal volume (p less than 0.05) and minute ventilation (p less than 0.05). A significant reduction of slope was obtained only for minute ventilation. Linear regression of respiratory rate changes during carbon dioxide stimulation, did not reach statistical significance. In conclusion, these data indicate that epidural buprenorphine, despite a high lipid solubility, causes respiratory depression to the same extent as epidural morphine. Surveillance of patients who receive epidural buprenorphine for postoperative pain relief is necessary.