AN INTRATHECAL FENTANYL DOSE-RESPONSE STUDY IN LOWER-EXTREMITY REVASCULARIZATION PROCEDURES

Background: Intrathecal opioids routinely are administered to surgical patients to provide prolonged postoperative analgesia. This study eva luated the dose-response effects of intrathecal fentanyl in an elderly patient population undergoing lower extremity revascularization proce dures. Methods: Surgical anesthesia was induced using a continuous spi nal technique. No patient received perioperative antiemetics or opioid s. Postoperatively, after complete regression of spinal anesthesia, pa tients received via the spinal catheter either 0, 5, 10, 20, 40, or 50 mu g fentanyl. Blood pressure, heart rate, respiratory rate, oxyhemog lobin saturation, and visual analog pain scores were recorded approxim ately every minute for 15 min after study drug administration. After t his initial observation period, blood pressure, heart rate, respirator y rate, oxyhemoglobin saturation were recorded every 15 min for the ne xt 2 h, then every 30 min thereafter. A verbal analog pain score, with 0 equivalent to no pain and 10 the worst pain imaginable, was obtaine d with each set of vital signs. The study was concluded when the verba l analog pain score was greater than or equal to 3, the patient was me dicated, and the time was recorded. Any side effects, such as respirat ory depression, nausea, vomiting, and pruritus, were recorded. Results : Minimal analgesia was derived from the 0-, 5-, and 10-mu g doses. Be ginning at 20 mu g, Patients experienced the onset of satisfactory ana lgesia (visual analog pain scores < 3) within 4 min. All patients in t he 40- and 50-mu g groups had excellent analgesia (visual analog pain scores < 1) within 10 min. No patient experienced respiratory depressi on (respiratory rate < 9 breaths/min), hypoxemia (oxyhemoglobin satura tion < 90%), or any hemodynamic alterations (20% change greater or les s than baseline heart rate or blood pressure). In the 50-mu g group, f ive of ten patients complained of pruritus. Conclusions: Results indic ate that 40 mu g intrathecal fentanyl provides satisfactory analgesia for approximately 5 h in an elderly patient population, with a low inc idence of side effects.