Spinal or systemic analgesia after extensive spinal surgery: comparison between intrathecal morphine and intravenous fentanyl plus clonidine

Abstract

Study objective: To compare two different methods of postoperative analgesia after extensive spinal fusion.

Design: Double-blind, randomized study.

Setting: University-affiliated hospital.

Patients: Twenty four adult patients undergoing scoliosis correction.

Interventions: Before the end of surgery, patients received either intravenous clonidine 0.3 micrograms/kg/hr and fentanyl 25 micrograms/kg (after an hourly dose of clonidine 2.5 micrograms/kg) or intrathecal morphine 0.3 mg. A saline infusion was administered to patients receiving morphine intrathecally.

Measurements and main results: Pain and sedation scores, hemodynamic data, and blood gases were collected in the recovery room at tracheal extubation and then every 2 hours for the next 14 hours. Tracheal extubation was performed at the same time in both groups (i.e., an average of 4 hours after the analgesic regimens were started). Intrathecal morphine provided a mean score of 20 mm on a visual analog scale ranging from 0 mm (no pain) to 100 mm (severe pain), but it resulted in increased PaCO2 at extubation (44 +/- 7 mmHg) and 2 hours later (42 +/- 7 mmHg). PaCO2 was greater than 50 mmHg in four patients receiving intrathecal morphine. Fentanyl-clonidine resulted in equipotent analgesia but was accompanied by sedation (sleeping but arousal by light tactile stimulation) and moderate hypotension (up to 69 +/- 9 mmHg for mean arterial pressure).

Conclusions: This study shows that there is a major risk of respiratory depression with a single intrathecal dose of morphine 0.3 mg to control postoperative pain after scoliosis surgery. Systemic clonidine-fentanyl may be a possible approach to the postoperative pain treatment of this surgery.