A Prospective, Double-blind, Randomized, Placebo-controlled Study of Dexmedetomidine As an Adjunct to Epidural Analgesia After Thoracic Surgery

Objective: The purpose of this study was to test the hypothesis that after thoracic surgery, the supplementation of a low-dose thoracic epidural (ED) bupivacaine (0.125%) infusion by intravenous (IV) dexmedetomidine decreases analgesic requirement without causing respiratory depression. The primary endpoint was the need for additional ED bupivacaine administered through patient-controlled epidural analgesia (PCEA). Secondary endpoints included the requirement for supplemental opioids and the impact of dexmedetomidine on CO2 retention.

Design: A prospective, randomized, double-blinded study.

Setting: A major US tertiary care university hospital.

Patients: Twenty-eight patients scheduled to undergo elective thoracotomy for wedge resection, lobectomy, or pneumonectomy.

Interventions: On intensive care unit arrival, the thoracic ED catheter was loaded with 0.125% bupivacaine to a T4 sensory level and a continuous infusion of 0.125% bupivacaine without opioid was commenced at 4 mL/h. Patients were then randomized into 1 of 2 groups. The dexmedetomidine group received an IV loading dose of dexmedetomidine of 0.5 microg/kg over 20 minutes, followed by continuous IV infusion at 0.4 microg/kg/h. The placebo group received IV saline at the same calculated loading and infusion rates by volume. If necessary, supplemental analgesia (increased ED rate, ED fentanyl, ketorolac [IV]) was provided to ensure a visual analog scale (VAS) score of < or =3.

Measurements: The analgesic effect was monitored by the VAS, and the requirement for PCEA dosing and additional analgesics was recorded. Heart rate, blood pressure, and blood gases were also monitored.

Main Results: There was no significant difference in PCEA use and VAS score between the 2 groups, but requirement for supplemental ED fentanyl analgesia was significantly greater in the placebo group (66.1 +/- 95.6 v 5.3 +/- 17.1 microg, p = 0.039). Mean PaCO2 was also significantly greater in the placebo group (40.3 +/- 4.1 v 43.9 +/- 4.3 mmHg, p = 0.04). Patients in the dexmedetomidine group exhibited significantly decreased heart rate (1 patient required and responded to atropine) and blood pressure (4 patients required and readily responded to IV fluid) compared with the placebo group.

Conclusion: The authors conclude that in postthoracotomy patients, IV dexmedetomidine is a potentially effective analgesic adjunct to thoracic ED bupivacaine infusion and may decrease the requirement for opioids and potential for respiratory depression.