Analgesia after thoracotomy: Effects of epidural fentanyl concentration/infusion rate

After thoracotomy some patients have discomfort, primarily in the rostral portion of their incisions. In this prospective, randomized study in 66 patients after lateral thoracotomy we evaluated whether, for equal fentanyl dosage in micrograms per kilogram, epidural infusion (lumbar catheter) of fentanyl 5 μg/mL provided better segmental analgesia (including the rostral portion of the incision) than a 10-μg/mL concentration infused at a rate half that used in the 5-μg/mL group. Ketorolac was used as an analgesic adjunct for nonincisional pain. Postoperative epidural fentanyl infusion included a 1-μg/kg initial dose and an initial infusion rate of 1 μg · kg^-1 · h^-1 in both the 5-μg/mL and 10μg/mL groups. Patients were evaluated for comfort level and pain relief while resting, taking a deep breath, coughing, and ambulating at eight times over 3 days using two visual analog scales for overall comfort and a verbal rating score (VRS) for segmental analgesia. There were no significant differences in demographics, surgical procedure, intraoperative fentanyl dose, side effects, rates of epidural fentanyl infusion, or total epidural fentanyl doses at 12, 24, 36, 48, and 60 h postbolus. Analgesia was effective in both groups. Although overall comfort levels were lower (i.e., indicated greater comfort) in the 5- μg/mL group in 6 of 8 visual analog scores (VASs) for comfort level and 20 of 24 VRSs for comfort level scores, and mean VRSs for the rostral portion of the incision were lower (i.e., indicated greater comfort) in the 5-μg/mL group at 21 of 24 evaluation subsets (one statistically significant), statistical significance was achieved in only six evaluation subsets. There were no significant differences between the two groups in averages of comfort level scores for the upper, middle, and lower portions of the incisions. Ketorolac was not a confounding variable. Lumbar epidural infusions of fentanyl can provide effective analgesia after thoracotomy; using lower concentrations at higher infusion rates is beneficial for some patients.