THORACIC VERSUS LUMBAR EPIDURAL FENTANYL FOR POSTTHORACOTOMY PAIN

Thirty patients were prospectively randomized to receive either thorac ic or lumbar epidural fentanyl infusion for postthoracotomy pain. Epid ural catheters were inserted, and placement was confirmed with local a nesthetic testing before operation. General anesthesia consisted of ni trous oxide, oxygen, isoflurane, intravenous fentanyl citrate (5 mug/k g), and vecuronium bromide. Pain was measured by a visual analogue sca le (0 = no pain to 10 = worst pain ever). Postoperatively, patients re ceived epidural fentanyl in titrated doses every 15 minutes until the visual analogue scale score was less than 4 or until a maximum fentany l dose of 150 mug by bolus and an infusion rate of 150 mug/h was reach ed. The visual analogue scale score of patients who received thoracic infusion decreased from 8.8 +/- 0.5 to 5.5 +/- 0.7 (p less-than-or-equ al-to 0. 05) by 15 minutes and to 3.5 +/- 0.4 (p less-than-or-equal-to 0.05) by 45 minutes. The corresponding values in the lumbar group wer e 8.8 +/- 0.6 to 7.8 +/- 0.7 at 15 minutes and 5.3 +/- 0.9 at 45 minut es (p less-than-or-equal-to 0.05). The infusion rate needed to maintai n a visual analogue scale score of less than 4 was lower in the thorac ic group (1.55 +/- 0.13 mug . kg-1 . h-1) than in the lumbar group (2. 06 +/- 0.19 mug . kg-l . h-1) during the first 4 hours after operation (p less-than-or-equal-to 0.05). The epidural fentanyl infusion rates could be reduced at 4, 24, and 48 hours after operation without compro mising pain relief. Four patients in the lumbar group required naloxon e hydrochloride intravenously. Three of these patients had respiratory rates of less than 6/min and were difficult to arouse. The fourth pat ient was difficult to arouse and had an arterial carbon dioxide tensio n of 83 mm Hg. We conclude that thoracic epidural fentanyl infusion is better than lumbar infusion for postthoracotomy pain control because of more rapid onset, smaller dose requirements, and less respiratory d epression.