Monday, November 28, 2005

Epidural methadone for dyspnea

Chest has published an open-label trial of epidural methadone to relieve dyspnea from COPD. The idea behind the study was that the authors had noticed a marked reduction in dyspnea in COPD patients after lung-volume reduction surgery who received epidural analgesia for post-operative pain. The authors enrolled 9 patients with advanced COPD (FEV1 <35% of predicted), placed a T4-5 epidural catheter in each (these were external devices...not implanted pumps), and infused methadone at 6mg/day. They were followed for one month. After a month 3 had dropped out--one for a catheter infection and two due to catheter migration. Essentially, all the findings were positive: at 1 week and 1 month dyspnea & quality of life had improved compared to baseline; the 6 minute walk test (a standard test of exercise capacity in lung disease) had improved; and there was no evidence of CO2 retention (in fact pCO2 decreased a touch in the group). Given that the major putative benefits of epidural vs. systemic opioids are fewer side effects I was disappointed that they appeared to not collect ANY data on the typical & limiting opioid side effects (nausea, somnolence, dysphoria, constipation, etc). In addition, the authors noted that, after completion of the month, most of the remaining patients eventually discontinued the pump due to migration or infection--problems partially due to the use of external pumps. To me, this study has provided "proof of principle" that epidural methadone can palliate dyspnea--that it offers some benefits. What is clearly needed now is a comparison study with systemic opioids to see if the risks & costs involved outweigh those benefits.

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