In Reply:--We did not intend to mislead readers regarding the lipid solubility of hydromorphine, and Boswell agrees that the octanol/water coefficient of hydromorphone lies between that of morphine and of fentanyl. Please note that the apparently small difference between hydromorphone and morphine coefficients results in appreciable clinical differences in opioid-sparing (epidural consumption:intravenous consumption) between the two drugs (approximately 1:8 and 1:2 for morphine and hydromorphone, respectively). In contrast, the large difference in coefficients between hydromorphone and fentanyl results in a much smaller difference in opioid-sparing (1:2 and 1:1, respectively). Thus, differences between opioids in lipid solubility only provide a guide, and clinical studies are necessary to determine efficacy of epidural opioid administration.
We agree with Boswell's suggestion that administration of ketorolac may have obscured differences in analgesia between epidural and intravenous hydromorphone, and this was stated in our discussion. The use of ketorolac and the entire multimodal recovery program was to determine whether epidural hydromorphone provided advantages in recovery of gastrointestinal function after optimization of multiple recovery parameters. Such a multimodal approach was endorsed by the American Society of Anesthesiologists Task Force on Acute Pain Management. Within the context of such a program, epidural hydromorphone does not appear to provide clinical advantages over intravenous hydromorphone.
Spencer Liu, M.D., Randall L. Carpenter, M.D., Department of Anesthesiology, Virginia Mason Medical Center 1100 Ninth Avenue P.O. Box 900 Seattle, Washington 98111.
(Accepted for publication April 29, 1995.)