In Reply:--Both Waltuck and Pas speculate that the administration of epinephrine in the epidural local anesthetic solution was a likely contributing factor to the neurologic deficit observed in our case. We contend that there is no scientific evidence to support this assumption. We are unaware of any research data in humans examining the relation of epinephrine administered by either the subarachnoid or epidural route to spinal cord blood flow. On the contrary, in an animal model, Kozody et al. * reported that lumbar subarachnoid injection of 200 micro gram epinephrine had no effect on spinal cord blood flow in the cervical, thoracic, and lumbosacral regions. It should be noted that 200 micro gram epinephrine frequently is administered with local anesthetics in the subarachnoid area to augment surgical anesthesia in a wide variety of patients (including patients with severe peripheral vascular disease) without apparent detrimental neurologic effects. Given that the total dose of epinephrine used in our case was 40 micro gram and given the lack of support from either clinical observation or animal studies of adverse outcome with neuraxial (epidural or subarachnoid) administration of epinephrine on spinal cord blood flow, we suggest that the contribution of epinephrine in this case remains speculative and highly unlikely.
We do not regard the selection of a thoracic epidural for postoperative analgesia in this case as either "overzealous" or "aggressive." Our patient had inadequate analgesia, with evidence of deteriorating pulmonary status (inability to cough and poor oxygen saturations) despite patient-controlled analgesia morphine. He was facing the possibility of reintubation and ventilation when the surgical service asked us to consider epidural catheter placement. The benefits of thoracic epidural analgesia are well recognized in this setting. The incidence of adverse neurologic events from thoracic epidurals is unknown and probably exceedingly rare. As such, decisions regarding postoperative analgesia should be made on an individual basis and with the clinical situation in mind.
Dermot R. Fitzgibbon, M.B., B.Ch., F.F.A.R.C.S.I., Acting Assistant Professor.
L. Brian Ready, MD, F.R.C.P.(C.), Professor and Director of Pain Service, Department of Anesthesiology, University of Washington Medical Center, Seattle, Washington 98105.
*Kozody R, Palahniuk RJ, Wade JG, Cumming MO: The effect of subarachnoid epinephrine and phenylephrine on spinal cord blood flow. Can Anaesth Soc J 1984; 31:503–8.