The letter by Eisenach et al. certainly represents the most important aim in medicine. We partly agree with the authors that extensive testing regarding the safety should always be performed before the introduction of new drugs and new techniques in humans. However, before using isoproterenol , we were confident that necessary precautions were taken. As outlined in the Discussion of our article, three studies have been published addressing this issue. In two studies, in which isoproterenol was injected intrathecally and epidurally, no histopathological changes of the spinal cord were found .1 In another study, no change could be detected in amplitude or latency of somatosensory evoked potentials after the epidural administration of 50 [micro sign]g isoproterenol in chronically instrumented, awake sheep . Therefore, after an extensive discussion in our ethics committee, the drug was considered safe for epidural use.
(1) Marcus MAE, Vertommen JD, Van Aken H, Van Lommel A. Light microscopic neuropathological observations after intrathecal bolus injections of isoproterenol [abstract]. Anesthesiology 1994;81:A1175.
We agree with the statement of Eisenach et al. that the approval from a national drug regulatory committee would be advisable. However, in most European countries, this is not possible in the way described by the authors.
In our opinion, the continuous use of epinephrine is more dangerous than the introduction of isoproterenol. Isoproterenol is a beta-adrenergic agonist and therefore will unlikely harm the spinal cord by vasoconstriction of the arterial supply.
M. A. E. Marcus, MD, PhD
W. Gogarten, MD
H. Buerkle, MD
H. Van Aken, MD, PhD, FRCA
Klinik und Poliklinik fur Anasthesiologie und operative Intensivmedizin; Westfalische Wilhelms-Universitat; D-48149 Munster, Germany
1. Marcus MAE, Vertommen JD, Van Aken H, et al. The effects of adding isoproterenol to 0.125% bupivacaine on the quality and duration of epidural analgesia in laboring parturients. Anesth Analg 1998;86:749-52.
2. Norris MC, Arkoosh VA, Knobler R. Maternal and fetal effects of isoproterenol in the gravid ewe. Anesth Analg 1997;85:389-94.
4. Marcus MAE, Bruyninckx FL, Vertommen JD, et al. Spinal somatosensory evoked potentials after epidural isoproterenol in an awake sheep. Can J Anaesth 1997;44:85-9.