We thank Dr. Heerdt for his comments, which support our hypothesis of persisting effects of volatile anesthetics after the end of anesthesia. However, the approaches chosen by Heerdt et al.  and our group were widely divergent.

Heerdt et al.  1found changes in the protein expression of the sarcoplasmatic endoreticular calcium adenosine triphosphatase subtype 2a in rabbit hearts after 1, 3, and 5 h of halothane anesthesia. This study differs from ours2with respect to animals (rabbits vs.  rats), volatile anesthetic (halothane vs.  desflurane), target organ (heart vs.  brain), and minimum alveolar concentration (0.7 vs.  1.0). Another major difference is the killing time, which was immediately after 1, 3, or 5 h of anesthesia in the study of Heerdt et al. , whereas it was either immediately or 24 or 72 h after 3 h of anesthesia in our study. These different experimental approaches make it difficult to compare both studies directly, although the line of evidence is similar. Interestingly, both findings may be based on a common principle of interaction between drug and protein expression, challenging the current hypothesis of a complete reversibility of the effects of volatile anesthetics.

Because of our strict statistical prerequisites, we cannot exclude that a homologue of sarcoplasmatic endoreticular calcium adenosine triphosphatase subtype 2a is also differentially expressed in the brain. Moreover, the technical limits of our approach did not allow us to investigate integral membrane proteins such as sarcoplasmatic endoreticular calcium adenosine triphosphatase subtype 2a, because our protocol isolates cytosolic proteins.

Therefore, our current approach follows the line suggested in the editorial by Dr. Hogan.3Based on our previous exciting findings regarding desflurane anesthesia in the brain, we are currently investigating further volatile anesthetics (i.e. , sevoflurane and isoflurane) in different organs (i.e. , heart, liver, and kidney) with respect to changes in protein expression profiles of specific tissues.

* Faculty of Clinical Medicine Mannheim, Mannheim, Germany. c.fuetterer@pio1.uni-heidelberg.de

Heerdt PM, Markov N: Time-dependence of halothane effects on left ventricular contractility: Evidence for anesthetic-induced myocardial molecular remodeling (abstract). Anesthesiology 2003; 99:A-725
Fütterer CD, Maurer MH, Schmitt A, Feldmann RE Jr, Kuschinsky W, Waschke KF: Alterations in rat brain proteins after desflurane anesthesia. Anesthesiology 2004; 100:302–8
Hogan K: Long-lasting changes in brain protein expression after exposure to an anesthetic. Anesthesiology 2004; 100:209–12