In Reply:-We appreciate the interest shown by Drs. Aoki and Mizobe in our manuscript. [1] However, we believe that the effect of ethanol used to dilute the anesthetics can not explain our finding with sevoflurane. We used the same range of ethanol to dilute all the concentrated anesthetics (including halothane, sevoflurane and isoflurane) and isoflurane with ethanol did not affect platelet aggregation (Figure 1). The concentration of ethanol stated in the manuscript (less than 0.5%) was the possible maximal concentration, and was calculated basing on the total volume of ethanol divided by the volume of platelet-containing solution in the test tubes. Because of the presence of a gas space in the parafilm-sealed tube, the concentration of ethanol in the liquid phase could have been lowered as that in the gas phase increased during incubation at 37 [degree sign] Celsius. In contrast, the concentration of volatile anesthetics mentioned was, of course, that in the liquid phase, confirmed by gas chromatography. This may explain why ethanol did not affect platelet aggregation during our experimental conditions.
Figure 1. Effects of sevoflurane and isoflurane on platelet aggregation. (A) Sevoflurane (0.13 mM), with 0.225% ethanol, completely suppressed epinephrine (4 micro Meter)-induced secondary aggregation. (B) Isoflurane (0.56 mM), with 0.5% ethanol, did not affect epinephrine (3 micro Meter)-induced platelet aggregation.
Figure 1. Effects of sevoflurane and isoflurane on platelet aggregation. (A) Sevoflurane (0.13 mM), with 0.225% ethanol, completely suppressed epinephrine (4 micro Meter)-induced secondary aggregation. (B) Isoflurane (0.56 mM), with 0.5% ethanol, did not affect epinephrine (3 micro Meter)-induced platelet aggregation.
As Drs. Aoki and Mizobe pointed out, no clinical report has ever suggested increased blood loss or blood transfusion during general anesthesia with sevoflurane. This situation can also be extended to halothane anesthesia, although many investigators have reported suppressive effects of halothane on platelet aggregation. [2–4] The fact that the amount of hemorrhage during surgery depends on the surgical technique or skill of the surgeon probably makes clinical studies in this field difficult.
Hideo Hirakata, M.D.
Kumi Nakamura, M.D.
Department of Anesthesia; Kyoto University Hospital; Kyoto 606–01, Japan
Email: H-Hirakata@msn.com
