Response to letter to the editor
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KeywordsBispectral index Desflurane Sevoflurane Surgical pleth index
To the Editor:
Recently, Ryu et al.  demonstrated that both bispectral index (BIS) and surgical pleth index (SPI) during anesthesia with desflurane were lower than those with sevoflurane at age-corrected 1 minimum alveolar concentration (MAC). In addition to our findings , they have shown that SPI was also different between equi-MAC desflurane and sevoflurane with tetanic stimulation . They proved that the required dose of remifentanil with 1 MAC desflurane was smaller than that with 1 MAC sevoflurane to achieve SPI of 20–50 .
BIS does not reflect the degree of noxious stimuli or level of analgesia and no objective measurements for nociception or surgical stress existed before. SPI is a simple numerical index (0–100) for estimating the balance of surgical stress and analgesia, with the value of 50 corresponding to the mean stress level. Based on the aforementioned results, Ryu et al. have shown that analgesic potency is different between 1 MAC desflurane and sevoflurane, which show equal potential in preventing spinal reflex in response to skin incision. SPI is influenced by cardiovascular agents, and obtained data with those agents require careful interpretation. We sincerely expect clinical introduction of SPI in our country.
No funding was received.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.