LAUSR

Surgical pleth index (SPI) monitoring is a representative objective nociception monitoring device that measures nociception using photoplethysmographic signals. It is easy to apply to patients, and the numerical calculation formula is intuitively easy to understand; therefore, its clinical interpretation is easy. Its efficacy and usefulness have been demonstrated in several studies. The SPI detects the degree of nociception during surgery under general anesthesia better than hemodynamic parameter, thereby better guiding the administration of various opioids, including remifentanil, fentanyl, and sufentanil. Compared with conventional analgesia, SPI-guided analgesia usually reduces intraoperative opioid consumption, facilitates patient recovery, and provides comparable or reduced postoperative pain and adverse events. In addition, SPI monitoring makes it possible to predict the degree of postoperative pain and analgesic requirements through the SPI values immediately before patient arousal. However, because the patient's age, effective circulating volume, posture, concomitant medication and anesthetic administration, and level of consciousness may function as confounding factors in SPI monitoring, clinicians must be careful when interpreting SPI values. In addition, as the SPI value can differ depending on the anesthetic and analgesic management or the patient's underlying disease, it is necessary to be aware of their effects and understand the advantages and disadvantages of SPI monitoring compared to other nociception monitoring devices. Overall, this review aimed to help anesthesiologists perform optimal SPI-guided analgesia in the clinical field and establish future research designs by suggesting the usefulness and limitations of SPI monitoring in perioperative pain management.