Predictive value of the surgical pleth index for the hemodynamic responses to trachea intubation and skin incision

Surgical pleth index (SPI) has been widely investigated in assessing the nociceptive level. The aim of this study was to investigate the relationship between SPI level and patient responses to trachea intubation and skin incision. A total of 40 patients undergoing open abdominal general surgery were recruited for analyses. The patients were monitored with electrocardiogram, non-invasive blood pressure, SpO(2), invasive blood pressure and SPI before anesthesia induction. Anesthesia was induced with midazolam, propofol, sufentanil and rocuronium and maintained with sufentanil and sevoflurane. Blood pressure, heart rate and SPI were recorded for analyses during the peri-intubation and peri-incision periods. A receiver operating characteristic (ROC) curve analysis was performed to analyze the predictive value of blood pressure, heart rate (HR) and SPI for hemodynamic responses for trachea intubation and skin incision. SPI had a similar changing trend to systolic blood pressure (SBP) and diastolic blood pressure (DBP). The SPI level was linearly correlated with SBP, DBP and HR. SPI increased significantly after intubation and incision in patients with positive but not negative responses to intubation and incision. The ROC analysis showed that only SBP level is predictive of intubation responses. These data suggested that SPI elevated under the noxious stimulation by intubation and incision, but it was not predictive of the hemodynamic responses to intubation and incision.