Incidence of intraoperative hemodynamic events. Hypertension and tachycardia were defined as a 20% increase above the baseline blood pressure or heart rate. The total numbers of blood pressure and heart rate measurements during anesthesia were 194 in surgical pleth index (SPI)-guided group and 249 in control group. The number of hypertension events was 70 (36.1%) in SPI-guided group and 62 (24.9%) in control group. The incidence of hypertension was significantly higher in SPI-guided group than in control group (P = 0.012). The number of tachycardia events was 123 (63.4%) in SPI-guided group and 158 (63.5%) in control group, and there was no significant difference between the two groups. Control group = the conventional analgesia group; SPI-guided group = the SPI-guided analgesia group. *P < 0.05 between the two groups.