Objective To evaluate the effect of index of consciousness (IoC) monitoring, that is the combination of sedation (IoC1) and anesthesia (IoC2) monitoring on stress‑induced hyperglycemia in elderly patients undergoing lumbar spinal fusion. Methods A total of 72 elderly patients, with American Society of Anesthesiologists (ASA) grades Ⅱ or Ⅲ, who underwent lumbar spinal fusion from July 2020 to December 2020 were selected. According to the random number table method, they were divided into two groups (n=36): a control group (group C) and an experimental group (group E). Both groups were subject to endotracheal intubation for general anesthesia. Anesthesia was maintained by target‑controlled infusion of propofol and remifentanil as well as intermittent intravenous injection of rocuronium. For group C, the plasma target concentrations of propofol and remifentanil were adjusted, based on vital signs such as heart rate and invasive arterial pressure. For group E, the plasma target concentrations of propofol and remifentanil were adjusted according to the changes of IoC1 and IoC2 values, respectively. The IoC1 and IoC2 values were maintained at 40−60 and 35−45, respectively. Their general and surgical information were recorded. The intraoperative dosages of propofol, remifentanil, sufentanil, esmolol and norepinephrine, as well as the occurrence of hypertension, hypotension, tachycardia, and bradycardia were recorded. The blood glucose and cortisol concentrations were measured before anesthesia induction (T0), at the end of surgery (T1), and at postoperative 24 h (T2) and 72 h (T3). The incidence of stress‑induced hyperglycemia was recorded. The Visual Analog Scales (VAS) score at rest and on coughing were recorded at T2 and T3. Results There was no statistical difference in general and surgical information between the two groups (all P>0.05). Compared with group C, group E showed increases in the intraoperative dosage of remifentanil (P<0.05), decreases in the incidence of intraoperative hypertension (P<0.05), decreases in the incidence of stress‑induced hyperglycemia (P<0.05), and decreases in glucose and cortisol concentrations at T1 and T2 (all P<0.05). The glucose and cortisol concentrations in both groups at T1 and T2 were higher than those at T0 (all P<0.05). There was no statistical difference in VAS scores at rest and on coughing between the two groups at T2 and T3 (all P>0.05). Conclusions IoC1 and IoC2 monitoring is beneficial for suppressing stress response and reducing the incidence of stress‑induced hyperglycemia in elderly patients undergoing lumbar spinal fusion.