Pre-induction nociception indices are associated with post-induction hypotension during general anesthesia in older...

We investigated whether pre-induction High Frequency Variability Index (HFVI)/Analgesia Nociception Index (ANI) and Nociception Level (NOL) values could predict hypotension during general anesthesia induction in older patients. This prospective observational study included patients aged ≥ 65 years undergoing elective surgery under general anesthesia. After recording HFVI/ANI and NOL values, remifentanil was administered at 0.2 µg/kg/min for 2 min, followed by a rapid intravenous bolus administration of propofol at 2 mg/kg. Noninvasive blood pressure was measured at 1-min intervals over 5 min. Hypotension was defined as mean arterial pressure (MAP) < 65 mmHg. Predictive performance was evaluated using receiver operating characteristic (ROC) curves. Additionally, the area under MAP < 65 mmHg (AUT-65), a continuous metric integrating the depth and duration of hypotension, was calculated and correlated with nociception index values. We analyzed 51 patients (19 men; 22 in the hypotension group and 29 in the nonhypotension group). The hypotension group demonstrated lower HFVI/ANIi values (58.7 ± 11.1 vs. 69.0 ± 15.1, p = 0.010) and higher NOL values (17.2 ± 9.1 vs. 10.7 ± 8.8, p = 0.013). HFVI/ANIi (AUC = 0.72, cutoff = 62.5) and NOL (AUC = 0.71, cutoff = 13.5) moderately predicted hypotension. AUT-65 was significantly correlated with HFVI/ANIi (Spearman rho = - 0.35, p = 0.013) and NOL (rho = 0.47, p = 0.0005). Pre-induction HFVI/ANI and NOL were associated with the occurrence and cumulative burden of post-induction hypotension in patients aged ≥ 65 years, suggesting their potential utility as pre-induction screening tools.Trial registration This study was approved by the Ethics Committee of Yamagata University Hospital on January 18, 2024 (approval number 2023 - 280). Before commencement, the study was registered as a prospective observational study in the UMIN Clinical Trials Registry (UMIN000053529).