Effects of Ephedrine on the Nociception Level and Analgesia Nociception Index

Nociceptive monitor values are influenced by vasopressors; however, no study has investigated this in detail. In this study, we aimed to investigate the effect of ephedrine on nociceptive monitors using the Analgesia Nociception Index (ANI) and Nociception Level (NOL). This prospective observational study was conducted between February and April 2023. Data were obtained during anesthesia induction only to exclude surgical invasion. Blood pressure, heart rate, ANI, and NOL were measured 5 min after ephedrine administration during hypotension. Low ANI and high NOL values indicated severe pain. Statistical analyses were performed on the values before and after ephedrine administration for each parameter. Eight patients (six men and two women) with a mean age of 72 years were included. The ANI and NOL, before versus after ephedrine administration were 76.3±11.8 versus 33.6±8.1 (p<0.001) and 2.1±1.5 versus 27.6±10.5 (p<0.001), respectively. The mean time beyond the pain threshold (ANI<50 and NOL>25) for ephedrine was 58.0 s for the ANI, and 29.3 s for the NOL, respectively. The administration of ephedrine, albeit for a short duration, significantly altered nociceptive monitor values, occasionally surpassing thresholds indicative of pain.