Effect of Perioperative Factors on the Analgesia Nociception Index

The Analgesia Nociception Index (ANI) is a new unitless marker derived from Heart Rate Variability spectral analysis, ranging between 0 and 100 and expressing the parasympathetic tone. The ANI is proposed as surrogate marker for the analgesia nociception balance. However, many perioperative factors such as medications, position, maneuvers may influence the ANI values and may lead to misinterpretation. Moreover the ability of the ANI to guide opioid dosing has never been tested. Therefore, the aim of our study is to collect in a database all the perioperative factors and to study their influence on the ANI.