Variability of the Analgesia Nociception Index During Painful Procedures in Noncommunicative Patients at the End of Life: A Prospective, Observational Pilot Study

<b><i>Introduction:</i></b> Monitoring parasympathetic activity by the Analgesia Nociception Index (ANI) is reliable for assessing nociception during general anesthesia or in sedated critically ill patients. The aim of our study is to evaluate the variability of the ANI during painful procedures in noncommunicative patients at the end of life (EOL). <b><i>Methods:</i></b> This study was a blinded, prospective, observational study. Consecutive noncommunicative EOL patients were recruited from the palliative care unit. The minimum ANI score and the Critical Care Pain Observation Tool (CPOT) scale were collected before, during, and after a painful procedure. <b><i>Results:</i></b> Twenty patients were included; five were sedated. We found that ANI scores decreased significantly (<i>p</i> < 0.001) and CPOT scores increased (<i>p</i> = 0.006) during painful procedures. ANI changed more frequently than CPOT. There was no correlation between ANI and CPOT scores. <b><i>Conclusion:</i></b> In this preliminary study, we found that the ANI was effective in detecting discomfort during painful procedures at the EOL.