The Analgesia Nociception Index (ANI) is a numerical value used to assess the balance between analgesia (pain relief) and nociception (pain response) in patients under anesthesia. By analyzing heart rate variability, the ANI aims to provide real-time information about a patient's level of comfort or discomfort during surgical procedures. Essentially, the index helps anesthesiologists tailor the administration of pain-relieving medications more precisely, ensuring that patients receive adequate pain control while minimizing potential side effects or complications related to overmedication or undermedication.