Iranian Journal of Nursing and Midwifery Research1735-906631220260517214218ENDepartment of Pediatrics, Division of Neonatology – School of Medicine, Tehran University of Medical Sciences, Children’s Medical Center, Tehran, IranDepartment of Pediatrics, Division of Neonatology – School of Medicine, Tehran University of Medical Sciences, Children’s Medical Center, Tehran, IranDepartment of Pediatrics, Division of Neonatology – School of Medicine, Tehran University of Medical Sciences, Children’s Medical Center, Tehran, IranDepartment of Pediatrics, Division of Neonatology – School of Medicine, Tehran University of Medical Sciences, Children’s Medical Center, Tehran, IranDepartment of Pediatrics, Division of Neonatology – School of Medicine, Tehran University of Medical Sciences, Children’s Medical Center, Tehran, IranDepartment of Pediatrics, Division of Neonatology – School of Medicine, Tehran University of Medical Sciences, Children’s Medical Center, Tehran, Iran2026051320260513<p><strong>Background: </strong>The Perfusion Index (PI) is considered an important tool for evaluating the condition of infants, but there are few studies on the correlation between PI and pain assessment in infants. Therefore, this study aimed to investigate the correlation between PI and pain scale in infants undergoing surgery. <strong>Materials and Methods: </strong>This prospective, cross‑sectional study was conducted in the Neonatal Intensive Care Unit (NICU) of the Children’s Medical Center in Tehran, Iran, between April 2020 and April 2023. Using the Crying Requires, Oxygen, Increased vital signs, Expression, and Sleeplessness and right‑hand mean PI, using a Masimo pulse oximeter, pain scales were recorded immediately after surgery in the NICU and every 4 h for a total of 24 h by a skilled nurse unaware of the study. The correlation between PI and factors such as age, weight, NICU admission length, and pain scale was analyzed. <strong>Results: </strong>Our study found an inverse correlation between the pain scale and PI (<em>p </em>&lt; 0.05; <em>r</em>: −0.385). Additionally, age, gestational age, and PI had a positive correlation with weight (<em>p </em>&lt; 0.05; <em>r</em>: 0.233, 0.132, and 0.044, respectively). The age of the infant was also correlated with PI (<em>p </em>&lt; 0.05; <em>r</em>: 0.307). Moreover, NICU admission length was inversely related to the PI scale (<em>p </em>&lt; 0.05; <em>r</em>: −0.119).m <strong>Conclusions: </strong>The ease of use and objective measurement method of the PI makes it a valuable nursing tool for pain measurement in infants, in addition to other methods. However, further studies are needed to confirm the effectiveness of this correlation.</p><p> </p>http://ijnmr.mui.ac.ir/index.php/ijnmr/article/view/2361http://ijnmr.mui.ac.ir/index.php/ijnmr/article/download/2361/70707951