The NIPE (Newborn Infant Parasympathetic Evaluation) monitor is a rapid, continuous and objective tool for the evaluation of neonatal discomfort. In order to adequately treat and be aware of neonatal pain, an adequate assessment of neonatal pain is essential. The objectives of the present study were to describe the changes in NIPE after blood collection and the factors involved in its variation in the patient admitted to the neonatal ICU.