NIRS is a non-invasive measurement of cerebral or somatic blood saturation. It is used in cardiovascular surgery to monitor perfusion during cardiopulmonary bypass (CEC), its use is considered standard of care in pediatric patients taken to a correction of congenital heart disease, but there are no studies describing the frequency of these events. Methods: Data were collected from 48 pediatric patients from July to September 2019 at the Fundación Cardioinfantil who were taken to correct congenital heart disease in bypass and with NIRS monitoring. A univariate analysis was performed: the qualitative variables are presented in percentage and absolute number, the quantitative variables are presented as average and standard deviation or interquartile range. A bi-varied analysis was performed: 2x2 contingency tables, media difference tests, Student's T or Mann-Whitney U. Results: 21 were women and 27 men, the average age was 31.81 months. The average of desaturations was 1.27 for each case, 35 patients had desaturation events, 13 patients had no desaturation events so they are excluded from the analysis. The most performed intervention was to increase the mean blood pressure (59%). In 49 NIRS decrease events, a single intervention (80%) was performed, in the remaining 12 events more than one intervention (16.2%) was performed. Desaturation events occur in 72.9% of cases. The frequency of NIRS fall events in the pediatric population that should be considered as a tool in intraoperative monitoring