There is scant data regarding thresholds for intraoperative hypo tension (IOH) in children less than 1 year of age. We used anesthesia information management systems (AIMS) data to develop reference values for normal per operative blood pressures (BPs) and IOH in the infant population undergoing thoracic surgery. Manipulating large data sets such as AIMS vital sign data can be challenging, thus, we developed custom software in Python to organize the data, parse the files, perform the appropriate calculations, and output the information in graphical form. In general, the results show that BP values at each percentile gradually increase as the patient's age increases. We plan to develop a broader set of reference values for normal BPs under anesthesia and thresholds for IOH, irrespective of the type of surgery. These can be used to ascertain the relationship of IOH to morbidity and mortality in the perioperative period and beyond.