Peer-reviewed evidence (Class IIa, Level B) suggests that arterial blood temperature should be limited to 37 degrees C during cardiopulmonary bypass. We implemented a regional quality improvement initiative to reduce regional variability in our performance around this recommendation at four northern New England medical centers between January 2006 and June 2010. Cardiovascular perfusionists at four medical centers collaborated by conference calls regarding blood temperature management. Evidence from the recommendations were reviewed at each center, and strategies to prevent hyperthermia and to improve performance on this quality measure were discussed. Centers submitted data concerning highest arterial blood temperatures among all isolated coronary artery bypass grafting procedures between 2006 through June 2010. Scope and focus of local practice changes were at the discretion of each center. The timing of each center's quality improvement initiatives was recorded, and adherence to thresholds of 37 degrees C and 37.5 degrees C were analyzed. Data were collected prospectively through our regional perfusion registry. Data were available for 4909 procedures (1645 before interventions, 3264 after interventions). Prior to the quality improvement interventions, 90% of procedures had elevated arterial line temperatures (37 degrees C or more), and afterwards it was 69% (p < .001) for an absolute difference of 21%. Prior to the intervention, 53% of procedures had temperatures beyond a threshold of 37.5 degrees C versus 19% subsequent to interventions, for an absolute difference of 34% (p < .001). This regional effort to reduce patient exposure to elevated arterial line temperatures resulted in a significant sustained reduction in high arterial outflow temperatures at three of the four centers. A regional registry provides a means for assessing performance against evidence-based recommendations, and evaluating short and long-term success of quality improvement initiatives.