BACKGROUND: Current trends in pediatric cardiac surgery and anesthesiology include goal-directed allogeneic blood transfusion, but few studies address the transfusion of platelets and cryoprecipitate. We report a quality improvement initiative to reduce the transfusion of platelets and cryoprecipitate in infants having cardiac surgery with cardiopulmonary bypass (CPB). METHODS: Data from 50 consecutive patients weighing four to ten kilograms having cardiac surgery with CPB were prospectively collected after the institution of a policy to obtain each patient's platelet and fibrinogen levels during the rewarming phase of CPB. Data from 48 consecutive patients weighing four to ten kilograms having cardiac surgery with CPB prior to the implementation of the policy change were retrospectively collected. Demographics, laboratory values and blood product transfusion data were compared between the groups, using the Chi-square/Fisher's exact test or the T-Test/Wilcoxon Rank-Sum test, as appropriate. RESULTS: The results showed more total blood product exposures in the control group during the time from bypass through the first twenty-four post-operative hours (median of 2 units versus 1 unit in study group, p=0.012). During the time period from CPB separation through the first post-operative day, 67% of patients in the control group received cryoprecipitate compared to 32% in the study group (p=0.0006). There was no difference in platelet exposures between the groups. CONCLUSION: Checking laboratory results during the rewarming phase of CPB reduced cryoprecipitate transfusion by 50%. This reproducible strategy avoids empiric and potentially unnecessary transfusion in this vulnerable population.