Abstract
Cold haemagglutination is a primary or acquired autoimmune disease involving antibodies that lead to agglutination of red blood cells at low temperature followed by complement fixation and haemolysis on rewarming. This disease can lead to adverse consequences in patients undergoing cardiothoracic surgery, especially when hypothermic cardiopulmonary bypass is applied. The authors discuss the management of two patients who underwent mitral valve replacement surgery while cold agglutinins were detected in the perioperative period. In the first patient, the diagnosis was made preoperatively followed by administration of glucocorticoids to achieve acceptable level of antibody titers. The second patient experienced haemoglobinuria during her intensive care unit stay. The case report describes the pathophysiology of cold agglutination, relevant laboratory investigations such as antibody titers and thermal amplitude, identification of at-risk patients, and management strategies to avoid serious complications.