Transient Cold Hemagglutinin Disease (CHAD) During Cardiac Surgery: An Unexpected Complication from Hypothermia.

A 74-year-old male with mild non-specific anaemia underwent elective mitral and tricuspid valve surgery. Following initiation of cardiopulmonary bypass (CPB), systemic cooling to 34℃ and cardioplegia at 4℃, upon cardiotomy, clumps of blood were noted in the left atrium and left ventricle. ACT was confirmed to be in range, therefore a blood sample from CPB machine was collected and when exposed to ice demonstrated clumps, while they disappeared once at normal temperature. Hence, the patient was rewarmed to 37℃, subsequent cardioplegia doses were delivered warm and the heart chambers were washed out. Mitral and tricuspid valve repair were carried out uneventfully and the patient made an uncomplicated recovery. Positive direct antiglobulin test confirmed CHAD, a form of autoimmune haemolytic anaemia involving IgM autoantibodies against red blood cells triggered by low temperature. The prompt intraoperative identification and subsequent modifications of surgical strategy potentially averted severe embolic and ischemic complications.