We present an example of a patient with confirmed cold agglutinin disease who underwent cardiac surgery in hypothermia to illustrate a known fact that, when exposed to cold, cold agglutinins induce haemolysis of erythrocytes and that cryoglobulins and cryofibrinogens may, upon exposition to cold during a surgery under hypothermia, precipitate or gelify and thus increase plasma viscosity and damage microcirculation. Detailed immunological and haematological investigations in all patients awaiting cardiac surgery with a risk of developing hypothermia is not advantageous considering the low number of patients with clinical and laboratory signs of cold agglutinin disease, autoimmune haemolytic anaemia or paroxysmal cold haemoglobinuria and considering that these investigations, in addition, might not detect cryoglobulinaemia and cryofibrinogenemia. Identification of in-risk patients from the warning signs in the medical history, physical or basal laboratory testing who would subsequently undergo confirmatory investigations to verify the presence of these entities and define them accurately might be a potential solution to this clinical issue. Cardiac surgery strategy and peri-operative care should be tailored to the results of these investigations. Well-structured, practiced and functional cooperation between clinicians and laboratory personnel is a prerequisite for success in these circumstances.