Hypothermic cardiopulmonary bypass surgery in a 7-year-old boy with a cold agglutinin

Abstract

Dear Editor, Cold agglutinins (CA) are predominately IgM auto-antibodies that optimally react with surface antigens on red blood cells (RBCs) at low temperatures. Subsequently, agglutination of RBCs can occur followed by complement fixation and haemolysis. CAs seldom cause significant intraand extravascular haemolysis under normothermic conditions. However, they could be of relevance in patients undergoing cardiac surgery when hypothermic cardiopulmonary bypass (CPB) and cardioplegia are used [1]. There are conflicting opinions in the literature about screening patients for CAs prior to hypothermic CPB. CAs are rare and low levels can be found in healthy individuals. The incidence of CAs in screened cardiac surgery patients is approximately 0.8–4 % [1–4]. Although serious complications (haemolysis, micro-vascular occlusion and organ failure) have been described, it has also been demonstrated that patients with low titre, low thermal amplitude CAs can safely undergo CPB [1–4]. Therefore, and following Dutch guidelines recommendations (CBO consensus Bloedtransfusie, http://www.cbo.nl/thema/Richtlijnen/ Overzicht-richtlijnen/Bloedtransfusie/), we do not screen for CAs in adults. However, as described also by others recently, we do perform screening for CAs in children undergoing cardiac surgery for which deep hypothermia is indicated [5]. A 7-year-old boy was referred for serological testing prior to hypothermic cardiac surgery. The patient’s blood group was O positive and antibody screening tests were negative. The cold agglutinin assay (saline, 16 °C) revealed the presence of a cold autoantibody with IH specificity. CAs are often directed against the Ii blood group collection [1]. Anti-IH antibodies have been implicated as the cause of a haemolytic transfusion reaction in a couple of cases [6–8]. CAs are generally produced in response to infections or secondary to a lymphoproliferative disorder [9]. Our patient had recently been treated with antibiotics for an infection. The importance of a CA is determined by the thermal amplitude (highest temperature at which the antibody binds to RBCs) and titre. The IH-antibody in our patient displayed wide thermal amplitude (28 °C; titre 1:2). Because of the associated risk of intravascular haemolysis during CPB, and the fact that postponing the elective surgery was safe for the patient, the procedure was cancelled. The presence of CAs is often transient and therefore the thermal amplitude of the antibody was determined periodically. The thermal amplitude decreased slowly to 24 °C after 3 months (titre 1:1) and 22 °C after 5 months (Fig. 1). After 7 months, the thermal amplitude of the antibody remained stable and we decided to perform the procedure under less extensive hypothermic conditions. The patient was cooled to 24.9 °C and surgery was performed successfully. The antibody did not show any reactivity at this temperature and accordingly, the patient did not show signs of hemolysis. The patient received 2 units of RBC, as a consequence of the CPB procedure, and had stable post-surgery haemoglobin of 11.3 g/dL, without any signs of hemolysis. In conclusion, CAs can cause haemolysis in patients undergoing hypothermic cardiac surgery. Although screening for CAs in all patients is not recommended it can be useful in specific patient groups (e.g. children undergoing I. Hubeek :W. W. van Solinge :K. M. K. de Vooght Department of Clinical Chemistry and Haematology, University Medical Center Utrecht, Utrecht, The Netherlands