The effect of hypothermic cardiopulmonary bypass on patients with low-titer, nonspecific cold agglutinins.

The effect of hypothermic cardiopulmonary bypass (CPB) was studied in 5 patients with strongly positive cold agglutination at 4 degrees C (experimental group) and in 10 controls. In the in vitro part of the study, the characteristics of the cold agglutinin antibodies in the experimental group included a low thermal amplitude (28 degrees C or less), a low 4 degrees C agglutination titer (1:32 or less), and nonspecificity (non-anti-I and non-anti-i). The in vivo portion of the study revealed a fall in total urine and serum free hemoglobin in both groups on going on bypass, followed by a rise for the remainder of bypass. Statistical comparison between observed and expected total free hemoglobin for both groups showed a significant rise (p less than 0.05) after bypass, thereby indicating ongoing hemolysis. No statistically significant difference between preoperative and post-operative blood urea nitrogen and creatinine levels and gross neurological status was observed in the experimental group. It was concluded that the patient with nonspecific cold agglutinins whose antibody is characterized by a low titer, a low thermal amplitude, and a lack of clinical symptomatology can undergo hypothermic CPB without increased threat of a hemolytic or vascular occlusive crisis.