A 42-year-old patient with acute hemorrhage and class III blood loss underwent blood transfusion and got 1,8 l of preserved blood and erythromass of the same group and Rh. After the transfusion the patient complained of unpleasant retrosternal sensations, his arterial pressure dropped to 100/60 mm Hg, there appeared convulsions. Blood serum calcium was at the rate of 1,7 millimole/liter. What is the mechanism of this complication development?