Transfusion Reactions Resulting from Mismatched Blood Types
If donor blood of one blood type is transfused into a recipient who has another blood type, a transfusion reaction is likely to occur in which the red blood cells of the donor blood are agglutinated. It is rare that thetransfused blood causes agglutination of the recipient’scells, for the following reason: The plasma portion ofthe donor blood immediately becomes diluted by all the plasma of the recipient, thereby decreasing the titer of the infused agglutinins to a level usually too low to cause agglutination. Conversely, the small amount of infused blood does not significantly dilute the agglutinins in the recipient’s plasma. Therefore, the recipient’s agglutinins can still agglutinate the mis-matched donor cells.
As explained earlier, all transfusion reactions even-tually cause either immediate hemolysis resulting from hemolysins or later hemolysis resulting from phagocy-tosis of agglutinated cells. The hemoglobin released from the red cells is then converted by the phagocytes into bilirubin and later excreted in the bile by the liver.The concentration of biliru-bin in the body fluids often rises high enough to cause jaundice—that is, the person’s internal tissues and skinbecome colored with yellow bile pigment. But if liver function is normal, the bile pigment will be excreted into the intestines by way of the liver bile, so that jaun-dice usually does not appear in an adult person unless more than 400 milliliters of blood is hemolyzed in less than a day.
Acute Kidney Shutdown After Transfusion Reactions. One ofthe most lethal effects of transfusion reactions is kidney failure, which can begin within a few minutesto few hours and continue until the person dies of renal failure.
The kidney shutdown seems to result from three causes: First, the antigen-antibody reaction of the transfusion reaction releases toxic substances from the hemolyzing blood that cause powerful renal vasocon-striction. Second, loss of circulating red cells in the recipient, along with production of toxic substances from the hemolyzed cells and from the immune reac-tion, often causes circulatory shock. The arterial blood pressure falls very low, and renal blood flow and urine output decrease. Third, if the total amount of free hemoglobin released into the circulating blood is greater than the quantity that can bind with “hapto-globin” (a plasma protein that binds small amounts of hemoglobin), much of the excess leaks through the glomerular membranes into the kidney tubules. If this amount is still slight, it can be reabsorbed through the tubular epithelium into the blood and will cause no harm; if it is great, then only a small percentage is reab-sorbed. Yet water continues to be reabsorbed, causing the tubular hemoglobin concentration to rise so high that the hemoglobin precipitates and blocks many of the kidney tubules. Thus, renal vasoconstriction, circu-latory shock, and renal tubular blockage together cause acute renal shutdown. If the shutdown is com-plete and fails to resolve, the patient dies within a week to 12 days, unless treated with an artificial kidney.
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