Adverse effects and alternatives to blood products

The use of blood and blood products may carry certain risks and cause adverse reactions. Let us not forget that blood is another tissue of the body and its administration to a patient can cause rejection reactions. The optimization of these products by separating them into different fractions, as well as the use of blood group determination tests and cross-compatibility tests, have decreased the occurrence of adverse reactions.

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These reactions are classified into 2 groups: immune-mediated and non-immune-mediated adverse reactions. The first are basically hemolytic reactions, whether acute or delayed. Acute reactions are caused by the presence of preformed antibodies in the recipient and cause type I or type II hypersensitivity reactions. Symptoms include tremors, tachycardia, tachypnea, hyperthermia (1ºC above the temperature before transfusion), vomiting, urticaria, hemoglobinemia, hemoglobinuria and even in some cases DIC, acute renal failure due to hemoglobinemia or death. If any of these signs are detected, the transfusion should be suspended immediately, supportive fluid therapy should be instituted, and rapid-acting intravenous corticosteroids should be administered. They are the most serious reactions. Late reactions are less dangerous, occurring between 3 and 15 days after transfusion and causing decreases in hematocrit, with fever and anorexia. They are treated with corticosteroids at immunosuppressive doses. Neonatal isoerythrolysis and post-transfusion purpura are included in this category.

 

Nonimmune-mediated reactions include hemolysis, circulatory overload due to vascular volume overload, sepsis due to contamination of the blood product, hypocalcemia due to citrate, hyperammonemia, dilutional coagulopathy, and iatrogenic infections due to administering blood from infected donors.

 

Animals with heart disease and normovolemic anemia are susceptible to vascular overload in a transfusion. Clinical signs consist of tachypnea, cough, congestive mucous membranes, and distention of the jugular veins. In these patients, the transfusion should be performed at rates lower than normal and if these signs are detected, the transfusion should be suspended and furosemide and oxygen therapy should be administered. Cats are more susceptible than dogs to vascular overload.

Hypocalcemia can also occur due to an excess of anticoagulant in the blood product. The clinical signs that we will observe are typical of hypocalcemia (tremors and arrhythmias). Treatment consists of the administration of slow intravenous calcium gluconate, monitoring the patient with a continuous electrocardiogram. Patients with liver failure are more susceptible to this problem.

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Sometimes, we can find febrile reactions and vomiting after a transfusion, reactions with little clinical relevance.

Alternatives to blood products.

An alternative to transfusion in cases of chronic anemia (oncology patients or patients with chronic renal failure) could be the administration of recombinant human erythropoietin. Although the complete DNA sequence of canine and feline erythropoietin is known, none of them have yet been manufactured or marketed. Human erythropoietin, unfortunately, can cause allergic reactions, consequently blocking any type of response from the bone marrow.

 

There are also intravenous oxygen-carrying solutions. These solutions immediately increase the capacity to transport oxygen and vascular volume, their use being indicated in patients with acute bleeding, hemolysis or bone marrow problems. They do not contain clotting factors or platelets, so they cannot perform the functions of these elements. There are two main groups of oxygen carrier solutions: those based on perfluorocarbon and oxygen carriers based on hemoglobin (TOBH), the latter being the only one authorized for use in companion animals.

 

TOBH-201 is a solution of ultrapurified and, therefore, acellular, bovine hemoglobin, dark purple in color. Its concentration of polymerized hemoglobin is 13g/dl. This solution does not provide red blood cells to the patient, so after its use, the hematocrit count will not increase, but the hemoglobin count will. It can be stored for up to 36 months without refrigeration and does not require blood group determination, since erythrocyte membranes are removed during manufacturing. Its use is indicated in cases where we do not have compatible blood. The recommended dose in dogs is 10 to 30 ml/kg intravenously, with the initial dose being the lowest. Although its use has not been authorized in cats, it has already been administered successfully in this species.

 

The adverse effects of the use of these derivatives consist of transient intense purple color of the mucous membranes and urine, although without causing interference with pulse oximetry of the mucosa. The presence of oxyglobin alters laboratory analyzes by colorimetry, especially in the determinations of bilirubin, liver enzymes, creatinine, glucose and urine strips. Regarding the appearance of anaphylactic reactions, they have not been described so far, although its sole use is recommended to prevent them.