EN/DE: From the Blood Bank / aus der Blutdatenbank
Verfasst: Do 28. Feb 2019, 15:29
Übersetzung folgt:
https://www.greyhoundhealthinitiative.o ... r-2019.pdfFROM THE BLOOD BANK
RED BLOOD CELLS, ANEMIAS AND IMMUNE-MEDIATED HEMOLYTIC ANEMIA
Amanda “Nellie” Nelson RVT
Red blood cells (RBC’s) main function is to carry oxygen to the tissues. Oxygen molecules from the lungs attach themselves to hemoglobin in red blood cells. Hemoglobin is the iron-containing proteins in red blood cells that give the cells their red color. Oxygen is then delivered to all body tissues by the hemoglobin within red blood cells.
Oxygen is used by cells to produce energy that the body needs. Carbon dioxide is left behind as a waste product during this process. The red blood cells then carry that carbon dioxide away from the tissues and back to the lungs, where it is exhaled. The total number of red cells, and thus the oxygen-carrying capacity, should be stable over time in a health animal. Mature red blood cells have a limited life span and the rate of blood cell production is determined by the body’s needs. The production and destruction of red blood cells in circulation must be carefully balanced.
Erythropoietin, a hormone, plays a key role in determining whether to increase the number of stem cells entering red blood cell production, to shorten maturation time of the red blood cells, or to cause early release of red blood cells. Erythropoietin increases if the body lacks oxygen. The kidney is both the sensor organ that determines how much oxygen the body’s tissues are receiving and the major site of erythropoietin production.
Production of red blood cells begins with stem cells in the bone marrow and ends with the release of mature red blood cells released into the circulation. The stem cell divides to form immature forms of red blood cells, white blood cells, or a platelet-producing cell. As the red blood cells age or become damaged, they will be removed from the bloodstream.
Factors that may prevent red blood cell production include bone marrow failure or malignancy, loss of erythropoietin due to chronic kidney failure leading to anemia. Exposure to toxins such as lead or rat poison, chronic diseases, or antibodies targeted at developing red blood cells. Additional factors that affect red blood cell production are the supply of nutrients, such as iron and certain vitamins.
When the number of red blood cells is too low, this is called anemia, and a dog who is anemic will show symptoms related to a lack of oxygen. Having too few red blood cells means the blood carries less oxygen to the tissues, resulting in lethargy and weakness. The number of circulating red blood cells may become reduced if there is a decrease in production in the bone marrow, lysis (or destruction), or if there is an increase in blood loss from circulation as seen with hemorrhage. The outlook and treatment depend on the underlying cause of the anemia.
An animal’s metabolism is geared to protect both the red blood cells and the hemoglobin from damage. Anemia is not a disease itself, but rather is a symptom of a disease process or condition. Anemia is a medical term referring to a reduced number of circulating red blood cells, hemoglobin or both. Diagnosis of anemia is done in the laboratory with blood tests called a packed cell volume (PCV) and a complete blood count (CBC). The PCV indicates the percentage of red blood cells in the bloodstream. A PCV is lower than the normal range indicates anemia. The CBC can offer more detailed information regarding the anemia, like whether the body is losing red blood cells or destroying them, and if it’s producing new red blood cells to replace them. The number of red blood cells will be counted, and the cells will be examined under a microscope to determine their size and shape. Acute conditions causing anemia can be blood loss due to severe injury or trauma that causes bleeding externally or internally. Acute bleeding into the gastrointestinal tract as a result of disease or severe inflammation can cause anemia. Gastrointestinal bleeding can also be a reaction to certain medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs), cancer may lead to bleeding into the gastrointestinal tract or bleeding from a tumor. Chronic conditions include chronic disease, immune-mediated blood cell destruction, cancer, chemotherapy reactions, bleeding from an inherited condition, liver failure, bone marrow failure, or kidney failure. Some disorders are the direct result of abnormal red blood cell metabolism. Immune-mediated hemolytic anemia (IMHA) is an immune system disease in which the body attacks and destroys its own red blood cells. In dogs with IMHA, red blood cells are still being manufactured in the bone marrow, but once released into the circulation, they have a shorter-than-normal life span. In primary IMHA, the dog's immune system is not working properly, and it incorrectly makes antibodies that target its own red blood cells. In secondary IMHA, the surface of the red blood cells becomes altered by an underlying disease process or a toxin. The dog's immune system then recognizes the altered red blood cells as foreign' invaders that must be destroyed. This form of IMHA may be triggered by cancer, infections such as Ehrlichia, blood borne parasites such as Babesia, drug reactions, snakebites, chemicals, toxins, or bee stings. Cancer appears to be the most common cause of secondary IMHA. As the red blood cells are destroyed hemoglobin will be released. The liver will attempt to break down these excess levels of hemoglobin, increasing the workload of this organ.
Dogs with IMHA have severe anemia will be listless and lethargic, tiring easily. This happens when there are not enough red blood cells to carry oxygen to the tissues. The dog may faint or appear disoriented due to low oxygen levels in the brain. To compensate for the lack of oxygen to the tissues, heart rate and respiration rate will increase. The dog may vomit or may have a poor appetite.
Their gums will be very pale rather than the normal pink to red color. As the disease progresses, excessive levels of bilirubin, a breakdown product of red blood cell hemolysis, build up within the body. Excessive levels of bilirubin cause the skin, gums, and other mucous membranes to appear yellow or jaundiced. If the dog's anemia is so severe that it is life-threatening, a blood transfusion will be needed. The main purpose of a blood transfusion is to stabilize the dog while the underlying cause of the anemia is determined and other treatments can begin to take effect.
Packed red blood cells (PRBCs) are a concentrated source of red blood cells. PRBC’s are obtained by taking of blood from donor dogs using in a refrigerated centrifuge the red blood cells are separated from the plasma. The plasma is then frozen to be sold as fresh frozen plasma and the PRBC’s are sold as the preferred source of red blood cells in veterinary medicine.
In dogs, there are at least 12 different canine blood groups. Blood groups are determined by the presence or absence of different antigens on the surface of the dog’s red blood cells. As with humans, there is a “universal donor” blood group for dogs. Dogs can suffer adverse reactions to transfused blood from dogs with types that are different from their own, which is why GHI Blood Bank uses “universal donors”.
Blood products from an animal blood bank have the advantage of consistent quality, prepared according to acceptable veterinary transfusion medicine standards. Veterinary medicine has become increasingly sophisticated, with trends paralleling those in human medicine, including the increased demand for canine blood and therefore more blood banking services.
For information on Penn State clinical trials for IMHA in canines:
https://www.vet.upenn.edu/research/clin ... ha-in-dogs