Lecture 6 - Haem 3 Flashcards
What clinical signs are observed as a result of intravascular haemolysis?
Haemoglobinemia and haemoglobinuria
What clinical signs are seen as a result of extravascular haemolysis?
Phagocytosis by cells of the mononuclear phagocyte system and increased bilirubin and icterus
What are the differentials that should be considered in haemolytic anaemia?
- Immune-mediated erythrocyte destruction 2. Erythrocyte parasite 3. Other infectious agents 4. Oxidant compounds or other chemicals and plant compounds 5. Fragmentation 6. Hereditary erythrocyte defects
What are the two different types of immune mediated haemolytic anaemia?
1st degree - if we cannot identify and agent (autoimmune) 2nd degree - parasites, drugs etc.
In immune mediated hemolytic anaemia what is the relative proportion of intravascular haemolysis to extravascular haemolysis?
20% of IMHA is intravascular haemolysis 80% of IMHA is extravascular phagocytosis
What are the clinical signs that are seen in immune-mediated haemolytic anaemia (IMHA)?
- Weakness - Lethargy, exercise intolerance - Pallor mucous membranes - Icterus = pre-hepatic hyperbilirubinemia - Tachypnoea, tachycardia causes hypoxia secondary to severe anaemia - Hepatosplenomegaly = increased erythrophagocytosis
What is the first step in the diagnosis of IMHA?
Check for auto-agglutination - this will be positive in 60% of IMHA - Coomb’s test and additional tests are not neccesary
What is the condtion that can be seen in the image below? (the left is for reference)
Macroscopic aggultination in dog with immune-mediated haemolytic anaemia
What are the clinical pathological changes seen with immune-mediated haemolytic anaemia (IMHA)?
Anaemia = severe (mean hct 15%)
Strongly regenerative or pre-regenerative if onset is acute - macrocytic and hypochromic
Non regenerative if antibodies against erythroid precursors
Hyperbilirubinaemia (about 75%) = increased erythropahgocytosis
Leukocytosis due to neutrophilia and left shift and monocytosis (>80%) - probably due to ischemic necrosis within tissues
Thrombocytopenia usually not severe. If IMT = Evans syndrome
Briefly explain what neontal isoerythrolysis is an what species it is commonly seen in:
IMHA that develops in neonatal animals following the ingestion of colostrum containing antibodies against antigens on their eryhtrocytes. This only occurs in horses and cats. Only about 10% of horses have naturally occuring RBC antibodies and hence they generally need to be sensitised during previous parturition. Cats with type B blood have naturally high anti-A antibody titres so there is no need to be sensitised.
Briefly explain what a transfusion reaction is an when it may occur:
Transfusion reactions occur when plasma of the recipient contains antibodies against one or more antigens on surface of donor eytrhocytes. Generally, transfusion reactions generally don’t occur at time of the first reaction.
Briefly describe the appearance of blood that has had exposure to oxidant compounds:
Moderate to severe, regenerative, macrocytic, hypochromic anaemia + Heinz bodies, + eccentrocytes, +/- methemoglobinemia
Name the types of fragements in the picture below:
Fragmentations:
Schistocytes = RBC fragments with pointed extremities
Acanthocytes = RBCs with irregularly spaced, variably sized spicules due to fragmentation or lipid disorders (hypercholesterolemia)
What is the conditions can cause fragmentations in the blood?
Microangiopathy, haemangiosarcom, vena cava syndrome - eryhtrocytes are forced to flow through altered vascular channels or are exposed to turbulent blood flow
DIC - mechanical fragmentation occurs as the cells pas through the fibrin meshwork of a microthrombus
