Cause: hemorrhagic (acute or chronic) or hemolysis (see Anemia: immune-mediated ).
Signs: hypovolemic shock (acute), signs of anemia (chronic), eg pale mucous membranes, lethargy, tachypnea, tachycardia, exercise intolerance, may be no signs.
Diagnosis: packed cell volume (PCV), total serum protein (TSP), reticulocyte count, cytology; evaluate homeostasis.
Treatment: depends on cause and rate of development.
Prognosis: can be good with appropriate treatment.
Presenting signs
Lethargy.
Depression.
Acute presentation
Death - loss of >30% blood volume can cause death due to hypovolemic shock.
Signs usually triggered by blood loss > 20% total blood volume (50-70ml in adult cat).
Acute blood loss
Inciting cause proportional loss of all major blood components PCV and TSP normal for first 12-24 hours.
Reflex splenic contraction boosts red cell numbers (PCV) initially, so TSP drops before PCV.
Hypovolemia recovery of volume expansion dilutes PCV (12-24 hours after bleeding episode) and TSP (1-4 hours after bleeding).
Rapid increase in protein synthesis normalizes serum protein. Patients that survive hypovolemic shock are unlikely to have lost >30% of circulating red cells and will not be severely anemic unless bleeding continues.
3-4 days later erythrocyte regeneration peaks 5-7 days. Do not see regenerative response immediately following hemorrhage.
Chronic blood loss
Initially see regenerative response with anisocytosis, polychromasia (new red blood cells are bigger and stain slightly darker blue) but continued blood loss to iron deficiency and non-regenerative anemia and microcytosis (small red blood cells). Kittens have poor iron stores and are therefore very susceptible to iron deficiency.
Continued blood loss reduced oxygenation of kidneys erythropoietin release bone marrow increases RBC production and release.
Also, increased levels of erythrocyte 2,3-diphosphoglycerate (2,3-DPG) improves release of oxygen from hemoglobin into tissues.
Insufficient circulating hemoglobin tissue hypoxia pale mucous membranes, lethargy and weakness, and compensatory responses of the sympathetic nervous system, ie tachypnea, tachycardia, bounding pulse.
Chronic external blood loss iron-deficiency (likely in unweaned kittens - rare in adult cats) and non-regenerative anemia .
Timecourse (incubation, duration)
PCV normal within 2-3 weeks; TSP normal within 1 week.
PCV - falls 12-24 hours following blood loss. Patients with acute anemia are typically severely affected when PCV <0.2 l/l; patients with chronic anemia may be stable with a PCV as low as 0.10 l/l.
Regenerative response:
Peaks 5-7 days after initial single episode of blood loss.
Aggregated reticulocyte count rises after 3-4 days.
Anisocytosis, polychromasia, nucleated RBCs on a stained smear. May see increase in Howell-Jolly bodies.
With prolonged hemorrhage the anemia is poorly regenerative, microcytic and hypochromic.
Platelet count may fall during an episode of bleeding. This then may be followed by a rebound thrombocytosis.
Evaluate homeostasis:
Prothrombin time (OSPT = one stage prothrombin time).
Partial thromboplastin time APTT = activated partial thromboplastin time).
Activated clotting time .
Buccal mucosal bleeding time .
Reactive leucocytosis occurs within 24 hours.
Urinalysis
Investigate potential hemorrhage by urine dipstick and sedimentation
Fecal analysis
Investigate potential gastrointestinal hemorrhage by fecal occult blood (requires meat-free diet for 3 days prior to sampling to avoid false positives) and endoparasitic flotation .
Radiography
Thoracic and abdominal radiographs to investigate potential body cavity hemorrhage.
If gastrointestinal hemorrhage is suspected, barium series may be indicated.
Biochemistry
TSP : - falls 1-4 hours after blood loss.
Serum iron is reduced in severe iron deficiency chronic external blood loss (but also in acute phase reactions, hypoproteinemias and renal disease). Iron deficiency is rare except in kittens with external blood loss. In cases of internal blood loss the iron is recycled and so serum levels are not significantly reduced.
Ferritin assay is best method of assessing iron body stores.
Ferritin is reduced in iron deficiency. Most accurate way of assessing body iron stores is by examination of bone marrow aspirate stained with Pearls/Prussian blue (iron stores stain blue/black).
Confirmation of diagnosis Discriminatory Diagnostic features
History.
Signs.
PCV.
Definitive Diagnostic features
Hematology.
Evaluation of source of blood loss (intracavitatory, gastrointestinal, urogenital).
acute blood loss.
Patients that survive hypovolemic shock are unlikely to have lost >30% of circulating red cells and will not be severely anemic unless bleeding continues.
Do not see regenerative response immediately following hemorrhage.