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Anemia: blood loss
Synonym(s): Anaemia
Introduction
- Cause: hemorrhagic (acute or chronic) or hemolysis (see Anemia: immune-mediated Anemia: immune-mediated hemolytic).
- 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.
Pathogenesis
Etiology
- Trauma (RTA/surgery) to major vessels or vascular organs → acute blood loss.
- Surgery.
- Any chronic hemorrhage:
- Refractory epistaxis Epistaxis.
- Bleeding neoplasms, eg intestinal neoplasm, splenic hemangiosarcoma, ruptured abdominal mast cell tumor.
- Severe hematuria Hematuria, eg FLUTD Feline lower urinary tract disease (FLUTD).
- Gastrointestinal ulceration.
- Endoparasitism (rare).
- Ectoparasitism - fleas.
- Coagulophathies.
Pathophysiology
- Signs usually triggered by blood loss > 20% total blood volume (50-70 ml 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 Anemia: overview.
Timecourse
- PCV normal within 2-3 weeks; TSP normal within 1 week.
- Persistent anemia, hypoproteinemia Hypoproteinemia suggests persistent blood loss.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
Other sources of information
- Helm J & Knottenbelt C (2010) Blood transfusions in dogs and cats. 1. Indications. In Practice 32, 184-189.
- Helm J & Knottenbelt C (2010) Blood transfusions in dogs and cats. 2. Practicalities of blood collection and administration. In Practice 32, 231-237.
- Raskin R E (2010) Haematological Disorders. In: Clinical Medicine of the Dog and Cat. 2nd edn. Ed Schaer M, Manson Publishing Ltd, London, pp 227-231.
- Mills J (2000) Anaemia. In: Manual of Canie and Feline Haematology and Transfusion Medicine. 1st edn. Eds Day M J, Mackin A & Littlewood J D. BSAVA Publications, Gloucester, pp 29-42.