11: Anemia 1

Definition of anemia

Low RBC mass

Tests used to clinically assess anemia

• PCV

• HCT

• RBC count

• HgB

PCV vs HCT measurements

PCV is a physical measurement of percentage, HCT is a calculated value

Only circumstance where we really use HgB to assess anemia

If we are concerned about low iron interfering with reticulocyte production

Clinical manifestations of anemia

• Lethargy, weakness, collapse

• Exercise intolerance

• Pica (cats, mostly)

• Icterus

• Bleeding

Why might anemic patients be icteric

If it is a hemolytic anemia

What causes icterus

Build up of bilirubin, a hemoglobin breakdown byproduct

If there is bilirubin in the skin of an icteric patient, where will you also likely find hemoglobin

Urine

Changes to skin/mm on physical exam that may indicate anemia

Pale to pale pink or yellow coloring

Changes to HR on physical exam that may indicate anemia

Tachycardia

Changes to RR on physical exam that may indicate anemia

Tachypnea

Changes to pules on physical exam that may indicate anemia

Bounding pulses

Changes to heart auscultation on physical exam that may indicate anemia

Grade 2-3 murmur due to changes in blood viscosity

Normal PCV for dogs

35-57% (from Merck Vet Manual)

Normal PCV for cats

30-45% (from Merck Vet Manual)

Additional RBC indices that help us characterize anemia

• Mean cell volume (MCV)

• Mean corpuscular hemoglobin concentration (MCHC)

• Reticulocyte count

What must be done for a CBC to be complete

Blood smear!!

What happens if you have an anemia with no reticulocytes

May be non-regenerative or pre-regenerative

Changes in TP that may be associated with anemia and why

Decreased TP → hemorrhage

Changes in bilirubin that may be associated with anemia and why

Increased bili → hemolysis

Changes in kidney values that may be associated with anemia and why

Increased BUN and creatinine → CKD → lack of EPO

Changes in electrolytes that may be associated with anemia and why

• Low K⁺/P → needed to support RBC development

• High Na⁺ → increased osmolarity → change in RBC structure

Changes on a UA that may be associated withe anemia and why

• Low USG → CKD

• Pigmenturia → bilirubin, HgB, MgB

How do you differentiate hematuria from hemoglobinuria or myoglobinuria

Spin the urine down and look for RBCs in the sediment

Additional general diagnostics that may help you determine cause of anemia

Rads or US

Specific tests that can be used to diagnose IMHA

• Saline agglutination test

• Coomb’s test

• Flow cytometry

Specific tests that can be used to diagnose infectious causes of anemia

• FeLV/FIV testing

• Vector borne disease testing

• Fecal float

Specific test that can be used to diagnose specific cases of non-regenerative anemia

Bone marrow aspirate

Causes of regenerative anemia

Hemorrhage and hemolysis

Causes of non-regenerative anemia

• Pre-regenerative

• Primary (intrinsic) bone marrow disease

• Secondary (extrinsic) bone marrow disease

How long is the pre-regenerative phase of anemia

2-5 days

Changes in RBC morphology and characteristics commonly seen with regenerative anemia

• Polychromasia/reticulocytosis

• nRBCs

• Macrocytic (high MCV)

• Hypochromic (low MCHC)

Changes in RBC morphology and characteristics commonly seen with non-regenerative anemia

• Normo or microcytic

• Normo or hypochromic

Common cause of non-regenerative anemia

Anemia of chronic disease/inflammation

Primary bone marrow diseases that result only in anemia

• Precursor immune mediated anemia

• Pure red cell aplasia

• Other erythroid hypoplasias

Primary bone marrow diseases that result in pancytopenias

• Myelofibrosis

• Myelophthisis

• Myelodysplasia

Myelofibrosis

Inflammation and deposition of scar tissue in the marrow that results in decreased production of blood cell precursors

Myelophthisis

Commonly a paraneoplastic syndrome where normal cells are replaced by tumor cells that suppresses normal marrow cell activity

Myelodysplasia

Abnormal maturation of blood cells

Common causes of secondary bone marrow disease

• Anemia of inflammatory/chronic disease

• CKD

• Endocrine diseases: hypothyroidism, hypoadrenocorticism

• Iron deficiency

Common blood finding also associated with iron deficiency anemia

Thrombocytosis

Non-iron causes of thrombocytosis

Chronic inflammation and glucocorticoid administration

Why is iron deficiency anemia tricky

• Often chronic, TP may be normal

• Only non-regen in the later stages

MOST common cause of mild anemia

Secondary bone marrow disease: chronic inflammation/disease, CKD, endocrine, iron deficiency

Most common cause of moderate anemia

Literally anything :)

Most common cause of severe and very severe anemia

Bone marrow disease, either primary or iron deficiency anemia

Bone marrow diagnostics

Marrow aspirate or marrow biopsy

Sites of bone marrow sampling

• Proximal humerus

• Proximal femur

• Iliac crest

How do you know if your marrow sample is good enough quality

You want little blood and a high number of spicules (fragments/aggregates of bone marrow cells)

Why might we run an IFA or PCR on a bone marrow sample

To look for a focal or latent FeLV infection

Why might we run a Coomb’s test or flow cytometry on a bone marrow sample

Looking for immune mediated destruction of blood cell precursors

When would we give a blood transfusion for anemia

If the patient is clinical for anemia (acute or <19%)

Treatment for immune mediated erythroid hypoplasias (PIMA/PRCA)

Immunosuppressants

Treatment for myelophthisis

Chemo or antimicrobials, depending on cause

Treatment for myelofibrosis

Intermittent blood transfusion and maybe immunosuppressive medications?

Treatment for anemia of chronic disease or endocrine disease

Treat the disease :)

Treatment for anemia associated with CKD

Erythropoietin supplementation

Treatment for iron deficiency anemia

Treat any underlying disease and supplement iron