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60 Anemia, Immune-Mediated Hemolytic

hemolysis. Hemoglobinemia/-uria with ○ Acetaminophen: N-acetylcysteine diluted canine PK deficiency, hemangiosarcoma,
intravascular hemolysis. Total protein normal in saline at 140 mg/kg IV, then 70 mg/ DIC.
VetBooks.ir occurring concurrently or anemia is from • Hypophosphatemia: potassium phosphate PEARLS & CONSIDERATIONS
kg q 6h × 6 doses (p. 10)
unless separate protein-losing disorder is
0.01-0.06 mmol/kg/hr IV until normal
blood loss, not hemolysis. Rule out
hypophosphatemia.
• Decision to transfuse should be based on
Babesiosis, and Cytauxzoonosis (pp. 105,
• Slide agglutination (and if negative, Coombs’ • Infection: see Hemotropic Mycoplasma, Comments
test) to rule out IMHA 235, and 438) clinical signs rather than PCV alone.
• Fecal floatation and heartworm serology: rule However, when PCV is < 12%, patients
out parasites (e.g., hookworms, heartworm) Chronic Treatment generally decompensate and require
• Coagulation panel to assess for DIC (if • Avoid excitement/exercise with PFK transfusion.
thrombocytopenia or evidence of hemostatic deficiency. • Although IMHA is the most common cause
defect on exam) • Prednisolone and splenectomy in canine and of hemolysis in dogs, other causes of hemo-
• Radiographs to rule out metallic gastro- feline PK deficiency lysis should be considered, especially in
intestinal foreign body (zinc); ultrasound for young or old dogs.
neoplasia or splenic abnormalities (e.g., Possible Complications
torsion, hemangiosarcoma), echocardiogram • Hypercoagulation/pulmonary thromboem- Prevention
for caval syndrome bolism Ectoparasite and heartworm prophylaxis; avoid
• Transfusion reactions (p. 989) breeding pets with congenital defects; avoid
Advanced or Confirmatory Testing ○ Dogs: blood typing should be performed breeding type B queens to type A toms.
• Polymerase chain reaction (PCR) and/or before transfusion. If recipient is not
serologic testing for Mycoplasma (especially typed, donor should be negative for Technician Tips
cats), Babesia (especially pit bull or DEA-1.1. Previously transfused dogs In addition to mucous membrane color, capil-
greyhound) require a cross-match before transfusion. lary refill time, and heart and respiratory rates,
• DNA tests for PK/PFK deficiency; porphy- ○ Cats: have naturally occurring alloantibod- mentation and pulse strength are external
rins in urine and RBCs for porphyria ies. Fatal transfusion reactions can occur indicators of severity of anemia and are very
• Bone marrow aspiration: not indicated if if transfusion is given arbitrarily, and cats useful for patient monitoring.
regenerative; erythroid hyperplasia must be typed and cross-matched before
any transfusions. Client Education
TREATMENT • Counsel clients on causes of oxidative damage
Recommended Monitoring and that acetaminophen should especially
Treatment Overview During hospitalization, monitor packed cell be avoided.
Treatment consists of stabilizing the patient volume (PCV) every 12-24 hours initially and • Counsel owners and breeders on heritable
with fluid support and blood transfusions (as monitor heart rate, respiratory rate, mucous defects to avoid breeding of affected dogs.
needed, based on clinical signs), followed by membrane color, and capillary refill time (CRT)
specific therapy to resolve the underlying cause frequently to determine need for repeat SUGGESTED READING
of hemolysis. transfusion. Owen JL, et al: Hemolytic anemia in dogs and cats
due to erythrocyte enzyme deficiencies. Vet Clin
Acute General Treatment North Am Small Anim Pract 42:73-84, 2012.
• If severe, may require transfusion: packed PROGNOSIS & OUTCOME
RBCs (6-10 mL/kg IV) or whole blood EDITOR: Jonathan E. Fogle, DVM, PhD, DACVIM
AUTHOR: Alicia K. Henderson, DVM, DACVIM
(10-20 mL/kg IV) (p. 1169) • If cause of hemolysis is resolved, prognosis
• Intoxication: is good after patient is stabilized.
○ Zinc foreign body: remove by endoscopy/ • Some causes of hemolysis carry a poor
surgery (p. 1098) prognosis: cytauxzoonosis, isoerythrolysis,

Anemia, Immune-Mediated Hemolytic Bonus Material Client Education
Sheet
Online
BASIC INFORMATION • Evans syndrome occurs when IMHA develops beagle, English springer spaniel, and Jack Russell
with concurrent immune-mediated throm- terrier are overrepresented.
Definition bocytopenia (IMTP, p. 972).
Immune-mediated hemolytic anemia (IMHA) is Epidemiology RISK FACTORS
a common cause of anemia in dogs. IMHA results • In dogs, IMHA is most often a primary or
from increased destruction or phagocytosis of red SPECIES, AGE, SEX idiopathic condition. Infection and neoplasia
blood cells (RBCs) that have been coated with • More common in dogs are the most common causes of secondary
immunoglobulin (Ig), complement (c′), or both. • Dogs: 1-13 years old (mean, 6 years); females IMHA.
IMHA can be classified as primary (idiopathic) slightly overrepresented • In cats, IMHA is most commonly a second-
or secondary (identifiable underlying cause). • Cats: 0.5-9 years old; most are ≤ 3 years ary condition with Mycoplasma haemofelis
old; males may be overrepresented infections, feline leukemia virus (FeLV),
Synonyms feline immunodeficiency virus (FIV), and
• Autoimmune hemolytic anemia GENETICS, BREED PREDISPOSITION lymphoma being the most common underly-
• Pure red cell aplasia (PRCA, p. 63): con- Cocker spaniel, shih tzu, Bichon frisé, old ing causes.
sidered an IMHA variant in which RBC English sheepdog, collie, miniature schnauzer, • Recent vaccination is suggested as a trigger
precursors in the bone marrow are destroyed Maltese, Labrador retriever, poodle, dachshund, of IMHA in some cases (dogs, cats).

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