Page 1403 - Small Animal Internal Medicine, 6th Edition

CHAPTER 85 Leukopenia and Leukocytosis 1375

with toxic neutrophils (24.2 versus 11.7%, P < 0.001); the 12,000 50,000
cost of hospitalization was also significantly higher. Inter-
VetBooks.ir estingly, toxic neutrophil changes were also significantly 10,000 40,000
associated with acute renal failure, immune-mediated hemo-
lytic anemia, and disseminated intravascular coagulation.
Similar results were found in a study of 150 cats (Segev 8000 30,000
et al., 2006); cats with toxic neutrophils had a similar mor-
tality rate than control cats (20% versus 15%), but the dura- Neutrophils (/µL) 6000 Platelets (×10/µL)
tion of hospitalization was significantly longer (3.0 versus 20,000
1.1 days). 4000
In a recent study of 31 cats (Klainbart et al., 2017), sepsis
was associated with pyothorax (32%), septic peritonitis 2000 10,000
(23%), feline panleukopenia virus infection (16%), bite
wounds (16%), cellulitis/abscesses (10%), and pyometra 0
(3%). Most cats had tachycardia and were febrile. Most cats 1 2 3 4 51524344554 0
(88%) had toxic neutrophils and/or a left shift (73%). The Prednisone
30-day survival rate was 63%. (day)
Evaluation of sequential leukograms in neutropenic dogs
and cats is helpful in excluding transient or cyclic neutrope- FIG 85.4
Response to therapy in a 6-year-old, female, spayed
nia (or cyclic hematopoiesis). Airedale Terrier with steroid-responsive neutropenia
If the pathogenesis of neutropenia cannot be ascertained, and thrombocytopenia. Note the rapid response to
sophisticated diagnostic techniques such as testing for anti- immunosuppressive doses of prednisone. –•–,
neutrophil antibodies, leukocyte nuclear scanning, or leuko- Polymorphonuclear neutrophils (in microliters); –Δ–, platelets
3
cyte kinetic studies can be performed. As noted, normal cats (×10 /µL).
and Greyhounds can have low neutrophil counts. Therefore,
if a cat or a Greyhound with a neutrophil count of 1800
to 2300/µL is brought in for evaluation (or, more likely,
if the “neutropenia” is detected during a routine hemato- with aggressive intravenous (IV) antibiotic therapy. My
logic evaluation), a conservative approach (e.g., repeat the treatment of choice consists of a combination of ampi-
CBC in 2-3 weeks) is indicated as long as no other clini- cillin (20 mg/kg IV q8h) and enrofloxacin (5-10 mg/kg
cal or hematologic abnormalities are found (e.g., left shift, IV q24h).
toxic changes). Neutrophil production can be stimulated by the admin-
Because corticosteroid-responsive (or immune-mediated) istration of human recombinant granulocyte colony-
neutropenia has been well characterized in cats and dogs, if stimulating factor (G-CSF; 5 µg/kg subcutaneously q24h).
most infectious and neoplastic causes of neutropenia have Although results are spectacular, the responses are usually
been ruled out in an asymptomatic neutropenic animal, an short-lived because of the counteractive effects of anti-CSF
in-hospital therapeutic trial of immunosuppressive doses of antibodies produced by the affected dog or cat. Lithium
corticosteroids (prednisone, 2-4 mg/kg/day orally [PO] for carbonate (10 mg/kg PO q12h) can increase the neutrophil
dogs, or dexamethasone, 4 mg/cat PO once a week) can be counts in dogs; the therapeutic trough serum concentration
instituted. Responses are usually observed within 24 to 96 of lithium is 0.8 to 1.5 mmol/L. This drug should be used
hours of the start of treatment in these patients. Treatment with caution in dogs with a decreased glomerular filtration
is continued as for dogs with immune hemolytic anemia and rate because it is primarily excreted by the kidneys. Lithium
other immune-mediated disorders (see Chapters 72 and 73; carbonate does not appear to be effective in cats and may
Fig. 85.4). be toxic.
Asymptomatic, afebrile neutropenic dogs and cats should
be treated with broad-spectrum bactericidal antibiotics NEUTROPHILIA
because they are at high risk for sepsis. My drug of choice Neutrophilia is defined as an absolute increase in the number
for dogs is trimethoprim-sulfamethoxazole, 15 mg/kg PO of neutrophils; it is the most common cause of leukocytosis
q12h; another drug that can be used in dogs and is preferred in dogs and cats. Several terms used to characterize neutro-
in cats is enrofloxacin (or another fluoroquinolone), 5 to philia are defined in the following text.
10 mg/kg PO q24h. Antibiotics with an anaerobic spectrum The term mature neutrophilia refers to an increase in
should not be used because they deplete intestinal anaerobes, the number of segmented (mature) neutrophils, without an
a protective bacterial population; recent research has clearly increase in the number of immature forms (e.g., bands).
illustrated the role of the microbiome in modulating the The term neutrophilia with a left shift refers to an increase in
immune response in mammals. the number of mature and immature neutrophils (>300/µL,
9
Neutropenic febrile (or symptomatic) cats and dogs or 0.3 × 10 /L bands). A regenerative left shift is associ-
constitute a medical emergency and should be treated ated with increased numbers of immature neutrophils in