Page 129 - Problem-Based Feline Medicine

8 – THE CYANOTIC CAT 121

and most cats will be in heart failure, so are poor anes- If all veins draining an area are obstructed, edema,
thetic risks. cyanosis and necrosis may occur.
Thrombolytic therapy using tissue plasminogen Cranial vena caval obstruction results in edema of the
activator reduces time to reperfusion and ambu- neck, ventral head, cranial thorax and forelimbs.
lation, however 50% of treated cats died during clin-
ical trials. Diagnosis

Pain treatment in the early stages of the disease using Diagnosis is based on historical and clinical findings.
oxymorphone (0.05–0.15 mg/kg IM or IV every 6
hours) and butorphanol (0.02–0.4 mg/kg every 4 hours
Treatment
IM or SC) is essential.
Thrombosis is usually self-limiting once catheters are
Acetylpromazine (0.05–0.1 mg/kg IV) may be useful
removed. Broad-spectrum antibiotic cover may be nec-
as an anxiolytic.
essary for septic lesions.
Treatment of the heart failure must also be undertaken.
Surgical management is by drainage of abscesses and
hematomas, and debulking of tumors where indicated.
VENOUS OBSTRUCTION
Treat the underlying cause of lymphadenopathy using
antibiotics, chemotherapy or surgical excision where
Classical signs
appropriate.
● Localized cyanosis and edema referable to
site of obstruction. Prognosis
● Edema of neck, ventral head, cranial thorax
and forelimbs (vena cava obstruction). Prognosis depends on the primary disease process.

Pathogenesis
ABNORMAL HEMOGLOBIN WITH
Localized peripheral hypoxia resulting from venous DECREASED OXYGEN-CARRYING
obstruction is usually the result of thrombosis, phlebitis CAPACITY
or venous obstruction from external compression.
● Thrombosis is typically caused by blunt trauma
and perforating injury, such as venepuncture or pro- ACETAMINOPHEN (USA)/PARACETAMOL
longed venous catheterization. (EUROPE, AUSTRALIA) TOXICITY
● Phlebitis may result from tissue inflammation
extending to the veins, or originate from a venous Classical signs
intimal lesion. ● Salivation, vomiting and depression and
● Venous obstruction may be caused by compression cyanosis.
by abscesses, hematomas, tumors or enlarged ● Subcutaneous edema of face and
lymph nodes. extremities.
● Lacrimation and facial pruritis.
Clinical signs ● Hematuria and hemolysis.
Clinical signs depend on the anatomic location and
the extent of the obstructive process, the collateral ves-
sel reserve and the capacity of the draining lymphatics. Pathogenesis

Large lesions may result in edema and cyanosis in the Feline hemoglobin is particularly susceptible to oxida-
area, which is usually short-lived because of large col- tive damage, and therefore to the formation of methe-
lateral circulation. moglobin and Heinz bodies in erythrocytes.