Page 128 - Problem-Based Feline Medicine

120 PART 2 CAT WITH LOWER RESPIRATORY TRACT OR CARDIAC SIGNS

Typically there is an acute onset of posterior pare-
PERIPHERAL HYPOXIA – LOCALIZED
sis/paralysis.
Weakness or absence of one or both femoral pulses is
ARTERIAL THROMBOEMBOLISM**
evident.
Classical signs There is early severe pain in hindlimb muscles which
are swollen and turgid. The pain subsides as sensory
● Acute onset of posterior paresis/paralysis.
nervous input is lost over several hours.
● Cyanosis of footpads and cold extremities.
● Marked pain and swollen, turgid hind limb Pallor and cyanosis of footpads and coldness of
muscles. extremities are evident.
● Weak or absent femoral pulses.
Later over days to weeks, depending of the degree of
arterial obstruction, neurological deficits begin to
See main reference on page 915 for details (The Weak
resolve.
and Ataxic or Paralyzed Cat).
Other organs may be affected depending on deposi-
Pathogenesis tion of emboli.
Arterial thromboembolism is a relatively common
and serious sequela to feline cardiomyopathy.
Diagnosis
Thrombi form in the left atrium due to a combina-
tion of factors including sluggish blood flow, Diagnosis is based primarily on clinical findings.
endothelial damage and increased blood coagulabil-
Lack of blood flow to hindlimbs can be confirmed using
ity. The blood flow through the atria of cats with car-
a Doppler arterial blood pressure monitor.
diomyopathy is normal to slow. Slow blood flow
enables red cells and other blood factors to clump Echocardiography is valuable to identify cardiomy-
together and platelet aggregability in cats with car- opathy.
diomyopathy is reported to be increased.
Biochemical profiles may help to identify other organ
Once a thrombus is formed it may remain in the atrium involvement.
and cause no symptoms. It may become an embolus
and travel to the distal aorta and extend down the
external iliac arteries forming a “saddle thromboem- Differential diagnosis
bolus” obstructing blood flow to the hindlimbs. Ninety
Other causes of posterior paresis/paralysis such as
percent of cats with arterial thromboembolism are thus
road traffic accidents and trauma should be consid-
affected.
ered.
It is thought that the embolus releases serotonin and
thromboxane A , which are powerful vasoconstric-
2
tors. This results in very poor collateral blood flow Treatment
beyond the embolus, leading to tissue hypoxia and
muscular ischemia. Treatment is mostly palliative, such as cage rest and
consider the administration of drugs such as aspirin,
Other emboli may obstruct the femoral, brachial, heparin or arteriolar dilators. Heparin is given to pre-
renal, mesenteric, coronary or cerebral arteries caus- vent new thrombus formation at an initial dose of 220
ing a wide variety of clinical signs. U/kg IV followed by a maintenance dose of 70–200
U/kg SC every 6 hours. The dose should be tailored to
Clinical signs increase the activated thromboplastin time to at least
1.5 times baseline.
Many cats are in heart failure and therefore are
tachypneic and dyspneic, and may have a heart mur- Surgical intervention to remove the embolus and bal-
mur or a gallop rhythm. loon embolectomy may lead to reperfusion syndrome