Page 254 - Small Animal Internal Medicine, 6th Edition

226 PART I Cardiovascular System Disorders

BOX 12.2 arrhythmias (if present). Other supportive care is given to
improve and maintain adequate tissue perfusion, minimize
VetBooks.ir Common Clinical Findings in Cats With Systemic further endothelial damage and blood stasis, optimize organ
function, and allow time for collateral circulation develop-
Arterial Thromboembolism
Acute limb paresis ment. (Box 12.3). The treatment of CHF in cats is outlined in
Chapter 8 and Box 8.1. General supportive care in acute ATE
Posterior paresis includes active external warming for hypothermia, rotation
Monoparesis of position and recumbency (if nonambulatory), assistance
±Intermittent claudication
Characteristics of affected limb(s) with litter box posturing or bladder expression, and physical
Painful therapy once the patient is stable.
Cool distal limbs An analgesic is indicated for cats with ATE, especially for
Pale footpads the first 24 to 36 hours after the embolic event, because this
Cyanotic nailbeds is a painful condition. For caudal arterial obstruction, anal-
Absent arterial pulse gesic administration into a more cranial site is recommended
Contracture of affected muscles (especially to improve absorption (e.g., IV into the cephalic vein or IM
gastrocnemius and cranial tibial) into the cranial lumbar area). Drugs that are most useful
Tachypnea/dyspnea include µ-opioids such as fentanyl citrate (IV bolus followed
Rule out congestive heart failure versus pain or other by infusion), buprenorphine HCl, hydromorphone, metha-
pulmonary disease done, oxymorphone, or morphine (see Box 12.3). A fentanyl
Vocalization (pain and distress)
Hypothermia patch (25 µg/h size) applied to a shaved area of skin can be
Anorexia used for pain relief for up to 3 days, but because this formula-
Lethargy/weakness tion takes about 12 hours to become effective, another anal-
Signs of heart disease (inconsistent) gesic is used simultaneously during this initial period.
Systolic murmur Respiratory depression and reduced gastrointestinal (GI)
Gallop sounds motility are potential adverse effects of opioids. Narcotics
Arrhythmias sometimes cause dysphoria in cats. Acepromazine is not rec-
Cardiomegaly ommended for animals with ATE, despite its vasodilatory
Signs of congestive heart failure α-adrenergic receptor–blocking effects. Improved collateral
Pulmonary edema flow has not been documented, and hypotension and exac-
Cavitary effusions erbation of dynamic ventricular outflow obstruction (in cats
Hematologic and biochemical abnormalities
Azotemia with hypertrophic obstructive cardiomyopathy) are potential
Increased creatine kinase activity adverse effects.
Increased aspartate aminotransferase activity Antiplatelet therapy is used to inhibit platelet aggregation
Increased alanine aminotransferase activity and to reduce production of vasoconstrictive substances
Increased lactate dehydrogenase activity released from activated platelets. Platelet inhibitors are con-
Increased cardiac biomarkers (Troponin I, NT-proBNP) sidered especially important for inhibiting thrombus forma-
Hyperglycemia (stress) tion within arteries, where blood flows under high shear
Lymphopenia (stress) rates and platelet adhesion via von Willebrand factor is criti-
Disseminated intravascular coagulation cal for clot formation. Clopidogrel (Plavix) has replaced
aspirin as the standard of care for antiplatelet therapy in cats
with ATE. Clopidogrel is a second-generation thienopyri-
secondary to widespread muscle injury. Cats with ATE dine with antiplatelet effects that are more potent than
usually have normal coagulation parameters (PT and PTT), aspirin. A double-blind randomized controlled trial in 75
though fibrinogen and D-dimers might be elevated. Labora- cats (Feline Arterial Thromboembolism: Clopidogrel versus
tory tests can reveal abnormalities associated with other Aspirin Trial; FATCAT) (Hogan, 2015) demonstrated that
underlying disease as well, such as eosinophilia from HWD. clopidogrel was superior to aspirin for secondary prevention
Thyroxine (T 4 ) levels should be measured in older cats to of ATE and resulted in longer survival times post-ATE.
screen for hyperthyroidism. The thienopyridines inhibit ADP-binding at platelet
Other causes of acute posterior paresis to be considered receptors and subsequent ADP-mediated platelet aggrega-
include intervertebral disk disease, spinal neoplasia (e.g., tion. Clopidogrel irreversibly antagonizes platelet membrane
lymphoma), trauma, fibrocartilaginous infarction, diabetic ADP 2Y12 receptors, which inhibit a conformational change of
neuropathy, and possibly myasthenia gravis. the GPα IIb β 3 complex, resulting in reduced binding to
fibrinogen and von Willebrand factor. Clopidogrel also
Treatment and Prognosis impairs platelet release of serotonin, ADP, and other vaso-
The goals of treatment are to prevent extension of the constrictive and platelet-aggregating substances. Clopido-
embolus and additional thrombus formation, promote grel’s antiplatelet effects occur after the drug is transformed
collateral circulation, and manage concurrent CHF and in the liver to an active metabolite. Similar to humans, there