Proceedings of the Congreso Ecuatoriano de Especialidades Veterinarias CEEV Nov , 2011 Quito, Ecuador

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1 Close this window to return to IVIS Proceedings of the Congreso Ecuatoriano de Especialidades Veterinarias CEEV 2011 Nov , 2011 Quito, Ecuador Reprinted in IVIS with the permission of CEEV

2 CATS ARE NOT DOGS ON EMERGENCY Helio Autran de Morais, DVM, PhD, DACVIM (Small Animal Internal Medicine and Cardiology) Oregon State University Many diseases are different in cats. Clinical signs differ from those seen in dogs, whereas some diseases may be more prevalent in one species versus the other. Unlike dogs, cats with pancreatitis are not prone to vomiting, whereas arterial thromboembolism is a manifestation of heart disease in cats, but not in dogs. Hypoadrenocorticism may occur in cats, but is extremely rare when compared with its prevalence in dogs. A few disease are specific of cats (feline viral leukemia, feline viral immunodeficiency, hyperthyroidism). Cats also respond differently to acidosis and shock and go from being a stable patient to a critical one much faster than dogs. A cat in the emergency room CANNOT be treated as a small dog. Cats react poorly to shock. The sympathetic response is blunted and hypotension is often accompanied by bradycardia. Cats are also prone to hypothermia and hypoglycemia during shock. This conjunction of factors creates a feedback loop where hypotension leads to hypothermia and bradycardia, which furthers decrease arterial pressure. Cats also have a smaller circulatory volume than dogs that limits the maximum rate of fluids that can be safely given during shock limited to 45 to 65 ml/kg/h. In some cats in critical condition, tt might be very difficult to maintain adequate blood pressure. The main differentials for a cat who has hypotension that is resistant to fluid therapy are Systemic Inflammatory Response Syndrome (SIRS), hypoxia, hypothermia/bradycardia or occult cardyomyopathy. Inotropic support may be necessary in selected patients. Systemic Inflammatory Response Syndrome is the common inflammatory response mounted by the organism against several different stimuli. Sepsis is the SIRS secondary to bacterial infection, whereas severe sepsis is sepsis that is accompanied by organ dysfunction (Multiple Organ Dysfunction or MODS), hypoperfusion or hypotension. Septic Shock occurs when severe sepsis is accompanied by hypotension refractory to fluids. Human criteria for diagnosing SIRS have been adapted to cats. SIRS is diagnosed in cats whenever three of the following criteria are met:

3 1) Temperature > 40 o C or < 37,7 o C 2) Heart rate > 225 or < 140 bpm 3) Respiratory rate > 40 rpm 4) White blood cell count > /µl or < 5.000/µl or > 5% bands Like in humans, there is a tendency to overdiagnose SIRS in cats by strictly following these criteria. Any cat that fits the criteria for SIRS should be closely evaluated and monitored even when the cat is not too sick. Cats do not have the classic hyperdynamic phase of sepsis. There is no hyperemia of the mucous membrane, tachycardia or evidences of vasodilation During severe sepsis, cats may have pale mucous membranes, diffuse abdominal pain, tachypnea, bradycardia, hypothermia, jaundice, anemia, and hypoalbuminemia. Some laboratory abnormalities are unique in cats. Hypoglicemia is associated with hypotension, whereas hyperglycemia may occur with stress. Hyperglycemia is much higher in stressed cats than in dogs and can even surpass renal threshold (250 mg/dl in cats). Hypophosphatemia occur in cats after prolonged anorexia or in patients just started in insulin for diabetes mellitus leading to hemolytic anemia, if severe. Hypokalemia causes muscular weakness (especially in the neck with ventroflexion of head) and polymyopathy, decrease in consciousness and renal failure. The main cause of hypokalemia in cats is renal failure. Bradycardia in cats with hyperkalemia is less pronounced than in dogs. Cats with hyperkalemia and bradycardia are usually dying. Hyperammonemia is much more common in cats than in dogs as a cause for decreased consciousness. Cats are also less efficient than dogs to compensate for metabolic acidosis. It is not clear if they compensate at all. During renal failure, hyperphosphatemia appears to be an important reason for metabolic acidosis in cats. Cats with renal failure that are depressed, acidemic, and hyperphosphatemic must be treated with sodium bicarbonate, because bicarbonate drives phosphorus inside the cell, increasing ph. Maintenance of adequate oxygenation and ventilation is very important in cats. A common mistake is to wait until the cat is severely distressed before starting oxygenation. Nasal oxygen or oxygen cage are adequate for most cats. In case it is deemed necessary,

4 cats can be sedated with butorphanol 0.2 to 0.4 mg/kg IV or IM. Cats have a hyperreactvie bronchial tree and can have bronchoconstriction during stress. They should be manipulated with care to avoid stress-induced bronchoconstriction. Subcutaneous terbutaline (0.01 mg/kg) is very effective inducing bronchodilation within minutes. Heart rate increases and respiratory rate decreases after the injection. Aminophyilline can also be used parenterally to induce bronchodilation, but it should be used carefully because it may induce vomiting in a dyspneic cat. Cats may develop pulmonary edema due to increased vascular permeability during SIRS. This pulmonary edema may be clinically silent until is too late. Patients with SIRS should be closed monitored for signs of respiratory distress. Pleural effusion is also very common in cats. Thoracocentesis should be attempted in all cats with an expiratory or mixed dyspnea with decreased respiratory sounds. Cats show pain by becoming depressed, anorexic, restless and irritable. Tachycardia may occur, but it is rare. Pain control is mandatory. Moderate pain can be controlled with butorphanol ( mg/kg q2h q8h). Morphine (0.1 mg/kg IM) associated with diazepam (0.2 mg/kg IV) or epidural morphine can be used in more severe pain. Cats are small. Frequent blood withdraw can cause or worsen a pre-existent anemia and should be avoided. Cat s red blood cells tend to clump together ( roulleau ) and this can be confused with auto-agglutination. Addition of a few drops of saline is necessary to differentiate between rolleau and auto-agglutination. Hemoplasmosis caused by Mycoplasma haemofelis (formerly Haemobartonella felis Ohio) can exacerbate during stress causing hemolytic anemia. Careful evaluation of the blood smear for presence of hemoplasmae is very important in all cats with acute anemia. Presence of macrocytosis in the absence of anemia, suggests that the cat has feline luekemia virus infection or hyperthyroidism. Blood transfusion should be considered in all cats with PCV < 15% or in cats with acute anemia and PCV < 20%. Cats with type B blood can never receive blood type A. There is also a chance of reaction when type A cats receive blood type B in about 30% of the cases. Because prevalence of blood types varies among different regions and breeds a cross-matching should be performed before transfusing a cat.

5 It is important to remember that cats are not dogs on emergency. Physiology, metabolism, and diseases are different. Hypothermia, bradycardia, hypoglycemia, and hypotension refractory to fluids are serious problems that are common in critical cats. References Brady CA, Otto CM, Van Winkle TJ et al. Severe sepsis in cats: 29 cases ( ). J Am Vet Med Assoc, 217: , 2000 Chew DJ and de Morais HSA. Fluid Therapy. In: Sherding RG (ed). The Cat: Diseases and Clinical Management. 2 nd ed. New York, Churchill Livingstone, 1994, pp: Cowgill, LD, Elliot, DA. Acute renal failure. In: Ettinger SJ, Feldman, EC. Textbook of Veterinary Internal Medicine. 5 th ed. Philadelphia, WB Saunders, pp de Morais HSA. Mixed acid-base disorders. In: DiBartola SP (ed). Fluid Therapy in Small Animal Practice. 2 nd ed., Philadelphia, WB Saunders, 2000, pp: DiBartola SP, de Morais HSA. Disorders of potassium: Hyperkalemia and hypokalemia. In: DiBartola SP (ed). Fluid Therapy in Small Animal Practice. 2 nd ed., Philadelphia, WB Saunders, 2000, pp: Haskins SC. Treatment of Shock. In: Fox PR, Sisson DD, Möise NS (ed). Textbook of Canine and Feline Cardiology. 2 nd ed., Philadelphia, WB Saunders, 2000, pp: Kirby R, Rudloff E, Wilson W. Cats are not dogs on emergency. In: Bonagura, JD. Kirk s Current Veterinary Therapy XIII. 13 rd ed. Philadelphia, WB Saunders, pp