TREATMENT
The goal when treating septic cats is the same as when treating any other critically ill patient: Maximize perfusion and oxygen
delivery to the tissues. Cardiac output is calculated as heart rate x stroke volume. Stroke volume can be improved by maximizing
preload with fluid administration. The shock bolus in cats is 50 to 60 ml/kg of crystalloid fluids or 5 ml/kg of colloids
given intravenously. Start with small crystalloid boluses of 10 to 20 ml/kg given to effect (normalization of blood pressure
or central venous pressure).
Drug therapy
In cats that remain hypotensive despite adequate volume replacement and normothermia, exogenous catecholamine therapy may
be necessary. Dopamine (2.5 to 15 µg/kg/min intravenously) is a vasopressor with positive inotropic, chronotropic, and vasoconstrictive
effects. It is often the first-line drug given to septic cats. At low doses (0.5 to 5 µg/kg/min), dopamine leads to renal
vasodilation in dogs; cats lack dopaminergic receptors in their kidneys.22 In cats, dopamine is used predominantly for its beta-adrenergic effects leading to positive inotropy at 2.5 to 10 µg/kg/min
and its alpha-adrenergic effects leading to vasoconstriction at > 10 µg/kg/min.22,23 Dobutamine also exhibits positive inotropic and chronotropic effects and improves cardiac output and oxygen delivery in
experimental models of sepsis. Cats treated with dobutamine (at continuous infusions between 2 and 20 µg/kg/min intravenously)
should be observed closely as seizures may occur in cats treated with dobutamine continuous rate infusions for more than 24
hours.24 In cats with severe hypotension or those that fail to respond to dopamine or dobutamine, norepinephrine (0.1 to 3 µg/kg/min
intravenously) or epinephrine (0.1 to 2 µg/kg/min intravenously) are often effective. Vasopressor drugs are administered as
a continuous infusion, and the dose is adjusted according to the physiologic response (i.e. blood pressure, heart rate). As the cat is able to maintain its blood pressure, the dose is reduced until the infusion can
be discontinued.
Supplemental oxygen
Supplemental oxygen is often necessary in septic cats. Increased inspired oxygen can improve oxygen saturation (SpO2) as well as the partial pressure of oxygen in the blood (PaO2), thereby improving oxygen delivery to the tissues. As discussed previously, fluid overload and pulmonary edema are common
in septic cats. Inflammatory lung disease (acute respiratory distress syndrome) and pneumonia can also contribute to hypoxia
and decreased oxygen delivery. In most cats, treatment in an oxygen cage or oxygen administration by mask is sufficient, but
in severe cases, positive pressure ventilation may be necessary.
Blood transfusion
Septic cats are often anemic and may have a coagulopathy. Administering red blood cells to an anemic patient improves the
oxygen-carrying capacity of the blood and, thus, improves oxygen delivery to tissues. In addition, replacing coagulation factors
by administering plasma minimizes further blood loss and provides colloidal support. Consider a red blood cell transfusion
in any septic cat with clinical signs of decreased oxygen delivery (tachypnea, tachycardia or bradycardia, pale gums) and
with a packed cell volume < 20. Administer plasma to cats with prolonged coagulation times. Cats with type B blood have autoantibodies
to type A blood,25 so blood typing is essential before any blood transfusion. Cats that have been previously transfused should also only be
transfused with blood to which they have been crossmatched.
Antibiotics
Appropriate antibiotic therapy is an integral part of the treatment of septic cats. In people, inadequate antimicrobial therapy
has been associated with increased mortality.26 Use bacterial cultures and antimicrobial sensitivity testing to identify effective antibiotics. Administer broad-spectrum
intravenous antibiotics pending antimicrobial sensitivity test results. The empiric selection of the initial antibiotic can
be guided by the most likely source of sepsis and the commonly associated bacteria. For example, in septic peritonitis, enteric
bacteria are the typical source of infection, so gram-negative coverage (e.g. a fluoroquinolone, third-generation cephalosporin, or aminoglycoside) and anaerobic coverage (e.g. metronidazole or penicillins) should be considered. All antibiotic choices must consider the tissue penetration, route of
administration, toxicity profile, and origin of infection (i.e. community acquired or nosocomial), so they should be individualized for each patient.
Source control
A critical component of treating the septic patient is removal of the source of infection. Surgical resection of infected
tissue is essential. In the case of feline pyothorax, however, placement of thoracostomy tubes to allow lavage and drainage
is effective.12
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