Page 356 - Feline Cardiology

Chapter 24: Comorbidities 371

explained further in the section on fluid therapy, of pulmonary crackles or intensity of murmur.
below, and in Chapter 1. Radiographic results may be normal (e.g., pulmonary
• Manage coexistent electrolyte abnormalities, espe- thromboembolism in patient with nephrotic syn-
cially hypokalemia. Serum potassium levels should drome), may confirm pulmonary edema, may identify
be measured from blood drawn into a green-top large-volume pleural effusion rather than pulmonary
(lithium heparin) tube. Plain red-top vacuum tubes edema (which can be immediately removed by cente-
allow blood clotting, a process that releases potassium sis, reducing or avoiding acute doses of diuretics), or
from activated platelets (Sevastos et al. 2008). may reveal a third disorder such as airway disease as
Therefore, hypokalemia may be masked by this in the cause of dyspnea.
vitro artifact (Sevastos et al. 2008). When hypokale- • If radiographic findings are uncertain, have radio-
mia is confirmed, treatment to correct it (e.g., with graphs interpreted by radiologist/cardiologist. Both
supplementation when the patient is receiving intra- false-positive and false-negative results are common
venous fluids) is important on two counts. First, hypo- for pulmonary edema, cardiomegaly, and other rele-
kalemia causes skeletal muscle weakness, and may vant cardiovascular interpretations.
decrease appetite and general demeanor (DiBartola • In addition to characterizing the type of underlying
and de Morais 2006). All of these abnormalities can heart disease, an echocardiogram may be useful
confer a negative prognosis to an owner and lead to simply to determine the likelihood of congestive heart
an early decision for euthanasia. Second, normal failure in questionable cases. For example, if the left
serum potassium levels are necessary for the function- atrial size is normal, and there is no precipitating acute
ing of cellular sodium channels on which many intra- factor, then left-sided congestive heart failure is very
venously administered antiarrhytmics, such as unlikely.
lidocaine and procainamide, act (Singh and Williams • Removal of large-volume body cavity effusions in
1971). In hypokalemia, these drugs can be ineffective acute states: centesis is superior to diuretics for acute
(DiBartola and de Morais 2006; Singh and Williams stabilization and efficacy, and based on human studies
1971). Since hypokalemia itself also increases the of cirrhotic ascites, centesis carries less potential for
tendency to ventricular tachyarrhythmias, a synergis- adverse effects (Ginès and Arroyo 1993). With cente-
tic negative sequence can easily occur where ven- sis, the diuretic dose can be minimized since the
tricular arrhythmias are more likely to occur and patient has been acutely stabilized via fluid removal.
intravenous treatment is administered repeatedly in an
attempt to convert the arrhythmia to normal sinus Chronic management strategies for cats with coexist-
rhythm but is ineffective. Since hypokalemia abol- ing cardiac and renal problems can include the following:
ishes only the antiarrhythmic effect, but not the neu-
rotoxic effects of these drugs, patients whose • Verify client compliance with drug administration— Comorbidities
hypokalemia escapes detection may develop ataxia both client diligence and patient cooperation. This is
and seizures iatrogenically as the clinician continues often overlooked, and a common mistaken impres-
to administer increasing doses of antiarrhythmics that sion when heart failure has recurred is that the dosage
have reduced efficacy in patients with low serum of diuretics must be inadequate. If the medication is
potassium concentrations. not reaching the cat, the incorrect assumption is that
• Consider diuretic constant rate infusion instead of the heart disease must be worsening, and the diuretic
intermittent injections for superior natriuresis. In dosage is then increased. Over time, if compliance
dogs, and likely in cats, calculating the total daily remains poor, the very high diuretic dosages lead to a
projected dosage of furosemide and administering it belief that no higher a dosage may be given without
via syringe pump as a constant rate infusion produces severe risk of renal or electrolyte disturbances, and the
superior diuresis (significantly more urine produced) client may decide to have the cat euthanized under
than boluses (Adin et al. 2003). such circumstances. Instead, if poor compliance is rec-
• Change medications to injectable form (e.g., diuretic) ognized as a problem, alternative medication strate-
while managing the crisis in-hospital, and temporarily gies may be used. Specific points to address with the
(i.e., for 24 hours) suspend administration of oral client include consistency of administration, monitor-
medications with benefits that are long-term only, not ing for the cat’s deglutition after a tablet is adminis-
short-term (e.g., oral ACE inhibitors, beta blockers, tered, and administration of tablets with a food treat
calcium channel blockers, and most drugs used for or bolus of water to reduce the risk of midesophageal
treating chronic kidney disease). entrapment (German et al. 2005). Hollow treats (“Pill
• Confirm suspicions. Is dyspnea from congestive heart Pockets”) are one way of disguising medication and
failure? Thoracic radiographs are indicated regardless many cats enjoy eating these. Having medications