Page 354 - Feline Cardiology

Chapter 24: Comorbidities 369

Which Disorder Is Predominant? screening (concurrent isosthenuria and mild azotemia).
When a cat shows no overt clinical signs referable to either
In a cat with concurrent heart disease (e.g., cardiomy- the heart problem or the kidney problem, treatment of
opathy) and renal disease (e.g., chronic kidney disease), either one, or both, can be pursued as indicated in the
the initial approach depends on which one of the two absence of the other disorder. That is, prophylactic treat-
disorders is the predominant clinical concern. Generally, ment of the kidney or heart disorder is administered as
patients are presented for management of decompensa- deemed appropriate for the isolated disorder irrespective
tion of one disorder at a time. Two common scenarios of the other. Typically, such treatments could include beta
are the patient with acute congestive heart failure whose blockade for hypertrophic obstructive cardiomyopathy
renal function has previously been known to be com- and a protein-optimized diet for chronic kidney disease,
promised (cardiac dominant), and the patient with overt for example. Although fluid therapy may be prescribed to
signs of kidney failure who has previously been docu- be administered at home, subcutaneous fluids, like intra-
mented to have asymptomatic heart disease (renal domi- venous fluids, increase circulating blood volume and
nant). In these situations, treatment decisions should be constitute an unproven but anecdotally well-recognized
strongly influenced by the history and physical examina- risk factor for iatrogenic congestive heart failure.
tion. A patient presenting with overt signs of congestive Occult/“early” chronic kidney disease in cats with isos-
heart failure, such as dyspnea, requires treatment for the thenuria is classified as International Renal Interest
dyspnea including diuretics for pulmonary edema or Society (IRIS) stage 1, where serum creatinine <1.6 mg/
thoracocentesis for large-volume pleural effusion, dl (<140 umol/l), or stage 2, where serum creati-
regardless of renal values on a serum biochemistry nine = 1.6 − 2.8 mg/dl (140−246 umol/l) (Polzin 2010).
profile. Conversely, a patient presenting with overt signs In both categories, the disease is usually found inciden-
of renal failure such as anorexia, lethargy, signs of dehy- tally because no overt signs of uremia are apparent.
dration, halitosis, and uremic oral ulcers, requires intra- Prophylactic subcutaneous fluid therapy for cats with
venous fluid therapy regardless of abnormal IRIS stage 1 and 2 CKD is not universally accepted. Even
echocardiographic measurements. It is very uncommon in the absence of heart disease, the sodium load admin-
for a patient to present for the first time with concurrent istered via such balanced electrolyte solutions as lactated
spontaneous decompensation of both renal and cardiac Ringer’s or 0.9% sodium chloride may be detrimental to
abnormalities. That is, the cat with simultaneous dyspnea the kidneys (Weir and Fink 2005). The intravenous route
from pulmonary edema/cardiogenic pleural effusion of fluid administration used in-hospital allows careful
and systemic signs of end-stage kidney failure is far less titration of fluid rate and modification of fluid type, as
common than the cat with one of the two dysfunctions needed, but such changes are impractical in the home
predominating, which allows the clinician to decide setting of subcutaneous fluid administration. Oral fluid
whether to implement treatments that judiciously supplementation for cats with chronic kidney disease Comorbidities
increase, or decrease, intravascular volume. When both may be considered, and an essential—but easily
body systems decompensate simultaneously in the overlooked—approach is to instruct the cat’s owner to
absence of any modifiable or correctable factors, the ensure that the cat with kidney disease has copious, fresh
context is almost always a patient that has had an ongoing drinking water available through sources that are attrac-
history of treatment for failure of one of the two body tive to a cat, including cat water fountains or slowly drip-
systems for some time (typically months to years). ping faucets that allow the cat to consume moving water,
Therefore, the coexistence of concurrent heart and in addition to water provided in bowls and changed at
kidney disease with one of the two predominating is least daily. Some have advocated administration of water
more common, and it warrants a guarded, but not poor, by syringe or via feeding tube to maintain the hydration
long-term prognosis because other aspects of the case of cats with CKD at home (Polzin 2010). Such an
can offer therapeutic opportunities (see below). approach requires excellent tolerance on the part of both
Another situation often occurs in practice: cats are owner and patient and may be considered on an indi-
presented much earlier in the disease processes, and the vidual case basis. In summary, since no evidence exists
clinician must manage both kidney and cardiac problems that identifies a benefit of subcutaneous fluid adminis-
when neither one is clinically overt. An example is the tration at home in cats with IRIS stage 1 or 2 chronic
asymptomatic cat with hypertrophic cardiomyopathy kidney disease, such therapy should only be prescribed
identified based on an incidentally ausculted heart for these cats (with concurrent asymptomatic heart
murmur and chronic kidney disease identified during disease not requiring diuretics) in the following instances:
routine abdominal palpation (small kidneys) and/or lab- the owner observes a clear-cut clinical improvement with
oratory tests performed as part of preemptive or annual treatment in the individual cat; the owner is aware and