Today's Veterinary Practice

MAR-APR 2018

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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PEER REVIEWED 32 CE: CARDIOVASCULAR AND RENAL DISEASE sudden changes in volume status and derangements in renal autoregulatory mechanisms. There is little consensus on how much of a serum creatinine increase is acceptable, although most clinicians accept a <30% increase from baseline. 10 If creatinine levels increase substantially (>30%) within the first 2 weeks of initial administration or during long-term use of an ACE inhibitor, the drug should be discontinued or its dose decreased. In some instances, azotemia in a patient with heart failure is tolerated and no adjustments are needed. If the Primary Condition is Renal Disease For dogs with AKI and degenerative mitral valve disease with normal heart size, fluid therapy should be administered to address the renal injury and optimize the chances of recovery, while closely monitoring for fluid overload. For dogs with primarily renal disease that show signs of volume overload during fluid therapy, fluids should be discontinued until the volume overload is resolved. Diuretics can be administered if necessary. Often, the first indication of volume overload is increased resting respiratory rate, which should be checked every hour during fluid administration. Heart rate may also increase if fluids are poorly tolerated. Monitoring for increased body weight can also be helpful. Cats If the Primary Condition is Cardiovascular Disease Medical therapy for heart disease in cats is not well defined. ACE inhibitors, which block profibrotic effects of angiotensin II and aldosterone, have an inconsistent effect. 11 In a small retrospective evaluation of cats with preclinical and clinical hypertrophic cardiomyopathy, enalapril did not adversely affect blood pressure or creatinine levels. 12 Therapy for CHF typically consists of furosemide and an ACE inhibitor to reduce fluid accumulation. 13 Complications that can be encountered while managing heart failure and that contribute to reduced renal perfusion include systemic hypotension and dehydration/volume contraction associated with diuretic therapy. Several retrospective studies of cats with CHF from multiple forms of cardiomyopathy with and without systolic dysfunction have reported use of inodilator therapy (pimobendan). 14–16 Although this drug did seem to prolong survival, caution is recommended for its use in cats with known or suspected left ventricular outflow tract obstruction. 15 Whether pimobendan affects renal perfusion has yet to be investigated, but its use did not significantly affect creatinine concentrations. Diuretic therapy can cause hypokalemia in cats and may be exacerbated by hyporexia. Low or borderline serum potassium concentrations should be addressed promptly with oral potassium gluconate because potassium depletion will affect renal function, impairing urine concentrating ability and possibly causing muscle weakness and acute myopathy. If the Primary Condition is Renal Disease In cats, fluid therapy for CKD may quickly unmask occult heart disease, regardless of administration route. SC fluid administration is not inherently safer than IV administration because fluids still enter the vascular compartment and cannot be discontinued if problems occur. For severely azotemic cats, long-term SC fluid therapy may help maintain well-being; however, for cats with modest CKD, it is best avoided because the inevitable sodium loading predisposes these cats to volume overload and can increase systemic blood pressure, irrespective of underlying cardiac function. If the Dog or Cat has Concurrent Cardiovascular and Renal Disease For dogs and cats with overt cardiac and renal disease, fluid therapy should be administered with caution. Fluid deficits should be estimated carefully and replaced over 24 hours. Concurrent maintenance fluid needs should be met with a lower sodium fluid, such as Normosol-M with 5% dextrose ( ) or 0.45% saline 17 and discontinued as soon as possible. Fresh water should be provided at all times. If both systems are involved, focus your management strategy on the system causing the most severe clinical signs.

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