Veterinary Medicine - December 2007 - (Page 794)

Chronic kidney disease O P E E R - R E V I E W E D total body potassium concentrations and kidney function failed to yield conclusive findings.8 Once therapeutic targets have been attained, re-evaluate dogs and cats in stages 2 through 4 every three to four months to ensure continued compliance and therapeutic success at maintaining the target. Hyperkalemia. Hyperkalemia has primarily been of concern in chronic kidney disease stage 4 when the kidneys are no longer able to excrete the daily potassium load. However, it may also occur in patients with less advanced chronic kidney disease in association with therapeutic blockade of the renin-angiotensin system and with hyporeninemic hypoaldosteronism. The primary clinical consequence of hyperkalemia is cardiotoxicosis. Treatment usually involves reducing potassium intake; however, hyperkalemia resulting from therapeutic blockade of the renin-angiotensin system may require lowering the drug dosage should a clinically important risk of cardiotoxicosis develop. Correct metabolic acidosis. Intervention to correct metabolic acidosis is indicated in dogs and cats with chronic kidney disease stages 1 through 4 when the blood bicarbonate concentration drops below the therapeutic target range of 18 to 24 meq/L (19 to 25 meq/L for total carbon dioxide concentration; evidence grade 4). Metabolic acidosis in chronic kidney disease results primarily from impaired renal ammoniagenesis, although impaired acid excretion and bicarbonate reabsorption may contribute as well. Metabolic acidosis also occurs in patients with renal tubular acidosis (RTA) either due to impaired bicarbonate reabsorption (proximal RTA) or impaired urine acidification (distal RTA). The clinical effects of metabolic acidosis may include progressive renal injury and increased protein catabolism with loss of lean tissue. 1 Treatment involves administering an alkalinizing #5 salt, usually sodium bicarbonate or potassium citrate, in an amount sufficient to increase the blood bicarbonate concentration into the normal range. Oral sodium bicarbonate is the most commonly used alkalinizing agent for patients with metabolic acidosis of chronic renal insufficiency or failure. Because the effects of gastric acid on oral sodium bicarbonate are unpredictable, the dosage should be individualized for each patient. A suggested initial dose is 8 to 12 mg/kg given every eight to 12 hours. Unfortunately, many dogs and cats find sodium bicarbonate distasteful unless given as tablets. Sodium bicarbonate is available as 5- and 10-grain tablets. Potassium citrate may offer the advantage, especially in cats, of allowing for the simultaneous treatment of both hypokalemia and acidosis with a single drug. Metabolic acidosis when accompanied by potassium or magnesium depletion may respond poorly to alkali therapy alone. However, since potassium doses required for ade- TABLE 3 A Summary of Chronic Kidney Disease Substage Based on Results of Blood Pressure Measurement and Signs of End-Organ Damage or Complications* Systolic Blood Diastolic Blood Pressure (mm Hg) Pressure (mm Hg) < 150 150 to 159 160 to 179 = 180 < 95 95 to 99 100 to 119 = 120 Comparison of the Blood Pressure Measurement to a Breed-Specific Reference Range (If Available) < 10 mm Hg above the reference range 10 to 20 mm Hg above the reference range 20 to 40 mm Hg above the reference range = 40 mm Hg above the reference range Substage of Disease These animals have a minimal risk of end-organ damage. These animals have a low risk of end-organ damage. These animals have a moderate risk of end-organ damage. These animals have a high risk of end-organ damage. Assess Clinical Signs of Hypertension The patient has no signs of complications or end-organ damage. The patient has evidence of end-organ damage and complications. The patient's blood pressure has not been measured. *Adapted from www.iris-kidney.com and the ACVIM hypertension consensus statement at www.acvim.org. Substage of Disease No complications Complications are present Risk of end-organ damage is not determined 794 December 2007 VETERINARY MEDICINE http://www.iris-kidney.com http://www.acvim.org

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Veterinary Medicine - December 2007 Contents Letters Editors' Guest Thanking Our Valued Reviewers The Veterinary Medicine Interview: Dr. Joseph Harari Clinical Exposures Idea Exchange Answers to Three Commonly Asked Questions About Lyme Disease Practical Ideas for Managing Common Internal Medicine Problems A Tip for Interpreting Leptospira Species Titers Investigating Proteinuric Kidney Disease Counseling New Puppy Owners: Normal Play vs. Aggressive Tendencies 11 Guidelines for Conservatively Treating Chronic Kidney Disease CE Form Product Preview Advertiser Index Marketplace/Classifieds Mind Over Miller Merial Insert

Veterinary Medicine - December 2007

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