Page 119 - Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice

Disorders of Potassium: Hypokalemia and Hyperkalemia 109

A

B

C

D
Figure 5-12 Electrocardiograms of a cat and dog with hyperkalemia. A, Electrocardiogram from an 8-year-
old female domestic short-haired cat with oliguric acute renal failure and serum K concentration of
þ
7.8 mEq/L. B, Electrocardiogram of the same cat after 2 mEq/kg NaHCO 3 administered intravenously over
30 minutes. C, Electrocardiogram of a dog with serum K concentration of 9.6 mEq/L before treatment.
þ
Note tall, tented T waves and absence of P waves. D, Electrocardiogram of the same dog 15 minutes after
infusion of NaHCO 3 . (Parts C and D from Chew DJ, DiBartola SP. Manual of small animal nephrology and
urology. New York: Churchill Livingstone, 1986: 132.)

from ICF to ECF and potassium follows because of sol- mellitus have confirmed that hyperkalemia is uncommon
vent drag and as a result of the increased ICF potassium and that 44% to 70% of affected cats had hypokalemia at
29,44,133,173
concentration resulting from cellular water loss. Most presentation. Hypokalemia may also develop
diabetic patients have total body depletion of potassium after treatment with insulin despite potassium supple-
caused by urinary losses, muscle mass loss, anorexia, mentation of fluids. 118 Consequently, the clinician must
and vomiting. A normal or low serum potassium concen- pay close attention to potassium supplementation of
tration in a patient with untreated diabetic ketoacidosis patients with diabetic ketoacidosis.
indicates serious total body depletion of potassium and Massive tissue breakdown may lead to transient
the need for diligent potassium supplementation. hyperkalemia until the kidneys excrete the released potas-
Hypokalemia at presentation is more common than sium. Severe exercise may cause release of potassium from
hyperkalemia in diabetic dogs and cats. In one study, cells and transient hyperkalemia in humans, and this effect
43% of dogs and 83% of cats with diabetes mellitus were is less pronounced in conditioned subjects. In untrained
hypokalemic at presentation as compared with 10% of dogs, exercise to the point of exhaustion resulted in an
affected dogs and 8% of affected cats that were increase in mean serum potassium concentration from
hyperkalemic. 66 Other studies of cats with diabetes 4.4 to 6.0 mEq/L. 108 Exhaustive exercise was not