Sodium Sodium

Many older dogs have endocardiosis which, even in compensated patients, results in sodium retention through activation of the renin-angiotensin-aldosterone pathway. Also, hypertension is a common proin chronic renal failure in dogs and excess sodium load may make this worse. In humans clinically normal people with high salt intakes have higher blood pressure, and there is an age-related increase in blood pressure as well. Although primary hypertension is rare in cats and dogs some dogs are known to have salt-sensitive hypertension and recent studies at the Royal Veterinary College have demonstrated an increase in blood pressure with advancing age in cats and dogs (Bodey 1995 personal communication).

In the presence of congestive heart failure sodium intake should be minimised to decrease its effects on preload. While conventional treatof dogs with endocardiosis states that treatment is unnecessary until heart failure is decompensated the author considers early introduction of reduced sodium diets helpful, particularly as the hypothalamic-pituitary-adrenal axis is stimulated early in the disease and switching old dogs from a relatively high sodium content ration to a relatively low sodium content ration can be difficult in some individuals due to acquired taste preference for salt (see Chapter 2 ).