Diabetes mellitus, metabolic shift

Ammonia can diffuse freely into the urine through the tubule membrane, while the ammonium ions that are formed in the urine are charged and can no longer return to the cell. Acidic urine therefore promotes ammonia excretion, which is normally 30-50 mmol per day. In metabolic acidosis (e.g., during fasting or in diabetes mellitus), after a certain time increased induction of glutaminase occurs in the kidneys, resulting in increased NH3 excretion. This in turn promotes H"" release and thus counteracts the acidosis. By contrast, when the plasma pH value shifts towards alkaline values alkalosis), renal excretion of ammonia is reduced. 

Physical therapists and occupational therapists may help reinforce the importance of patient compliance during pharmacologic management of diabetes mellitus. Therapists can question whether patients have been taking their medications on a routine basis. Regular administration of insulin is essential in preventing a metabolic shift toward ketone body production and subsequent ketoacidosis, especially in patients with type 1 diabetes. In addition, therapists can help explain that adequate control of blood glucose not only prevents acute metabolic problems but also seems to decrease the incidence of the neurovascular complications. 

The shift decreases the concentration of bicarbonate ions and increases the concentration of carbonic acid. As a result, the HC03 /H2C03 ratio decreases, as does the blood pH. Metabolic acidosis is often a serious problem in nncontrolled diabetes mellitus, and it also occnrs temporarily after heavy exercise. Other causes include severe diarrhea and aspirin overdose. 

A partial failure of kidney function consequently is reflected by the ionic composition, by the alkali reserve, and possibly by the pH of blood. The regulation by the lungs also may lose its effectiveness and permit corresponding shifts of the alkali reserve (= respiratory acidosis or alkalosis). Finally, a metabolic defect may cause overproduction of organic acids, as has been known longest in the case of diabetes mellitus. The last situation is termed metabolic acidosis. There are other pathological shifts of acid-base equilibria and of the electrolyte balance that are not discussed here. 

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