Acidosis
Acidosis is an abnormal or pathologic condition caused by an imbalance in the acid-base equilibrium of the body. The body does not maintain an exactly neutral pH of 7, but rather a blood serum ph of 7.3-7.5. Accordingly, a pH of 7.293--although in strict terms an alkaline pH--is for the body an acidic rather than an alkaline state.
Acidosis is indicated by a lowering of blood pH that corresponds to an elevated hydrogen ion concentration in reaction to depletion in the normally counterbalancing alkaline sodium bicarbonate levels found in tissues and plasma. The depletion of neutralizing alkaline agents may result from a disruption or failure in the acid basis chemical buffers that maintain pH levels within a small and normal range of variation.
With regard to acid-base imbalance, the opposite end of the disease spectrum is characterized by alkalosis.
Many systems can become acidiotic. Diabetic acidosis results from a surplus of ketones. Metabolic acidosis results from excessive levels of by-products of fat metabolism termed keto acids.
Acidosis can occur directly, by the addition of acidic agents, failure to remove acidic agents, or by the removal of alkaline sodium bicarbonate. The loss of bicarbonate is usually due to a failure in the renal reuptake mechanism that preserves bicarbonate and protects the body from excessive bicarbonate loss. Such renal tubular acidosis is indicated by high levels bicarbonate in the urine, which, of course, becomes highly alkaline. Diarrhea frequently accompanies metabolic acidosis as the loss of excretory fluid results in a severe loss of sodium bicarbonate--lost before it can be reabsorbed by the kidneys--lowers the blood pH.
The respiratory system can also suffer acidosis, and this is specifically distinguished from metabolic acidosis by being termed respiratory acidosis. With respiratory acidosis, a lowering of blood pH can result from inadequate ventilation of carbon dioxide (CO2). In many cases it is not the lack of oxygen that causes damage in obstructed airways, rather it is the acute (sudden) onset of severe acidosis caused by an inability to vent carbon dioxide. Chronic (occurring over a long term) acidosis may result as a consequence of a gradual deterioration in the ability to ventilate carbon dioxide. The effects chronic acidosis may be masked by a compensating action in the kidneys, where increased levels of sodium bicarbonate may be retained to neutralize the acidic buildup in the lung. With acute acidosis, however, the slower reacting kidneys do not have time to perform this compensating action.
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