ACIDOSIS

From : Merck Manual Home Edition_files

Acidosis is excessive blood acidity caused by an overabundance of acid in the blood or a loss of bicarbonate from the blood (metabolic acidosis), or by a buildup of carbon dioxide in the blood that results from poor lung function or slow breathing (respiratory acidosis).
If an increase in acid overwhelms the body's pH buffering systems, the blood will become acidic. As the blood pH drops, the parts of the brain that regulate breathing are stimulated to produce faster and deeper breathing, which increases the amount of carbon dioxide exhaled.
The kidneys also try to compensate by excreting more acid in the urine. However, both mechanisms can be overwhelmed if the body continues to produce too much acid, leading to severe acidosis and eventually coma.

Causes
Metabolic acidosis develops when the amount of acid in the body is increased through ingestion of a substance that is, or can be metabolized to, an acid—such as wood alcohol (methanol), antifreeze (ethylene glycol), or large doses of aspirin. Metabolic acidosis can also occur as a result of abnormal metabolism. The body produces excess acid in the advanced stages of shock and in poorly controlled type 1 diabetes mellitus. Even the production of normal amounts of acid may lead to acidosis when the kidneys are not functioning normally and are therefore not able to excrete sufficient amounts of acid in the urine.
Respiratory acidosis develops when the lungs do not expel carbon dioxide adequately, a problem that can occur in diseases that severely affect the lungs (such as emphysema, chronic bronchitis, severe pneumonia, pulmonary edema, and asthma). Respiratory acidosis can also develop when diseases of the nerves or muscles of the chest impair breathing. In addition, a person can develop respiratory acidosis if overly sedated from opioids (narcotics) and strong sleeping medications that slow respiration.

Major Causes of Metabolic Acidosis
1) Kidney failure 2) Renal tubular acidosis (a form of kidney malfunction) 3) Diabetic ketoacidosis (buildup of ketones) 4) Lactic acidosis (buildup of lactic acid) 5)Poisons such as ethylene glycol, methanol, paraldehyde, acetazolamide, ammonia chloride, or aspirin overdose 6)Loss of bases, such as bicarbonate, through the digestive tract from diarrhea, an ileostomy, or a colostomy

Symptoms
A person with mild metabolic acidosis may have no symptoms but usually experiences nausea, vomiting, and fatigue. Breathing becomes deeper and slightly faster (as the body tries to correct the acidosis by expelling more carbon dioxide). As the acidosis worsens, the person begins to feel extremely weak and drowsy and may feel confused and increasingly nauseated. Eventually, blood pressure can fall, leading to shock, coma, and death.
The first symptoms of respiratory acidosis may be headache and drowsiness. Drowsiness may progress to stupor and coma. Stupor and coma can develop within moments if breathing stops or is severely impaired, or over hours if breathing is less dramatically impaired.

Treatment
The treatment of metabolic acidosis depends primarily on the cause.
For instance, treatment may be needed to control diabetes with insulinor to remove the toxic substance from the blood in cases of poisoning.
The treatment of respiratory acidosis aims at improving the function of the lungs. Drugs to improve breathing may help people who have lung diseases such as asthma and emphysema. People who have severely impaired lung function, for whatever reason, may need mechanical ventilation to aid. Acidosis may also be treated directly. If the acidosis is mild, the administration of intravenous fluids may be all that is needed. When acidosis is severe, bicarbonate may be given intravenously; however, bicarbonate provides only temporary relief and may cause harm—for instance, by overloading the body with sodium and water.