What is acidosis?

Causes and Symptoms

Acidosis is a state of excess acidity in the body’s fluids. For metabolism to function normally and oxygen to be delivered properly to tissues and organs, blood pH must remain within a narrow, slightly alkaline range between 7.35 and 7.45. Acids and bases (alkalies) in bodily fluids kindle the chemical reactions that support living. The organs that largely regulate the acid-base balance are the kidneys and lungs.

Acidosis arises from either a decrease of base bicarbonate (bicarbonate combined with such minerals as calcium, magnesium, or phosphorous—a base) or an increase of carbonic acid (combined carbon dioxide and water—an acid). Medicine recognizes both metabolic and respiratory acidosis, although clinically the two are often intertwined. Metabolic acidosis involves the kidneys, which metabolize, neutralize, or excrete any acid but carbon dioxide. Respiratory acidosis involves the ability of the lungs to exhale carbon dioxide, which is a gas but readily combines with water to form carbonic acid. Acidosis can be verified through an analysis of arterial blood gases.

Metabolic acidosis occurs when metabolism is impaired, sometimes by ingestion of a substance that exceeds the capacity of the kidneys to buffer. Acidifying ingestibles include wood alcohol (methanol), antifreeze (ethylene glycol), and salicylates such as aspirin in large doses. Certain infections can cause metabolic acidosis. Poorly controlled type 1 diabetes mellitus causes metabolic acidosis when inadequate insulin levels enable ketone bodies from fat breakdown to acidify the blood. When overexertion exceeds the ability of the blood to supply
muscles, lactic acid is produced; the same thing occurs when poor blood supply exceeds normal oxidative metabolism. To remedy acidic blood, the body leeches buffering minerals such as calcium, magnesium, sodium, and potassium from organs and bones.

Respiratory acidosis occurs when the lungs cannot expel enough carbon dioxide. It is often caused by diseases such as emphysema, chronic bronchitis, advanced pneumonia, pulmonary
edema, or asthma, all of which damage the lungs or bronchi. It can also occur with diseases of the nerves or muscles that move the chest or diaphragm. Apnea that interrupts sleep breathing or hyperventilation can cause respiratory acidosis. It can also result from oversedation with narcotic opioids or strong sedatives that slow breathing. In cardiac arrest, metabolic and respiratory acidoses are concurrent.

Acidosis can be chronic or acute. Its symptoms can range from unnoticed to vague and unspecific to disturbing or life-threatening. Because their causes differ, metabolic and respiratory acidosis also vary in their symptoms. Symptoms of metabolic acidosis include nausea, vomiting, and fatigue from blood-borne acids and a tendency (which may be absent in infants) to breathe quickly and deeply as the body attempts to expel more carbon dioxide. Respiratory acidosis can cause headache, confusion, and breathing that is shallow, slow, or both in the effort to expel carbon dioxide.

Treatment and Therapy

Metabolic acidosis is treated by determining the cause and correcting the imbalance. The acidic substance in the blood must be removed or buffered, although this may prove difficult. Treatments vary for metabolic acidosis caused by kidney disease, shock, cancer, poisoning, diabetes, and cardiac arrest. In mild cases, acidosis may be corrected by giving intravenous fluids. In severe cases, bicarbonate can be given intravenously. This provides only temporary relief, however, and may create further problems with excessive sodium.

Respiratory acidosis is generally controlled by improving lung function. Diseases such as asthma or emphysema may respond to bronchodilators, which open the airways. Children under five years of age may develop simultaneous metabolic and respiratory acidosis from salicylate poisoning; vomiting can then be induced with ipecac syrup. Whenever breathing is impaired sufficiently to prevent the exchange of carbon dioxide and oxygen, mechanical ventilation may be required.

Perspective and Prospects

Properly functioning bodily processes require oxygen. The more acidic the blood, however, the less oxygen it can carry. The simple process of living produces quantities of metabolic and respiratory acids that, in health, the body continually and silently buffers. In the Western world, people further challenge the acid-base balance through diet, with animal products such as meat, eggs, and dairy as well as with processed foods such as white four and sugar and beverages such as coffee and soft drinks. Many common drugs are acid-forming, as are artificial sweeteners. As long as they function normally, the lungs and kidneys oppose the tendencies of bodily fluids to exceed normal pH parameters. Having healthy lung and kidney function, and avoiding or balancing acid in the diet, can help maintain optimal internal chemistry.

Bibliography:

"Acidosis." MedlinePlus, Mar. 22, 2013.

Gennari, F. John, et al., eds. Acid-Base Disorders and Their Treatment. Boca Raton, Fla.: Taylor & Francis, 2005.

Hogan, Mary Ann, et al. Fluids, Electrolytes, and Acid-Base Balance. 2d ed. Upper Saddle River, N.J.: Pearson/Prentice Hall, 2007.

Lewis, James L., III. “Acidosis.” In The Merck Manual Home Health Handbook: Third Home Edition, edited by Robert S. Porter. Whitehouse Station, N.J.: Merck Research Laboratories, 2009.

"Metabolic Acidosis." MedlinePlus, Mar. 22, 2013.

"Respiratory Acidosis." MedlinePlus, Mar. 22, 2013.