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Metabolic alkalosis is a pH imbalance in which the body has accumulated too much of an alkaline substance, such as bicarbonate, and does not have enough acid to effectively neutralize the effects of the alkali.
Metabolic alkalosis, as a disturbance of the body's acid/base balance, can be a mild condition, brought on by vomiting, the use of steroids or diuretic drugs, or the overuse of antacids or laxatives. Metabolic alkalosis can also indicate a more serious problem with a major organ such as the kidneys.
Causes and symptoms
Metabolic alkalosis occurs when the body has more base than acid in the system. Chemists use the term "pH" to decribe how acidic or alkaline (also called basic) a substance is. Based on a scale of 14, a pH of 7.0 is neutral. A pH below 7.0 is an acid; the lower the number, the stronger the acid. A pH above 7.0 is alkaline; the higher the number, the stronger the alkali. Blood pH is slightly alkaline, with a normal range of 7.36-7.44. Conditions that lead to a reduced amount of fluid in the body, like vomiting or excessive urination due to use of diuretic drugs, change the balance of fluids and salts. The blood levels of potassium and sodium can decrease dramatically, causing symptoms of metabolic alkalosis.
In cases of metabolic alkalosis, slowed breathing may be an initial symptom. The patient may have episodes of apnea (not breathing) that may go on 15 seconds or longer. Cyanosis, a bluish or purplish discoloration of the skin, may also develop as a sign of inadequate oxygen intake. Nausea, vomiting, and diarrhea may also occur. Other symptoms can include irritability, twitching, confusion, and picking at bedclothes. Rapid heart rate, irregular heart beats, and a drop in blood pressure are also symptoms. Severe cases can lead to convulsions and coma.
Metabolic alkalosis may be suspected based on symptoms, but often may not be noticeable. The condition is usually confirmed by laboratory tests on blood and urine samples. Blood pH above 7.45 confirms the condition. Levels of other blood components, including salts like potassium, sodium, and chloride, fall below normal ranges. The level of bicarbonate in the blood will be high, usually greater than 29 mEq/L. Urine pH may rise to about 7.0 in metabolic alkalosis.
Treatment focuses first on correcting the imbalance. An intravenous line may be started to administer fluids (generally normal saline, a salt water solution) and allow for the quick injection of other drugs that may be needed. Potassium chloride will be administered. Drugs to regulate blood pressure or heart rate, or to control nausea and vomiting might be given. Vital signs like pulse, respiration, blood pressure, and body temperature will be monitored. The underlying cause of the metabolic alkalosis must also be diagnosed and corrected.
If metabolic alkalosis is recognized and treated promptly, the patient may have no long-term complications; however, the underlying condition that caused the alkalosis needs to be corrected or managed. Severe metabolic alkalosis that is left untreated will lead to convulsions, heart failure, and coma.
Patients receiving tube feedings or intravenous feedings must be monitored to prevent an imbalance of fluids and salts, particularly potassium, sodium, and chloride. Overuse of some drugs, including diuretics, laxatives, and antacids, should be avoided.
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DuBose, Thomas D., Jr. "Acidosis and Alkalosis" In Harrison's Principles of Internal Medicine, ed. Anthony S. Fauci, et al. New York: McGraw-Hill, 1997.
"Fluid, Electrolyte, and Acid-Base Disorders." In Family Medicine Principles and Practices. 5th ed. New York: Springer-Verlag, 1998.
"Fluid & Electrolyte Disorders." In Current Medical Diagnosis and Treatment, 1998. 37th ed. Ed. Stephen McPhee, et al. Stamford: Appleton & Lange, 1997.
pH — A measurement of the acidity or alkalinity of a solution based on the amount of hydrogen ions available. Based on a scale of 14, a pH of 7.0 is neutral. A pH below 7.0 is an acid; the lower the number, the stronger the acid. A pH above 7.0 is a base; the higher the number, the stronger the base. Blood pH is slightly alkaline (basic) with a normal range of 7.36-7.44.
an alkalosis associated with an increased arterial plasma bicarbonate concentration, possibly resulting from an excessive intake of alkaline materials or an excessive loss of acid in the urine or through persistent vomiting; the base excess and standard bicarbonate are both elevated.
See also: compensated alkalosis.
See also: compensated alkalosis.
an abnormal condition characterized by the significant loss of acid in the body or by increased levels of base bicarbonate. Loss of acid may be caused by excessive vomiting, insufficient replacement of electrolytes, hyperadrenocorticism, or Cushing's disease. Increased levels of base bicarbonate may have various causes, such as the ingestion of excessive amounts of bicarbonate of soda or other antacids during the treatment of peptic ulcers or the administration of excessive volumes of IV fluids containing high concentrations of bicarbonate. Severe, untreated metabolic alkalosis can lead to coma and death. Compare respiratory alkalosis. See also metabolic acidosis, respiratory acidosis.
observations Signs and symptoms of metabolic alkalosis may include apnea, headache, lethargy, muscle cramps, hyperactive reflexes, tetany, shallow and slow respirations, irritability, nausea, vomiting, and atrial tachycardia. Confirmation of the diagnosis is commonly based on laboratory findings that show a blood pH greater than 7.45, a carbonic acid concentration greater than 29 mEq/L, and alkaline urine. The electrocardiogram of a patient with this condition may show atrial tachycardia with a low T wave merging with a P wave.
interventions Treatment seeks to eliminate the underlying cause of alkalosis. Ammonium chloride may be given intravenously to release hydrogen chloride and restore chloride levels, except in patients with liver or kidney disease. Potassium chloride and normal saline solutions usually replace fluid losses from gastric drainage but are contraindicated in patients with associated congestive heart failure.
nursing considerations Nurses closely monitor the status of the patient and cautiously administer any prescribed IV solutions. Too-rapid infusion of ammonium chloride may hemolyze red blood cells, and an excessive dosage may overcorrect alkalosis and cause acidosis. The fluid intake and output of the patient are carefully noted, and the respiration rate is regularly checked. Decreased respiratory rate indicates an effort to compensate for alkalosis and may cause respiratory acidosis.
metabolic alkalosisA condition in which there is an increased pH due to either a decrease in acids or an excess of bicarbonate in tissues.
Slow, shallow breathing; irritability; confusion.
Loss of acids due to hyperemesis, gastric suction, loss of K+ due to increased renal excretion (e.g., diuretic therapy), steroid use, excess/overuse of antacids.
The lungs compensate for metabolic alkalosis by retaining CO2 with slower respiration; the kidneys are less effective than the lungs in compensating for metabolic acidosis, which act by increasing bicarbonate excretion.
metabolic alkalosisPhysiology A condition in which there is a ↑ pH due to either an ↓ in acids or excess bicarbonate Lab pH > 7.42, HCO3– > 26 mEq/L, PaCO2 > 45 mm Hg Etiology Loss of acids due to hyperemesis, gastric suction, loss of K+ due to ↑ renal excretion–eg, diuretic therapy, steroid use, excess–eg, overuse of antacids Clinical Slow shallow breathing, irritability, confusion. See Metabolic acidosis, Respiratory acidosis, Respiratory alkalosis.
met·a·bol·ic al·ka·lo·sis(met'ă-bol'ik al'kă-lō'sis)
A disorder associated with an increased arterial bicarbonate concentration, resulting from an excessive intake of alkaline materials or an excessive loss of acid in the urine or through persistent vomiting; the base excess and standard bicarbonate are both elevated.
See also: compensated alkalosis
See also: compensated alkalosis
a pathological condition resulting from accumulation of base, or from loss of acid without comparable loss of base in the body fluids, and characterized by decrease in hydrogen ion concentration (increase in pH). Alkalosis is the opposite of acidosis. See also acid-base balance.
a condition in which compensatory mechanisms have returned the pH toward normal.
associated with deficit in free body water, hypotonic fluid losses or increased sodium levels.
alkalosis due to loss of gastric fluid because of persistent vomiting. See also hypochloremic alkalosis (below).
a metabolic alkalosis in which gastric losses of chloride are disproportionately greater than sodium loss because of corresponding increase in potassium loss.
a metabolic alkalosis associated with a low serum potassium level; retention of alkali or loss of acid occurs in the extracellular (but not intracellular) fluid compartment; although the pH of the intracellular fluid may be below normal.
a disturbance in which the acid-base status shifts toward the alkaline because of uncompensated loss of acids, ingestion or retention of excess base, or potassium depletion. The condition can occur with vomiting or accompany treatment with diuretics.
reduced carbon dioxide tension in the extracellular fluid caused by excessive excretion of carbon dioxide through the lungs (hyperventilation). Conditions commonly associated with respiratory alkalosis include pain, hypoxia, fever, high environmental temperature, poisoning, early pulmonary edema, pulmonary embolism and central nervous system disease.