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Respiratory Alkalosis

Definition

Respiratory alkalosis is a condition where the amount of carbon dioxide found in the blood drops to a level below normal range. This condition produces a shift in the body's pH balance and causes the body's system to become more alkaline (basic). This condition is brought on by rapid, deep breathing called hyperventilation.

Description

Respiratory alkalosis is an alkali imbalance in the body caused by a lower-than-normal level of carbon dioxide in the blood. In the lungs, oxygen from inhaled air is exchanged for carbon dioxide from the blood. This process takes place between the alveoli (tiny air pockets in the lungs) and the blood vessels that connect to them. When a person hyperventilates, this exchange of oxygen for carbon dioxide is speeded up, and the person exhales too much carbon dioxide. This lowered level of carbon dioxide causes the pH of the blood to increase, leading to alkalosis.

Causes and symptoms

The primary cause of respiratory alkalosis is hyperventilation. This rapid, deep breathing can be caused by conditions related to the lungs like pneumonia, lung disease, or asthma. More commonly, hyperventilation is associated with anxiety, fever, drug overdose, carbon monoxide poisoning, or serious infections. Tumors or swelling in the brain or nervous system can also cause this type of respiration. Other stresses to the body, including pregnancy, liver failure, high elevations, or metabolic acidosis can also trigger hyperventilation leading to respiratory alkalosis.

Hyperventilation, the primary cause of respiratory alkalosis, is also the primary symptom. This symptom is accompanied by dizziness, light headedness, agitation, and tingling or numbing around the mouth and in the fingers and hands. Muscle twitching, spasms, and weakness may be noted. Seizures, irregular heart beats, and tetany (muscle spasms so severe that the muscle locks in a rigid position) can result from severe respiratory alkalosis.

Diagnosis

Respiratory alkalosis may be suspected based on symptoms. A blood sample to test for pH and arterial blood gases can be used to confirm the diagnosis. In this type of alkalosis, the pH will be elevated above 7.44. The pressure of carbon dioxide in the blood will be low, usually under 35 mmHg.

Key terms

Hyperventilation — Rapid, deep breathing, possibly exceeding 40 breaths/minute. The most common cause is anxiety, although fever, aspirin overdose, serious infections, stroke, or other diseases of the brain or nervous system.

pH — A measurement of acid or alkali (base) 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 alkali with a normal range of 7.36-7.44.

Treatment

Treatment focuses on correcting the underlying condition that caused the alkalosis. Hyperventilation due to anxiety may be relieved by having the patient breath into a paper bag. By rebreathing the air that was exhaled, the patient will inhale a higher amount of carbon dioxide than he or she would normally. Antibiotics may be used to treat pneumonia or other infections. Other medications may be required to treat fever, seizures, or irregular heart beats. If the alkalosis is related to a drug overdose, the patient may require treatment for poisoning. Use of mechanical ventilation like a respirator may be necessary. If the respiratory alkalosis has triggered the body to compensate by developing metabolic acidosis, symptoms of that condition may need to be treated, as well.

Prognosis

If the underlying condition that caused the respiratory alkalosis is treated and corrected, there may be no long-term effects. In severe cases of respiratory alkalosis, the patient may experience seizures or heart beat irregularities that may be serious and life threatening.

Resources

Books

"Fluid, Electrolyte, and Acid-Base Disorders." In Family Medicine Principles and Practices. 5th ed. New York: Springer-Verlag, 1998.

alkalosis /al·ka·lo·sis/ (al″kah-lo´sis) a pathologic condition due to accumulation of base in, or loss of acid from, the body. Cf. acidosis. alkalot´ic

altitude alkalosis increased alkalinity in blood and tissues due to exposure to high altitudes.

compensated alkalosis a form in which compensatory mechanisms have returned the pH toward normal.

hypochloremic alkalosis metabolic alkalosis marked by hypochloremia together with hyponatremia and hypokalemia, resulting from the loss of sodium chloride and hydrochloric acid due to prolonged vomiting.

hypokalemic alkalosis metabolic alkalosis associated with a low serum potassium level.

metabolic alkalosis a disturbance in which the acid-base status shifts toward the alkaline side because of retention of base or loss of noncarbonic, or fixed (nonvolatile), acids.

respiratory alkalosis a state due to excess loss of carbon dioxide from the body, usually as a result of hyperventilation.

respiratory alkalosis

Alkalosis resulting from abnormal loss of carbon dioxide due to hyperventilation.

respiratory alkalosis,

an abnormal condition characterized by a high plasma pH resulting from increased alveolar ventilation. The consequent acceleration of carbon dioxide excretion lowers the plasma level of carbonic acid, thus raising plasma pH. The hyperventilation may be caused by pulmonary and nonpulmonary problems. Some pulmonary causes are acute asthma, pulmonary vascular disease, and pneumonia. Some nonpulmonary causes are aspirin toxicity, anxiety, fever, metabolic acidosis, inflammation of the central nervous system, gram-negative septicemia, and hepatic failure. Compare metabolic alkalosis. See also metabolic acidosis, respiratory acidosis.

observations Deep and rapid breathing at rates as high as 40 breaths per minute is a major sign of respiratory alkalosis. Other symptoms are lightheadedness, dizziness, peripheral paresthesia, tingling of the hands and feet, muscle weakness, tetany, and cardiac arrhythmia. Confirming diagnosis is often based on a PaCO₂ below 35 mm Hg and a pH greater than 7.45. PaO₂ may be higher than 100. In the acute stage, blood pH rises in proportion to the fall in PaCO₂, but in the chronic stage it remains within the normal range of 7.35 to 7.45. The carbonic acid concentration is normal in the acute stage of this condition but below normal in the chronic stage.

interventions Treatment of respiratory alkalosis concentrates on removing the underlying causes. Severe cases, especially those caused by extreme anxiety, may be treated by having the patient breathe into a paper bag and inhale exhaled carbon dioxide to compensate for the deficit being created by hyperventilation. Sedatives may also be administered to decrease the ventilation rate.

nursing considerations The nurse monitors neurologic, neuromuscular, and cardiovascular functions, arterial blood gases, and serum electrolyte levels. The patient benefits from explanations of laboratory tests and treatment.

alkalosis (alk

lō´sis),

n a disturbance of acid-base balance and water balance, characterized by an excess of alkali or a deficiency of acids.

alkalosis, compensated,

n a condition in which the blood bicarbonate is usually higher than normal but compensatory mechanisms have kept the pH level within normal range. See also alkalosis, uncompensated.

alkalosis, hypochloremic,

n a metabolic abnormality caused by an increase in blood bicarbonate after significant chloride loss.

alkalosis, respiratory,

n alkalemia produced by hypoventilation. Plasma bicarbonate is therefore decreased in respiratory alkalosis but raised in metabolic alkalosis.

alkalosis, uncompensated,

n alkalemia usually accompanied by an increased blood bicarbonate.

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.

compensated alkalosis

a condition in which compensatory mechanisms have returned the pH toward normal.

concentration alkalosis

associated with deficit in free body water, hypotonic fluid losses or increased sodium levels.

gastric alkalosis

alkalosis due to loss of gastric fluid because of persistent vomiting. See also hypochloremic alkalosis (below).

hypochloremic alkalosis

a metabolic alkalosis in which gastric losses of chloride are disproportionately greater than sodium loss because of corresponding increase in potassium loss.

hypokalemic alkalosis

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.

metabolic alkalosis

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.

respiratory alkalosis

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.

respiratory alkalosis

Metabolism A condition characterized by ↑ pH due to excess CO₂ excretion Etiology Hyperventilation–eg, due to anxiety, pain, panic attacks, psychosis, CVA, fever, encephalitis, meningitis, tumor, trauma, hypoxemia–severe anemia, high altitude, right-to-left shunt, drugs–progesterone, methylxanthines, salicylates, catecholamines, nicotine, hyperthyroidism, pregnancy, ↑ ambient temperature, lung disease–pneumo/hemothorax, pneumonia, pulmonary edema, PE, aspiration, interstitial lung disease, etc–sepsis, liver failure, mechanical ventilation, heat exhaustion, recovery from metabolic acidosis DiffDx Asthma, A Fib, flutter and tachycardia, heatstroke, metabolic acidosis or alkalosis, acute MI, and other causes of RA Clinical Hyperventilation, paresthesia, twitching–positive Chvostek and Trousseau signs, N&V, focal neurologic signs, depressed consciousness, or coma Lab pH > 7.42, HCO₃- < 22 mEq/L–if compensating, PaCO₂ < 35 mmHg. See Metabolic acidosis, Metabolic alkalosis, Respiratory acidosis.