Acid-Base Imbalances: Metabolic Acidosis and Alkalosis; Respiratory Acidosis and Alkalosis
To explore Nursing Central - view these FREE monographs:
-- The first section of this topic is shown below --
DRG Category: 640
Mean LOS: 5.1 days
Description MEDICAL: Nutritional and Miscellaneous Metabolic Disorders with Major CC
The hydrogen ion concentration ([H+]) of the body, described as the pH or negative log of the [H+], is maintained in a narrow range to promote health and homeostasis. The body has many regulatory mechanisms that counteract even a slight deviation from normal pH. Acid-base imbalance can alter many physiological processes and lead to serious problems or, if left untreated, to coma and death. A pH below 7.35 is considered acidosis and above 7.45 is alkalosis. Alterations in hydrogen ion concentration can be metabolic or respiratory in origin, or they may have a mixed origin.
Metabolic acidosis, a pH below 7.35, results from any nonpulmonary condition that leads to an excess of acids over bases. Renal patients with chronic acidemia may show signs of skeletal problems as calcium and phosphate are released from bone to help with the buffering of acids. Children with chronic acidosis may show signs of impaired growth. Metabolic alkalosis, a pH above 7.45, results from any nonpulmonary condition that leads to an excess of bases over acids. Metabolic alkalosis results from one of two mechanisms: an excess of bases or a loss of acids. Patients with a history of congestive heart failure and hypertension, who are on sodium-restricted diets and diuretics, are at greatest risk for metabolic alkalosis. Metabolic alkalosis can also be caused by prolonged vomiting, hyperaldosteronism, and diuretic therapy.
Respiratory acidosis is a pH imbalance that results from alveolar hypoventilation and an accumulation of carbon dioxide. It can be classified as either acute or chronic. Acute respiratory acidosis is associated with a sudden failure in ventilation. Chronic respiratory acidosis is seen in patients with chronic pulmonary disease, in whom long-term hypoventilation results in a chronic elevation (> 45 mm Hg) of Paco2 levels (hypercapnia), which renders the primary mechanism of inspiration, an elevated Paco2, unreliable. The major drive for respiration in chronic pulmonary disease patients becomes a low oxygen level (hypoxemia). Respiratory alkalosis is a pH imbalance that results from the excessive loss of carbon dioxide through hyperventilation (Paco2 < 35 mm Hg). Respiratory alkalosis is the most frequently occurring acid-base imbalance of hospitalized patients. Improper use of mechanical ventilators can cause iatrogenic respiratory alkalosis, whereas secondary respiratory alkalosis may develop from hyperventilation stimulated by metabolic or respiratory acidosis. Patients with respiratory alkalosis are at risk for hypokalemia, hypocalcemia, and hypophosphatemia.