Acid–base disorder

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Acid–base disorder

An acid–base disorder is a pathologic condition that leads to an imbalance in the pH levels of the blood and other bodily fluids. The human body maintains a delicate balance of acids and bases, primarily through the bicarbonate buffer system, the respiratory system, and the renal system. Disruptions in this balance can lead to significant health issues.

Types of Acid–Base Disorders

Acid–base disorders are generally classified into four main types:

• Metabolic acidosis: Characterized by a decrease in bicarbonate (HCO₃⁻) and a decrease in pH. Common causes include diabetic ketoacidosis, lactic acidosis, and renal failure.
• Metabolic alkalosis: Characterized by an increase in bicarbonate and an increase in pH. Common causes include prolonged vomiting, diuretic use, and hyperaldosteronism.
• Respiratory acidosis: Characterized by an increase in carbon dioxide (CO₂) and a decrease in pH. Common causes include chronic obstructive pulmonary disease (COPD), respiratory depression, and airway obstruction.
• Respiratory alkalosis: Characterized by a decrease in carbon dioxide and an increase in pH. Common causes include hyperventilation, anxiety, and high altitude.

Pathophysiology

The body regulates acid–base balance through three main mechanisms:

• Buffer systems: The bicarbonate buffer system is the primary buffer system in the blood. It helps to neutralize excess acids or bases.
• Respiratory compensation: The respiratory system can adjust the levels of carbon dioxide in the blood by changing the rate and depth of breathing.
• Renal compensation: The kidneys help to maintain acid–base balance by excreting hydrogen ions and reabsorbing bicarbonate from the urine.

Diagnosis

Diagnosis of acid–base disorders typically involves:

• Arterial blood gas (ABG) analysis: Measures the pH, partial pressure of carbon dioxide (PaCO₂), and bicarbonate levels in the blood.
• Serum electrolytes: Measures levels of sodium, potassium, chloride, and bicarbonate in the blood.
• Anion gap: Helps to differentiate between different types of metabolic acidosis.

Treatment

Treatment of acid–base disorders depends on the underlying cause:

• Metabolic acidosis: Treatment may include administration of bicarbonate, treatment of the underlying cause (e.g., insulin for diabetic ketoacidosis), and dialysis in severe cases.
• Metabolic alkalosis: Treatment may include administration of chloride, potassium supplements, and addressing the underlying cause.
• Respiratory acidosis: Treatment may include improving ventilation, treating underlying lung disease, and in some cases, mechanical ventilation.
• Respiratory alkalosis: Treatment may include rebreathing into a paper bag, addressing anxiety, and treating underlying conditions.

See also

• Acidosis
• Alkalosis
• Bicarbonate buffer system
• Arterial blood gas
• Electrolyte imbalance