Key Acid-Base Imbalances to Know for Pathophysiological Concepts in Nursing

Acid-base imbalances are crucial in understanding patient health. They can arise from metabolic or respiratory issues, affecting blood pH and leading to various symptoms. Recognizing these imbalances helps nurses provide effective care and manage underlying conditions.

1. Metabolic acidosis

   • Characterized by a decrease in blood pH due to excess acid or loss of bicarbonate.
   • Common causes include diabetic ketoacidosis, renal failure, and lactic acidosis.
   • Symptoms may include rapid breathing, confusion, and fatigue.
   • Anion gap can be used to differentiate between types of metabolic acidosis.

2. Metabolic alkalosis

   • Defined by an increase in blood pH due to excess bicarbonate or loss of acid.
   • Often caused by prolonged vomiting, diuretic use, or excessive bicarbonate intake.
   • Symptoms may include muscle twitching, hand tremors, and lightheadedness.
   • Can lead to hypokalemia and hypocalcemia.

3. Respiratory acidosis

   • Occurs when there is an accumulation of carbon dioxide (CO2) due to inadequate ventilation.
   • Common causes include chronic obstructive pulmonary disease (COPD), respiratory failure, and drug overdose.
   • Symptoms may include confusion, lethargy, and shortness of breath.
   • Compensation occurs through renal retention of bicarbonate.

4. Respiratory alkalosis

   • Results from excessive loss of CO2 due to hyperventilation.
   • Common causes include anxiety, fever, and high altitude.
   • Symptoms may include dizziness, tingling in the extremities, and palpitations.
   • Compensation occurs through renal excretion of bicarbonate.

5. Mixed acid-base disorders

   • Occur when two or more primary acid-base disorders are present simultaneously.
   • Can complicate diagnosis and treatment, requiring careful analysis of ABG results.
   • Examples include metabolic acidosis with respiratory compensation or metabolic alkalosis with respiratory acidosis.
   • Understanding the underlying conditions is crucial for effective management.

6. Compensatory mechanisms

   • The body attempts to restore normal pH through respiratory or renal compensation.
   • Respiratory compensation involves changes in ventilation to alter CO2 levels.
   • Renal compensation involves adjusting bicarbonate reabsorption or hydrogen ion excretion.
   • Full compensation may not always occur, leading to persistent acid-base imbalances.

7. Anion gap

   • A calculated value used to help identify the cause of metabolic acidosis.
   • Normal anion gap is typically between 8-12 mEq/L; elevated levels suggest accumulation of unmeasured anions.
   • Common causes of elevated anion gap include ketoacidosis, lactic acidosis, and renal failure.
   • Normal anion gap metabolic acidosis may be due to gastrointestinal bicarbonate loss or renal tubular acidosis.

8. Arterial blood gas (ABG) interpretation

   • ABG analysis provides critical information about a patient’s acid-base status and oxygenation.
   • Key components include pH, PaCO2, and HCO3- levels.
   • Interpretation involves assessing the primary disorder (metabolic vs. respiratory) and compensation status.
   • Understanding the relationship between these values is essential for diagnosis and treatment.

9. pH, PaCO2, and HCO3- normal ranges

   • Normal pH: 7.35 - 7.45
   • Normal PaCO2: 35 - 45 mmHg
   • Normal HCO3-: 22 - 26 mEq/L
   • Values outside these ranges indicate acid-base imbalances that require further evaluation.

10. Causes of each acid-base imbalance

    • Metabolic acidosis: Diabetic ketoacidosis, renal failure, lactic acidosis, diarrhea.
    • Metabolic alkalosis: Vomiting, diuretic use, excessive bicarbonate intake, hypokalemia.
    • Respiratory acidosis: COPD, respiratory failure, drug overdose, neuromuscular disorders.
    • Respiratory alkalosis: Hyperventilation, anxiety, fever, high altitude.