Acid Base Imbalances

Acid-Base Imbalance Overview

  • Acidosis: A condition characterized by an excess of hydrogen ions (H+) and carbon dioxide (CO2) in the blood, leading to a decrease in blood pH (below 7.35).

  • Alkalosis: A condition characterized by an excess of bicarbonate (HCO3-) leading to an increase in blood pH (above 7.45).

Normal Ranges

  • pH: 7.35 - 7.45

  • CO2 (Carbon Dioxide): 35 - 45 mmHg

  • HCO3 (Bicarbonate): 22 - 26 mEq/L

  • SaO2 (Oxygen Saturation): > 92%

Mechanisms of Regulation

  • The body regulates pH balance through metabolic (kidney function) and respiratory (lung function) mechanisms.

  • Metabolic compensation: Bicarbonate is released by the kidneys to increase pH during acidosis.

  • Respiratory compensation: CO2 is exhaled during respiratory alkalosis to increase acidity.

Hydrogen Ions and Potassium Movement

  • The concentration of hydrogen ions inversely affects pH:

    • High H+ concentration = Low pH (Acidosis)

    • Low H+ concentration = High pH (Alkalosis)

  • Potassium Movement:

    • During acidosis, potassium is pushed out of cells (leading to hyperkalemia).

    • During alkalosis, potassium moves into cells (leading to hypokalemia).

Impact of pH Imbalance on Electrolytes

  • Acidosis: Elevated H+ leads to hyperkalemia due to potassium moving out of cells.

  • Alkalosis: Decreased H+ leads to hypokalemia due to potassium moving into cells.

  • Calcium levels may also be affected:

    • In Acidosis: Calcium can cause hypercalcemia due to mobilization from bones.

    • In Alkalosis: Calcium binds to albumin, potentially causing hypocalcemia.

Interpreting Arterial Blood Gas (ABG) Values

  • Steps to interpret ABG:

    1. Identify if the pH is normal.

    2. Assess CO2 levels (35-45 mmHg).

    3. Assess HCO3 levels (22-26 mEq/L).

    4. Correlate CO2 and HCO3 with pH to determine whether the primary issue is respiratory or metabolic.

    5. Check if compensation is occurring by observing the opposite component (e.g., metabolic vs. respiratory compensation).

    6. Assess O2 saturation (SaO2).

Clinical Manifestations

Respiratory Acidosis

  • pH < 7.35, CO2 > 45 mmHg.

  • Symptoms: confusion, headache, restlessness, shortness of breath, tachycardia, warm flushed skin.

  • Management: bronchodilators, oxygen therapy, monitor for hyperkalemia, and vital signs.

Respiratory Alkalosis

  • pH > 7.45, CO2 < 35 mmHg.

  • Symptoms: anxiety, rapid shallow breaths, paresthesia, possible tetany.

  • Management: calming techniques, breathing into a bag, monitor vital signs.

Metabolic Acidosis

  • pH < 7.35, HCO3 < 22 mEq/L.

  • Symptoms: Kussmaul respirations, hypotension, lethargy.

  • Management: monitor vital signs, IV fluids, and medications.

Metabolic Alkalosis

  • pH > 7.45, HCO3 > 26 mEq/L.

  • Symptoms: hypoventilation, muscle twitching, possible cyanosis.

  • Management: monitor vital signs, oxygen therapy, fall precautions.

Compensation Mechanisms

  • Respiratory issues may see renal compensation (bicarbonate regulation) and vice versa.

  • Understanding compensation is crucial to identify the severity and type of acid-base disturbance.