Acid Base Imbalance-ORTILLA

LEARNING OBJECTIVES

  • Differentiate between acidosis and alkalosis, metabolic and respiratory in terms of pathophysiology and compensatory mechanisms.

  • Interpret ABG values.

ACID-BASE BALANCE

Background

  • Acid-base homeostasis is vital for life, maintaining cellular function within a specific pH range.

  • pH is determined by hydrogen ion (H+) concentration:

    • Acids: Release H+

      • pH < 7

    • Alkalines/Bases: Accept H+

      • pH > 7

Body Fluids

  • Normal pH range: 7.35 – 7.45 (pH of 7 is neutral).

  • Arterial blood pH:< 7.35 is acidic; > 7.45 is alkaline.

Acids and Bases in the Body

  • Body constantly produces weak acids (e.g., carbonic, lactic, hydrochloric acids).

  • Bicarbonate is the major base regulating acid-base balance.

BICARBONATE

  • Present in ICF and ECF, regulates acid-base balance. Normal range: 22-26 mEq/L.

  • Function: Component of the bicarbonate-carbonic acid buffer system.

  • Imbalances:

    • Metabolic Acidosis: < 22 mEq/L

    • Metabolic Alkalosis: > 26 mEq/L

BODY REGULATION OF ACID-BASE BALANCE

Buffer System

  • Maintains pH within normal range through:

    • Carbonic acid-sodium bicarbonate buffer system.

  • Quick response to restore blood pH (7.35 - 7.45).

Respiratory Mechanisms

  • Regulate by eliminating/retaining CO2:

    • Too Acidic: Increased respiration, CO2 excreted.

    • Too Alkaline: Decreased respiration, CO2 retained.

Renal Mechanisms

  • Excrete/retain H+ and bicarbonate to maintain pH.

    • Too Acidic: Excrete H+, reabsorb bicarbonate.

    • Too Basic: Retain H+, excrete bicarbonate.

ARTERIAL BLOOD GASES (ABGs)

  • Normal Values:

    • pH: 7.35 - 7.45

    • PaCO2: 35 - 45 mm Hg

    • HCO3ˉ: 22 - 26 mEq/L

Steps for ABG Analysis

  1. Analyze pH.

  2. Analyze CO2.

  3. Analyze HCO3.

  4. Match CO2 or HCO3 with pH.

  5. Check for compensation.

  6. Analyze pO2 and O2 saturation.

ACID-BASE IMBALANCE

Classifications

  • Acidosis: H+ concentration increases; pH < 7.35.

  • Alkalosis: H+ concentration decreases; pH > 7.45.

  • Origin of the problem: Respiratory vs. Metabolic.

Disorders

  • Primary Disorders: Simple or combined, affecting acid-base balance.

  • Compensation: Response to primary disorders, striving to correct pH.

TREATMENT

Urgency

  • Significant acidosis/alkalosis can lead to altered mental status, brain function, and cellular dysfunction.

  • Direct Treatment: Correct precipitating conditions; avoid direct treatment of imbalance initially.

TYPES OF ACID-BASE IMBALANCES

Respiratory Acidosis

  • pH < 7.35; PaCO2 > 45 mm Hg.

  • Causes include airway obstruction, oversedation, chronic lung disease.

  • Symptoms: Confusion, respiratory failure, increased intracranial pressure.

Respiratory Alkalosis

  • pH > 7.45; PaCO2 < 35 mm Hg.

  • Causes: Hyperventilation, anxiety, fever, mechanical ventilation.

  • Symptoms: Lightheadedness, palpitations.

Metabolic Acidosis

  • pH < 7.35; HCO3 < 22 mEq/L.

  • Causes: Lactic acidosis, ketoacidosis, renal failure.

  • Symptoms: Headache, weakness, Kussmaul’s respirations.

Metabolic Alkalosis

  • pH > 7.45; HCO3 > 26 mEq/L.

  • Causes: Excessive vomiting, diuretics, bicarbonate ingestion.

  • Symptoms: Muscle spasms, dizziness.