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Respiratory Alkalosis

Jun 27, 2024

Respiratory Alkalosis

Introduction

  • Lecture on understanding respiratory alkalosis.
  • Comprehensive notes and illustrations available for enhancing learning.

Definition

  • Respiratory alkalosis: a condition where there is a decrease in CO2 in the blood, leading to an increase in blood pH.
  • Abnormalities in patient’s ABG:
    • pH: Normal range 7.35 - 7.45; the example given shows a pH of 7.48 (alkaline).
    • CO2: Normal range 35 - 45 mmHg; the example given shows 28 mmHg (hypocapnia).
    • Bicarbonate (HCO3): Normal range 22 - 26 mEq/L; low in the given example (compensation response).
    • PO2: Very low at 45 mmHg (moderate hypoxia).

Diagnostic Approach

  • Alkalemia: pH is high.
  • Hypocapnia: Low levels of CO2 indicating respiratory origin.
  • Compensation: Partial (bicarbonate decreased but not enough to normalize pH).
  • Hypoxia: Moderate level of hypoxia (PO2 45 mmHg).

Physiology and Pathophysiology

  • Medullary Respiratory Centers: VRG and DRG in the medulla control breathing.
  • Normal Breathing Process: Involves diaphragm and intercostal muscles for inspiration and expiration.
  • CO2 Loss Impact: Reduces protons in blood, shifting pH upwards.
  • Causes of CO2 Loss: Must investigate why excessive CO2 is being lost.

Causes

Central Causes

  1. Drug-Induced Stimulation
    • Salicylates (Aspirin)
    • Methylxanthines
    • Nicotine
  2. Infection
    • Gram-negative sepsis
  3. Liver Failure
    • Hepatic encephalopathy causing ammonia buildup.
  4. Endocrine
    • Hyperthyroidism (Thyrotoxicosis)
  5. Pregnancy
    • High levels of progesterone stimulating respiration.
  6. Anxiety, Pain, Fear
    • Stimulates hypothalamus leading to increased respiratory rate.
  7. Fever
    • Raises metabolic rate, impacts hypothalamus.
  8. Tumors
    • Mid-brain tumors causing hyperventilation.

Peripheral Causes

  1. Pulmonary Edema
    • Fluid between alveoli and blood vessels causing impaired gas exchange.
  2. Acute Respiratory Distress Syndrome (ARDS)
    • Fluid in lungs impairing oxygen transfer.
  3. Pneumonia
    • Infection causing impaired gas exchange.
  4. Pulmonary Embolism
    • Clots blocking blood flow affecting oxygen exchange.

Diagnosis and Treatment

Diagnosis

  • ABG analysis for pH, CO2, HCO3, and PO2 levels.

Treatment

  1. Drug Overdose
    • Aspirin: Use antidote (activated charcoal, supportive treatments).
    • Methylxanthines, Nicotine: Manage based on severity.
  2. Infection
    • Treat gram-negative sepsis with antibiotics.
  3. Liver Failure
    • Use agents like lactulose, rifaximin to reduce ammonia levels.
  4. Hyperthyroidism
    • Antithyroid medications (propothyluracyl, methimazole).
  5. Pregnancy
    • Limited intervention; manage symptoms.
  6. Anxiety, Pain, Fear
    • Relaxation techniques, medications, breathing exercises.
  7. Fever
    • Treat with antipyretics like Tylenol.
  8. Ventilator Settings
    • Adjust respiratory rate to suitable levels.
    • For ICP crises: temporary hyperventilation.

Specific Conditions

  1. Pulmonary Embolism
    • Anticoagulants (Heparin, TPA), embolism removal.
  2. ARDS
    • Proper mechanical ventilation, supportive care.
  3. Pulmonary Edema
    • Diuretics (Lasix) to reduce fluid volume.
  4. Pneumonia
    • Antibiotics to treat underlying infection.
  5. Ventilation Issues
    • If patient is overbreathing ventilator: sedatives, opioids to suppress respiratory drive.

Conclusion

  • Understanding respiratory alkalosis involves recognizing the underlying cause, diagnosing via ABG, and applying appropriate treatment strategies.

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