Lecture on Acid-Base Disorders

Introduction

• Discussion on acid-base disorders
• Part of clinical medicine section
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Primary Acid-Base Disorders

• Metabolic Acidosis
• Metabolic Alkalosis
• Respiratory Acidosis
• Respiratory Alkalosis

Metabolic Acidosis

Anion Gap Metabolic Acidosis (AGMA)

• Pathophysiology: Elevated anion gap due to organic acids
• Causes:
  • Diabetic Ketoacidosis (DKA)
  • Uremic Acidosis
  • Lactic Acidosis
  • Toxic Ingestions (Methanol, Ethylene Glycol)
• Mechanism: Organic acids release protons, depleting bicarbonate

Non-Anion Gap Metabolic Acidosis (NAGMA)

• Pathophysiology: Normal anion gap
• Causes:
  • Renal losses (Renal Tubular Acidosis)
  • Gastrointestinal losses (Diarrhea)
• Mechanism: Chloride increase drives bicarbonate down

Complications

• Electrolyte disturbances (Hyperkalemia)
• Respiratory compensation (Increased ventilation)
• Cardiac output reduction (Hypotension)

Metabolic Alkalosis

Pathophysiology

• Causes:
  • Renal loss of protons
  • Gastrointestinal loss of protons
• Mechanism: Loss of protons increases bicarbonate, raising pH

Complications

• Hypokalemia leading to arrhythmias
• Neuromuscular irritability (Tetany)
• Hypoventilation (Compensatory)

Respiratory Acidosis

Pathophysiology

• Mechanism: Hypoventilation leads to CO2 retention
• Causes:
  • Respiratory depression (Opioids, Benzodiazepines)
  • Neuromuscular diseases (ALS, Guillain-Barre)
  • Airway obstruction (COPD, Asthma)

Complications

• Increased intracranial pressure
• Chronic compensation via renal bicarbonate reabsorption

Respiratory Alkalosis

Pathophysiology

• Mechanism: Hyperventilation reduces CO2
• Causes:
  • Anxiety, Pain
  • Hypoxemia
  • Metabolic toxicity (Aspirin)

Complications

• Reduced cerebral blood flow
• Syncope
• Compensatory renal bicarbonate excretion

Diagnostic Approach

Determining Acid-Base Disorder

• Use arterial blood gas for pH, CO2, and bicarbonate levels
• Calculate Anion Gap for metabolic acidosis
• Delta-Delta ratio for mixed disorders

Identifying Etiology

• AGMA: Check ketones, BMP, lactate, osmolar gap
• NAGMA: Check urine anion gap
• Respiratory Disorders: History, physical exam, response to treatment

Treatment

• Metabolic Acidosis: Treat underlying cause (Insulin for DKA, fluids for lactic acidosis)
• Metabolic Alkalosis: Fluid replacement, correct electrolyte imbalances
• Respiratory Acidosis: Remove depressants, improve ventilation
• Respiratory Alkalosis: Treat underlying cause (oxygen for hypoxemia)

Conclusion

• Importance of understanding and diagnosing acid-base disorders
• Thank you and encouragement for further study