Lecture on Metabolic and Respiratory Acidosis and Alkalosis

Overview

• Importance of maintaining normal pH: Slight variance can be life-threatening.
• Kidneys and lungs work together to correct pH imbalances.
  • Kidneys compensate for lung shortcomings.
  • Lungs compensate for kidney shortcomings.

Blood pH

• Normal pH range: 7.35 - 7.45
• Blood pH < 7.35: Acidic
• Blood pH > 7.45: Alkaline

Role of Lungs

• Regulate pH by controlling partial pressure of carbon dioxide (PaCO2).
  • Decrease in respiratory rate/depth → CO2 retention → Respiratory Acidosis
  • Increase in respiratory rate/depth → CO2 removal → Respiratory Alkalosis

Conditions Affecting Respiratory Rate

• Increased Rate (Respiratory Alkalosis):
  • Panic attacks
  • Pulmonary embolism
  • High altitude
  • Drug overdoses (e.g., salicylates)
• Decreased Rate (Respiratory Acidosis):
  • Airway obstruction
  • Lung diseases
  • Sedatives and opioids
  • Strokes
  • Diaphragm/chest wall dysfunction

Role of Kidneys

• Regulate pH by altering bicarbonate ion concentration.
  • pH too acidic → Absorb bicarbonate
  • pH too alkaline → Excrete bicarbonate

Metabolic Acidosis

• Causes:
  • Buildup of hydrogen ions:
    • Ingestion of substances (e.g., ethylene glycol)
    • Diabetic ketoacidosis
    • CKD
  • Removal of bicarbonate:
    • Severe diarrhea
    • Addison's disease
    • Diuretics (e.g., spironolactone, acetazolamide)
  • Normal saline
  • Total parenteral nutrition

Metabolic Alkalosis

• Causes:
  • Loss of hydrogen ions:
    • Vomiting
    • Nasogastric tube suctioning
    • Diuretics
  • Retention of bicarbonate
  • Hypokalemia
  • Renal tubular disorders

Compensation Mechanisms

• Respiratory Acidosis may be compensated by Metabolic Alkalosis.
• Respiratory Alkalosis may be compensated by Metabolic Acidosis.
• Metabolic Acidosis may be compensated by Respiratory Alkalosis.
• Metabolic Alkalosis may be compensated by Respiratory Acidosis.

Next Steps

• Next video: Analyzing results of an Arterial Blood Gas (ABG).

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