Metabolic Acidosis Lecture Notes

Introduction

• Metabolic Acidosis: Occurs when too many acids are in the body, leading to a decrease in blood pH and bicarbonate (HCO3) levels.
  • Causes:
    • Excessive acid production.
    • Failure to excrete acids.

Causes and Mnemonic: "ACIDS"

• A: Accumulation of lactate (Lactic acidosis, occurs in sepsis).
• C: Chronic diarrhea (loss of bicarbonate through stool).
• I: Impaired renal function (kidneys fail to excrete hydrogen ions).
• D: Diabetic ketoacidosis (increase in ketone production).
• S: Salicylate toxicity (excess acidic substances).

Acid-Base Balance

• Acid Metabolism: Breakdown of fats, carbs, proteins produces acids.
• Definition of Acids: Release hydrogen ions in solution.
• pH Range: 7.35 to 7.45 is normal.
  • Below 7.35: Acidic.
  • Above 7.45: Alkaline.
• Hydrogen Ions: Affect pH level.
• Base to Acid Ratio: 20:1 for balance.
• Neutralization: Bases neutralize acids.

Systems Involved

• Respiratory System: Controls carbon dioxide (either retains or exhales CO2).
  • Fast, deep breathing (Kussmaul breathing) to exhale CO2 and reduce acidity.
• Renal System: Slower response.
  • Modulates bicarbonate levels to neutralize acids.
  • Can excrete hydrogen ions to balance pH.

Carbonic Acid

• Formed from CO2 and H2O, breaks down to hydrogen ions.

Understanding Arterial Blood Gases (ABGs)

• Blood pH: Normal is 7.35 to 7.45; in acidosis, it's < 7.35.
• Bicarbonate (HCO3): Normal 22-26 mEq/L; in acidosis, < 22.
• PaCO2: Normal 35-45 mm Hg; can be normal or < 35 if compensating.

Example Problem and Interpretation

• ABG Problem: pH 7.26, HCO3 17, PaCO2 39
  • Method: Tic-tac-toe for categorization.
  • Result: Metabolic acidosis with no compensation.

Patient Assessment

• Breathing: Fast, deep breathing (to reduce CO2).
• Neurological Signs: Confusion, weakness.
• Blood Pressure: Affected.
• ECG Changes: Monitor T waves for hyperkalemia.

Nursing Interventions and Treatments

• Identify and Treat Cause: Depends on underlying cause (refer to ACIDS mnemonic).
• Monitor Electrolytes: Especially potassium for hyper/hypokalemia.
• Neurostatus: Ensure safety.
• IV Fluids: Sodium bicarbonate or normal saline.
• Renal Failure: Dialysis might be needed.

Conclusion

• Recap on metabolic acidosis.
• Additional resources available for further learning.