Metabolic Alkalosis

Overview

• Metabolic alkalosis results in:
  • Elevated blood pH
  • Elevated bicarbonate (HCO3-) levels
• Causes:
  • Excessive loss of acids (e.g., hydrogen ions)
  • Increase in bases (e.g., bicarbonate)

Causes of Metabolic Alkalosis: Remember "ALKALI"

• Acid loss via stomach
  • Over-suctioning, vomiting = loss of hydrogen ions
• Low chloride levels
  • Leads to reduced excretion of bicarbonate by kidneys
• K loss (Hypokalemia)
  • Hydrogen ions move into cells, reducing their extracellular concentration
• Aldosterone increase
  • Conditions like hyperaldosteronism cause sodium retention and hydrogen ion loss
• Loop & thiazide diuretics
  • Increase urinary output of potassium, leading to hypokalemia and affecting hydrogen ion concentration
• Infusing too much sodium bicarbonate IV
  • Happens when treating metabolic acidosis, flipping patient into alkalosis

Understanding Bases

• Bases neutralize acids by binding with hydrogen ions
• High hydrogen ion concentration = low blood pH (acidic)
• Low hydrogen ion concentration = high blood pH (alkaline)
• Optimum blood pH range: 7.35 to 7.45
• Bases-to-acids ratio: 20:1
• Important base in the body: Bicarbonate (HCO3-)

Body's Acid-Base Regulatory Systems

Respiratory System

• Affects carbon dioxide (CO2) levels through changes in respiratory rate and depth
  • Fast & deep breathing: blows off CO2, beneficial in acidosis
  • Slow breathing: retains CO2, beneficial in alkalosis

Renal System

• Retains hydrogen ions and excretes bicarbonate
• Essential for long-term acid-base balance

Arterial Blood Gas (ABG) Analysis in Metabolic Alkalosis

• Key indicators:
  • Blood pH: > 7.45 (alkaline)
  • Bicarbonate: > 26 mEq/L (elevated)
  • PaCO2: normal (35-45 mm Hg) or elevated if compensating

Tic-Tac-Toe Method for ABG Analysis

• Example ABG values:
  • pH: 7.53 (alkaline)
  • PaCO2: 49 mm Hg (acidic, compensating)
  • HCO3-: 28 mEq/L (alkaline)
• Compensation status: Partially compensated (PaCO2 elevated, trying to retain CO2)

Signs and Symptoms

• Bradycardia: slow respirations, can lead to respiratory failure
• ECG changes:
  • Depressed ST segment
  • Inverted T-wave
  • Potential presence of U-wave
• Hypokalemia: muscle cramps, tremors, tetany

Nursing Interventions

• Monitor:
  • ECG, respiratory status, neuro status
  • Electrolyte levels (potassium and chloride)
• Manage vomiting with antiemetics
• Adjust diuretics (loop and thiazide) if needed
• Possible administration of acetazolamide (Diamox) to decrease bicarbonate reabsorption