Surgical Critical Care: Metabolic Alkalosis

Causes

• Gastrointestinal Hydrogen Loss
  • Vomiting
  • High Nasogastric Tube Output
• Renal Hydrogen Loss
  • Furosemide (Lasix)
  • Bartter Syndrome
  • Gitelman Syndrome
  • Conn Syndrome (Primary Mineralocorticoid Excess)
• Intracellular Shift of Hydrogen
  • Hypokalemia
• Contraction Alkalosis
  • Loss of Fluid (High in Sodium & Chloride) without Proportional Loss of Bicarbonate
    • Also Possibly Effected by RAAS Activation Increasing Bicarbonate Reabsorption
  • Causes: Furosemide, Emesis, Cystic Fibrosis, Congenital Chloride Diarrhea, etc.

Physiologic Changes

• *See Surgical Critical Care: Acid-Base Disorders – Physiologic Changes

Chloride-Responsiveness

• Additional Test to Determine the Cause of Metabolic Alkalosis
• Responsiveness Based on Urine Chloride (UrCl)
• UrCl < 15: Chloride Responsive
  • Alkalosis Caused by Loss of Hydrogen Atoms
  • Includes: Vomiting, High NG Output & Furosemide
• UrCl > 25: Chloride Resistant
  • Alkalosis Caused by Increased Bicarbonate
  • Includes: Conn Syndrome, Bartter Syndrome or Hypokalemia

Treatment

• Treatment of Underlying Etiologies
• Contraction Alkalosis – IV Fluids (NS – Chloride Replacement is Most Important)
  • May Consider Acetazolamide (Diamox) if Additional Diuresis is Required