Acute and Chronic Metabolic Alkalosis (Base bicarbonate excess)

Definition: metabolic alkalosis is a clinical disturbance characterized by a high pH (decrease H+ concentration) and a high plasma bicarbonate concentration

It can be produced by a gain of bicarbonate or a loss of H+ (khanna and khurtzman 2001) Probably the most common cause of metabolic alkalosis is vomiting or gastric function with loss of hydrogen and chloride ions

This order also occurs in pyloric stenosis, in which only gastric fluid is lost Gastric fluid has an acid pH (usually 1-3)

Therefore loss of highly acidic fluid increase the alkalinity of body fluids Other loss of K+ such as diuretic therapy that promotes excretion of K+ (furosemide)

Hypokalemia produces alkalosis In two ways

  1. The kidney conservative potassium
  2. Cellular K+ moves out of the cell into ECF

Chronic metabolic alkalosis can occur with long term diuretic therapy, villous adenoma, external drainage of gastric fluids, cystic fibrosis and chronic ingestion of milk and calcium carbonate

Clinical Manifestation

  • Primary symptoms related to decreased calcium ionization such as tingling of the finger and toes, dizziness, and hypertonic muscles Serum Ca+ level decreased in alkalosis as more Ca+ combines with serum proteins
  • Respirations are depressed as compensatory action by the lungs
  • Arterial tachycardia may occur As pH increases above 7.6 and hypokalemia develops Ventricular disturbance may occur
  • Decreased motility and paralytic ileus may also occur Symptoms of chronic metabolic alkalosis are same as for acute metabolic alkalosis
  • ABG’s – pH greater than 7.45 and serum bicarbonate concentration greater than 20mEq/L Serum electrolytes – decreased Ca+ + K+

Management

  • Treatment aimed at reversing the underlying disorder
  • Sufficient chloride must be supplied for kidney to absorb sodium with chloride Restoring normal fluids by Na+Cl fluids
  • To maintain alkalosis Administer K+CL
  • Histamine – 2 – receptor antagonists (cimitidine)
  • Management of chronic metabolic alkalosis is aimed to correct underlying acid- base disorder

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