A 42-year-old woman presents to her primary care physician with a chief complaint of paresthesias that started in her fingers and toes about 1 week ago. Since then, her symptoms have progressed to include paresthesias and muscle weakness in her lower legs. A nerve conduction study is performed and shows slowed nerve conduction velocities.
As her disease progresses, which of the following acidbase disorders would she be expected to develop?
A. Metabolic acidosis (anion-gap) B. Metabolic acidosis (non-anion-gap) C. Metabolic alkalosis D. Respiratory acidosis E. Respiratory alkalosis
Respiratory acidosis-the correct answer is d. this patient has guillain-barre syndrome. guillain-barre syndrome is a demyelinating disease of peripheral nerves causing acute and progressive weakness. a major complication of this syndrome is respiratory paralysis leading to hypoventilation. hypoventilation leads to an inability of the lungs to excrete the carbon dioxide the body produces, leading to retention of carbon dioxide. this causes a drop in ph and a compensatory retention of bicarbonate. these acid-base abnormalities are consistent with respiratory acidosis. hypoventilation (from a variety of etiologies) is a primary cause of respiratory acidosis.answer a is incorrect. an increase in anions would be consistent with anion-gap metabolic acidosis. metabolic acidosis is indicated by the presence of low ph with low plasma bicarbonate and low carbon dioxide and an increased anion gap, measured by ([na+] [cl] [hco3 ]), which is normally 1016 meq/l. the main causes are lactic acidosis, diabetic ketoacidosis, and renal failure.answer b is incorrect. non-anion-gap metabolic acidosis is the presence of low ph with low plasma bicarbonate without an elevated anion gap. the cause is generally gastrointestinal losses of bicarbonate (i.e., diarrhea, biliary drains, emesis, nasogastric tube losses). another important and common cause of a metabolic non-anion-gap acidosis is the presence of an ileal conduit or bladder reconstruction from colonic tissue. the gastrointestinal tissue absorbs chloride from the urine in exchange for bicarbonate. other causes include renal tubular acidosis and hyperchloremia.answer c is incorrect. metabolic alkalosis would present with a high ph, a high bicarbonate, and (with respiratory compensation) a high carbon dioxide. the causes of metabolic alkalosis include vomiting, diuretic therapy, and chloride restriction. the compensation is hypoventilation.answer e is incorrect. respiratory alkalosis can be caused only by an increase in ventilation, leading to excessive loss of carbon dioxide that is balanced by an increased excretion of bicarbonate. hence, a low carbon dioxide and low bicarbonate indicate respiratory alkalosis. this is caused by hyperventilation.