Metabolic alkalosis

Disease Description (Causes and Symptoms)

• Definition: Metabolic alkalosis is a condition in which blood pH exceeds 7.45 and blood bicarbonate (HCO3−) is increased, representing a metabolic (nonrespiratory) abnormality of acid-base balance.
• Main causes: Excessive loss of gastric juices (persistent vomiting, nasogastric suction), contraction alkalosis due to reduced body fluid volume (dehydration and diuretic use), excess aldosterone (primary/secondary aldosteronism), excessive use of antacids (bicarbonate), massive blood transfusion (citrate), reduced renal excretory capacity, etc.
• Pathophysiology summary: Loss of H+ and Cl− or reduced body fluid volume increases renal HCO3− reabsorption or suppresses its excretion, resulting in increased alkalinity in the blood. Hypokalemia and hypochloremia commonly occur together and worsen symptoms.
• Main symptoms: Neuromuscular hyperexcitability (tingling, tremors, muscle cramps/rigidity, muscle weakness), numbness, reduced intestinal motility (paralytic ileus), arrhythmias, confusion·disorientation·delirium·seizures (in severe cases), slow and shallow breathing (respiratory compensation), alkaline urine.
• Test findings: Arterial blood gas shows pH>7.45 and increased HCO3−; hypokalemia and hypochloremia are often present; measuring urine chloride (urine Cl−) can help determine the cause (Cl− <20 mmol/L: chloride-responsive — such as vomiting/fluid depletion; Cl− >20 mmol/L: chloride-resistant — such as aldosterone excess).

Treatment Methods and Precautions

• General principles: Correct the cause (treat vomiting/suction, discontinue antacids, adjust diuretics, treat aldosterone excess), correct electrolytes (especially K+ and Cl−) and fluid status, and prevent symptoms and complications.
• Fluid and electrolyte replacement
  • Restore fluid volume and promote urinary HCO3− excretion with 0.9% sodium chloride normal saline (IV).
  • If hypokalemia is present, replace potassium with potassium chloride (KCl) (oral treatment for mild cases; intravenous treatment for moderate to severe cases).
• Medication treatment
  • If caused by diuretics, discontinue the diuretic or adjust its dose.
  • When fluid cannot be administered because of edema or heart failure (concern about salt overload), or when promotion of urinary HCO3− excretion is needed, use acetazolamide (a carbonic anhydrase inhibitor).
  • If the cause is aldosterone excess, use mineralocorticoid antagonists such as spironolactone or eplerenone.
  • In severe or treatment-resistant cases (such as impaired consciousness or risk of arrhythmia due to severe alkalosis), adjust pH in the intensive care unit with IV HCl or an ammonium salt (in extremely rare cases) (administered under the direction of a specialist).
• Monitoring: Continuously monitor serum electrolytes (especially K+, Cl−, and Na+), blood gases, electrocardiogram (for arrhythmia monitoring), body weight, urine output, and clinical symptoms.
• Complication precautions: Fatal arrhythmias due to severe hypokalemia, muscle weakness·respiratory failure, and neurological complications (confusion·seizures).
• Self-care precautions: Do not take excessive antacids (bicarbonate), consult a medical professional promptly in case of dehydration, and consult a medical professional about continuing or stopping prescribed diuretics and supplements.

Outpatient Visit Checklist (Items to Bring and Example Questions)

• Items/information to bring
  • A list of all currently used medications and supplements (including diuretics, antacids, and supplements).
  • Recent blood test results (electrolytes and kidney function) and arterial blood gas results, if available.
  • Notes recording when symptoms began and how they have progressed (including whether vomiting occurred, diarrhea, weight changes, changes in urine output, and muscle weakness).
  • Existing diagnoses (such as heart failure, liver disease, and endocrine disease) and a history of previous hospitalizations and surgeries.
  • A copy of a recent electrocardiogram (ECG), if available.
• Key information to provide to the medical professional during the outpatient visit
  • A recent history of vomiting, nasogastric suction, or antacid use; the duration and dosage of diuretic use; and changes in fluid intake.

Examples of General Questions to Ask the Doctor

• "What additional tests do I need to determine the cause of this condition with certainty?"
• "How low or high are my current electrolyte levels, especially potassium, and do I need hospitalization or intravenous treatment?"
• "What are the main side effects and precautions of the medication you plan to prescribe?"
• "What is the prognosis after treatment (the likelihood of complete recovery and the risk of recurrence)?"

Examples of Condition-Specific Questions

• "If vomiting is suspected to be the main cause, how does a urine chloride (urine Cl−) test help with interpreting the results?"
• "If I am using diuretics, when should I stop them, and what alternative medications or management methods are available?"

(When necessary, the medical professional will individualize the determination of the cause and the treatment plan based on the test results and clinical symptoms provided.)