What acid-base imbalance can frequent vomiting cause?

Frequent vomiting can lead to various acid-base imbalances, mainly including metabolic alkalosis, metabolic acidosis, respiratory alkalosis, and respiratory acidosis. If abnormalities occur, prompt medical attention is recommended. The specific analysis is as follows:

1. Metabolic Alkalosis

Frequent vomiting leads to excessive loss of gastric fluid, resulting in significant depletion of acidic substances in the stomach. This causes a decrease in hydrogen ion concentration in the body. Meanwhile, alkaline substances such as bicarbonate are excessively absorbed, leading to elevated levels of bicarbonate ions in the blood. Symptoms may include shallow and slow breathing, nausea, headache, lethargy, and reduced urine output. Mild metabolic alkalosis can be corrected by replenishing electrolyte solutions; severe cases may require intravenous administration of sodium chloride or ammonium chloride.

2. Metabolic Acidosis

Although metabolic alkalosis is the primary type of acid-base disturbance associated with frequent vomiting, metabolic acidosis may also occur if dietary habits are poor during episodes of vomiting—such as regularly consuming acidic foods—or due to prolonged fasting or starvation. In these cases, excess intake or production of acidic substances disrupts acid-base balance. Symptoms may include pallor, fatigue, increased heart rate, and continued vomiting. Mild to moderate metabolic acidosis is typically managed by administering normal saline or electrolyte solutions; severe cases require treatment under medical guidance using lactated Ringer’s solution or compound sodium chloride solution.

3. Respiratory Alkalosis

Vomiting can increase intrathoracic pressure, impairing pulmonary ventilation and causing excessively rapid elimination of carbon dioxide, thereby reducing CO₂ levels in the body. To maintain normal plasma pH, the body increases respiratory rate to expel more CO₂, further accelerating its decline and leading to respiratory alkalosis. Symptoms may include rapid breathing, numbness in hands and feet, and dizziness. Mild respiratory alkalosis can be alleviated by deep breathing and muscle relaxation; in severe cases, rebreathing into a paper bag covering the mouth and nose may help increase CO₂ reabsorption.

4. Respiratory Acidosis

Frequent vomiting may elevate intra-abdominal pressure, causing upward displacement of the diaphragm and compression of the lungs, impairing ventilation and preventing timely exhalation of CO₂. This results in CO₂ retention and hypercapnia, eventually triggering respiratory acidosis. Symptoms may include rapid or labored breathing, dyspnea, and confusion. Mild respiratory acidosis can be treated with oxygen therapy via face mask; severe cases require medications such as bronchodilators as directed by a physician.

In daily life, it is advisable to maintain adequate fluid intake to prevent dehydration and support normal acid-base balance.