Vomiting can significantly disrupt the body’s internal balance, leading to a condition known as metabolic alkalosis. The physiological changes triggered by vomiting, particularly those affecting the body’s acid-base equilibrium, are complex. Understanding this connection involves examining how the body maintains its pH and the specific impact of losing stomach contents.
The Body’s Acid-Base Foundation
The human body meticulously maintains a stable internal environment, including its pH, a measure of acidity or alkalinity. Blood pH is kept within a narrow, slightly alkaline range of 7.35 to 7.45. Deviations from this range can impair normal bodily functions, as enzymes and proteins operate optimally within specific pH levels. When blood pH rises above 7.45, it indicates alkalosis, meaning there is too much alkalinity or insufficient acid.
Stomach Acid’s Role in Digestion
The stomach produces gastric acid, primarily hydrochloric acid (HCl), secreted by parietal cells in the stomach lining. This acid’s pH typically ranges from 1 to 3. Its strong acidity breaks down food, particularly proteins, by denaturing them and activating digestive enzymes like pepsin. The acidic environment also serves as a protective barrier, killing harmful bacteria and pathogens.
The Direct Impact of Vomiting
Vomiting directly expels the highly acidic contents of the stomach, leading to an immediate loss of hydrochloric acid. This loss removes hydrogen ions (H+), the primary determinants of acidity. This reduction in hydrogen ions shifts the body’s acid-base balance toward a more alkaline state. Concurrently, for every hydrogen ion secreted into the stomach, a bicarbonate ion (HCO3-) is released into the bloodstream. The sustained loss of gastric acid through vomiting prevents its neutralization, resulting in bicarbonate accumulation in the blood and contributing to metabolic alkalosis.
Kidney and Electrolyte Adjustments
The kidneys maintain the body’s acid-base balance by regulating bicarbonate and hydrogen ion excretion. In prolonged vomiting, kidneys can inadvertently worsen metabolic alkalosis. Vomiting causes fluid and electrolyte depletion, including chloride (Cl-) and potassium (K+). Low chloride levels (hypochloremia) cause kidneys to conserve bicarbonate, exacerbating the alkaline state.
Fluid loss also activates hormonal systems, prompting kidneys to conserve sodium. This sodium conservation often increases potassium and hydrogen ion excretion, contributing to hypokalemia and worsening alkalosis. As potassium moves out of cells, hydrogen ions shift into cells to maintain electrical neutrality, further reducing extracellular acidity.