What is the first electrolyte imbalance that occurs from SBO due to loss of hydrochloric acid?

In the scenario of a small bowel obstruction (SBO), vomiting frequently occurs, leading to the loss of hydrochloric acid from the stomach. Hydrochloric acid is primarily composed of hydrogen ions and chloride ions, and its loss ultimately affects the body's acid-base balance. When hydrochloric acid is lost through vomiting, there is a decrease in hydrogen ion concentration in the body, resulting in a relative increase in bicarbonate ions. This shift creates a more alkaline environment, leading to metabolic alkalosis.

Metabolic alkalosis is characterized by an elevated blood pH due to excess bicarbonate or a deficit of hydrogen ions. This is the primary reason why alkalosis is the first electrolyte imbalance seen in this context.

Other electrolyte imbalances might follow as the body continues to compensate for ongoing fluid and electrolyte losses, but the immediate consequence of the loss of hydrochloric acid is the elevation of pH, indicative of alkalosis.