Accurate assessment of the relationship between abnormal blood gas findings and a patient’s overall clinical condition is a common challenge for pediatric critical care nurses. To meet this challenge, nurses must understand the mechanisms underlying acid-base balance and the common causes of acid-base imbalance. Typically, acid-base balance is maintained by cellular buffers, the respiratory system, and the renal system. Often, when one or more mechanisms are compromised by illness or injury, the acid-base balance is also compromised. Clinically, the resulting imbalances are described as respiratory acidosis, respiratory alkalosis, metabolic acidosis, and metabolic alkalosis.
In this article, I focus on metabolic acidosis, which can occur in a variety of clinical contexts in the pediatric intensive care unit. I review the basic concepts of acid-base balance; examine the 2 types of metabolic acidosis, normal and elevated anion gap acidosis; and discuss the common causes of each type of metabolic acidosis. Case studies...