Acid-Base Disorders.

Abstract

1. Benson S. Hsu, MD, MBA* 2. Saquib A. Lakhani, MD† 3. Michael Wilhelm, MD‡ 1. *Pediatric Critical Care, University of South Dakota, Sanford School of Medicine, Sioux Falls, SD. 2. †Pediatric Critical Care, Yale School of Medicine, New Haven, CT. 3. ‡Pediatric Critical Care, University of Wisconsin School of Medicine and Public Health, Madison, WI. To treat critically ill children, a physician must have a clear understanding of acid-base balance. After completing this article, readers should be able to: 1. Describe the mechanisms regulating acid-base physiology and identify blood gas abnormalities associated with an acid-base imbalance. 2. Recognize the differential diagnosis and clinical and laboratory features associated with metabolic acidosis and metabolic alkalosis as well as how to manage each appropriately. 3. Calculate an anion gap and formulate a differential diagnosis associated with various anion gap values. 4. Identify factors contributing to compensatory changes associated with primary metabolic and respiratory acidoses and alkaloses. The body’s ability to maintain acid-base homeostasis is based on a complex set of interactions between the respiratory and metabolic systems. This article reviews normal acid-base physiology and examines disorders of acid-base imbalances, first within a primary metabolic cause and then within a primary respiratory cause. Covering the complex nuances of acid-base control within a limited-scope review article is impossible. Thus, this article focuses on the traditional model based on the Henderson-Hasselbalch equation rather than the strong ion (or Stewart) model, which explores the difference between all the dissociated cations and anions. Using the traditional model, the authors explore the various metabolic and respiratory disturbances while addressing the implications of the anion gap on metabolic acidoses. ### The Henderson-Hasselbalch Equation Homeostatic control of acid-base balance is critical for all metabolic and physiologic functions of the human body. The Henderson-Hasselbalch equation describes the relationship between pH and the bicarbonate buffering system (the predominant buffering system in plasma) to establish this homeostasis:![Formula][1] ![Formula][2] When accounting for H2CO3, … [1]: /embed/graphic-1.gif [2]: /embed/graphic-2.gif