Integrative basic sciences: change in mental status.

This case discussion is part of the Integrating Basic Science Into Clinical Teaching Initiative. It examines the presentation of altered mental status and describes the underlying physiology, which explains the basic laboratory findings in an attempt to reach a diagnosis. This article describes a 13-year-old boy who presented to the emergency department with altered mental status after being found unconscious and alone in an abandoned building. He was unresponsive to painful and verbal stimuli, with otherwise normal findings on physical examination. Basic laboratory studies, including arterial blood gas, electrolytes, and serum osmolality, were obtained. The case discussion uses fundamentals of anatomy to build a focused differential diagnosis. The laboratory studies are interpreted using basic physiologic principles, including acid-base balance, anion gap, and osmolar gap, to determine the most likely cause of this patient's altered mental status. Subsequent investigation confirms a diagnosis of ethanol toxic effects. An understanding of electrolyte and acid-base physiology allows the clinician to use basic laboratory studies to build a focused differential diagnosis for altered mental status. This case discussion demonstrates how basic science principles of anatomy and physiology can be applied in clinical settings.