Arousal: The Disoriented, Stuporous, Agitated or Somnolent Patient

Abstract

Arousal refers to the maintenance of an appropriate level of cerebral activity to successfully complete the task in which one is engaged. Arousal occurs on a continuum from hypoarousal to hyperarousal and may fluctuate quickly. Appropriate arousal is a necessary prerequisite for consciousness. Arousal is anatomically mediated through the ascending reticular activating system (RAS), which has projections arising from the medulla and pons, projecting to the midbrain, thalamus and hypothalamus (see Chap. 3 for more details). Stimulation of the RAS is essential for maintaining consciousness at a basic neurophysiologic level. Hyperarousal produces states of agitation. States of arousal vary from coma to normal and are typically classified or categorized clinically as below. Table 5.1 presents categorical classification of arousal, response to attempts to influence arousal and course of arousal with varying stimulation.