The intensive care unit (ICU) can be a challenging environment for health care practitioners who are not trained in critical care medicine. A structured approach to patient care is necessary in order to achieve optimal clinical outcomes. The purpose of this two-part article is to review essential highlights of critical care medicine for the nonintensivist. We provide a structured overview of the management of the critically ill patient and focus on problems commonly encountered in the heterogeneous ICU patient population. In Part 1 we review (a) altered states of consciousness and sedation, (b) respiratory failure and ventilators, (c) cardiovascular monitoring and management, and (d) fluid and electrolyte disorders.