The administration of intravenous crystalloids is ubiquitous in the care of the critically ill. Commonly available crystalloid solutions contain a broad spectrum of electrolyte compositions including a range of chloride concentrations. Recent studies of associated higher fluid chloride content with acute kidney injury and mortality but no large, randomized trials have been conducted. In preparation for a large, cluster-randomized, multiple-crossover trial comparing 0.9% sodium chloride to physiologically-balanced isotonic crystalloids (Lactated Ringers or Plasmalyte-A) in intensive care unit patients, this pilot study will enroll all patients admitted to the medical intensive care unit at a single tertiary center for a sixth month period. The primary objective will be to test the ability of an electronic order entry tool to ensure administration of assigned study fluid or record contraindications to assigned study fluid. The pilot study will also demonstrate the feasibility of collecting demographic, severity of illness, fluid management, vital sign, laboratory, acute kidney injury and renal replacement therapy, and outcome data in an automated, electronic fashion.