Principles of Fluid Therapy

Administering intravenous (IV) fluid is one of the most common interventions in the intensive care unit (ICU). Although IV fluid can be used to replace free water, electrolytes, glucose, and plasma constituents (e.g., albumin), most IV fluid in the ICU is given to increase intravascular volume. Critically ill adults frequently experience either absolute hypovolemia (resulting from blood loss, diarrhea, decreased oral intake) or effective hypovolemia (increased venous capacitance resulting from sepsis, medications, adrenal insufficiency). IV fluid resuscitation can increase ventricular preload, cardiac output, and oxygen delivery, restoring hemodynamic stability and tissue perfusion. This chapter discusses the physiologic rationale for fluid therapy in the ICU; the volume, rate, and end points of fluid resuscitation; choice of fluid; and areas of ongoing controversy.