Volume status is a balance between water and solutes, the majority of which is Na. Volume depletion (also known as hypovolemia) refers to a loss of both water and Na, whereas dehydration refers only to a loss of water. Dehydration is primarily caused by decreased water intake and presents with increased thirst and can progress to altered mental status and low blood pressure if severe. Volume depletion can be caused by GI losses, renal losses, bleeding, poor oral Na intake, or third spacing of fluids. The clinical presentation has relatively nonspecific symptoms but will ultimately cause low blood pressure if severe. The diagnosis of these imbalances is based on lab findings in addition to clinical symptoms and signs, which can be subtle and unreliable. Management requires differentiation between these 2 conditions. The treatment is to administer fluids with tonicity similar to those lost; isotonic fluids are used for volume depletion, and hypotonic fluids are used for dehydration.
Last updated: Feb 28, 2023
Dehydration refers only to a loss of water, while volume depletion refers to a loss of both water and Na+.
The relative differences between losses of water and Na determine how water shifts between the fluid compartments of the body. With volume depletion and dehydration, there are fluid shifts between the compartments.
The clinical presentation of dehydration and volume depletion varies greatly depending on the severity, from asymptomatic to potentially fatal hypovolemic shock Shock Shock is a life-threatening condition associated with impaired circulation that results in tissue hypoxia. The different types of shock are based on the underlying cause: distributive (↑ cardiac output (CO), ↓ systemic vascular resistance (SVR)), cardiogenic (↓ CO, ↑ SVR), hypovolemic (↓ CO, ↑ SVR), obstructive (↓ CO), and mixed. Types of Shock.
Determining the volume status Volume Status ACES and RUSH: Resuscitation Ultrasound Protocols is often challenging, and the history, physical exam, and lab results must be integrated. Outside of extremes, signs and symptoms of dehydration are subtle and unreliable and should not be used alone for detecting dehydration and volume depletion.
The primary management of hypovolemia Hypovolemia Sepsis in Children is to replace the fluids lost with similar tonicity Tonicity Plasma tonicity refers to the concentration of only the osmotically active solutes in blood Renal Sodium and Water Regulation of fluids; electrolytes Electrolytes Electrolytes are mineral salts that dissolve in water and dissociate into charged particles called ions, which can be either be positively (cations) or negatively (anions) charged. Electrolytes are distributed in the extracellular and intracellular compartments in different concentrations. Electrolytes are essential for various basic life-sustaining functions. Electrolytes must also be monitored.
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