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: 29 Apr, 2022
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.
Distribution of total body water Total body water Body Fluid Compartments within the body
Image by Lecturio.Dehydration: Summary of
Isotonic
Isotonic
Solutions having the same osmotic pressure as blood serum, or another solution with which they are compared.
Renal Sodium and Water Regulation and
Hypotonic
Hypotonic
Solutions that have a lesser osmotic pressure than a reference solution such as blood, plasma, or interstitial fluid.
Renal Sodium and Water Regulation.
BNa+= total body
sodium
Sodium
A member of the alkali group of metals. It has the atomic symbol na, atomic number 11, and atomic weight 23.
Hyponatremia
SIADH
SIADH
Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a disorder of impaired water excretion due to the inability to suppress the secretion of antidiuretic hormone (ADH). SIADH is characterized by impaired water excretion leading to dilutional hyponatremia, which is mainly asymptomatic but may cause neurologic symptoms. S
Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) =
syndrome of inappropriate antidiuretic hormone secretion
Syndrome of inappropriate antidiuretic hormone secretion
Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a disorder of impaired water excretion due to the inability to suppress the secretion of antidiuretic hormone (ADH). SIADH is characterized by impaired water excretion leading to dilutional hyponatremia, which is mainly asymptomatic but may cause neurologic symptoms. S
Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH)
Review of disorders of water and Na
NaHCO3:
sodium
Sodium
A member of the alkali group of metals. It has the atomic symbol na, atomic number 11, and atomic weight 23.
Hyponatremia
bicarbonate
Bicarbonate
Inorganic salts that contain the -HCO3 radical. They are an important factor in determining the ph of the blood and the concentration of bicarbonate ions is regulated by the kidney. Levels in the blood are an index of the alkali reserve or buffering capacity.
Electrolytes
The clinical presentation Presentation The position or orientation of the fetus at near term or during obstetric labor, determined by its relation to the spine of the mother and the birth canal. The normal position is a vertical, cephalic presentation with the fetal vertex flexed on the neck. Normal and Abnormal Labor 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.
Decreased
skin
Skin
The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue.
Skin: Structure and Functions turgor (i.e.,
skin
Skin
The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue.
Skin: Structure and Functions tenting when pinched):
A sign of decreased total body Na+.
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.