Volume depletion is characterised by a reduction in extracellular fluid volume that occurs when salt and fluid losses exceed intake on a sustained basis.
The most common aetiologies are haemorrhage, vomiting, diarrhoea, diuresis, or third-space sequestration.
A detailed history and physical examination are crucial in determining the aetiology.
Signs and symptoms may include some of the following: postural dizziness, fatigue, confusion, muscle cramps, chest pain, abdominal pain, postural hypotension, or tachycardia.
Clinical symptoms usually do not manifest until large fluid losses have occurred.
Without proper assessment and timely resuscitation, volume depletion can lead to circulatory collapse and shock.
May be accompanied by electrolyte disturbance or acid-base disturbance.
In most situations, isotonic saline is the best initial treatment for volume depletion.
Volume depletion is a reduction in extracellular fluid volume that occurs when salt and fluid losses exceed intake on a sustained basis.    It may result from renal losses (diuresis) or extrarenal losses (from the gastrointestinal tract, respiratory system, skin, fever, sepsis, or third-space sequestration).  Without proper assessment and timely resuscitation, volume depletion can lead to circulatory collapse and shock. 
Dehydration and volume depletion are not the same, although they can co-exist in the same patient at the same time. Although often used interchangeably, it is important to distinguish one from the other. Dehydration implies a total body water deficit, alone or in excess of sodium loss, with a subsequent increase in plasma tonicity that usually comes to clinical attention as hypernatraemia. This hypertonicity implies intracellular water contraction whereas volume depletion implies blood volume contraction.  Symptoms of pure water loss arise from the effects of increased osmolality and reflect the cellular responses to hypertonicity: confusion, thirst, impaired sensorium, and, in more extreme cases, coma or seizures. By contrast, clinical symptoms of volume depletion are a result of the haemodynamic effects of the reduction in intravascular volume and usually do not involve neurological changes.
Feinberg School of Medicine
SKH is an author of a reference cited in this monograph.
Division of Nephrology and Hypertension
Department of Internal Medicine
Northwestern Memorial Hospital
DB is an author of a reference cited in this monograph.
Dr Syed K. Haque and Dr Daniel Batlle would like to gratefully acknowledge Dr Maria Aurora Posadas Salas, Dr Jason Eckel, and Dr Arthur Greenberg, previous contributors to this monograph. MPS, JE, and AG declare that they have no competing interests.
Infection Control Lead for Medical Directorate
Derby City Hospital
NK declares that he has no competing interests.
Chicago Medical School
Rosalind Franklin University
IM declares that he has no competing interests.
Department of Internal Medicine
Division of Nephrology
University of Iowa Hospital and Clinics
MS declares that he has no competing interests.
Washington Hospital Center
JHV declares that she has no competing interests.
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