The key difference between hypovolemia and dehydration is that hypovolemia is a condition where there is a low extracellular fluid volume that is normally secondary to combined sodium and water loss, while dehydration is a condition where the body loses more fluid than it takes in.
Hypovolemia and dehydration are two medical conditions of salt and water depletion that may occur concurrently or independently. These two terms are often used interchangeably. However, they represent different pathophysiologic conditions that often overlap. In hypovolemia, the fluid loss is from the extracellular compartment, but in dehydration, the fluid loss is from both intracellular and extracellular compartments.
1. Overview and Key Difference
2. What is Hypovolemia
3. What is Dehydration
4. Similarities – Hypovolemia and Dehydration
5. Hypovolemia vs Dehydration in Tabular Form
6. Summary – Hypovolemia vs Dehydration
What is Hypovolemia?
The physiologic definition of hypovolemia is a balanced loss of sodium/potassium salts and water, which causes low extracellular fluid volume. It is also defined as volume depletion. Hypovolemia can also be due to a decrease in blood volume. Hypovolemia can occur due to causes related to the kidney: loss of body sodium and consequent intravascular water, osmotic diuresis, overuse of pharmacologic diuretics, impaired response to hormones controlling salt and water balance, and kidney tubular injury. The other causes include loss of bodily fluid due to gastrointestinal losses, skin losses, respiratory losses, build-up of fluid in the empty spaces of the body due to acute pancreatitis, intestinal obstruction, increase in vascular permeability, hypoalbuminemia, and loss of blood.
The early signs of hypovolemia include headache, fatigue, weakness, thirst, and dizziness. The most severe symptoms of this condition may include oliguria, cyanosis, abdominal and chest pain, hypotension, tachycardia, old hands and feet, and progressively altering mental status. Hypovolemia can be diagnosed through physical examination and diagnostic laboratory tests (blood tests, central venous catheter, arterial line, urine output measurement, blood pressure, SpO2, or oxygen saturation monitoring). The treatments for hypovolemia may include fluid replacement through intravenous fluid tube injectors, blood transfusion, giving crystalloid solutions, giving colloids, and addressing other causes of hypovolemia such as treating an infection or illness, healing a wound, and providing missing nutrients.
What is Dehydration?
The physiologic definition of dehydration is the fluid loss that is predominantly due to water loss that contains little or no salt (sodium or potassium). In normal physiology, dehydration is the lack of total body water with a disruption of metabolic processes. This condition occurs when free water loss exceeds free water intake. The causes usually include exercise, fever, disease (hyperglycaemia and diarrhoea), high environmental temperature, as a side effect of certain drugs, and immersion diuresis. The symptoms of dehydration are headaches, general discomfort, loss of appetite, decreased urine volume, confusion, unexplained tiredness, purple fingernails, seizures, and impaired cognitive function.
Dehydration can be diagnosed through physical signs and symptoms, blood tests, and urinalysis. Furthermore, the treatments for dehydration may include replacing lost fluid and lost electrolytes, using over-the-counter rehydration solutions, drinking more water or other fluids, using sports drinks containing electrolytes and a carbohydrate solution while exercising. In emergency situations after hospitalization, salts and fluids can be delivered intravenously.
What are the Similarities Between Hypovolemia and Dehydration?
- Hypovolemia and dehydration are two medical conditions of salt and water depletion that may occur concurrently or independently
- These two terms are often used interchangeably.
- Both conditions can be diagnosed through physical signs and blood tests.
- They are easily treatable conditions by delivering water or other fluids intravenously.
What is the Difference Between Hypovolemia and Dehydration?
Hypovolemia refers to a condition characterized by low extracellular fluid volume normally secondary to combined sodium and water loss, while dehydration refers to a condition when the body loses more fluid than it takes in. This is the key difference between hypovolemia and dehydration. Furthermore, in hypovolemia, the fluid loss is from the extracellular compartment, while in dehydration, the fluid loss is from both intracellular and extracellular compartments.
The following table summarizes the difference between hypovolemia and dehydration.
Summary – Hypovolemia vs Dehydration
The terms hypovolemia and dehydration are commonly used interchangeably. But they refer to different physiological conditions resulting from different types of fluid loss. These two medical conditions of salt and water depletion may occur concurrently or independently. In hypovolemia, there is low extracellular fluid volume, which is normally secondary to combined sodium and water loss. In dehydration, there is a lack of total body water with a disruption of metabolic processes when free water loss exceeds free water intake. This is the key difference between dehydration and hypovolemia.
1. “170225 CVS Hypovolemic Shock Pathophysiology of Disease” By Doyouseewhy7 – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Woman drinking water” (CC0) via Pxhere