03.03 Fluid Volume Deficit

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Study Tools



  1. Fluid volume deficit
    1. Intravascular
    2. Intracellular
    3. Interstitial

Nursing Points


  1. Less fluid volume = dehydration
  2. Isotonic dehydration
    1. Equal loss of solutes and water
      1. Trauma
      2. Diarrhea
      3. Vomiting
      4. Excessive sweating
  3. Hypertonic dehydration
    1. Blood has MORE substance and LESS water
    2. Cells shrink/dry up
      1. Polyuria
      2. DKA -> blood full of glucose and ketones
      3. End stage renal failure -> blood not filtered of electrolytes
      4. Water deprivation
  4. Hypotonic dehydration
    1. Blood has MORE water and LESS substance
      1. hyponatremia
      2. Cells swell
  5. Third spacing
    1. Fluid moves from vessels to interstitial
    2. Generalized
  6. Complications
    1. Diminished organ perfusion
    2. Hypovolemic shock
    3. MODS


  1. Presentation
    1. Low blood pressure (fluid shifting)
    2. High heart rate (compensate for low volume)
    3. Weak pulses
    4. Consentrated urine
    5. Thirsty
  2. Doctor order
    1. Urine osmolality (measures solutes in urine)
    2. Electrolyte measurement (sodium)

Therapeutic Management

  1. Intake and output monitoring
  2. Vital signs
  3. Weigh patient daily
  4. Doctor orders
    1. IV fluid resusitation
      1. Treat cause of fluid loss
      2. Isotonic
        1. 0.9% Normal saline
        2. Lactated ringers
      3. Hypotonic
        1. 0.45% Normal Saline
        2. More water than solutes
        3. Pushes water into cells
      4. Hypertonic
        1. D5NS
        2. D5 0.45%NS
        3. More solutes than water
        4. Pulls water out of cells
    2. Electrolyte administration as needed
    3. Blood transfusions (trauma)

Nursing Concepts

  1. Perfusion
    1. Decreased volume = decreased perfusion
  2. Fluid and Electrolyte Balance
    1. Imbalanced electrolytes
    2. Decreased fluid volume
  3. Elimination
    1. Too much elimination = fluid volume deficit

Patient Education

  1. Plan everyday activities -> stay hydrated and cool
    1. Elderly need reminders often (decrease in thirst)
  2. Manage diabetes
    1. Check BS levels regularly
    2. Take prescribed medication
    3. Diabetic diet
  3. Manage renal failure
    1. Dialysis
    2. Renal diet


Hey guys! Welcome to the lesson on fluid volume deficit where we will explore the different ways that the body may be lacking fluid and how it affects our patients. 

So when a patient is fluid volume deficit, they don’t have enough fluid in the body for proper functioning resulting in dehydration. Our patients lack fluid intravascularly which means less fluid in the blood vessels. Intracellular fluid deficit means less fluid in the cells, so the cells are dehydrated. Interstitial fluid deficit means not enough fluid interstitially which is in the space outside of the vessels. Next let’s review osmolality to get a good grasp on fluid movement in the body.

Osmolality is the concentration of solutes in water. So our body likes things to be equal, this is called homeostasis, so there should be equal solute and water both inside and outside of the cells like in this picture. If there is more solute inside of the cell, the fluid will move into the cell to try and equal it out. Remember, where solute goes, water goes. If there is more solute outside of the cells, fluid will move out off the cells and into the vascular space. Now you’re ready to explore the three different categories of dehydration, isotonic, hypertonic, an hypotonic.  Let’s start with isotonic. 

Isotonic dehydration is where there is an equal deficit of solutes and water in the body. This might be caused by trauma where the patient lost a lot of blood, diarrhea, vomiting, or excessive sweating. Think of anything that causing loss of both water and solutes or substances such as sodium. Now let’s talk about hypertonic dehydration.

In hypertonic dehydration, the patient has lost water leaving them with more substance and less water in the body. Examples are polyuria, DKA, end stage renal failure, or water deprivation. Let’s focus on renal failure. So with renal failure the kidneys are unable to filter the solutes out of the blood. The solutes build up in the bloodstream, and cause the fluid to leave the cells and go into the bloodstream leaving the cells dehydrated. Now let’s discuss hypotonic dehydration. 

In hypotonic dehydration, there is more water, and less substance, so the patient is lacking in solutes in the bloodstream causing the fluid to move into the cells, making them swollen and at risk for exploding. This patient is at risk for cerebral edema where the patient will be confused.

So with hyponatremia, the patient doesn’t have enough sodium in the bloodstream, so the fluid goes into the cells. So anything that may cause low sodium, like prolonged use of thiazide diuretics for example, may result in hypotonic dehydration. Okay, next let’s talk about fluid shifting. 

So fluid shifting or third spacing is where fluid moves from the vessels and into the interstitial space. This leaves less volume in the bloodstream, making it harder to perfuse the organs. The patient will probably have generalized edema from that fluid sitting in the interstitial space. Fluid shifting will result in hypovolemic shock, and eventually the organ systems will shut down because they aren’t getting the oxygen and nutrients that they need. Check out the lesson on SIRS and MODS to get more details on multiple organ dysfunction syndrome. Now let’s talk about what this patient might look like. 

So the patient that is fluid volume deficit will probably have a low blood pressure from the decreased volume of fluid in the bloodstream. The heart rate will go up to compensate for that low volume. The pulses may feel weak because there isn’t a lot of pressure in the bloodstream. The patient’s urine may be dark and concentrated and they might feel thirsty. If they have hypotonic dehydration, they may be confused from those cells being swollen in the bloodstream and into the brian. 

When the doctor suspects that the patient is deficit of fluid, they may order electrolyte lab draws like sodium to check to help decide on a treatment plan for the patient. Urine osmolality may be ordered as well to measure the solutes in the urine. Now let’s explore management of hypovolemia. 

So it’s important to measure the intake and output of the patient. This means measuring any liquid that the patient consumes, and anytime the patient urinates, vomits, or any other output from the body. The doctor might order foley catheter placement to make sure we are getting super accurate numbers. This helps to keep track to make sure that intake and output are relatively equal. If it’s not, the doctor may change orders accordingly. VItal signs are important to assess for hypovolemic shock. We should weigh the patient’s daily because quick changes in weight can indicate fluid deficit or overload. Next let’s talk about doctor orders.

Depending on the lab draw levels, the doctor may order electrolytes by mouth or IV. Blood transfusions may be needed for trauma patients. IV fluids are the main treatment of fluid volume deficit, so let’s talk about the three different categories of IV fluids. 

Isotonic solutions are most commonly used for treatment of all types of dehydration because there is an equal solute to water ratio. Isotonic solutions include 0.9 percent normal saline or lactated ringers solution. Hypotonic solution has more water than solute in it, like half normal saline. This may be ordered to treat hypertonic dehydration to push water back into the cells. Hypertonic IV fluid has more solute than water like D5 normal saline or D5 half normal saline. These fluids have dextrose and saline which are both solutes. Hypertonic IV solutions might be ordered to treat hypotonic dehydration to bring the fluid back out of the cells and into the bloodstream. Now let’s move on to patient education. 

So our patients should be educated to stay hydrated. This is easier to do if they plan out their daily activities. The elderly need reminders to drink as they have a decrease in thirst. Our patients need to know how to manage their chronic illnesses like diabetes and chronic kidney disease by eating the right diets and following doctor orders. 

Our priority nursing concepts for the patient with fluid volume deficit include perfusion, fluid and electrolyte balance, and elimination.

Okay, let’s review the key points about fluid volume deficit. There are different types of dehydration. In isotonic dehydration, the depletion of water and solutes are equal. In hypotonic dehydration, the depletion of water is greater than the depletion of solutes. This makes the water move into the cells where there are more solutes, causing them to swell and possibly burst. Hypertonic dehydration is when the body is more depleted of solutes than water. This causes the fluid to move from the cells, causing them to shrink. Complications include fluid shifting from intravascular to the interstitial space. Hypovolemic shock may occur where isn’t enough fluid volume in circulation to perfuse the body. Eventually organs will shut down, leading to MODS, and then death if not treated. The patient should be educated to stay hydrated and plan daily activities. Elderly need reminders to drink as they have a decrease in thirst. Patient’s need educated on managing their chronic illnesses like diabetes and chronic kidney disease to avoid complications that result in fluid volume deficit. 

I know that was a lot of information, but I hope you have a good grasp on the different ways the body may be deficit in fluid. Now go out and be your best self today, and as always, happy nursing!