One of the most common fluid imbalances is dehydration.  This is also known as Extracellular Fluid Volume Deficit or ECFVD.  Basically, there is a lack of fluid around the cells and in the vascular spaces.  I’m not going to go into all the details of how this process works, but basically there is a loss of extracellular fluid.  This loss changes the osmolality of the extracellular space and causes it to pull the fluid out of the cells by osmosis (remember those words from the last post?).  This causes a loss of intracellular fluid which eventually leads to a decreased urine output.

There are three types of dehydration; mild, moderate, and severe.  Mild is a loss of 2% of body weight.  Moderate is a loss of 5% of body weight.  Severe is a loss of 8% of body weight.  There are also three categories that go along with these, which are used to determine how to treat the dehydration.  We’ll talk more about that next time.  These three categories are isotonic (water and electrolyte losses are equal), hypotonic (more electrolytes are lost than fluid), and hypertonic (more fluid is lost than electrolytes).

So what causes dehydration?  There are three main causes of ECF loss.  These are: lack of intake, or not drinking enough fluids; excess fluid losses, especially from vomiting or diarrhea; and third spacing, which is common with burns.

Signs and symptoms to look for- rapid weight loss, thirst, decreased urine output, a rapid heart rate, postural hypotension (a drop in blood pressure when standing), prolonged capillary refill, dry mucous membranes, tenting of the skin, changes in mental status, and muscle weakness.  Watch for these!

Alright, here are your questions!

Define the following dehydrations:









White, B. (2009). Clients with fluid imbalances. In Black, J. M., & Hawks, J. H. (Eds). Medical-surgical nursing. Clinical management for positive outcomes, (Vol 1., 8th Ed), (pp. 127-150). St. Louis, MO: Elsevier Inc.

McCarthy, M. & Olsen, K. (2011). Clients with fluid imbalances [PowerPoint Slides].


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