Third spacing

The human body essentially keeps fluids in two spaces called compartments.  The first compartment is inside of cells.  This is called intracellular fluid.  It holds about 60% of the body’s fluids.  The second compartment is outside of the cells in the extracellular fluid, which holds about 40% of the body’s fluids.  This second compartment includes spaces like the interstitial compartment and the intravascular compartment.  The interstitial compartment is the fluid that surrounds the cells in tissues.  The intravascular component is mostly blood. 

Third spacing is when body fluids collect somewhere that is not in one of the two compartments where your body can use it.  When fluids are inside cells, your body can use it for chemical reactions.  When fluids are in the interstitial and intravascular compartments, your body can use it for lubrication, chemical reactions and moving chemicals from one place to another.  Fluid in third spaces is outside of the circulatory system and cannot be used by the body.
A common third space is in the abdominal cavity.  When fluid becomes trapped between the tissues and organs of the abdomen, it is called “ascites.”  When fluid accumulates in the interstitial area around the lungs, it is called “pulmonary edema.”  When fluid is found between the layers of the skin or mucous membranes, it is called “angioedema.”
Third spacing is a problem for multiple reasons.  The first is that it compresses the structures around the fluid, like when angioedema puts pressure on the throat and makes it difficult to breathe.  The fluid sometimes affects organ function.  Another reason third spacing is problematic is because it can cause the fluid level in the circulatory system to drop.  This means the amount of blood moving through the body is less than it should be, which decreases blood pressure and increases heart rate.  This can be very dangerous.  If there is not enough blood for the heart to pump, it will stop pumping.
People with a lot of third spacing often have symptoms of dehydration.  This includes things like excessive thirst, fatigue, and reduced urine output. 
Third spacing occurs as a result of anaphylaxis.  It is also a common problem for people with mast cell disease in the absence of anaphylaxis due to “leaking” of chemicals like histamine that push fluid out of the blood vessels and into the tissues.  Fluid replacement is very important to staying stable.
There is a lot of anecdotal information that suggests that IV fluids are helpful to counteracting third spacing in people with mast cell disease.  I get 2L of fluids overnight three times a week, and it has helped immensely.  For me, the IV fluids have stabilized my blood pressure, decreased my heart rate and keep my GI tract moving.  My abdominal pain has improved significantly since starting the IV fluids. My energy is better.  I don’t think that it has been formally written up in article form, but this is a treatment that is quickly gaining momentum in the mast cell community.   

18 Responses

  1. Audrey January 3, 2015 / 9:53 am

    Very interesting! Thanks so much for sharing!

  2. shaunamom January 3, 2015 / 1:26 pm

    Thanks for this one – that is one of the simplest, easy-to-understand explanations for third spacing I’ve seen in a while!

  3. Mar January 9, 2015 / 2:14 am

    Thank-you so much for this info. Lisa! Gives a clearer picture of what is going on.

  4. Jessica June 29, 2015 / 7:55 am

    Thank you for this article! Please excuse me but I am new to all of this, could you please tell me what type of IV fluids you recieve? Saline?? Thanks so much!

    • Lisa Klimas June 29, 2015 / 4:47 pm

      I get D5/LR (dextrose 5% in Lactated Ringer’s solution).

  5. Jane Yount July 13, 2015 / 6:09 pm

    I just found this in an internet search. I am already a subscriber. Would it be possible to add a search function to your site? (With all the extra energy you DON’T have if you’re like the rest of us, which I’m sure you are… Sorry! Maybe that’s what you get for being so knowledgeable, so helpful?)

    • Lisa Klimas July 13, 2015 / 6:12 pm

      It has one. It’s the magnifying glass icon in the upper right hand corner.

  6. Janie July 25, 2015 / 4:55 am

    Is there a test to diagnosis third spacing?

    • Lisa Klimas July 25, 2015 / 9:36 pm

      It depends where it is. It can sometimes be determined by ultrasound, but not always.

  7. Andrea September 8, 2015 / 10:16 am

    Hi, thank you for this well examined article. It is one of the best I’ve read.
    My question is how do I get tested?
    I defiantly have third spacing, but my doctors ignore me when I bring it up. It’s a real problem for me in my abdomen, arms and legs. I’m in the Nyc area , can you recommend a doctor for me? Ty!!

    • Lisa Klimas September 8, 2015 / 10:53 am

      There isn’t a test for third spacing per se, it depends one where it is. If it’s in your abdomen, it may show up on ultrasound. It depends a lot on how much fluid is trapped and where it is.

  8. Carol September 8, 2015 / 3:17 pm

    Thanks for sharing. That is the best explanation I have heard yet.

  9. Teresa January 22, 2016 / 11:04 am

    Any research done on the effects of Ketogenic diet and this third spacing, I have fewer issues with abdominal swelling when I avoid trigger items and stick to a low carb diet, I have even found I’m able to consume some histamine releasing food without reaction while on a ketogenic diet. I know cellular repair is common with ketogenic diet hence it is used in treating epileptic patients. Wondering if their is a study on this? Not to say ketogenic is a cure, but maybe good for symptom management.

  10. Annette February 8, 2016 / 4:26 pm

    I love your articles, thank you so much for all this work you do.

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