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Darrow-Yannet Diagrams simplified

What are Darrow Yannet diagrams?

They are graphs that tell you the osmolarity and volume changes of body fluids.

X axis represents volume.
Y axis represents solute concentration.

Total body water = 2/3 ICF (Intracellular fluid) + 1/3 ECF  (Extracellular fluid)

Remember:
All volume disturbances originate in the ECF compartment.
Changs in ICF are in response to changes in ECF.

How to make the graph in your head -
Step 1. Figure out what happens to the osmolarity and volume in theECF compartment (ECF is the smaller compartment)
Step 2. Think how is ICF affected?

Let’s review some examples to make sure we understand the concept!
Loss of whole blood, adult diarrhea.

What will happen to volume in ECF compartment?
Will decrease.

What will happen to osmolarity in ECF compartment?
Will not change. (Why? Isotonic fluid is lost.)

What will happen to ICF volume and osmolarity?
No osmotic gradient, therefore, will not change :)

That was easy!
Let’s look at a similar example.
Infusion of excessive isotonic saline.

What will happen to volume in ECF compartment?
Will increase.

What will happen to osmolarity in ECF compartment?
Will not change. (Why? Isotonic fluid is lost.)

What will happen to ICF volume and osmolarity?
No osmotic gradient, therefore, will not change.

See? It’s very simple!
Loop diuretics, Addison’s disease.

(Loops make you lose sodium and water, but more of sodium than water.
Addison’s disease is adrenal insufficiency. Aldosterone makes you retain sodium so in the absence of aldosterone, you will lose sodium.)

What will happen to osmolarity in ECF compartment?
Will decrease. (Why? You are losing sodium.)

What will happen to volume in ECF compartment?
Will decrease. (Why? Fluid moves from ECF to ICF)

What will happen to ICF volume?
Will increase. (Decrease in osmolarity shifts the fluid into ICF)
SIADH, compulsive water drinker.

(SIADH: You are conserving too much water due to ADH.
Water drinker: You are having too much water =P )

What will happen to osmolarity in ECF compartment?
Will decrease. (Why? You are diluting by adding water.)

What will happen to volume in ECF compartment?
Will  increase. (Why? You are adding fluid.)

What will happen to ICF volume?
Will increase. (Decrease in osmolarity shifts the fluid into ICF)
Right heart failure, Cirrhosis, Nephrotic syndrome.

What will happen to osmolarity in ECF compartment?
Will decrease.

What will happen to volume in ECF compartment?
Will  increase.

What will happen to ICF volume?
Will increase.

Can’t figure why? Well.. Here’s why!
In all three conditions, there is a decreased effective circulatory volume (Effective arterial blood volume)
[See diagram]

This leads to decreased renal blood flow and pressure and increased ADH secretion and activates the renin angiotensin aldosterone system, increasing sodium and water reabsorption.

Note: Total body sodium is increased, however, serum sodium is decreased.
Why?
The alteration in Starling forces redirects the sodium containing fluid in the interstitial space (leading to edema)

*phew* That was work! Let’s see what happens during sweating ;)
Sweating.

What will happen to volume in ECF compartment?
Will decrease.

What will happen to osmolarity in ECF compartment?
Will increase. (Why? Hypotonic fluid is lost.)

What will happen to ICF volume?
Will decrease.

Your sweat doesn’t taste salty.. That’s how I remember it’s hypotonic, not hypertonic like tears T_T
Insensible water loss in fever, diabetes insipidus, alcohol.

What will happen to volume in ECF compartment?
Will decrease. (Water is lost. Why? ADH action is lost in Diabetes insipidus, alcohol inhibits pitutary secretion of ADH, water evaporates from the warm skin surface in fever)

What will happen to osmolarity in ECF compartment?
Will increase.

What will happen to ICF volume?
Will decrease.

Note: The ECF contraction is mild because there has been no loss of sodium.

Next one is easy too.. Keep going! <3

Infusion of sodium bicarbonate, sodium containing antibiotics.

What will happen to osmolarity in ECF compartment?
Will increase.

What will happen to volume in ECF compartment?
Will increase. (Why? Fluid moves from the ICF to ECF)

What will happen to ICF volume?
Will decrease.

..And the last one!!! :D
Hyperosmolar nonketotic coma, diabetic ketoacidosis.


What will happen to osmolarity in ECF compartment?
Will increase. (Why? Glucose is an osmotically active particle)

What will happen to ICF volume?
Will decrease. (Why? Fluid moves from the ICF to ECF)

This gets a little tricky.. ^__^”
What will happen to volume in ECF compartment?
Will decrease.
Why?
Glucose in urine acts as an osmotic diuretic and the water from ECF is lost.


That’s all!

This blog post took me forever to write.. I feel the color coding makes it easier to see the changes in the diagrams :)
Hope you had fun learning and revising with me and see you in the next post <3

-IkaN
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