FLUID DISTRIBUTION REVIEW
What is osmosis?
The shifting of water from one fluid compartment to another via a semi-permeable
membrane. Water will always want to move from an area with a lesser concentration of
solutes to an area with a greater concentration of solutes. "Concentration calls!"
What is osmolality?
A measurement of how concentrated a compartment is (the proportion of solutes-to-
water that is in a compartment's fluid).
Clinically we can measure the solute concentration of the blood by doing a serum
osmolality and have an idea about what fluid shifts to anticipate since osmolality
(concentration) rules osmosis.
What is tonicity?
the "saltiness" of a fluid or how much of it is made of salt. This is interchangeable with
the term salinity. The normal tonicity (salinity) of the blood is 0.9%
What is osmotic pressure?
The pressure exerted by all of the solutes in a compartment. It correlates with
osmolality. Remember, concentration calls!
What are some common causes for pathologic water loss?
inadequate intake (patient too sick to drink)
increased output (vomiting, diarrhea, increased urination)
end result: dehydration or fluid volume deficit
What are common symptoms of dehydration or fluid volume deficit?
dry mucuous membranes, poor skin turgor, sunken eyes, sunken fontanels in babies,
oliguria, increased urine concentration, low BP, acute CNS changes, high serum
osmolality.
Which body systems compensate for fluid volume deficit?
RAAS and ADH secretion
, How does the RAAS work in patients with fluid volume deficit?
Kidneys secrete renin which stimulates the secretion of angiotensin I. Angiotension I is
converted into angiotension II with the help of angiotension converting enzyme (ACE).
Angiotension II causes peripherial vasoconstriction (to help with perfusion of central
organs) and the release of aldosterone (which causes kidney tubules to hold onto Na
and water).
How does ADH work in patients with fluid volume deficit?
Antidiuretic hormone is secreted by the pituitary gland and works on the tubules
encouraging them to retain NA and water, decreasing urinary output.
Describe some examples of pathologic water gain:
excess intake such as water intoxication
too much IV fluid
low output like kidney failure
hormonal problems like SIADH
Identify three causes of hypoproteinemia
diminished protein production such as found in certain types of liver diseases.
diminished protein intake / malnutrition
plasma protein loss such as is found in certain types of kidney diseases.
A B to T fluid shift will make the patient appear to be in fluid volume _____________.
overload
What are some common causes for decreased blood concentration?
Any situation where pathologic water gain or solute / protein loss can occur.
End result: excess water or fluid volume overload (edema)
Edema can be found in what parts of the body?
under the skin (skin appears tight and puffy), in the lung tissue (cough, crackles, SOB),
in the brain cells (restlessness, confusion, unconsciousness, convulsions), and in the
abdominal cavity (abdominal distension).
What compensatory mechanism corrects fluid overload?
The naturetic peptide system (NPS).
What is osmosis?
The shifting of water from one fluid compartment to another via a semi-permeable
membrane. Water will always want to move from an area with a lesser concentration of
solutes to an area with a greater concentration of solutes. "Concentration calls!"
What is osmolality?
A measurement of how concentrated a compartment is (the proportion of solutes-to-
water that is in a compartment's fluid).
Clinically we can measure the solute concentration of the blood by doing a serum
osmolality and have an idea about what fluid shifts to anticipate since osmolality
(concentration) rules osmosis.
What is tonicity?
the "saltiness" of a fluid or how much of it is made of salt. This is interchangeable with
the term salinity. The normal tonicity (salinity) of the blood is 0.9%
What is osmotic pressure?
The pressure exerted by all of the solutes in a compartment. It correlates with
osmolality. Remember, concentration calls!
What are some common causes for pathologic water loss?
inadequate intake (patient too sick to drink)
increased output (vomiting, diarrhea, increased urination)
end result: dehydration or fluid volume deficit
What are common symptoms of dehydration or fluid volume deficit?
dry mucuous membranes, poor skin turgor, sunken eyes, sunken fontanels in babies,
oliguria, increased urine concentration, low BP, acute CNS changes, high serum
osmolality.
Which body systems compensate for fluid volume deficit?
RAAS and ADH secretion
, How does the RAAS work in patients with fluid volume deficit?
Kidneys secrete renin which stimulates the secretion of angiotensin I. Angiotension I is
converted into angiotension II with the help of angiotension converting enzyme (ACE).
Angiotension II causes peripherial vasoconstriction (to help with perfusion of central
organs) and the release of aldosterone (which causes kidney tubules to hold onto Na
and water).
How does ADH work in patients with fluid volume deficit?
Antidiuretic hormone is secreted by the pituitary gland and works on the tubules
encouraging them to retain NA and water, decreasing urinary output.
Describe some examples of pathologic water gain:
excess intake such as water intoxication
too much IV fluid
low output like kidney failure
hormonal problems like SIADH
Identify three causes of hypoproteinemia
diminished protein production such as found in certain types of liver diseases.
diminished protein intake / malnutrition
plasma protein loss such as is found in certain types of kidney diseases.
A B to T fluid shift will make the patient appear to be in fluid volume _____________.
overload
What are some common causes for decreased blood concentration?
Any situation where pathologic water gain or solute / protein loss can occur.
End result: excess water or fluid volume overload (edema)
Edema can be found in what parts of the body?
under the skin (skin appears tight and puffy), in the lung tissue (cough, crackles, SOB),
in the brain cells (restlessness, confusion, unconsciousness, convulsions), and in the
abdominal cavity (abdominal distension).
What compensatory mechanism corrects fluid overload?
The naturetic peptide system (NPS).
