Body Fluids Flashcards
(True/False) BUN is an effective osmole
False; BUN is not an effective osmole
* It freely crosses the cell membrane
* Glucose and sodium are effective osmoles because they cannot cross the cell membrane without specific transporters
mOsm/L represents _
mOsm/L represents osmolarity
mOsm/kg repreents _
mOsm/kg represents osmolality
(Osmolarity/ Osmolality) is used clinically
Osmolality is used clinically
* Because osmolarity measures volume which can change with temperature
Tonicity refers to _
Tonicity refers to the osmolality made up of solute that do not freely cross the cell membrane
* Tonicity = “effective osmolality”
* Exerts a pressure for water to move
BUN and EtOH are not effective osmoles but they do contribute to _
BUN and EtOH are not effective osmoles but they do contribute to total osmolality
ICF is _ proportional to tonicity
ICF is inversely proportional to tonicity
* Hypotonic solution? ICF will be high
* Hypertonic solution? ICF will be low
How do we calculate total osmolality?
Total osm = 2(Na+) + Glucose/18 + BUN/2.8
How do we calculate the tonicity?
Effective osm = 2(Na+) + Glucose/18
_ % of our body mass is made up of fluid
60% of our body mass is made up of fluid
Total Body Water (TBW)
Total Body Water (TBW) = .6 (body weight kg)
* 60% of our body mass will be water
* Ex: 0.6 (70 kg) = 42 L
About _ % of our body mass is found in the intracellular fluid specifically
About 40% of our body mass is found in the intracellular fluid specifically
About _ % of our body water is found in the extracellular fluid specifically
About 20% of our body water is found in the extracellular fluid specifically
25% of the ECF is _
25% of the ECF is plasma
75% of the ECF is _
75% of the ECF is interstitial fluid
The best IVF for initial fluid replacement is _
The best IVF for initial fluid replacement is saline (or lactated ringers)
* We want to give an isotonic solution such that it stays in the extracellular space
D5W is used in the context of _
D5W is used in the context of correcting hypernatremia
* I L water + 5% dextrose solution
* The solution is isotonic ouside of the body but when it goes in it becomes hypotonic (body uses up the glucose)
* It is like essentially giving the patient free water
* Used for hypernatremia, not for volume replacement
Normal saline (0.9% Na) is good for volume replacement because it is nearly isotonic; however, it is actually slightly _
Normal saline (0.9% Na) is good for volume replacement because it is nearly isotonic; however, it is actually slightly hypertonic ~308
D5W is _ osmotic and _ tonic
D5W is isosmotic and hypotonic
1/2 Normal saline solution is _ tonic
1/2 Normal saline solution is hypotonic
* It is a good maintanance fluid for patients that are dehydrated
KCl can be given to patients at a rate less than _
KCl can be given to patients at a rate less than 20 mEq/hour
Lactated ringer solution contains _ , _ , and _
Lactated ringer solution contains:
* 130 mEq Na
* 4 mEq K
* 28 mEq Lactate
3% hypertonic saline is used for the treatment of _
3% hypertonic saline is used for the treatment of symptomatic hyponatremia, specifically SIADH
* Allows us to correct Na+ very quickly
Where does normal saline go upon administration (ICF, ECF)?
Normal saline stays in the ECF
Where does 1/2 normal saline go upon administration (ICF, ECF)?
1/2 normal saline is hypotonic, it goes to all 3 compartments but mostly stays in the ECF
Where does D5W go upon administration (ICF, ECF)?
D5W is very hypotonic, it goes to all 3 compartments equally
Prostaglandins primarily _ the _ arteriole
Prostaglandins primarily vasodilate the afferent arteriole
* This increases RBF & GFR
* FF stays the same
NSAIDs have what effect on the arterioles, GFR, RBF?
NSAIDs block prostaglandin effect; therefore, they vasoconstrict the afferent arteriole
Angiotensin II primarily _ the _ arteriole
Angiotensin II primarily constricts the efferent arteriole
ACE inhibitors have what effect on the arterioles, RPF, and GFR?
ACE inhibitors dilate the efferent arteriole
The glomerulus basement membrane is (negatively/positively) charged
The glomerulus basement membrane is negatively charged
Molecules are filtered by size and change; molecules over _ A cannot be filtered
Molecules are filtered by size and change; molecules over 40 A cannot be filtered
Cl- is freely filtered due to its _
Cl- is freely filtered due to its small size despite being negative
Albumin does not get filtered due to its _
Albumin does not get filtered due to its larger size (36 A) and negative charge
GFR represents the volume of _ passing across the _ every minute
GFR represents the volume of ultrafiltrate passing across the glomeruli every minute
Glomerular hemodynamics under afferent constriction
Glomerular hemodynamics under efferent constriction
Glomerular hemodynamics under afferent dilation
Glomerular hemodynamics under efferent dilation
Glomerular hemodynamics under increased serum protein
Glomerular hemodynamics under urinary obstruction
Glomerular hemodynamics under angiotensin blockade
Glomerular hemodynamics under NSAIDs
At the glomerulus, the _ starling force predominates
At the glomerulus, the hydrostatic capillary pressure predominates
* This favors filtration at the glomerulus
At the peritubular capillary, the _ starling force predominates
At the peritubular capillary, the oncotic capillary pressure predominates
* This favors reabsorption of solutes back into the body
How does the body change pressure dynamics of the glomerulus during hypervolemia?
Hypervolemia –>
Increased effective arterial blood volume –>
Decreased ang II –>
Efferent arteriole dilation –>
Decreased filtration fraction –>
Decreased oncotic capillary pressure –>
Decreased proximal reabsorption
In SIADH, the estimated ECF will be _ but the actual ECF is _ and ICF is _
In SIADH, the estimated ECF will be normal (euvolemic) but the actual ECF is increased and ICF is increased
If a patient with SIADH is given furosemide, serum Na+ will _ and urine osmolality will _
If a patient with SIADH is given furosemide, serum Na+ will increase and urine osmolality will decrease
* Loop will increase free water excretion and increase Na+ concentration
* Urine osmolality will decrease due to excretion of water from the loop
* The loop inhibits generation of the medullary osmotic gradient
A dehydrated patient who consumes hypotonic fluids will have:
_ Total body water
_ ECF
_ ICF
_ Total body Na+
A dehydrated patient who consumes hypotonic fluids will have:
Decreased Total body water
Decreased ECF
Increased ICF
Decreased Total body Na+
