Body Fluid Compartments
Example: What is the volume of the ECF compartment if you inject 2.4 g of inulin, and the amount of inulin lost in the urine is 1.0 g. And the plasma concentration of inulin is 0.1 mg/mL?
**** BE CAREFUL OF UNITS, ALWAYS RIGHT YOUR UNITS OUT WHEN YOU ARE WORKING A PROBLEM,LOTS OF PEOPLE MAKE MISTAKES ON THE UNITS We know that Concentration = Q/V(ECF) V(ECF) = Q(injected) - Q(lost) / concentration V(ECF) = Q(injected) - Q(lost) / Q/V Therefore. 2,400 mg - 1,000 mg / 0.1 mg/mL = 14,000 mL = 14 L **notice the conversion that was necessary for the quantity to match the concentration, just make sure that all values are in the correct units
The values for TBW vary from 45 - 75% of body weight in kg because of what factors?
1. Age 2. Adipose tissue 3. Gender
What are the four organs that communicate the ECF with the external environment? (She gave some points about each in class but they aren't in the notes, the info is included in this notecard)
1. Alimentary canal (GI tract) - indiscriminate in its behavior some processes of absorption are regulated by mostly they are not so if we drink lots of water it will be absorbed even if we are in water balance 2. Lungs - water loss during respiration 3. Kidneys - most but not all regulation of water and electrolytes occurs here 4. Skin - water loss by sweating and insensible water loss (They are all in contact with the plasma compartment of the extracellular fluid compartment)
Total body water (TBW) is distributed amongst which compartments?
1. Blood plasma 2. Interstitial fluid (ISF) 3. Intracellular fluid (ICF)
What does the transcellular fluid compartment consist of?
1. Fluid in transit in the lumina of epithelial organs (e.g. the gall bladder, stomach, intestines, and urinary bladder) 2. Cerebrospinal fluid 3. Intraocular fluid
What are factors that can cause extracellular and intracellular volumes to change?
1. Ingestion of water 2. Dehydration 3. Intravenous infusion of different types of solution 4. Loss of large amounts of fluid from the gastrointestinal tact (vomit and diarrhea) 5. Loss of abnormal amounts of fluid be sweating or through the kidneys
Explains the effect of each of the types of tonic solution not the volume of the cell?
1. Isotonic solution: does not change the volume of a cell 2. Hypotonic solution: causes a cell to swell 3. Hypertonic solution: causes a cell to shrink
What are the characteristics of the substance to be used in the dilution method?
1. Nontoxic at the concentrations used 2. Neither synthesized nor metabolized (she also mentioned in lecture that it would need to be a substance that does not leave the compartment of interest - essentially all of these are saying that the quantity should not change) 3. Does not cause shifts in fluid distribution among the compartments.
Note that for the previous examples you should be able to predict how the cell will change if you were just given the osmolality of the surrounding solution becasue you should know what the normal value for osmolality is in the body which is?
280 mOsm/L according to this diagram because isotonic solution is 280 mOsm/l but in a previous slide and in the lecture she said 295 mOsm/L but for the purposes of calculations to make it easier we just use the value of 300 mOsm/L as normal.
Example: a 150 mmole/L solution of NaCl has an osmolarity of what?
300 mOsm/L, because each molecule of NaCl dissociates into a Na= and a Cl- ion
For a person with a TBW of 42 L and a plasma osmolarity of 300 mOsm, what would be the total body osmoles? What would be the osmoles of the ECF and what would be the osmoles of the ICF?
42L x 300 mOsm/L = 12,600 mosm ECF is 1/3 of TBW = 14 L 14 L x 300 mosm/L = 4200 mosm ICF is 2/3 of TBW 28. L x 300 mosm/L = 8,400 mosm
The total body water (TBW) is between ______ and ______% of body weight in kg is the TBW in L.
45 to 75%
What are the most commonly used values for TBW for both males and females?
60% of body weight for males 50% of body weight for females
For example, if you have a 70 kg male, what is his TBW?
70 kg male has 42 L TBW (Just multiply the typical value of 60% by the total body weight in Kg to get the TBW in L) 70 x 0.6 = 42
Plasma sodium concentration > ______ meq/L is rarely seen in alert adults with a normal thirst mechanism
>150 meq/L
Hyponatremia is usually seen with increased hypothalamic production of _______ such as in what syndrome?
ADH Such as in SIADH - syndrome of inappropriate ADH secretion
What is the approximate value of the osmolarity of the ICF, plasma and ISF compartments?
Approximately 295 mOsm/L
Age and TBW At birth ______% of neonate weight is water, with rapid ________ immediately following birth.
At birth 75% of neonate weight is water, with rapid decline immediately following birth
Why are there no chronic symptoms of hyponatremia?
Brain osmotic adaptation: 1. Cerebral swelling will increase the flow of Brain ISF toward the cerebrospinal fluid decreasing the amount of swelling 2. Solutes move out of brain cells decreasing the amount of brain cell swelling
What separates the plasma and ISF compartments?
Capillaries
What is the ionic composition of the intracellular fluid?
Cations - K+ and Na+ (lot more K+ than Na+) Anions - misc phosphates, Pr-, HCO3- and Cl- in that order for amounts I think The major point of the ionic composition slide is that Na+ and Cl- are high in the ECF but K+ is high in the ICF
What is the complication that arises when trying to determine the volume of the ECF compartment?
Complication —> inulin is excreted by the kidneys (because it can cross capillary membranes) —> take into account the amount of inulin lost from the body during the course of the measurement
A good estimate of osmolality is [Na+] time 2 but this approximation wouldn't not work in the case of a patient with _________ who has increased glucose or in the case of a patient with _________ who has a high concentration of urea in plasma.
Diabetes - high concentration of glucose A patient who has kidney problems who has a high urea in plasma
For _______ solutions the difference between osmolarity and osmolality is insignificant.
Dilute solutions
_________ methods for determining distribution of water in body compartments.
Dilution
Alterations in body fluid compartments: Principles for analysis of fluid shifts between ECF and ICF: 1. All solutes and water that enter or leave the body do so via the ________
ECF
What is the pH of ECF?
ECF is approximately 7.4
Plasma and ISF together constitute the __________ - _____% of body weight (about _______ of TBW)
Extracellular fluid (ECF) which is 20% of body weight (about 1/3 of TBW)
T or F: the ionic composition of the plasma and intersitital are drastically different
False the ionic composition of the plasma and interstitial fluid (ISF) are similar because they are separated by high permeable capillaries
Practice: for a man that has a 70 kg body weight, give the amount of water in L in each of the compartments
Intracellular fluid = 0.4 x body weight = 28 L Extracellular fluid (ECF) = 0.2 x body weight = 14 L Interstitial fluid = 3/4 of ECF = 10.5 L Plasma = 1/4 of ECF 3.5 L See slide four for the answers and how this works out
The percentage of total body water is ________ related to age.
Inversely related to age
What would be the factors that do and do not change about the volume and osmolarity of the body fluid compartments with isosmotic water shifts?
Isosmotic water shifts: CHANGE in ECF volume only, either increase or decrease depending on the situation No change in ICF volume or osmolarity (cells are not affected) No change in ECF osmolarity (cause it is isosmotic water shift, it is of the same osmolarity as the
What substance would we use for the determination of extracellular fluid volume by the dilution method? And why?
Substance used is inulin It can readily permeate capillary walls but not cell membranes —> it distributes in ECF
What is the substance used for the determination of plasma volume by the dilution method?
Substance used is serum albumin labeled with radioactive iodine (131I - albumin) or Evan's blue dye
What is the substance used for the determination of total body water by the dilution method?
Substance used. Is antipyrine or deuterated water or tritiated water Deuterated water is heavy water made up of deuterium atoms rather than hydrogen * Tritiated water is radioactive water where hydrogens are replaced by tritium *just found this info off google
What formula would you use to calculate the total body osmoles?
TBW x plasma osmolarity = total body osmoles Because Volume x concentration = quantity
What are the values for normal volume ICF and ECF on these Darrow-Yannet diagrams? What is the normal value for osmolarity? What is the major cation in the ECF and ICF?
The ECF is represented on the right. THe prominent ion is Na+ and it has a normal volume of 14L The ICF is represented on the left. The prominent ion is K+ and its normal volume is 28 L The value we have set as normal osmolarity for both ECF and ICF is 300 mOsm
For the Darrow-Yannet diagrams, the X-axis represents _______ and the Y-axis represents _______
The X-axis represents volume Y-axis represents osmolarity
Although, related to osmolarity, tonicity also takes into consideration, what factor?
The ability of a solute to cross a cell membrane
What is the effect of placing a cell within a hypertonic solution of 360 mOsm/L?
The cell shrinks Because if the cell is put into hypertonic solution,the water moves from the lower concentration inside the cell to the higher concentration outside of the cell thus shrinking the cell
What is the effect of placing a cell within a hypotonic solution of 200 mOsm/L?
The cell swells Be sure water moves from outside to inside of the cell
What is the major difference in ionic composition between the two compartments of the ECF?
The interstital fluid does not contain as many proteins (which would be negatively charged and contribute to the anions) because these do not traverse the capillary membrane easily
The percentage of TBW is ________ related to the degree of body fat. Why?
The percentage of TBW is Inversely related to the degree of body fat. Adipose tissue contains very little water
What are the differences in TBW seen between the genders? And why?
The percentage of TBW is lower in adult females than males due to the subcutaneous layer of adipose tissue
Which is the preferred term for biological systems, osmolarity or osmolality and why?
The preferred term for biological systems is osmolality. Because measurements of osmolarity are temperature dependent, because the volume of water varies with temperature
What are the symptoms of hyposmolarity (hyponatremia)?
The symptoms of hyponatremia are primarily neurologic 1. Acute symptoms with [Na+} plasma between 120 meq/L and 125 meq/L = nausea and malaise 2. Acute symptoms with [Na+] plasma between 110 meq/L and 120 meq/L = headache and lethargy 3. Acute symptoms with [Na+] below 110 meq/L = seizures, coma, permanent neurologic deficits, or death 4. Chronic symptoms: none
What is the effect of placing a cell within an isotonic solution of 280 mOsm/L?
There is no change in cell volume
What are some symptoms of hyper osmolarity (hypernatremia)?
They symptoms of hyperosmolarity (hypernatremia) are primarily neurological: 1. Early signs: lethargy, weakness, irritability 2. Symptoms progress to: twitching seizures, coma, and death 3. Symptoms related to the movement of water out of the brain cells down the osmotic
How would you determine the intracellular fluid compartment volume using the dilution method?
This cannot be measured directly experimentally but rather is determined by calculation V(ICF) = TBW - V(ECF)
How would you determine the interstitial fluid compartment volume using the dilution method?
This one would also have to be determined indirectly through calculation V(ISF) = V(ECF) - PV
"All physiological processes are designed to maintain the internal environment that bathes our cells, tissues, and organs"
This was a quote at the beginning that she didn't have on her slides from two years ago The notecards for this lecture were made from previous years recordings so make sure that you go back and listen to some of the material from this years recording for slides that may be different from before
The _______ of a solution is related to its effect on the volume of a cell.
Tonicity
There is a fourth small compartment, the ___________ fluid compartment. (____ to ____% of TBW).
Transcellular fluid compartment (2% to 4% of TBW)
T or F: the osmolarity of plasma, ISF, and ICF are all equal
True: since the capillaries and most plasma cell membranes permeable to water, the osmolarity of plasma, ISF and ICF compartments are equal
Most of our body is made up of what molecule?
Water
Which mechanism of generating a hyposmotic shift is more common?
Water gain is more common (so this would be a hyposmotic overhydration) Decrease in plasma [Na+] concentration ~ Na+ ECF meq content / increased TBW —> common
Cells swell and are hyposmotic because the ECF became hyposmotic by one of what two ways?
Water gain or Na+ loss
Cells shrink and are hyperosmotic because ECF becomes hyperosmotic by one of two ways, which way does it become hyperosmotic in a hyperosmotic dehydration?
Water loss (the two methods are water loss and Na+ retention) Increase in plasma [Na+] ~ Na+ ECF mEq content / decrease TBW —> common ( I think what she is showing in this equation is that an increase in plasma Na+ concentration can result from a decrease in TBW and that this situations is more common way of getting a hyperosmotic solution than the other method of Na+ retention)
Hyperosmotic water shift: overhydration or dehydration ECF became hyperosmotic by one of two ways: which are? (Not really clinical situations, just two ways that you can generate a hyperosmotic solution)
Water loss or Na+ retention
Alterations in body fluid compartments Principles for analysis of fluid shifts between ECF and ICF: 2. The ICF and ECF are in osmotic equilibrium. Meaning?
Water moves between these compartments only when an osmotic pressure gradient exists
Example: you inject 131I-albumin = 350,000 cpm When you determine the plasma concentration using scintillation counter I think? It is 131albumin = 100cpm/ml What is the volume of the plasma compartment?
We know that Concentration = Q/plasma volume PV = Q/concentration PV = Q/Q/V Therefore... PV = 350,000 cpm/ 100cpm/mL = 3,500 mL = 3.5 L
Describe the process of determining plasma volume?
You can use the dilution method where you inject a substance that stays within the plasma compartment (typically serum albumin labeled with radioactive iodine 131I or Evan's blue dye) which would be a substance that is too big to pass through the capillaries out of the plasma compartment (so it stays in the compartment and follows the rules of a substance used in the dilution method) So you would inject the labeled albumin intravenously, give it time to equilibrate and then measure the concentration of the plasma (the blood sample is taken out and then the plasma is separated from RBC and just the concentration of plasma is determined) and use the equation to determine the volume
Why do we use antipyrine, or deuterated water or tritiated water in calculating the total body water by the dilution method? What is a complication of this?
It can rapidly permeate cell membranes —> it distributes uniformly throughout the ECF and ICF compartments She doesn't have it listed in notes but she mentioned briefly that because it can cross not only capillary membranes but also cell membranes it can be lost not only Be kidneys in the urine but also by the lungs, skin and alimentary canal (she said that even though we have no way of measuring the loss in these last three organs the amount is not substantial) Never mind she had listed in later notes that the complication is that these substances are lost from the body via every route open for the loss of water
What are the major ICF ions?
K+
The body weight exclusive of storage fat is called _______ ______ ______.
Lean body mass (She had this underlined but didn't really cover it in previous years lecture)
What are the major ECF ions?
Na+ and Cl-
Of the two ways that the ECF can become hyperosmotic and generate hyperosmotic shift which is the method by which ECF osmolarity increases during hyperosmotic overhydration?
Na+ retention Increase in plasma [Na+] concentration ~ increases Na+ ECF mEq content/ TBW —> not so common (I think what she is showing by the equation is that an increase in the quantity of Na+ can lead to an increase in Na+ concentration and that this situation does not happen very often)
What are some common causes of increased ADH secretion?
Neuropsychiatric disorder Drugs Pulmonary disease Postoperative patient* (she had this one highlighted)
What are the changes in the graph and the types of situations in which you would get a hyposmotic dehydration?
Occurs when losing more salt than water (renal sodium wasting) by lack of aldosterone Decrease plasma [Na+] ~ decreased Na+ ECF meq content / TBW —> not so common In the new situation you are hyposmotic so even though you are losing water, the ICF volume will increase. You are losing water and there is a shift in water from ECF to ICF which means that there is a decrease in volume of ECF and there is a decreased osmolarity line
On slide 19 there are Darrow-Yannet diagrams of clinical relevant water shifts between body fluid compartments, make sure that you can recognize the normal one and the abnormal ones and situations that can cause them (do so after you finished going through notecards asking about them)
On previous year lecture, she emphasized multiple times that we should be able to identify the shift in the body fluid compartment make up based upon the diagram.
________: refers to the number of solute particles in 1 kg of water
Osmolality
What is an equation that can be used to get a clinical approximation for total osmolality?
Osmolality = 2 [Na+] + [glucose]/18 + BUN/2.8 [Na+] is plasma sodium concentration = 140 mEq/L [glucose] is plasma glucose concentration = 80mg/dl BUN is blood urea nitrogen = 15mg/dl So the typcial value of osmolality with these typical numbers gives you a value of 290 mOsmol/kg
________: refers to the number of solute particles per 1 L of water.
Osmolarity
Osmolarity = concentration x ______________.
Osmolarity = concentration x # dissociable particles mosm/L = mmol/L x #particles/mole
What are the ionic compositions in the plasma and interstital fluid? (Don't think we need to know the numbers, just give all of the different species of cations and anions present and which are of the greatest proportion)
Plasma 1. Anions - Cl-, HCO3-, and Pr- (with Cl- being the greatest) 2. Cations - Na+ and K+ (with Na+ being the greatest by quite a bit)
Protein concentration is greater in which compartment, ISF or plasma?
Plasma >> ISF —> capillaries sparingly permeable to proteins
The extracellular fluid compartment is made up of what two compartments?
Plasma and interstitial fluid
Example: tritiated isotope of water [3H]2O is injected into a 90 kg woman to determine her total body water. 10 to 6 dpm in 10ml of saline are given intravenously, 1% of this load is excreted. If 20 dpm/ml are measured in the plasma of this woman, what is the volume of body water?
Q [3H]2O injected = 1,000,000 dpm Q [3H]2O lost = 10,000 Plasm [3H]2O concentration = 20 dpm/ml TBW = Q(injected) - Q (lost) / concentration TBW = (1,000,000 dpm - 10,000 dpm) / 20 dpm/ml TBW = 49,500 ml = 49.5 L
Example: how would the osmoles of the body fluid compartments change with an infusion of 1.5 L of normal saline. (Normal saline = isotonic saline = 0.9% saline = 0.9 g NaCl/ 100 mL water = 300 mosm/L
Remember that the ICF and ECF are isosmotic at the start of all fluid shift problems (this is the point she showed the slide of how to calculate the osmoles for the normal circumstance as volume x concentration = quantity so make sure you can solve this first) Administration of 1.5 L will increase the ECF volume by 1.5 L because NaCl does not penetrate the ICF and there is no osmotic gradient. (Note that the osmolarity does not change in this type of water shift) TBW x plasma osmolarity = total body osmoles Start: 42 L x 300 mosm/L = 12,600 mosm +1.5L x 300 mosm/L = 450 mosm Final: 43.5 L x 300 mosm/L = 13,050 mosm ECF: 14 L x 300 mosm/L = 4,200 mosm +1.5 L x 300 mosm/L = 450 mosm = 15.5 L x 300 mosm/L = 4,650 mosm The ICF osmoles does not change from normal: 28L x 300 mosm/L = 8,400 mosm
What would be an example of a situation where there is an isosmotic overhydration and what would be the effect?
Saline infusion (it is an isosmotic solution so salt gain = water gain) Increase in ECF volume with saline infusion (all other variables are the same) -this is shown by an increase in the box of the ECF to a line for a volume that is greater than 14L
What separated the intracellular fluid from the extracellular fluid compartments?
Separated by cellular membranes
Alterations in body fluid compartments: Principles for analysis of fluid shifts between ECF and ICF: 3. Equilibration of ICF and ECF osmolality occurs primarily by shifts in _________ and not shifts in _______
Shifts in water and not shifts in solute
In the case of a hyperosmotic overhydration water shift, the cells __________ and are hyperosmotic.
Shrink (that is why it shows a decrease in ICF volume)
Adipose tissue contains very little water, most body water is found in the _____ and _____
Skin and muscle
What would and would not change in a hyperosmotic water shift: overhydration? And what is an example of when this might occur?
In the case of a hyperosmotic water shift overhydration the salt gain is greater than the water gain. This type of situation could occur if the patient gains more salt than water (sodium retention) by ingestion of salt tablets, infusion of hypertonic 5.0% NaCl solution. The ICF volume decreases (less than normal value of 28), ECF volume increases and the overall osmolarity increases (so the y-axis increases) check out the box on slide 24.
How would the graph change and water are some common situations in which a hyposmotic overhydration can occur?
In this cause you are gaining both salt and water but you are gaining more water than salt. Gaining more water than salt by excess renal water gain with inappropriate ADH secretion (ex: post-op SIADH syndrome of inappropriate ADH), or excessive thirst (polydipsia - prevalent in psychosis), also in the case of a pure water IV or 5% glucose IV (because the glucose is metabolized quickly, it is consumed and so it is like introducing 0 mosm of solute) The person is gaining water so the ECF increases in volume (line beyond the normal 14 L line), the hyposmotic solution causes the y-axis to be decreased (below the normal 300 mosm) and it causes water to shift so that there is an increase in the ICF (line is at higher volumes than the usual 28L)
Of the 20% of the body weight that is water in the extracellular fluid for a typcial man, what proportions are in the plasma and interstitial fluid?
Interstitial fluid is 3/4 of ECF Plasma is 1/4 of ECF
For a typical male who has a TBW that is 60% of his body weight, what proportion of this is distributed to the intracellular and extracellular fluid compartments?
Intracellular fluid (ICF) is 0.4 x body weight Extracellular fluid (ECF) is 0.2 x body weight
Intracellular fluid (ICF) is ________% of body weight (about _______ of TBW) The second blank is a fraction
Intracellular fluid (ICF) is 40% of body weight (about 2/3 of TBW)
What is the effect of hyperosmotic water shift: dehydration (how does the graph change) and what are some situations in which this type of water shift would occur?
Getting loss of both salt and water but a greater water loss than salt loss generating a hyperosmotic ECF solution. This can occur with sweating (because recall that sweat is a hyposmotic solution with less salt than water in it so it would mean losing more water than salt in severe sweating), excess renal water loss with decreased ADH secretion, or diminished thirst (hypodipsia which she said something about occurring in infants and those in an altered mental state) Because there is water loss, the volume of the ECF decreases (so new line is shown at volume less than 14 L) because hyperosmotic solution the cell shrinks and the ICF volume decreases (new line is at volume below the 28L line) and it generates a hyperosmotic solution so the y-axis has increased with the increased osmolality) (Recall that the osmolality is the same in all of the compartments so this line increases equally in both compartments - look at graph on slide 25)
Hypernatremia can also occur from a low ADH secretion (leads to excess renal water loss). What are common causes of decreased ADH?
Head trauma, hypoxic or ischemic encephalopathy
What would be an example of an isosmotic dehydration? And what would change about the diagram?
Hemorrhage, burns, GI loss in cholera where the salt loss = water loss These situations result in a decrease in the ECF volume only as shown by a new line on the diagram that is at a lower volume for the ECF than the normal value of 14L
Hypernatremia is usually seen in what kind of patients?
Hypernatremia is usually seen in adults with diminished mental status, patients with hypodipsia, or infants with intact thirst mechanism but cannot ask for water.
Example: 6 L of DW5 (5% dextrose in water, dextrose = 5.0 g of glucose in 100 ml water, 278 mosm/L) was given IV over 39 postoperative hours, to a 41 year old man weighting 70 kg. Urinary output was 0.5 L during the same period. What is the new osmolarity of his fluid compartments?
Hyposmotic overhydration: the body immediately metabolized the glucose to water and carbon dioxide leaving 6 L of water, 0.5 L were lost in urine so you add a total of 5.5 L 42 L x 300 mosm/L = 12,600 mosm + 5.5 L x 0 mosm/L = 0 mosm Final 47.5 L x 265 mosm/L = 12,600 mosm (To solve this problem you determine the total volume, the total osmoles and then use those values to determine the concentration which is equal to quantity divided by volume) For ECF, the volume added is 1/3 of the 5.5 which results in a volume fo 15.8 L and 4,200 mosm which means a concentration of 265 mosm For ICF, 2/3 of the volume will be added which results in 31.7 L and 8,400 mosm so a concentration of 265 mosm/L **note that the body fluid osmolarity is the same in all of the body compartments and note that it is decreased from it normal value of 300 mosm/L
What is the pH of ICF?
ICF pH is approximately 7.1 (slightly lower due to metabolic processes occurring in the cell)
How does the dilution method work?
If a certain quantity (Q) of a substance is injected into a fluid compartment having a volume (V), when an equilibrium (or steady state) is achieved: Concentration = Q/V If we know Q and can measure the concentration (Q/V), we can calculate V
