If there is a 70 kg man, what are the values of the following? - - Total body water - - ECF and ICF - - Interstital Fluid and Plasma

-- Total body water = 70 x 0.6 = 42 L - - ECF = 70 x 0.2 = 14 L - - ICF = 70 x 0.4 = 28 L - - Interstital Fluid = 14 x 0.75 = 10.5 L - - Plasma = 14 x 0.25 = 3.5 L

12- Renal Physiology Body Fluid Compartments Flashcards by Staci Thomas

What is the main function of the kidney?

Produce urine and regulate the volume and composition of the body fluids within narrow limits.

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Describe the amounts for body fluid compartment, starting with total body water.

Total Body Water = Solids and Water (50-70%)

50-70% Water breaks down into = 2/3 ICF and 1/3 ECF

1/3 ECF breaks down into = 80% Interstitial Fluid and 20% Plasma

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These compartments are 2/3 volume of body fluid and consist of cytosol within the cell.

ICF

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These compartments are 1/3 volume of body fluid and consist of plasma and interstitial fluid.

ECF

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What is the 60-40-20 rule?

- 60% of body weight is total body water
- 40% of body weight or 2/3 total body water is ICF
- 20% of body weight or 1/3 total body water is ECF

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If there is a 70 kg man, what are the values of the following?

- Total body water
- ECF and ICF
- Interstital Fluid and Plasma

– Total body water = 70 x 0.6 = 42 L

- ECF = 70 x 0.2 = 14 L
- ICF = 70 x 0.4 = 28 L
- Interstital Fluid = 14 x 0.75 = 10.5 L
- Plasma = 14 x 0.25 = 3.5 L

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________ is the only fluid that can be acted on directly to control its volume and composition. If the volume and composition of this is regulated, then the volume and composition of the Interstitial Fluid bathing the cells are also regulated.

Plasma

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Any control mechanism that operates on plasma in effect regulates the entire ________.

ECF

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T/F. ECF is an intermediary between the cells and the external environment. All exchanges of water and other constituents between the ICF and the external world must occur through the ECF. Water added to the body fluids always enters the ECF compartment first, and fluid always leaves the body via the ECF.

True

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In most cases, all fluid is normally contained in the intravascular, intracellular, or interstitial spaces. In certain instances, another shift occurs referred to as ________ ________ (part of ECF).

Third Spacing

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This occurs when too much fluid shifts from the blood vessels (intravascular) into the “nonfunctional” area of cells (fluid trapped between tissues and organs of the abdomen) – ascites, interstitial area around lungs – pulmonary edema, often as a result of burns.

Third Spacing

***This is problematic, fluid is being lost from the intravascular space.

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Fluid compartments are separated by a ________ ________. Utilizing osmosis, water moves from an area of higher concentration of water (more dilute solution, lower solute concentration) to an area of lower concentration of water (more concentrated solution, higher solute concentration).

Semipermeable Membrane

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ECF volume must be closely regulated to help maintain BP. Maintaining _______ balance is of primary importance in the long-term regulation of ECF volume.

Salt

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ECF osmolarity must be closely regulated to prevent swelling or shrinking of cells. Maintaining _______ balance is of primary importance in regulating ECF osmolarity.

Water

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There is presence of cell ________ in the ICF that cannot permeate the enveloping membranes to leave the cells.

Proteins

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Unequal distribution of Na+ and K+ and their attendant anions as a result of the action of the membrane-bound ________ present in all cells. This actively transports Na+ out of and K+ into cells.

Na+/K+ Pump

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_______ is the primary ECF cation and ________ is the primary ICF cation.

Na+

K+

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_______ is a universal solvent and dissolves various compounds that are either an electrolyte or non-electrolyte.

Water

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__________ contain covalent bonds that prevent them from dissociating in solution and therefore have no electrical charge (i.e., glucose, lipids, and urea).

Non-electrolytes

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__________ dissociate into ions (ionize) in water. Examples are Mg+, Na+, Cl-, and K+.

Electrolytes

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Electrolytes have a higher osmotic power than non-electrolytes because each electrolyte molecule dissociates into at least two ions. Electrolytes have a greater ability to cause a _______ _______.

Fluid Shift

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This is the measure of the number of osmotically active particles per kilogram of water.

Osmolality

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This is the number of osmotically active particles per liter of total solution.

Osmolarity

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All body fluid compartments have approximately the same (OSMOLARITY/OSMOLALITY), expressed as the number of osmotically active particles per kilogram of water (290 mOsm).

Osmolality

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This is the term for if you urinate >2.5 L/day. Normal is 1-2 L/day. Causes include Diabetes Mellitus, DI, excess caffeine or alcohol, kidney disease, diuretics, sickle cell anemia, excess water intake, etc.

Polyuria (excessive urine production)

This is the term for if you urinate 300-500 mL/day. Normal is 1-2 L/day. Causes include dehydration, blood loss, diarrhea, cardiogenic shock, kidney disease, and enlarged prostate.

Oliguria (output below the minimum volume)

This is the term for if you urinate <50 mL/day. Normal is 1-2 L/day. Causes include kidney failure or obstruction such as kidney stone or tumor.

Anuria (virtual absence of urine)

How can Obligatory Urine Volume be calculated?

Take the minimal amount of solutes that a person must excrete in a day (i.e., active person is 1000 mOsm/day). Divide it by 1200 mOsm/L (maximal volume of urine concentration by kidney). 1000 / 1200 = 0.83 L/Day ***Less than this is Oliguria for this person.

The rate of ________ ________ represents the rate at which solute-free water is excreted by the kidneys.

Free-Water Clearance

If free-water clearance is positive, then excess water is being excreted by the kidneys. This means urine is ________.

Dilute

In the cases when free-water clearance is negative, excess solutes are being removed from the blood by the kidneys and water is being conserved. This means urine is ________ because we're conserving water.

Concentrated

Whenever _______ osmolarity is greater than ________ osmolarity, free water clearance will be negative, indicating water conservation.

Urine | Plasma

Free-water clearance (CH2O) is calculated as the difference between water excretion (urine flow rate, V) and osmolar clearance. What does this equation look like?

CH2O = V - Cosm = V - [ (Uosm x V) / (Posm) ] ``` Uosm = Urine Osmolarity V = Urine Flow Rate P = Plasma Osmolarity ```

How can we measure the volume in fluid compartments?

Take a small amount of dye or other substance contained in a syringe and inject it into a chamber. The substance is allowed to disperse through the chamber until it is in equal concentrations everywhere. A sample of the fluid is removed and the concentration is analyzed. ***This works for virtually any compartment as long as 1) the indicator disperses evenly, 2) the indicator disperses ONLY in that compartment, and 3) the indicator is not metabolized or secreted.

The main solutes in the ECF are...

1. Sodium 2. Glucose 3. Urea ***Using these we can calculate serum osmolality!

What is the equation for serum osmolality?

Osmolality = (Sodium x 2) + (Glucose/18) + (BUN/2.8) ***Should equal 275-295 mOsm/kg!

What is the "eyeball" way to calculate plasma osmolality?

Plasma Osmolality = 2 (Plasma Na+)

This effect occurs when negatively charged proteins on one side of a semipermeable membrane create an osmotic and electrochemical gradient for water to enter the cell. The proteins are impermeable to the membrane.

Gibbs-Donnan Effect

What would happen if Gibbs-Donnan effects were not countered?

Intracellular proteins would result in an influx of water into the cell, resulting in cell swelling and eventually death.

The Na/K ATPase pump counteracts the inward force created by the Gibbs-Donnan effect by pumping _______ ions out in exchange for _______ ions pumped in. Net balance prevents excessive inward movement of water.

3 Na+ | 2 K+

Water moves between ICF and ECF compartments primarily as a function of ________ forces.

Osmotic

_______ is responsible for the ECF osmotic balances and _______ maintains the ICF osmotic balance.

Sodium | Potassium

Two factors make the free movement of fluid possible, which are...

1) Water molecules diffuse through the capillary walls faster than blood 2) There is a pressure difference between the inside and outside of the vessels (capillary filtration pressure)

As long as capillary blood pressure exceeds plasma colloid osmotic pressure then water and solutes can leave the capillaries and enter the interstitial fluid. This is called...

Filtration

When capillary blood pressure falls below plasma colloid osmotic pressure, then water returned to capillaries. This is called...

Absorption

Normally, capillary blood pressure exceeds plasma colloid osmotic pressure in the _________ end and falls below it in the ________ end. Occasionally, extra fluid filters out of the capillary and then this fluid shifts into the ________ vessels.

Arteriole Venule Lymphatic

Large proteins such as Albumin normally can't pass through capillary membranes. The osmotic, pulling force of Albumin (magnetic-like) in the intravascular space attracts water and holds it inside the blood vessel. This is referred to as...

Plasma Colloid Osmotic Pressure

This is palpable swelling produced by expansion of interstitial fluid volume.

Edema

What can cause edema?

1) Alteration in capillary hemodynamics (altered Starling forces with increased net filtration pressure) * **i.e, CHF 2) Renal retention of dietary Na+ and water expansion of ECF volume * **i.e., Primary renal disease

This type of edema are swollen cells due to increased ICF volume.

Non-pitting Edema

This type of edema is increased interstitial fluid volume.

Pitting Edema

The ________ of a solution is the effect the solution has on cell volume and whether the cell remains the same size, swells, or shrinks when the solution surrounds the cell.

Tonicity ***Cells have a NaCl concentration equal to 0.85% -- important for tonicity!

This type of cell environment has a NaCl concentration equal to 0.85%. If cells are placed in this solution, there will be equal movement of water in and out of the cell.

Isotonic

This type of cell environment has a NaCl concentration greater than 0.85%. If cells are placed in this solution, there will be a net movement of water out of the cell which will cause the cell to shrink.

Hypertonic

This type of cell environment has a NaCl concentration less than 0.85%. If cells are placed in this solution, there will be net movement of water into the cell which will cause the cell to swell.

Hypotonic

Blood contains both ECF (the fluid in plasma) and ICF (the fluid in the RBCs). Average blood volume of adults is about 7% of body weight, or about 5 liters. About ______ of the blood is plasma and _______ is RBCs.

60% | 40%

ECF volume (GAIN/LOSS) will result in increased total plasma protein (concentration).

Loss

ECF volume (GAIN/LOSS) will result in decreased total plasma protein (dilution).

Gain

What are the effects of ECF volume loss or gain on hematocrit?

ECF volume loss = Increased hematocrit (concentration) | ECF volume gain = Decreased hematocrit (dilution)

What are the effects of ICF volume loss or gain on hematocrit?

ICF volume loss = Decreased hematocrit (shrinkage of RBCs) ICF volume gain = Increased hematocrit (swelling of RBCs)

Replacement therapy is the infusion of IV solutions that have distinctive differences in composition that affect how the body reacts to and utilizes them. They are placed in 2 categories, which are...

Crystalloids | Colloids

These contain organic or inorganic salts dissolved in sterile water. They do not cross plasma membranes, remain in ECF. Distributed evenly within ECF, readily diffusing across capillary walls to equilibrate between intravascular (plasma ECV) and interstitial volume.

Crystalloids

What are the most commonly used solutes in Crystalloids?

Glucose NaCl ***Normal saline (0.9% NaCl) and lactated Ringer's (LR) are commonly used.

These contain large molecules that don't pass through semipermeable membranes. When infused, they remain in the intravascular compartment and expand intravascular volume by drawing fluid from extravascular spaces via their higher oncotic pressure. Examples are hydroxyethyl starches (HES) and Albumin.

Colloids

Changes in Na+ causes changes in _______ status.

Volume

Changes in water balance causes changes in _______ concentration and ________.

Na+ | Osmolarity

________ occurs due to a decreased water intake, increased fluid loss, or both. In elderly people, impaired thirst sensation, chronic illness, fever and sickness are common reasons for a decreased water intake.

Dehydration

The common reasons for increased fluid loss include vomiting, diarrhea, diuresis, and sweating. Working in hot weather without water replacement is another common reason of dehydration. Dehydration can be divided, according to the serum Na+ concentration, into __________ or __________ dehydration.

Hypernatremic | Hyponatremic

In this type of dehydration, loss of Na+ is greater than the loss of water in ECF. Serum Na+ concentration in the ICF is greater than that of the ECF. Water shifts from the ECF to the ICF to establish osmotic equilibrium. Serum Na+ and serum osmolality will be less than the normal range.

Hypotonic (Hyponatremic) Dehydration

In this type of dehydration, loss of water is greater than the loss of Na+ in the ECF. Serum Na+ concentration in the ECF is greater than in the ICF, water shifts from the ICF to the ECF. Serum osmolality will exceed 300 mOsm/kg and serum Na+ will be more than 150 mEq/L.

Hypertonic (Hypernatremic) Dehydration

Fluid shift disturbances are categorized according to whether they involve an increase or decrease in _______ volume.

ECF

Volume _________ means a decrease in ECF volume, also called volume _________. This causes decreased blood volume and decreased blood pressure.

Contraction | Depletion

Volume ________ means an increase in ECF volume. This can cause increased blood pressure and edema.

Expansion

Fluid shift disturbances are also categorized according to whether they cause a change in body fluid osmolarity: 1) ________ means no change in body fluid osmolarity 2) ________ means body fluid osmolarity is increased 3) ________ means body fluid osmolarity is decreased

Isosmotic Hyperosmotic Hyposmotic

These diagrams are used to study the effects of various clinical conditions, such as dehydration, shock, vomiting, and diarrhea on osmolality and volume of ECF and ICF.

Darrow-Yannet Diagrams

This can occur due to acute fluid loss conditions like hemorrhage, diarrhea, and vomiting. Diarrhea causes loss of isosmotic fluid from the GI tract. There is a decrease in ECF volume and no change in body osmolality and ICF volume.

Isosmotic Volume Contraction ***See slides for diagram

This occurs due to hypotonic fluid loss conditions like dehydration, diabetes insipidus, and alcoholism. There is insensible water loss from ECF and solute is left behind and become concentrated. There is a decrease in ECF volume and ICF volume, but an increase in body osmolality.

Hyperosmotic Volume Contraction ***See slides for diagram

This occurs from adrenal insufficiency due to loss of aldosterone leading to excessive loss of NaCl in urine. Transient response is that ECF osmolarity decreases and fluid shifts to ICF until osmolarity equilibrates. ICF volume increases, ECF volume decreases, osmolarity decreases.

Hyposmotic Volume Contraction

This occurs from and isotonic saline injection of NaCl. ECF volume expands, ICF does not change, osmolarity does not change.

Isotonic Volume Expansion

This occurs from a high NaCl intake. ECF volume increases, ICF volume decreases, and osmolarity increases. Transiently ECF osmolarity increases so volume shifts from ICF to ECF until osmolarity equilibrates.

Hypertonic Volume Expansion

This can occur due to conditions like excess water-drinking and SIADH (syndrome of inappropriate ADH). There is a gain of hypotonic fluid and and increase in ECF and ICF volume, but a decrease in body osmolarity.

Hyposmotic Volume Expansion

Patients with disease have low effective circulating volume due to decreased CO. It is sensed as low pressure and it has less carrying capacity.

Congestive Heart Failure (CHF)

In CHF, there is _______ and _______ retention resulting in edema in which venous and capillary hydrostatic pressure increase.

Na+ | Fluid

In CHF, patients continue to retain Na+, increasing the ________ volume without correcting the effective circulating volume.

ECF

In CHF, what are the 4 main ways the decreases in the effective circulating volume are counteracted?

1) Activation of RAAS 2) Stimulation of SNS via drop in pressure 3) Increased ADH secretion 4) Increased renal fluid retention (altered Starling's forces in peritubular capillaries)

Vascular volume sensors detect changes in ECF volume and signals to the kidneys. This results in adjustment to _______ and ______ excretion.

NaCl | Water

If ECF volume is ________, renal NaCl and water excretion are increased.

Expanded

If ECF volume is ________, renal NaCl and water excretion are reduced.

Contracted

What is the effect of renal sympathetic nerves?

Decrease NaCl excretion

What is the effect of RAAS?

Decrease NaCl excretion ***Controls BP by regulating blood volume and TPR

What is the effect of ADH/vasopressin?

Decreases water excretion

What is the effect of ANP/BNP/Urodilatin?

- - Increase NaCl excretion | - - Reduce Renin and ADH secretion

Renin is an enzyme secreted by the kidney. Release is stimulated by drop in BP and by __________ receptor activation.

B1-Adrenergic

Renin causes Angiotensinogen to be converted to _________ (inactive) in the blood.

Angiotensin I

Angiotensin I is converted to _________ (active) in the lungs and kidneys to begin the compensation mechanism. Angiotensin induces the release of _________.

Angiotensin II | Aldosterone