Types Examples

Iso-osmotic volume contraction Diarrhea,Burns

Hyperosmotic volume contraction Severe dehydration (sweating, fever, diabetes insipidus - ↓ ADH)

Hypo-osmotic volume contraction Adrenal insufficiency (↓ aldosterone)

Iso-osmotic volume expansion Infusion of isotonic saline

Hyperosmotic volume expansion High NaCl intake

Hypo-osmotic volume expansion Syndrome of inappropriate ADH secretion (SIADH)

SHIFTS OF WATER BETWEEN BODY FLUID COMPARTMENTS -

ISO-OSMOTIC VOLUME EXPANSION

1. ECF Fluid change ?

2. ECF Osmolarity ?

3. ICF Osmolarity ?

4. Hematocrit ?

ISO-OSMOTIC VOLUME CONTRACTION

1. ECF Fluid change ?

2. ECF Osmolarity ?

3. ICF Osmolarity ?

4. Hematocrit ?

HYPEROSMOTIC VOLUME EXPANSION

1. ECF Fluid change ?

2. ECF Osmolarity ?

3. ICF Osmolarity ?

4. Hematocrit ?

HYPEROSMOTIC VOLUME CONTRACTION

1. ECF Fluid change ?

2. ECF Osmolarity ?

3. ICF Osmolarity ?

4. Hematocrit ?

HYPO-OSMOTIC VOLUME EXPANSION

1. ECF Fluid change ?

2. ECF Osmolarity ?

3. ICF Osmolarity ?

4. Hematocrit ?

Hypo-osmotic volume contraction

1. ECF Fluid change ?

2. ECF Osmolarity ?

3. ICF Osmolarity ?

4. Hematocrit ?

• Loss of isotonic fluid that might be due to hemorrhage (neglect loss of intracellular fluid as RBC volume), isotonic urine, or the immediate consequences

• of diarrhea or vomiting:

• Loss of hypotonic fluid that might be due to sweating (dehydration), hypotonic urine, or diabetes insipidus:

• Ingestion of salt tablets:

• Person who drinks 1 liter of tap (or distilled) water:

• Infusion of hypotonic saline (half-normal saline):

• Infusion of isotonic saline:

• Infusion of hypertonic saline (or hypertonic mannitol; mannitol does not cross cell membranes easily):

• Primary adrenal insufficiency

A 23-year-old man is brought to the Emergency Department after collapsing during basketball practice. On admission he is lethargic and appears confused. His coach reports that it was hot in the gym and he was drinking a lot of water during practice. An increase in which of the following is the most likely cause of his symptoms?a. Intracellular tonicityb. Extracellular tonicityc. Intracellular volumed. Extracellular volumee. Plasma volume

A 70kg man is given a treatment intravenously. The diagram shows the intracellular(ICF) volume And extracellular fluid(ECF)volume before and after treatment. Which of the following treatments was likely administered to this man?

A. Hypertonic salineB. Hypotonic saline.C. Isotonic salineD. Isotonic glucose.

7.A 14-year-old boy has a craniotomy performed under general endotracheal anesthesia for removal of a craniopharyngioma. The anesthetic agent used is halothane, and when he is fully awake in the recovery room, he is extubated and sent to the floor. Five percent dextrose in one-third normal saline was dripping in his intra-venous line at a rate of 125 mL/h. Four hours later, the nurses report that he cannot be roused from a deep sleep. They also point out that his urinary output in each of those 4 hours was 1059, 1100, 980, and 1250 mL, respectively. Laboratory studies show: Sodium 156 mEq/LOsmolarity 312 mOsm/LpH 7.55pco2 28 mm HgBicarbonate 24 mEq/L

Which of the following best explains these findings? (A) Brain edema (B) Nephrogenic diabetes insipidus (C) Respiratory depression induced by unmetabolized anesthetic (D) Surgical trauma to the posterior pituitary (E) Water retention

Oral Rehydration Therapy Is Driven by Solute TransportOral administration of rehydration solutions has dramatically reduced the mortality resulting from cholera and other diseases that involve excessive losses of water and solutes from the gastrointestinal tract. The main ingredients of rehydration solutions are glucose, NaCl, and water. The glucose and Na+ ions are reabsorbed by SGLT1 and other transporters in the epithelial cells lining the lumen of the small intestine .

Deposition of these solutes on the basolateral side of the epithelial cells increases the osmolarity in that region compared with the intestinal lumen and drives the osmotic absorption of water. Absorption of glucose, and the obligatory increases in absorption of NaCl and water, helps to compensate for excessive diarrheal losses of salt and water.

• Principle: In humans, the volumes of the body fluid compartments are measured by the dilution method.

• The basic principle underlying this method is that a marker substance will be distributed in the body fluid compartments according to its physical characteristics.

The following steps are used to measure volumes of

body fluid compartments by the dilution method:1. Identification of an appropriate marker substance. Required criteria of tracers to measure the

following compartments:• Plasma: not permeable to capillary membranes, e.g.,

albumin• ECF: permeable to capillary membranes but not cell

membranes,e.g., inulin, mannitol, sodium, sucrose• Total body water: permeable to capillary and cell

membranes, e.g., tritiated water, urea

2. Injection of a known amount of the marker substance. The amount of marker

• substance injected into the blood is measured in milligrams (mg), millimoles (mmol), or units of radioactivity (e.g., millicuries [mCi]).

3. Equilibration and measurement of plasma concentration. The marker is allowed to

• equilibrate in the body fluids, correction is made for any urinary losses during the equilibration period, and the concentration of the marker is then measured in plasma.

• 4. Calculation of the volume of the body fluid compartment

• V × C = A, therefore V = A/C• V = Volume of the compartment to be

measured• C = Concentration of the tracer in the

compartment to be measured• A = Amount of the tracer

• If 300 mg of a dye was injected intravenously and at equilibrium,and the concentration in the blood was 0.05 mg/mL, the volume of the compartment that contained the dye would be:

• Volume = 300 mg/ 0.05 mg/mL or 6000 mL

Q

• If 1 milliliter of a solution containing 10 mg/ml of dye is dispersed into chamber B and the final concentration in the chamber is 0.01 milligram for each milliliter of fluid, the unknown volume of the chamber would be?

• A patient is injected with 500 mg of mannitol. After a 2-hour equilibration period, the concentration of mannitol in plasma is 3.2 mg/100 mL. During the equilibration period, 10% of the injected mannitol is excreted in urine. What is the patient's ECF volume

Q

• A 65-kg man is participating in a research study for which it is necessary to know the volumes of his body fluid compartments.

• To measure these volumes, the man is injected with 100 mCi of D2O and 500 mg of mannitol . During a 2-hour equilibration period, he excretes 10% of the D2O and 10% of the mannitol in his urine.

• Following equilibration, the concentration of D2O in plasma is 0.213 mCi/100 mL and the concentration of mannitol is 3.2 mg/100 mL.

• What is his total body water, his ECF volume, and his ICF volume? Is the man's total body water appropriate for his weight?

The man's total body water is 42.3 L, which is 65.1% of his body weight(42.3 L is approximately 42.3 kg; 42.3 kg/65 kg = 65.1%). This percentage falls within the normal range of 50% to 70% of body weight.

Distribution of intravenously administered fluids

• Vascular compartment: whole blood, plasma, dextran in saline.

• ECF: saline, mannitol. At least 2/3 of the fluid would enter the ISF.

• Total body water: D5W–5% dextrose in water. Once the glucose is metabolized,the water would distribute 2/3 ICF, 1/3 ECF.

Calculation of blood volume

Example:

• Hct = 50% (0.50)• Plasma volume = 3 L

• Blood volume =

Q• A woman runs a marathon on a hot September day

and drinks no fluids to replace the volumes lost in sweat. It is determined that she lost 3 L of sweat, which had an osmolarity of 150 mOsm/L.

• Before the marathon, her total body water was 36 L, her ECF volume was 12 L, her ICF volume was 24 L, and her body fluid osmolarity was 300 mOsm/L.

• Assume that a new steady state is achieved and that all of the solute (i.e., NaCl) lost from her body came from the ECF. What is her ECF volume and osmolarity after the marathon?

THE MICROCIRCULATION

• Filtration and Reabsorption

• Qf = k [(Pc + πIF) – (PIF + πC)]• Qf = fluid movement• k = filtration coefficient

Questions

1. Given the following values, calculate a net pressure:

PC = 25 mm HgPIF = 2 mm HgπC = 20 mm HgπIF = 1 mm Hg2. Calculate a net pressure if the interstitial

hydrostatic pressure is –2 mm Hg.

EDEMA

The edematous state requires two conditions for its development and maintenance:

1. An increase in the Starling forces, which promote the movement of fluid from the vascular compartment to the interstitium

2. Retention of sodium and water by the kidney

Peripheral edema expresses itself in two different forms

1. Non-pitting edema: This is often referred to as a lymphedema which is a disturbance of the lymphatic system. This can develop after the removal of systemic tissue such as after a mastectomy. Non-pitting edema does not respond to diuretics.

2. Pitting edema: This is the classical, most common type observed clinically. Pitting edema generally responds to diuretic therapy. Common causes include nephrotic syndrome, congestive heart failure, cirrhosis, pregnancy, idiopathic edema, and nutritional edema

Packed Cell Volume

• Percentage of the cellular elements (RBC’s,WBC’s and platelets) in the whole blood.

• PCV is considered equivalent to the volume of packed red cells or the so called haematocrit value, as the volume of WBC’s and platelets is very less.

• In 100ml of blood PCV is 45ml.• Haematocrit is the volume of RBC’s expressed as

percentage• Haematocrit value in males is about 45% Haematocrit value in females about 42%

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HEMATOCRIT (Htc)-Important Diagnostic Measurement

• Is the fraction of the blood volume made up of the formed elements (mainly RBC)

• Is determined by the centrifuging heparinised/anticoagulated blood in a standard calibrated tube of a small diameter

•When blood is allowed to clot or coagulate, the suspendingmedium is referred to as serum

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(Htc)-Important Diagnostic Measurement

Plasma (55% of whole blood)

Erythrocytes (45% of whole blood)

Buffy coat: Leucocytes and Platelets <1% of whole blood

Formed Elements

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HEMATOCRIT

Normal Anemia Polycythemia

Tube A Tube B Tube C

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HEMATOCRIT

• Values– Males: 40 – 54 vol% (mean – 47%; 0.47)– Females: 38 – 46 vol% (mean – 42%, 0.42)

• ↑ in persons leaving at high altitudes, polycythemia, etc. • ↓ in anemia, leukemia, bone marrow failure

• Importance– Determines blood viscosity– ↑ Htc → ↑ resistance to blood flow, load on the heart & BP

Determination of hematocrit values is a simple and important screening diagnostic procedure in the evaluation of hematological disease

The contribution of the WBC to hematocrit is only 0.08%. WBCs are lighter than the RBCs, they form a thin whitish layer between the sedimented RBCs and the plasma.