PHS 201 Body Fluid Compartment PDF

PHS 201 INTRODUCTORY PHYSIOLOGY, EXCITABLE TISSUE AND AUTONOMIC NERVEOUS SYSTEM TOPIC BODY FLUID COMPARTMENT LECTURER MR EPHRAIM IME EKANEM  BODY FLUIDS  Body is formed by solids and fluids.  Fluid part is more than two third...

PHS 201 INTRODUCTORY PHYSIOLOGY, EXCITABLE TISSUE AND AUTONOMIC NERVEOUS SYSTEM TOPIC BODY FLUID COMPARTMENT LECTURER MR EPHRAIM IME EKANEM  BODY FLUIDS  Body is formed by solids and fluids.  Fluid part is more than two third of the whole body.  Water forms most of the fluid part of the body.  In human beings, the total body water varies from 45% to 75% of body weight.  In a normal young adult male, body contains 60% to 65% of water and 35% to 40% of solids.  In a normal young adult female, the water is 50% to 55% and solids are 45% to 50%.  In females, water is less because of more amount of subcutaneous adipose tissue.  In thin persons, water content is more than that in obese persons.  In old age, water content is decreased due to increase in adipose tissue.  Total quantity of body water in an average human being weighing about 70 kg is about 40 L. SIGNIFICANCE OF BODY FLUIDS IN HOMEOSTASIS  Body cells survive in the fluid medium called internal environment or ‘milieu interieur’.  Internal environment contains substances such as glucose, amino acids, lipids, vitamins, ions, oxygen, etc. which are essential for growth and functioning of the cell.  Water not only forms the major constituent of internal environment but also plays an important role in homeostasis IN TRANSPORT MECHANISM  Body water forms the transport medium by which nutrients and other essential substances enter the cells; and unwanted substances come out of the cells.  Water forms an important medium by which various enzymes, hormones, vitamins, electrolytes and other substances are carried from one part to another part of the body. IN METABOLIC REACTIONS  Water inside the cells forms the medium for various metabolic reactions, which are necessary for growth and functional activities of the cells. IN TEXTURE OF TISSUES  Water inside the cells is necessary for characteristic form and texture of various tissues. IN TEMPERATURE REGULATION  Water plays a vital role in the maintenance of normal body temperature.  Composition of the human body  Water → 60% of the body weight.  Proteins → 18% of the body weight.  Fats → 18% of the body weight.  Minerals → 4% of the body weight.  COMPOSITION OF BODY FLUIDS  Body fluids contain water and solids.  Solids are organic and inorganic substances. ORGANIC SUBSTANCES  Glucose  Amino acids and other proteins  Fatty acids and other lipids  Hormones  Enzymes. INORGANIC SUBSTANCES  Sodium  Potassium  Calcium  Magnesium  Chloride  Bicarbonate  Phosphate  Sulfate COMPARTMENTS OF BODY FLUIDS – DISTRIBUTION OF BODY FLUIDS Total water in the body is about 40 L. It is distributed into two major compartments:  Intracellular fluid (ICF): Its volume is 22 L and it forms 55% of the total body water  Extracellular fluid (ECF): Its volume is 18 L and it forms 45% of the total body water. ECF is divided into 5 subunits: i. Interstitial fluid and lymph (20%) ii. Plasma (7.5%) iii. Fluid in bones (7.5%) iv. Fluid in dense connective tissues like cartilage (7.5%) v. Transcellular fluid (2.5%) that includes: a. Cerebrospinal fluid b. Intraocular fluid c. Digestive juices d. Serous fluid – intrapleural fluid, pericardial fluid and peritoneal fluid e. Synovial fluid in joints f. Fluid in urinary tract.  Volume of interstitial fluid is about 12 L.  Volume of plasma is about 2.75 L.  Volume of other subunits of ECF is about 3.25 L.  Water moves between different compartments  Body Water Variation of body H2O with age and sex as % of body weight AGE LIMITS Male FEMALE At birth 82% 82% Children & Adolescence 90% 70% 18-20 years 59% 57% 20-40 years 56% 51% 40-60years 55% 47% Over 60 years 52% 46% Fluid intake and output are balanced during steady-state conditions. DAILY INTAKE OF WATER: 1. It is ingested in the form of liquids or water in food (2L). 2. It is synthesized in the body by oxidation of carbohydrates, adding about 200 ml/day. DAILY LOSS OF BODY WATER 1. Insensible Water Loss. 2. Fluid Loss in Sweat. 3. Water Loss in Feces. 4. Water Loss by the Kidneys. Differences between extracellular fluid (ECF) and intracellular fluid (ICF) Substance ECF ICF Sodium 142 mEq/L 10 mEq/L Calcium 5 mEq/L 1 mEq/L Potassium 4 mEq/L 140 mEq/L Magnesium 3 mEq/L 28 mEq/L Chloride 103 mEq/L 4 mEq/L Bicarbonate 28 mEq/L 10 mEq/L Phosphate 4 mEq/L 75 mEq/L Sulfate 1 mEq/L 2 mEq/L Proteins 2 g/dL 16 g/dL Amino acids 30 mg/dL 200 mg/dL Glucose 90 mg/dL 0-20 mg/dL Lipids 0.5 g/dL 2-95 g/dL Partial pressure of oxygen 35 mm Hg 20 mm Hg Partial pressure of carbon dioxide 46 mm Hg 50 mm Hg Water 15 to 20 L (18) 20 to 25 L (22) pH 7.4 7.0 7.4 7.0  MEASUREMENT OF BODY FLUID VOLUME Total body water and the volume of different compartments of the body fluid are measured by indicator dilution method or dye dilution method. INDICATOR DILUTION METHOD Principle  A known quantity of a substance such as a dye is administered into a specific body fluid compartment.  These substances are called the marker substances or indicators.  After administration into the fluid compartment, the substance is allowed to mix thoroughly with the fluid.  Then, a sample of fluid is drawn and the concentration of the marker substance is determined.  Radioactive substances or other substances whose concentration can be determined by using colorimeter are generally used as marker substances. MEASURE THE VOLUME OF FLUID BY INDICATOR DILUTION METHOD: V=M C V = volume of fluid in the compartment M = Mass or total quantity of marker substance injected C = Concentration of the marker substances in the sample of fluid CORRECTION FACTOR Some amount of marker substance is lost through urine during distribution. Therefor, the formula is corrected as follows: Volume = M – Amount of substance excreted C Uses of Indicator Dilution Method  It is used to measure ECF volume, plasma volume and the volume of total body water. Characteristics of Marker Substances  It must be nontoxic.  Must have the ability to mix with the fluid compartment thoroughly within reasonable time.  It should not be excreted rapidly.  It should be excreted from the body completely within reasonable time.  It must not change the color of the body fluid.  It must not alter the volume of the body fluid. MEASUREMENT OF TOTAL BODY WATER  Deuterium oxide and tritium oxide mix with fluids of all the compartments within few hours after injection.  Since plasma is part of total body fluid, the concentration of marker substances can be obtained from sample of plasma.  The formula for indicator dilution method is applied to calculate total body water. V=M C V = volume of fluid in the compartment M = Mass or total quantity of marker substance injected C = Concentration of the marker substances in the sample of fluid  Antipyrine is also used to measure total body water.  But as it takes longer time to penetrate various fluid compartments, the value obtained is slightly low. MEASUREMENT OF EXTRACELLULAR FLUID VOLUME  Substances which pass through the capillary membrane but do not enter the cells, are used to measure ECF volume.  These substances remain only in ECF and do not enter the cell (ICF).  When any of these substances is injected into blood, it mixes with the fluid of all sub-compartments of ECF within 30 minutes to 1 hour.  Indicator dilution method is applied to calculate ECF volume.  Since ECF includes plasma, the concentration of marker substance can be obtained in the sample of plasma.  Some of the marker substances like sodium, chloride, inulin and sucrose diffuse more evenly throughout all sub-compartments of ECF.  The measured volume of ECF by using these substances is referred as sodium space, chloride space, inulin space and sucrose space. Example for Measurement of ECF Volume Quantity of sucrose injected (Mass) : 150 mg Urinary excretion of sucrose : 10 mg Concentration of sucrose in plasma : 0.01 mg/mL V=M C Sucrose space = Mass – Amount lost in urine Concentration of sucrose in plasma = 150 – 10 mg 0.01 mg/mL = 14,000 mL Therefore, the ECF volume = 14 L. MEASUREMENT OF PLASMA VOLUME  The substance which binds with plasma proteins strongly and diffuses into interstitium only in small quantities or does not diffuse is used to measure plasma volume.  Plasma volume is determined by using the formula, Volume = Amount of dye injected – Amount excreted Average concentration of dye in plasma MEASUREMENT OF INTERSTITIAL FLUID VOLUME  Volume of interstitial fluid cannot be measured directly.  It is calculated from the values of ECF volume and plasma volume. Interstitial fluid volume = ECF volume – Plasma volume MEASUREMENT OF INTRACELLULAR FLUID VOLUME  Volume of ICF cannot be measured directly.  It is calculated from the values of total body water and ECF. ICF volume = Total fluid volume – ECF volume. MEASUREMENT OF BLOOD VOLUME: Total blood volume = Plasma volume 1 - Hematocrit Marker substances used to measure body fluid compartments Fluid compartment Marker substances 1. Deuterium oxide Total body water 2. Tritium oxide 3. Antipyrine 1. Radioactive sodium, chloride, bromide, sulfate and thiosulfate. Extracellular fluid 2. Non-metabolizable saccharides like inulin, mannitol, raffinose and sucrose Plasma 1. Radioactive iodine 2. Evans blue CONCENTRATION OF BODY FLUIDS Concentration of body fluids is expressed in three ways:  Osmolality  Osmolarity  Tonicity.  OSMOLALITY  It is the concentration of osmotically active substance in the solution which can create osmotic pressure.  Osmolality is expressed as the number of particles (osmoles) per kilogram of solution (osmoles/kg H2O).  OSMOLARITY  It express the osmotic concentration.  It is the number of particles (osmoles) per liter of solution (osmoles/L).  Often, these two terms are used interchangeably.  Change in osmolality of ECF affects the volume of both ECF and ICF.  When osmolality of ECF increases, water moves from ICF to ECF.  When the osmolality decreases in ECF, water moves from ECF to ICF.  Water movement continues until the osmolality of these two fluid compartments becomes equal. However, in practice, the osmolarity and not osmolality is considered to determine the osmotic pressure because of the following reasons:  Measurement of weight (kilogram) of water in solution is a difficult process.  Difference between osmolality and osmolarity is very much negligible and it is less than 1%.  Mole and Osmole  A mole (mol) is the molecular weight of a substance in gram.  Millimole (mMol) is 1/1000 of a mole.  One osmole (Osm) is the expression of amount of osmotically active particles.  TONICITY  Tonicity is the measure of effective osmolality.  Movement of water between the fluid compartments is not influenced by small molecules like urea and alcohol, which cross the cell membrane very rapidly.  These small molecules are called ineffective osmoles.  On the contrary, the larger molecules like sodium and glucose, which cross the cell membrane slowly, can influence the movement of water.  Therefore, such molecules are called effective osmoles.  Osmolality that causes the movement of water from one compartment to another is called effective osmolality and the effective osmoles are responsible for this. In terms of tonicity, the solutions are classified into three categories namely:  Isotonic fluid  Hypertonic fluid  Hypotonic fluid.  Isotonic Fluid  Fluid which has the same effective osmolality (tonicity) as body fluids is called isotonic fluid.  Examples are 0.9% sodium chloride solution (normal saline) and 5% glucose solution.  Red blood cells or other cells placed in isotonic fluid (normal saline) neither gain nor lose water by osmosis  This is because of the osmotic equilibrium between inside and outside the cell across the cell membrane.  Hypertonic Fluid  Fluid which has greater effective osmolality than the body fluids is called hypertonic fluid.  Example is 2% sodium chloride solution.  When red blood cells or other cells are placed in hypertonic fluid, water moves out of the cells (exosmosis) resulting in shrinkage of the cells (crenation).  Hypotonic Fluid  Fluid which has less effective osmolality than the body fluids is called hypotonic fluid.  Example is 0.3% sodium chloride solution.  When red blood cells or other cells are placed in hypotonic fluid, water moves into the cells (endosmosis) and causes swelling of the cells.  The red blood cells become globular (sphereocytic) and get ruptured (hemolysis).  APPLIED PHYSIOLOGY  NEGATIVE WATER BALANCE  When the output of water is more than input, negative water balance develops. Types Negative Water Balance  Physiological Negative Water Balance  Occurs during exercise  Water loss when working in hot sun.  Pathological Negative Water Balance  Dehydration  Burns  Hemorrhage  Vomiting  Diarrhea  POSITIVE WATER BALANCE  When the intake is more than the output then a positive water balance develops. Types Positive Water Balance  Physiological Positive Water Balance  Growth  Convalescence  Pregnancy Pathological Positive Water Balance  Edema. DEHYDRATION Definition The Excessive loss of body water leading to a decline in body water level. Types of Dehydration  Mild Dehydration  It occurs when fluid loss is about 5% of total body fluids.  Dehydration is not very serious and can be treated easily by rehydration. Moderate Dehydration  It occurs when fluid loss is about 10%.  Dehydration becomes little serious and immediate treatment should be given by rehydration.  Severe Dehydration  It occurs when fluid loss is about 15% and when it is more than 15%, dehydration becomes very severe and life threatening.  Dehydration becomes severe and requires hospitalization and emergency treatment. Based on the ratio between water loss and sodium loss, dehydration is classified into three types:  Isotonic dehydration  Balanced loss of water and sodium as in the case of diarrhea or vomiting.  Hypertonic Dehydration  Loss of more water than sodium as in the case of fever.  Hypotonic Dehydration  Loss of more sodium than water as in the case of excess use of diuretics Causes  Excess urinary output due to renal disorders.  Prolonged physical activity without consuming adequate amount of water in hot environment  Excess sweating leading to heat frustration (extreme loss of water, heat and energy  Use of laxatives or diuretics in order to lose weight quickly.  Severe diarrhea and vomiting due to gastrointestinal disorders.  Excess loss of water through urine due to endocrine disorders such as diabetes mellitus, diabetes insipidus and adrenal insufficiency.  Insufficient intake of water.  Signs and Symptoms  Mild and Moderate Dehydration  Headache  Dizziness  Weakness  Cramps in legs and arms.  Dryness of the mouth  Excess thirst  Decrease in sweating  Decrease in urine formation  Severe Dehydration  Decrease in blood volume  Decrease in cardiac output  Low blood pressure  Hypovolemic cardiac shock  Fainting. Very Severe Dehydration  Renal failure  Convulsions  Damage of organs like brain, liver and kidneys  Mental depression and confusion  Coma.  Dehydration in Infants  Infants suffering from severe diarrhea and vomiting caused by bacterial or viral infection, develop dehydration.  If the lost body fluids are not replaced it becomes life threatening.  This occurs when parents are unable to recognize the signs.  Aging Effects on Dehydration  Elders are at higher risk for dehydration even if they are healthy.  It is because of increased fluid loss and decreased fluid intake.  In some cases, severe dehydration in old age may be fatal. Treatment  In Mild Dehydration  Drinking of more water and stopping fluid loss.  In Severe Dehydration  Drinking water alone is ineffective because it cannot compensate the salt loss.  The effective treatment for severe dehydration is oral rehydration therapy.  Oral rehydration therapy  This solution contains anhydrous glucose, sodium chloride, potassium chloride and trisodium citrate.  In Very Severe Dehydration  Intravenous administration of necessary water and electrolytes. WATER INTOXICATION OR OVERHYDRATION Definition  Water intoxication is the condition characterized by great increase in the water content of the body.  It is also called overhydration, hyperhydration, water excess or water poisoning. Causes  Water intoxication occurs when more fluid is taken than that can be excreted.  Water intoxication due to drinking excess water is rare when the body’s systems are functioning normally. CONDITIONS THAT CAN PRODUCE WATER INTOXICATION.  Renal disorders in which kidney fails to excrete enough water in urine.  Heart failure in which heart cannot pump blood properly.  Intravenous administration of unduly large amount of medications and fluids than the person’s body can excrete.  Hypersecretion of antidiuretic hormone as in the case of syndrome of inappropriate hypersecretion of antidiuretic hormone (SIADH).  Infants have greater risk of developing water intoxication in the first month of life, when the filtration mechanism of the kidney is underdeveloped and cannot excrete the fluid rapidly. An adult whose heart and kidneys are functioning normally \can develop water intoxication, if the person consumes about 8 L of water everyday regularly.  Water intoxication is also common in children having swimming practice, since they are more prone to drink too much of water while swimming. Signs and Symptoms  Behavioral changes due to vulnerability of the brain to water intoxication.  Nausea and vomiting occur.  Drowsy and inattentiveness.  There is sudden loss of weight, followed by weakness and blurred vision.  Anemia, acidosis, cyanosis, hemorrhage and shock are also common.  Muscular symptoms such as weakness, cramps, twitching, poor coordination and paralysis develop. Severe conditions of water intoxication result in  Delirium (extreme mental condition characterized by confused state and illusion).  Seizures (sudden uncontrolled involuntary muscular contractions).  Coma (profound state of unconsciousness, in which the person fails to respond to external stimuli and cannot perform voluntary actions). Treatment In Mild Water Intoxication  Requires only fluid restriction. In Very Severe Water Intoxication  Diuretics to increase water loss through urine  Antidiuretic hormone (ADH) receptor antagonists to prevent ADH- induced reabsorption of water from renal tubules  Intravenous administration of saline to restore sodium.  EDEMA DEFINITION  Edema is the swelling caused by excessive accumulation of fluid in the tissues.  Edema may be generalized or local.  Generalized Edema involves the entire body. Example: Cardiac edema, hepatic edema, renal edema, endocrine edema  Local Edema is the one that occurs is specific areas of the body such as abdomen, lungs and extremities like feet, ankles and legs. Example: Venous edema, lymphatic edema, angioedema, inflammation  Accumulation of fluid may be inside or outside the cell. Symptoms of Edema  Swelling or puffiness of the tissue directly under skin.  Stretched or shiny skin.  Skin that retains a dimple after being pressed for several seconds.  Increased abdominal size. TYPES OF EDEMA  Intracellular edema  Extracellular edema INTRACELLULAR EDEMA It is the accumulation of fluid inside the cell. Factors that causes intracellular edema  Inflammation of the tissues.  Poor metabolism  Malnutrition Edema due to Inflammation of Tissues  The permeability of cell membrane increases during inflammation of the tissues.  Thereby causing the movement of many ions, including sodium into the cells resulting in endosmosis and intracellular edema. Edema due to Poor Metabolism  Poor metabolism is caused by poor blood supply.  Poor blood supply leads to lack of oxygen which in turn results to poor function of cell membrane and edema. Edema due to Malnutrition  Malnutrition occurs because of poor intake of food or poor circulatory system, through which the nutritive substances are supplied.  The ionic pumps of the cell membrane are depressed leading to poor exchange of ions due to the lack of nutrition.  Sodium ions leaking into the cells especially cannot be pumped out.  Excess amount of sodium inside the cells causes endosmosis, resulting in intracellular edema. EXTRACELLULAR EDEMA  It is the accumulation of fluid outside the cell. Causes for extracellular edema  Obstruction of lymphatic vessels that prevents fluid return from interstitium to blood.  Abnormal leakage of fluid from capillaries into interstitial space Conditions which lead to extracellular edema  Increased endothelial permeability  Heart failure.  Renal disease.  Decreased amount of plasma proteins.  Lymphatic obstruction. Edema due to Increased Endothelial Permeability  In conditions like burns, inflammation, trauma, allergic reactions and immunologic reactions there is increase permeability of the capillary endothelium which lead to oozing out of fluid.  Accumulation of this fluids leads to the development of edema. Edema due to Heart Failure  Failure of the heart to pump blood from veins to arteries increases venous pressure and capillary pressure.  This leads to increased capillary permeability and leakage of fluid from blood into interstitial fluid, causing extracellular edema.  Fall in blood pressure during heart failure decreases the glomerular filtration rate in the kidneys, resulting in sodium and water retention.  Thereby causing the volume of blood and body fluid to increases which in turn increases the capillary hydrostatic pressure.  During heart failure blood supply to kidneys becomes low thereby increasing renin secretion, which in turn increases aldosterone secretion.  Aldosterone increases the reabsorption of sodium and water from renal tubules into ECF resulting in the development of extracellular edema. Edema due to Renal Diseases – Generalized Edema  The kidneys fail to excrete water and electrolytes particularly sodium in renal disease, leading to retention of water and electrolytes.  This fluid leaks from blood into interstitial space causing extracellular edema.  Edema develops in the legs first, but later it progresses to the entire body.  There is heavy loss of protein in the urine. Edema due to Decreased Amount of Plasma Proteins  When plasma proteins decreases, the colloidal osmotic pressure decreases thereby increasing the permeability of the capillary which in turn increased capillary filtration.  More amount of water leaks out of the capillary and accumulates in the tissue spaces resulting in extracellular edema.  The amount of plasma proteins decreases during the conditions like malnutrition, liver diseases, renal diseases, burns and inflammation. Edema due to Lymphatic Obstruction – Lymphedema  Lymphedema is the edema caused by lymphatic obstruction and is common in filariasis (disease caused by the presences of filariae In the tissue of the body, often resulting in occlusion of the lymphatic channels that can lead to elephantiasis).  In this disease condition, the parasitic worms live in the lymphatics and obstruct the drainage of lymph.  Accumulation of lymph along with cellular reactions leads to swelling that is very prominent in legs and scrotum.  Repeated obstruction of lymphatic drainage in these regions results in fibrosis and development of elephantiasis. Elephantiasis  Elephantiasis is a disorder of lymphatic system that is characterized by thickening of skin and extreme enlargement of the affected area, most commonly limbs (legs), genitals, certain areas of trunk and parts of head. Pulmonary Edema  It is the accumulation of fluid in pulmonary interstitium.  In the case of left heart failure, the blood is easily pumped into pulmonary circulation by right ventricle.  The blood cannot return from lungs to left side of the heart because of weakness of this side of the heart.  This increases pulmonary vascular pressure leading to leakage of fluid from capillaries into pulmonary interstitium thereby causing pulmonary edema which can be life threatening. Classification of Edema Pitting Edema  When pressure is applied to a small area, the indentation persists for some time after the release of the pressure.  Peripheral pitting edema is the more common type, resulting from water retention.  It can be caused by systemic diseases, pregnancy , as a result of heart failure, or local conditions such as varicose veins, thrombophlebitis, insect bites, and dermatitis. Example: Due to cardiac and renal causes, liver disease Varicose Veins: It is the condition of having abnormally dilated vein or swollen veins, especially in the legs. Thrombophlebitis: Inflammation of a vein caused by or associated with the formation of blood clot. Dermatitis: Inflammation of the skin. Non-Pitting Edema  It is observed when the indentation does not persist.  It is associated with such conditions as lymphedema, lipoedema and myxedema. Example: Myxedema, elephantiasis Lymphedema: is the edema caused by lymphatic obstruction. Lipoedema: Edema of the subcutaneous fat which cause painful swelling especially of the leg in women. Myxedema: A disease caused by decreased activity of the thyroid gland in adult and it is characterized by dry skin swelling around the lips and nose. Kwashiorkor  Edema caused by malnutrition defines. Pitting Edema Non-Pitting Edema Why does a patient with heart disease retain fluid?  Heart failure is the result of poor cardiac function and is reflected by a decreased volume of blood pumped out by the heart.  Heart failure can be caused by weakness of the heart muscle, which pumps blood out through the arteries to the entire body, or by dysfunction of the heart valves.  Decreased cardiac output is responsible for a decreased flow of blood to the kidneys.  Kidneys sense that there is a reduction of the blood volume in the body.  To counter the seeming loss of fluid, the kidneys retain salt and water.  This fluid increase ultimately results in the buildup of fluid within the lungs, which causes shortness of breath (pulmonary edema). How does venous insufficiency cause edema?  Veins of the legs have valves that prevent the backward flow of blood within them.  Venous insufficiency is incompetence of the veins that occurs because of dilation, or enlargement, of the veins and dysfunction of their valves.  This happens, for example, in patients with varicose veins.  Venous insufficiency leads to a backup of blood and increased pressure in the veins, thereby resulting in edema of the legs and Feet What is idiopathic edema?  Idiopathic edema is a pitting edema of unknown cause that occurs primarily in premenopausal women who do not have evidence of heart, liver, or kidney disease.