After completing this unit, you should be able to: Describe the normal characteristics of the cellular environment and the key homeostatic mechanisms that strive to maintain an optimal fluid and electrolyte balance; outline pathophysiological alterations in water and electrolyte balance and list their effects on body functions; describe the treatment of patients with particular fluid or electrolyte imbalances.
9/10/2012 Chapter 11 General Principles of Pathophysiology Lesson 11.1 Cellular Environment, Water and Electrolyte Balance Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 9/10/2012 Learning Objectives • Describe the normal characteristics of the cellular environment and the key homeostatic mechanisms that strive to maintain an optimal fluid and electrolyte balance • Outline pathophysiological alterations in water and electrolyte balance and list their effects on body functions • Describe the treatment of patients with particular fluid or electrolyte imbalances. Cells • Basic unit of higher life forms • Components – Cell membrane • Holds cell together • Separates internal cellular environment from external – Enzymes help biochemical processes – Internal membranes to encapsulate chemicals – Genetic material for replication Cells • Form four basic types of tissue – Epithelial tissue – Connective tissue – Muscle tissue – Nervous tissue Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 9/10/2012 Cellular Environment • Human body cells live in a fluid environment, consists mainly of water – Body water essential • Medium in which all metabolic reactions occur • Body’s health depends on precise regulation of volume and composition of this fluid – Body has two fluid compartments • Intracellular fluid (ICF) • Extracellular fluid (ECF) Intracellular Fluid and Extracellular Fluid • Intracellular fluid (ICF) – Found in all body cells – 40% of body weight • Extracellular fluid (ECF) – Fluid found outside of cells – 20% of total body weight – Blood plasma composes about 1/3 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 9/10/2012 Interstitial Fluid • Cellular fluid between cells and outside vascular bed • Includes cerebrospinal and intraocular fluid • Accounts for 15 to 16% of total body weight 10 Aging and Fluid Distribution • Body water accounts for 50 to 60% of the total weight in adults – With age, distribution and amount decrease to about 45 to 55% • Increases risk of dehydration, electrolyte abnormalities 11 Based on the causes of dehydration and your knowledge of anatomy and physiology, what two age groups do you think are at highest risk for dehydration? 12 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 9/10/2012 Water Movement Between ICF and ECF • Body fluids constantly move from one compartment to another – Remains about the same in healthy people • To keep volume stable – Osmosis – Diffusion – Mediated transport mechanism 13 Osmosis • For healthy body, molecules must be able to move within cell/across cell membrane • Semipermeable membranes – Separate fluid compartments – Allow fluid to pass freely – Regulate flow of solutes on the basis of size, shape, electrical charge • Maintain homeostasis – Channels within permit solute passage 14 Osmosis • Diffusion or spreading of water molecules across semipermeable membrane from lower solute concentration to higher solute concentration • Separates two solutions of different concentrations by blocking transport of salts or other solutes 15 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 9/10/2012 16 Osmosis • Osmotic pressure – Pressure that prevents the flow of fluid across a semipermeable membrane – Pressure to maintain equilibrium depends on • Number and molecular weight of particles on each side of the cell membrane • Membrane permeability to these particles 17 Solutions • Hypertonic solution – When a living cell is placed in solution with a higher solute concentration, lower water concentration than that inside the cell – When a cell is in solution, the osmotic pressure exerted produces net movement of water out of the cell – Causes cell to dehydrate, shrink, possibly die 18 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 9/10/2012 Solutions • Hypotonic solution – When a living cell is placed in solution with a lower solute concentration, higher water concentration than that inside the cell – Osmotic pressure draws water from the solution into the cell • Net movement of water into the cell • Can swell, possibly burst 19 What happens to a raisin when it is placed in a cup of water for an hour? Why does this change occur? Is the water hypotonic, hypertonic, or isotonic relative to the inside of the raisin? Does a concentration gradient exist? 20 Solutions • Isotonic solution – When a cell is placed in solution with the same solute and water concentration as the solution inside the cell • No net movement of water molecules 21 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 9/10/2012 22 Diffusion • Result of constant motion of all atoms, molecules, or ions in a solution • Passive process – Molecules or ions move from an area of higher concentration to an area of lower concentration – Area of high concentration has more solute particles than area of low concentration 23 Diffusion • Passive process – More solute particles move from higher concentration to lower one – Once at equilibrium, movement of solutes in one direction is balanced by equal movement in opposite direction 24 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 9/10/2012 25 Diffusion • Concentration gradient – When the concentration of the solute is greater at one point in the solvent than at another point • Solutes diffuse down their concentration gradients from high to low concentration until equilibrium is achieved • Some nutrients enter and some waste products leave the cell by diffusion – Maintenance of proper intracellular concentrations of certain substances depends on this process 26 Mediated Transport Mechanism • Required to move large, water‐soluble molecules, electrically charged molecules across cell membranes – Some vital molecules (glucose) cannot enter by diffusion – Some products (proteins) cannot exit by diffusion • Use carrier molecules – Proteins combine with solute molecules on one side of the membrane – Change shape, pass through the membrane, release solute molecule on other side 27 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 9/10/2012 28 Carrier‐Mediated Transport • Two types – Active transport – Facilitated transport 29 Carrier‐Mediated Transport • Active transport – Moves substances against concentration gradient, from areas of lower concentration to areas of higher concentration • Cell must expend energy to work against this concentration gradient • Occurs at faster rate than diffusion 30 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 10 9/10/2012 Neuroendocrine Regulation of Stress • Stress causes adrenal glands to release catecholamines, epinephrine, norepinephrine, dopamine into bloodstream – Hypothalamus stimulates pituitary gland to release ADH, prolactin growth hormone, adrenocorticotropic hormone (ACTH) – ACTH stimulates cortex of adrenal gland to release cortisol 301 Catecholamines • Stimulate two major classes of receptors – Alpha‐adrenergic receptors • Alpha‐1 receptors: postsynaptic, located on effector organs, stimulate contraction of smooth muscle • Alpha‐2 receptors: located on presynaptic nerve endings, stimulation serves as negative feedback mechanism, inhibits further release of norepinephrine 302 Catecholamines • Stimulate two major classes of receptors – Beta‐adrenergic receptors • Beta‐1 receptors: located mainly in the heart • Beta‐2 receptors: located primarily in bronchiolar, arterial smooth muscle • Beta receptors stimulate the heart, dilate bronchioles, blood vessels in skeletal muscle, brain, heart, aid glycogenolysis • Epinephrine excites alpha receptors 303 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 101 9/10/2012 Cortisol • Circulates in plasma • Mobilizes substances needed for cellular metabolism • Main metabolic effect is stimulation of gluconeogenesis • Enhances elevation of blood glucose – Reduces glucose utilization 304 Cortisol • Immunosuppressant, reduces reproduction of lymphocytes, particularly among T lymphocytes – Leads to decrease of cellular immunity • Reduces macrophage migration into inflamed area • Reduces phagocytosis by stabilizing lysosomal membranes 305 Cortisol • Decrease in immune cell activity may be beneficial – Prevents immune‐mediated tissue damage • Factors determine whether effects are adaptive or destructive – Stress event type – Stress exposure length 306 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 102 9/10/2012 Immune System Role • Believed immune, nervous, endocrine systems communicate through complex pathways, affected factors involved in stress reaction 307 Interrelationship of Stress, Coping, Illness • Stress damage determined by nature, intensity, duration of stressors – Also affected by way person perceives stressors, coping • Spotting signs of symptoms of stress is crucial to good health 308 Interrelationship of Stress, Coping, Illness • Stress reduction techniques help prevent harmful physiological, psychological illness from arising – Meditation – Exercise – Imagery 309 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 103 9/10/2012 Genetics, Familial Diseases • Born with genetic predisposition to development of certain diseases – Genetics of some diseases well understood (hemophilia, sickle cell anemia) – Patients either • Have no genetic predisposition • Are carriers of disease • Have disease – Other disease processes genetically linked but strongly associated with environmental factors 310 Factors Causing Disease • Genetic and environmental; have strong interaction – Genes cannot exert effects without environment to operate – Factors act differently on different people – Conversely, environment may be the same, people have unique genetic makeups 311 Factors Causing Disease • Genetic factors – Heredity, laws of chance, probability – Each pair of chromosomes randomly sorted when packaged into eggs, sperm – More than 100,000 genes involved in genetic makeup – Genetic diseases arise because of individual genetic changes, abnormalities involving entire chromosome 312 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 104 9/10/2012 Factors Causing Disease • Genetic factors – Entire chromosomal abnormalities lead to diseases • Down syndrome • Turner syndrome – More often, single chromosome gene is passed on, resulting in abnormal protein • Sickle cell anemia • Hemophilia 313 Factors Causing Disease • Genetic factors – Polygenic: conditions involving more than one gene, may have strong inherited component • Coronary artery disease • Hypertension • Cancer 314 Factors Causing Disease • Environmental factors – Common chronic diseases result in mismatch between genetic and environmental factors – Important environmental factors • • • • • Microorganisms, immunological exposure Personal habits, lifestyle Chemical substances Physical environment Psychosocial environment 315 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 105 9/10/2012 Factors Causing Disease • Environmental factors – Disease prevention goal is to find genetic, environmental influences leading to major diseases, help susceptible people – Change environmental factors, lessen risk 316 Think about how many risk factors you have for heart disease. Which of these factors are genetic, and which could you eliminate by modifying your habits or environment? 317 Factors Causing Disease • Age, gender – Play role in incidence of hereditary disease – Especially true for diseases not caused by single genetic defect – In polygenic disorders, combined effects of genes and environment play a role over time • Age‐related metabolism changes • Heart disease, hypertension, cancer seen more over age 40 318 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 106 9/10/2012 Factors Causing Disease • Age, gender – Gender associated to sex‐specific diseases arising from hormonal, anatomical differences • Breast cancer, women • Testicular cancer, men – Lifestyle, environmental differences also play a role • Differences may be responsible for predisposition to some diseases • Higher rate of lung cancer, coronary artery disease in male smokers 319 Disease Rates • Commonly used statistics assess society disease impact – Incidence rate • Number of new cases detected during given time period per number of people surveyed, usually 1 year – Prevalence rate • Number of people living with disease per number of people surveyed – Mortality rate • Number of people who died from disease during given time period per number of people surveyed, usually 1 year 320 Disease Rates • Risk factor analysis – Causal, noncausal risk factors – Causal risk factors • Removal, elimination of risk factors delays or prevents disease – Noncausal risk factors • Help predict chances of developing disease • No direct effect on underlying cause 321 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 107 9/10/2012 322 Familial Disease Tendency • In some cases, family members are more prone to some diseases than the general population – Risk factors: genetic or shared environmental factors • Heart disease, pulmonary disease from smoking, dietary fat 323 Familial Disease Tendency • Aging, age‐related disorders – Advanced age is risk factor for many diseases • Heart attack • Stroke • Cancer – Represents cumulative effects of genetics, environmental factors – Disorders such as dental cavities, strep throat, more common in younger ages – Degenerative disorders, arthritis, more common in older ages 324 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 108 9/10/2012 Familial Disease Tendency • Common familial diseases, associated risk factors – High‐risk individuals, take steps to avoid familial diseases • Coronary heart disease • Colorectal cancer 325 Summary • Two facts illustrate importance of body water – Is medium in which all metabolic reactions occur – Precise regulation of volume and composition of body fluids is essential to health • Water follows osmotic gradients established by changes in sodium concentrations • Sodium and water balance are closely related 326 Summary • Two abnormal states of body‐fluid balance can occur – If water gained exceeds water lost, a state of water excess, or overhydration, exists – If water lost exceeds water gained, a state of water deficit, or dehydration, exists 327 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 109 9/10/2012 Summary • Disturbances in the balance of electrolytes (other than sodium) may occur – These electrolytes include potassium, calcium, and magnesium – Imbalances can interfere with neuromuscular function • May cause cardiac rhythm disturbances 328 Summary • Treatment of isotonic dehydration may include volume replacement with isotonic or occasionally hypotonic solutions – Treatment of hypotonic dehydration may involve IV replacement with normal saline or lactated Ringer’s solution – Occasionally, hypertonic saline (e.g., in seizures caused by hyponatremia) is used – Interventions for overhydration depend on cause • May include water restriction, administration of a diuretic, or, if hyponatremia is present, administration of saline 329 Summary • In‐hospital treatment of hypokalemia involves IV or oral potassium replacement • Management of hyperkalemia may involve potassium restriction, enteral administration of a cation exchange resin, or intravenous administration of glucose and insulin, sodium bicarbonate, or calcium 330 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 110 9/10/2012 Summary • Treatment of hypocalcemia involves IV administration of calcium ions • Management of hypercalcemia may include controlling the underlying disease, hydration, and, occasionally, drug therapy such as with furosemide and other calcium‐lowering drugs 331 Summary • Hypomagnesemia typically is corrected by administration of IV magnesium sulfate • Most effective treatment for hypermagnesemia is hemodialysis – Calcium salts that antagonize magnesium may also be given 332 Summary • Healthy body is sensitive to changes in concentration of hydrogen ions (pH) – Tries to maintain pH of extracellular fluid at 7.4 • Accomplished through three interrelated compensatory mechanisms: carbonic acid–bicarbonate buffering, protein buffering, and renal buffering 333 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 111 9/10/2012 Summary • Metabolic acidosis occurs when amount of acid generated exceeds body’s buffering capacity – Four most common forms of metabolic acidosis encountered in the prehospital setting are lactic acidosis, diabetic ketoacidosis, acidosis resulting from renal failure, and acidosis caused by ingestion of toxins – Treatment for metabolic acidosis is aimed at correcting underlying cause 334 Summary • Loss of hydrogen is initial cause of metabolic alkalosis – May be caused by vomiting (hydrochloric acid loss), gastric suction, or increased renal excretion of hydrogen ion in the urine – Treatment is directed at correcting underlying condition – Volume depletion, if present, should be corrected with isotonic solutions 335 Summary • Respiratory acidosis is caused by retention of carbon dioxide – Leads to increase in Pco2 – Condition usually is caused by an imbalance in production of carbon dioxide and its elimination through alveolar ventilation – Treatment involves improving ventilation quickly to eliminate carbon dioxide 336 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 112 9/10/2012 Summary • Hyperventilation may produce respiratory alkalosis by decreasing Pco2 – Treatment is directed at correcting underlying cause of hyperventilation – Initial approach is to place patient on low‐ concentration oxygen • Another is to provide calming measures to assist patient with slow, controlled breathing 337 Summary • An understanding of the processes of disease is crucial – Requires knowledge of structural and functional reactions of cells and tissues to injurious agents – Changes in cells and tissues can be caused by adaptation, injury, neoplasia, aging, or death • An injured cell may have an abnormal physical shape or size – Cell injury has both cellular and systemic indications 338 Summary • Certain factors cause disease Thesefactorsmaybeclassifiedasgeneticor environmental ã Stronginteractionoccursbetweenthetwo 339 Copyright â 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 113 9/10/2012 Summary • The term hypoperfusion is used to describe inadequate tissue circulation – May result from decreased cardiac output – Decreased cardiac output can lead to shock, multiple organ dysfunction syndrome, and other disease states associated with impaired cellular metabolism – Negative feedback mechanisms important in maintaining cardiac output and tissue perfusion are baroreceptor reflexes, chemoreceptor reflexes, the central nervous system ischemia response, hormonal mechanisms, reabsorption of tissue fluids, and splenic discharge of stored blood 340 Summary • External barriers are body’s first line of defense against illness and injury – These barriers include skin and mucous membranes of the digestive, respiratory, and gastrointestinal tracts • When barriers are breached, chemicals, foreign bodies, or microorganisms are allowed to penetrate cells and tissues • Then the second and third lines of defense are activated • These are inflammatory response and immune response • Both external barriers and inflammatory response respond to all organisms using the identical nonspecific mechanism • Immune response is specific to individual pathogens 341 Summary • Immune responses usually are protective – Help to protect body from harmful microorganisms and other injurious agents – At times responses may be inappropriate • May even have undesirable effects • Examples of inappropriate responses include hypersensitivity and immunity or inflammation deficiencies 342 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 114 9/10/2012 Summary • Many immune‐related conditions and diseases are associated with stress – Exact mechanisms causing these illnesses have not yet been clearly defined • Believed that the immune, nervous, and endocrine systems communicate through complex pathways and that they may be affected by factions involved in the stress reaction 343 Summary • Factors that cause disease are complex – May involve genetic or environmental factors or a combination of both – Age and gender also influence illness 344 Questions? 345 Copyright © 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company 115 ... fluids to leak out? ?of? ?the blood vessels more freely. How could that affect cardiac output? 65 Pathophysiology? ?of? ?Edema • Clinical manifestations? ?of? ?edema – Generalized • In industrialized countries, most often caused by heart, ... 52 Pathophysiology? ?of? ?Edema • Factors? ?of? ?normal fluid flow through interstitial spaces – Permeability? ?of? ?capillaries, determines how easily fluid can pass through capillary wall – Presence? ?of? ?open lymphatic channels, which ... Molecules or ions move from an area? ?of? ?higher concentration to an area? ?of? ?lower concentration – Area? ?of? ?high concentration has more solute particles than area? ?of? ?low concentration 23 Diffusion