Transcript Bez nadpisu
Disturbances of body fluids Renata Péčová Dept. of Pathophysiology 2009 TOTAL BODY FLUID (TBF) • water - 60 % of the weight of men • - 50 % of the weight of women - more fat and a smaller muscle mass smaller amount of water in relation to total body weight (TBW Major Compartments of Body Fluid • 1. intracellular fluid (ICF) - 40 % (2/3) TBW (in the adult) • 2. extracellular fluid (ECF) - 20 % (1/3) – a. interstitial fluid (ISF) - compartment between the cells (15 %) – b. intravascular fluid (IVF) • in addition to the ISF and IVF, special secretions (cerebrospinal fluid, intraocular fluid, and gastrointestinal secretions) form a small proportion (1 % to 2 % of body weight) of the extracellular fluid called transcellular fluid Major compartments of body fluids TBF 60-65% of body weight; ECT:ICT=1:2; IVT:IST =1:4 Compartments of total body fluid bones lymph INTERSTITIAL FLUID TRANSCELLULAR FLUID thick connective tissue INTRACELLULAR FLUID „third space“ PERITONEAL CAVITY PLEURAL CAVITY PERICARDIAL CAVITY TBF 40 l . IVF (3 l) volume of erythrocytes (2 l) . . . ECF (15 l) ICF (25 l) . . . . . . . . blood volume (5 l) Normal water balance (24 h) Intake Cellular metabolism Normal water intake Loss 0,5 l Urine 1l Stool 0,1 l 1l Sweat 0,6-0,8 l Pulmonary TOTAL 1-2 l 2,5 l TOTAL 0,5 l 2,5 l Principles of normal water balance Sumit Kumar & Tomas Berl Major electrolytes and their distribution - 1 • • • • • • • • sodium (Na+) - chief cation of the ECF potassium (K+) - the chief cation of the ICF calcium (Ca++) magnesium (Mg++) chloride (Cl-) - chief anion of the ECF bicarbonate (HCO3- ) - chief anion of the ECF phosphate (HPO42--) - chief anion of the ICF sulfate(SO42-) Major electrolytes and their distribution - 2 Sodium plays a major role in controlling total body fluid volume; potassium is important in controlling the volume of the cell • The law of electrical neutrality states that the sum of negative charges must be equal to the sum of positive charges (measured in milliequivalents) in any particular compartment Major electrolytes and their distribution - 3 • Ionic composition of the ISF and IVF is very similar. • The main difference is that ISF contains very little protein as compared with the IVF. The protein in plasma plays a significant role in maintaining the volume of the IVF. Major electrolytes and their distribution MOVEMENT OF BODY FLUIDS AND ELECTROLYTES • there is a continual intake and output within the body as a whole, and between the various compartments • the composition and volume of the fluid is relativelly stable, a states called dynamic equilibrum or homeostasis. Movement of Solutes Between Body Fluid Compartments - 1 • Several factors affect how readily a solute diffuses across capillary and cell membranes • 1. membrane permeability refers to the size of the membrane pores. • 2. concentration and electric gradients interact to influence the movement of electrolytes termed the electrochemical potential. • 3. electrical potential Movement of Solutes Between Body Fluid Compartments - 2 • 4. pressure gradients - hydrostatic pressure gradient increases the rate of diffusion of solutes through the capillary membrane • - active transport systems - NaK-activated ATPase system (sodium-potassium pump) located in cell membranes (3 Na+ ions out of the cell in exchange for two K+) Movement of Water Between Body Fluid Compartments - controlled by 2 forces: 1. hydrostatic pressure 2. osmotic pressure Osmotic pressure refers to the drawing force for water exerted by soluted particles. Osmosis is the process of the net diffusion of water caused by a concentration gradient. Net diffusion of water occurs from an area of low solute concentration (dilute solution) to one of high solute concentration (concentrated solution) . Movement of Water Between the Plasma and Interstitial Fluid - Na+ does not play an important role in the movement of water between the plasma and interstital fluid compartments - the distribution is determined by o hydrostatic pressure of the capillary blood produced, mainly by the pumping action of the heart o colloid osmotic pressure produced primarily by serum albumin The accumulation of excess fluid in the interstitial spaces = edema Starling forces Factors favor edema formation: 1. capillary hydrostatic pressure (Pc) 2. plasma oncotic pressure (c) 3. capillary permeability (Kf) resulting in an in interstitial fluid colloid osmotic pressure 4. lymphatic obstruction ( interstitial oncotic pressure) Starling forces Lymph ICF ISF cell Kf Pi Pc capillary i IVF c Jr = Kf [(Pc – Pi) – (c - i)] Pathogenesis of edema formation 1. gradient of hydrostatic pressures (Pc – Pi) - Heart failure; venous insufficiency EABV R-A-A (SAS, ADH) Starling forces Lymph ICF ISF cell Kf Pi Pc capillary i IVF c Jr = Kf [(Pc – Pi) – (c - i)] Pathogenesis of edema formation 2. gradient of oncotic pressures (c - i) - plasma protein level EABV R-A-A (SAS, ADH) Pathogenesis of edema formation 3. capillary permeability (Kf) resulting in an interstitial fluid colloid osmotic pressure 4. lymphatic obstruction ( interstitial oncotic pressure) Pathogenesis of ascites Disturbance of liver plasma albumin Portal hypertension plasma oncotic pressure capillary pressure in splanchnic region inactivation of ADH and aldosteron plasma volume (retention of Na and water) Ascites ADH secretion plasma volume volumoreceptor stimulation Aldosteron secretion Movement of Water Between the ECF and the ICF - 1 - determined by osmotic forces: - because Na+ composes over 90 % of the particles in the ECF, it has a major effect on TBW and its distribution - ECF osmolality (becomes hyperosmotic) water shifts from the ICF to the ECF, decreasing cell volume: hypertonic solution (3 % saline) cell shrinkage Movement of Water Between the ECF and the ICF - 2 • Cell in hypertonic solution – water shifts from the ICF to the ECF – decreasing cell volume (cell shrinkage) – active of intracellular osmotic pressure - water shifts from the ECF to the ICF – increasing cell volume (general decreasing) Movement of Water Between the ECF and the ICF - 3 - determined by osmotic forces: - ECF osmolality (becomes hypoosmotic), water shifts from the ECF to the ICF, increasing cell volume hypotonic solution (0.45 % saline) cell swelling i.v. administration of isotonic saline no change in the ICF volume or osmolality Movement of Water Between the ECF and the ICF - 4 • Cell in hypotonic solution – water shifts from the ECF to the ICF – increasing cell volume (cell swelling) – active decreasing of intracellular osmotic pressure and water shifts from the ICF to the ECF – decreasing of intracellular volume (general increasing) Changes of red blood cells volume due to plasma osmolality disturbances TBF 40 l . IVF (3 l) volume of erythrocytes (2 l) . . . ECF (15 l) ICF (25 l) . . . . . . . . blood volume (5 l) Plasma osmotic activity = 2x [Na+] + urea + glucose = 2x [Na+ + K+] + 5 • Example: – Chronic renal insufficiency patient: • plasma Na+ level 125 mmol/l • plasma glucose level 5 mmol/l • plasma urea level 50 mmol/l Approximate osmolarity: 2 x 125 + 5 + 50 = 305 mmol/l Regulation of volume and osmolarity 1 • GIT • Kidney – main regulatory system releasing water and electrolytes • Circulatory system via – perfusion – distribution of water and electrolytes in body compartments (Starling forces) – renal perfusion releasing of water and electrolytes Regulation of volume and osmolarity 2 Signals for • GIT – thirst • Circulatory system – (sympathetic/ parasympathetic) nervous system • Kidneys – nervous system + 3 hormonal regulatory systems: – Antidiuretic hormon (ADH) – Atrial natriuretic factor (ANF) – Renin – angiotenzin – aldosteron (R-A-A) Regulation of volume and osmolarity 3 – Antidiuretic hormon (ADH) • Stimulus for releasing – plasma osmolarity – effective circulatory volume • secretion – Hypervolemia – Hypoosmolarity – Feed-back – ADH plasma level • Target - distal tubulus and collecting duct – water permeability – urea permeability • Effect – up to 10-20 min Regulation of volume and osmolarity 4 – Renin – angiotensin – aldosteron (R-A-A) – Activation of renin secretion: • kidney perfusion ( afferentation from vas afferens receptors; CO – baroreceptors – SNS activation • NaCl in macula densa region – Angiotensin I – Angiotensin II – Aldosteron Main cells of distal tubules have intracelullar receptors for aldosterón. Receptors after hormon-binding act as transcript factors and they induce intracellular proteins which increased reabsorption of Na+ from tubules and K + secretion into the urine. Intercallar cells – regulation of ABB.. Regulation of volume and osmolarity 5 – Atrial natriuretic factor (ANF) • Secretion timulus : – atrial filling • Effects: – Vessels – vasodilation of vas afferens – Endocrine system – secretion of ADH, renin and aldosteron – Kidneys – Glomerular hyperperfusion (via vasodilatation of vas afferens) GFR – Na+ reabsorption Na+ releasing Heart failure CO EABV Activation R – A - A Water retention (kidney) Venous return Diastolic filling ANF feed-back ANF Volume imbalances - affect ECF - involve relatively equal losses or gains of Na+ and water leading to an ECF volume deficit or excess - fluid will not be transferred from the ICF to the ECF as long as the osmolality in the two compartments remains the same Osmotic imbalances - affect ICF - involve relatively unequal losses or gains of Na+ and water - concentration of Na+ in the ECF water moves from the ECF to the ICF (cell swelling) - concentration of Na+ in ECF should water moves from the ICF to ECF (cell shrinkage) ECF volume deficit (hypovolemia) • Isotonic loss of body fluids; equal losses of sodium and water • Causes: • Blood or plasma loss • sequestration of fluid in soft tissue injuries (third spacing): burns, peritonitis ECF volume deficit - hypovolemia H2 O NaCl IVV ISV ECV ICV ECF volume deficit - hypovolemia H2 O NaCl IVV ISV ECV ICV ECF volume deficit (hypovolemia) • Consequences: • EABV ( venous return cardiac output hypotension) • Hemodynamic changes – Tachycardia – Peripheral vasoconstriction • Ht • ADH, R-A-A activation • Clinical features: - circulatory collapse and shock - hematocrit and serum protein levels are elevated - normal natremia Hyperosmolal hypohydratation - dehydration • Cause: increase loss of water than sodium (loss of hypoosmotic fluid) • A. Loss of hypoosmolatic fluid – – – – Vomiting Diarrhea Sweating Disturbances of urine creation • Polyuria in acute renal failure • Osmotic diuresis • Central or peripheral diabetes insipidus • B. Decrease waterr intake – Coma patients – Patient unable to communicate (babies) – feeling of thirst (old people, „after surgery people“) Hyperosmolal imbalance - dehydration H2 O NaCl IVV ISV ECV ICV Hyperosmolal imbalance - dehydration H2 O NaCl IVV ISV ECV ICV Hyperosmolal imbalance - dehydration H2 O NaCl IVV ISV ECV ICV Hyperosmolal hypohydratation - dehydration • Consequences: – ECF osmolaity – cell shrinkage (CNS) - neurological manifestation: agitation, coma, seizures thirst dry mucosa, tongue oliguria ECF volume excess • Cause: isoosmolar fluid retention • Accumulation of ECF • Pathogenesis - alteration in Starling forces - congestive heart failure, nephrotic syndrome, cirrhosis of the liver - cardiac output effective circulating volume renal sodium retention • Ht (or normal) Starling forces Lymph ICF ISF cell Kf Pi Pc capillary i IVF c Jr = Kf [(Pc – Pi) – (c - i)] Heart failure Hepatic cirrhosis CO Ascites Pc plasma albumin IVF interstitial space EABV SNS, R-A-A Na+ and water reabsorption Edema (hyperhydratation) Nephrotic syndrome plasma albumin ECF volume excess – generalised edema H2 O NaCl IVV ISV ECV ICV ECF volume excess – generalised edema H2 O NaCl IVV ISV ECV ICV Hypoosmolar imbalance – water intoxication • Cause: water intake or retention than sodium • water intake • ADH – Endogennous origin – hypothalamus – Ectopic creation ADH – bronchogenic CA, lymphomas,... • Disturbances of kidneys – Oligoanuric phase of acute renal failure Hypoosmolar imbalance – water intoxication H2 O NaCl IVV ISV ECV ICV Hypoosmolar imbalance – water intoxication H2 O NaCl IVV ISV ECV ICV Hypoosmolal imbalance – water intoxication H2 O NaCl IVV ISV ECV ICV