Disturbances of body fluids Renata Pov Dept of

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 P L A S M A INTRACELLULAR FLUID „third space“ PERITONEAL CAVITY PLEURAL CAVITY PERICARDIAL CAVITY

TBF 40 l. IVF (3 l) volume of erythrocytes (2 l) . . ECF (15 l) . . blood volume (5 l) ICF (25 l)

Normal water balance (24 h) Intake Cellular metabolism Normal water intake Loss 0, 5 l Urine 1 l Stool 0, 1 l 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 (HCO 3 - ) - chief anion of the ECF phosphate (HPO 42 --) - chief anion of the ICF sulfate(SO 42 -)

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 - Na. K-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) . . blood volume (5 l) ICF (25 l)

Plasma osmotic activity = 2 x [Na+] + urea + glucose = 2 x [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 + 50 = 305 mmol/l

Regulation of volume and osmolarity 1 • GIT • Kidney – main regulatory system via releasing water and electrolytes • Circulatory system – 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 – nervous system (sympathetic/ parasympathetic) • 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 • Na. Cl in macula densa region – 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 H 2 O Na. Cl 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 H 2 O Na. Cl 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 H 2 O Na. Cl 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 H 2 O Na. Cl IVV ISV ECV ICV

Hypoosmolal imbalance – water intoxication H 2 O Na. Cl IVV ISV ECV ICV