fluid and electrolyte balance disturbances Year 4 Paediatrics

fluid and electrolyte balance disturbances Year 4 · Paediatrics Collection: 4TH YEAR ALL NOTES / PAEDS / PAEDS 4.3 / Agisa -- Slide 1 Disturbances of fluid and electrolyte balance Slide 2 Homeostasis The maintenance of normal volume and normal composition of the extracellular fluid is vital to life. Homeostasis: the various physiologic arrangements which serve to restore the normal state, once it has been disturbed Fluid balance Electrolyte balance Osmotic balance Acid-base balance Slide 3 General principles Diffusion: movement of the particles in a solution from the area of high concentration to the area of lower concentration Electrolyte: inorganic substance that dissociates into ions Osmosis: diffusion of solvent molecules (water) into region in which there is a higher concentration of a solute (electrolyte) to which the membrane is impermeable Osmotic pressure: the pressure necessary to prevent solvent migration Osmol: concentration of osmotic active particles Slide 4 General principles Osmolarity: number of osmoles per liter of solution Osmolality: number of osmoles per kilogram of solvent Measurement: depression of freezing point\nCalculation (plasma): 2x(Na+K)+glucose+BUN (mmol/l) Tonicity: effective osmolality of a solution relative to plasma Colloids: high molecular weight particles ( 20000 D) Oncotic pressure (colloid osmotic pressure): the pressure necessery to prevent diffusion of solvent molecules (water) into region in which there is a higher concentration of a colloid to which the membrane is impermeable Slide 5 Intracellular space Extracellular space Interstitial space Intravasal\nspace Capillary wall Oncotic pressure Colloids Electrolytes Water Cell membrane Osmotic pressure Slide 6 Body Fluid Volumes Slide 7 Daily Water Balance (liters) FLUID INTAKE 1.5 IN FOOD 0,8 METABOLIC 0.3 Total 2,6 INSENSIBLE 0.8 SWEAT 0,1 FECES 0.2 URINE 1.5 Total 2.6 INPUT OUTPUT Slide 8 Fluid Na+ K + HCO3- Cl -\nICF 12 140 12 4\nPlasma 140 4-5 26 112 ISF 145 4,4 27 117 Liquor 147 3 23 113 Gastric juice 20-80 5-20 - 100-150\nH+: 40-60 Intestinal juice 120-140 5-15 20-40 10 Composition of fluids (mmol/l) Slide 9 Fluid replacement 0-10 kg: 100 ml/kg/d 11-20 kg: 50 ml/kg/d 20 kg: 20 ml/kg/d 4-2-1 (ml/kg/h) Patient (70 kgs) (4-2-1)\n 1-10 kg 4 ml/kg/h 40 ml/h\n11-20 kg 2 ml/kg/h 20 ml/h\n 20 kg 1 ml/kg/h 50 ml/h \n\nTogether: 110 ml/h 2640ml/d Slide 10 Fluid Balance The main way to regulate body water gain is by adjusting the volume of water intake, mainly by drinking more or less fluid. The thirst center in the hypothalamus governs the urge to drink. Although increased amounts of water and solutes are lost through sweating and exhalation during exercise, loss of excess water or excess solutes depends mainly on regulating excretion in the urine. The extent of urinary Na (and Cl) loss is the main determinant of body fluid volume, whereas the extent of urinary water loss is the main determinant of body fluid osmolarity. Slide 11 Fluid Balance Angiotensin II and aldosterone reduce urinary loss of Na+ and Cl- and thereby increase the volume of body fluids (baroreceptors: sinus caroticus, kidney) Stimulation of ANP production: elevation of atrial wall tension (Angiotensin) ANP promotes natriuresis, elevated excretion of Na+ (and Cl- ), which decreases blood volume. The major hormone that regulates water loss and thus body fluid osmolarity is ADH (Hypothalamus) The regulation of the volume of body fluids superior to the regulation of osmolarity Slide 12 Water Deficit INCREASED OSMOLARITY SENSED BY HYPOTHALAMIC RECEPTORS FALL IN ECF VOLUME FALL IN ARTERIAL BLOOD PRESSURE STIMULATION OF HYPOTHALAMIC\nNEURONS INCREASED THIRST INCREASED WATER INTAKE DECREASED PLASMA OSMOLARITY INCREASED VASOPRESSIN OPEN PORES IN COLLECTING DUCT MORE WATER REABSORBED FALL IN URINE OUTPUT ARTERIOLAR VASOCONSTRICTION DECREASED PLASMA OSMOLARITY RELIEVES RELIEVES Slide 13 Blood pressure and renal handling of sodium FALL IN SODIUM LOAD FALL IN ARTERIAL PRESSURE FALL IN GFR FALL IN FILTERED SODIUM INCREASE IN ALDOSTERONE SECRETION INCREASE IN\nSODIUM ABSORPTION FALL IN EXCRETION OF\nSODIUM, CHLORIDE, AND FLUID INCREASED CONSERVATION OF SODIUM AND FLUID RELIEVES Slide 14 Disturbances of fluid homeostasis Disturbance of fluid balance (intake≠output) Dehydraton, Overhydration (hyperhydration)\n\nDisturbance of osmolarity (electrolyte intake≠water intake) Isonatremic (isotonic) Hyponatremic (hypotonic) Hypernatremic (hypertonic) Slide 15 Disturbances of fluid homeostasis Diagnosis: Physical signs: skin turgor, oedema, mucous membranes, neck veins, puls, liver, level of consciousness, capillary refill, fontanel (children) Vital sings: blood pressure; heart rate; (respiratory rate); body temperature; CVP; urine output; serum and urine Na, osmolarity; Htk; serum total protein Slide 16 Dehydration Signs: increased thirst (except: advanced age, hypotonic dehydration), weakness, decreased skin turgor, dry mucous membranes, empty neck veins, decreased urine out