Fluid and electrolyte balance

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Fluid and electrolyte balance : 

Fluid and electrolyte balance MODERATOR: DR.C.S. PRAKASH H.O.D AND PROFESSOR DEPT OF ANAESTHESIA DR . RADHIKA ASSOCIATE PROFESSOR DEPT OF BIOCHEMISTRY PRESENTOR: DR . HARIHARAN. V IIND YR M.D. BIOCHEMISTRY

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DISTRIBUTION OF BODY WATER

COMPOSITION OF BODY FLUIDS : 

COMPOSITION OF BODY FLUIDS SOLUTES: ELECTROLYTES – Inorganic salts, acids, bases, and proteins NON ELECTROLYTES – Glucose, urea, creatinine FUNCTIONS: Secretory activity Neuro muscular excitability Controlling fluid movements

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CHIEF ELECTROLYTES IN BODY FLUID COMPARTMENTS

OSMOSIS : 

Osmosis is the net movement of water molecules across a Partially-permeable membrane DUE TO CONCENTRATION DIFFERENCE OF SOLUTES. OSMOSIS

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TO EXPRESS CONCENTRATION OF PARTICLES IN SOLUTION - OSMOLE 1 OSMOLE = 1 GRAM MOLECULAR WEIGHT OF OSMOTICALLY ACTIVE PARTICLES. EX : 180 Gms OF GLUCOSE = 1 OSMOLE. 58.5 Gms OF NaCl = 2 OSMOLE.

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OSMOLALITY Definition: Concentration of particles (osmotically active) in solution. It is usually expressed in millosmoles of solute per kg of solution. Osmolality is independent of valency. Osmolarity is expressed in milliosmoles of solute per litre of solution. Plasma: 280-300 mOsm/Kg Same in all body compartments Water distribution

TONICITY : 

TONICITY A property of a solution that depends on the osmotic force exerted across the membrane as influenced by the differing concentrations of solutes in and out of the cell. Isotonic Hypertonic Hypotonic

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HYPERTONIC SOLN

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HYPOTONIC SOLN

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Osmotic pressure 28 mmHg Arteriolar end Venous end Hydrostatic pressure (BP) 35 mm Hg Hydrostatic pressure (BP) 15 mm Hg Net inward pressure 6.7 mmHg Net outward pressure 13.3 mmHg FORCES THAT MAINTAIN FLUID BALANCE CAPILLARY Osmotic pressure 28 mm Hg Osmotic pressure 6.3 mm Hg Osmotic pressure 6.3 mm Hg

REGULATION OF BODY WATER : 

REGULATION OF BODY WATER Increased ECF water Restoration of ECF osmolality Increased water intake Stimulation of hypothalamic centre Renal water retention Redistribution of water from ICF Stimulation of vasopressin release Increased plasma osmolality Water loss

Fluid disturbances : 

Fluid disturbances

Electrolytes : 

Electrolytes

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SODIUM : DISTRIBUTION: TOTAL - 3000 mmol/l Free ions - 70% major in ECF . Complexed in bone - 30% BALANCE: Input - 100 -200 mmol/24 hr. Loss - < 10 mmol/24hr

REGULATION OF SODIUM BALANCE : 

REGULATION OF SODIUM BALANCE RENAL REGULATION: GFR ACTIVE REABSORPTION – PCT-70% ALDOSTERONE - DCT <5% ATRIAL NATRIURETIC PEPTIDE: DECREASES DISTAL TUBULAR REABSORPTION DECREASES RENIN SECRETION

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HYPONATREMIA NORMAL/HIGH PL.OSMOLALITY LOW PLASMA OSMOLALITY TRANSLOCATIONAL GLUCOSE MANNITOL MALTOSE PSEUDO HYPONATREMIA PROTEIN LIPID URINE OSMOLALITY <100mosm/kg WATER INTAKE EXCEEDS URINARY DILUTION LOW SOLUTE INTAKE CORRECTION PHASE OF HYPONATREMIA URINE OSMOLALITY >100mosm/kg HYPOVOLEMIA EUVOLEMIA HYPERVOLEMIA TBW TOTAL BODY Na TBW NO CHANGE IN TOTAL BODY Na TBW TOTAL BODY Na URINARY Na >20mmol/L DIURETIC EXCESS MINERALOCORTICOID DEFI PROXIMAL RTA URINARY Na <10mmol/l VOMITTING DIARRHOEA BURNS SWEATING URINARY Na >20mmol/L GLUCOCORTICOID DEF HYPOTHYROIDISM DIURETICS SIADH URINARY Na >20mmol/l ACUTE / CHRONIC RENAL FAILURE PREGNANCY <10mmol/l NEPHROTIC SYNDROME CIRRHOSIS HEART FAILURE

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HYPERNATREMIA ASSESS VOLUME HYPOVOLEMIA HYPERVOLEMIA T B W T B Na URINARY Na > 20mmol/l PRIMARY HYPER ALDOSTERONISM CUSHING HYPERTONIC DIALYSIS T B W T B Na URINARY Na > 20 mmol/L URINARY Na <20mmol/L EUVOLEMIA T B W T B Na NO CHANGE RENAL LOSS OSMOTIC /LOOP DIURETIC 2) POST OBSTRUCTION INTRINSIC RENAL DISEASE EXTRA RENAL LOSS EXCESS SWEATING 2) BURNS 3) DIARRHOEA URINARY Na INVARIABLE RENAL LOSS DIABETES INSIPIDUS EXTRA RENAL LOSS INSENSIBLE LOSS

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POTASSIUM: PREDOMINANT INTRACELLULAR ION DISTRIBUTION: FREE - 90% BOUND FORM – 10% ECF - 2% REGULATION: RENAL: REABSORPTION – PROXIMAL TUBULES SECRETION – DISTAL TUBULE- ALDOSTERONE GIT: SECRETED IN GASTRIC JUICE REABSORBED –SMALL INTESTINE SECRETED – COLON – ALDOSTERONE

CHLORIDE : 

CHLORIDE MAJOR ANION OF ECF. SECRETED IN GASTRIC JUICE 99% REABSORBED UNDER NORMAL PH CONDITIONS. CHLORIDE SHIFT DECREASED IN ACIDOSIS

BICARBONATE : 

BICARBONATE PRESENT IN ECF BUFFERING ACTION REABSORBED IN TUBULE AS CO2 FOR HYDROGEN ION.

CALCIUM : 

CALCIUM CALCITONIN- decreases bone resorption

Regulation of Renal Phosphate Excretion : 

Regulation of Renal Phosphate Excretion PTH play important role in regulating phosphate concentration through 2 effects: 1) PTH promotes bone resorption, thereby dumping large amounts of phosphate ions into the ECF from bones salts 2) PTH decreases the transport maximum for phosphate by the renal tubules

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Control of Renal Magnesium Excretion and Extracellular Magnesium Ion Concentration Total plasma magnesium concentration is about 1.8 mEq/L, more than one half bound to plasma proteins Regulation of magnesium excretion is achieved by mainly changing tubular reabsorption.

PRECAUTIONS : 

PRECAUTIONS COLLECTION OF BLOOD STORAGE TIME OF ANALYSIS HEMOLYSIS

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Normal Laboratory Values

References : 

References Tietz- clinical chemistry Vasudevan- textbook of biochemistry Harrison’s internal medicine Pubmed.com

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Thank you