1. Major extra and intracellular electrolytes
Md Yousuf Ansari
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2. Body Water Content
Infants: 73% or more water (low body fat, low bone mass)
Adult males: ~60% water
Adult females: ~50% water (higher fat content, less skeletal muscle mass)
Adipose tissue least hydrated of all
Water content declines to ~45% in old age

3. Fluid Compartments Total body water = 40 L Two main fluid compartments
Intracellular fluid (ICF) compartment: 2/3 in cells
Extracellular fluid (ECF) compartment: 1/3 outside cells
Plasma: 3 L
Interstitial fluid (IF): 12 L in spaces between cells
Usually considered part of IF: lymph, CSF, humors of the eye, synovial fluid, serous fluid, and gastrointestinal secretions

4. Intracellular fluid (ICF) Volume = 25 L 40% of body weight Plasma
The major fluid compartments of the body.
Total body water
Volume = 40 L
60% of body weight
Interstitial
fluid (IF)
Volume = 12 L
80% of ECF
Intracellular fluid (ICF)
Volume = 25 L
40% of body weight
Plasma
Volume = 3 L, 20% of ECF
Extracellular
fluid (ECF)
Volume = 15 L
20% of body weight

5. Electrolyte Concentration

6. Electrolyte Concentration
For single charged ions (e.g. Na+), 1 mEq = 1 mOsm
For bivalent ions (e.g. Ca2+), 1 mEq = 1/2 mOsm
1 mEq of either provides same amount of charge

7. Extracellular and Intracellular Fluids
Each fluid compartment has distinctive pattern of electrolytes
ECF
All similar
Major cation: Na+
Major anion: Cl–
Except: higher protein, lower Cl– content of plasma

8. Extracellular and Intracellular Fluids
ICF:
Low Na+ and Cl–
Major cation: K+
Major anion HPO42–
More soluble proteins than in plasma

9. Total solute concentration (mEq/L)
Electrolyte composition of blood plasma, interstitial fluid, and intracellular fluid.
160
140
120
Blood plasma
Interstitial fluid
Intracellular fluid
100
Na+
Sodium
Total solute concentration (mEq/L) 80 K+
Potassium
Ca2+
Calcium
Mg2+
Magnesium 60
HCO3–
Bicarbonate
Cl–
Chloride
HPO42–
Hydrogen
phosphate 40
SO42–
Sulfate 20
Na+ K+
Ca2+
Mg2+
HCO3–
Cl–
HPO42–
SO42–
Protein
anions

10. Lungs Gastrointestinal Kidneys tract Blood O2 CO2 Nutrients H2O, H2O,
Exchange of gases, nutrients, water, and wastes between the three fluid compartments of the body.
Lungs
Gastrointestinal
tract
Kidneys
Blood
plasma O2
CO2
Nutrients
H2O,
Ions
H2O,
Ions
Nitrogenous
wastes O2
CO2
Nutrients
H2O
Ions
Nitrogenous
wastes
Interstitial
fluid
Intracellular
fluid in tissue cells

11. Water Balance and ECF Osmolality
Water intake must = water output = ~ ml/day
Water intake: beverages, food, and metabolic water
Water output: urine (60%), insensible water loss (lost through skin and lungs), perspiration, and feces

12. Major sources of water intake and output.
100 ml
Feces 4%
Metabolism 10%
250 ml
Sweat 8%
200 ml
Insensible loss
via skin and
lungs 28%
Foods 30%
750 ml
700 ml
2500 ml
Urine 60%
1500 ml
1500 ml
Beverages 60%
Average intake
per day
Average output
per day

13. Disorders of Water Balance
Principal abnormalities of water balance
Dehydration
Hypotonic hydration
Edema

14. Disorders of Water Balance: Edema
Atypical accumulation of IF  tissue swelling (not cell swelling)
Result of  fluid out of blood or  fluid into blood
 fluid out of blood caused by
Increased capillary hydrostatic pressure or permeability
Capillary hydrostatic pressure increased by incompetent venous valves, localized blood vessel blockage, congestive heart failure,  blood volume
Capillary permeability increased by ongoing inflammatory response

15. Edema  fluid returning to blood result of
Imbalance in colloid osmotic pressures, e.g., hypoproteinemia ( plasma protein levels  low colloid osmotic pressure)
Fluids fail to return at venous ends of capillary beds
Results from protein malnutrition, liver disease, or glomerulonephritis

16. Electrolyte Balance
Electrolytes are salts, acids, bases, some proteins
Electrolyte balance usually refers only to salt balance
Salts control fluid movements; provide minerals for excitability, secretory activity, membrane permeability
Salts enter body by ingestion and metabolism; lost via perspiration, feces, urine, vomit

17. Central Role of Sodium Most abundant cation in ECF
Sodium salts in ECF contribute 280 mOsm of total 300 mOsm ECF solute concentration
Only cation exerting significant osmotic pressure
Controls ECF volume and water distribution
Changes in Na+ levels affects plasma volume, blood pressure, and ECF and IF volumes

18. Regulation of Potassium Balance
Hyperkalemia - too much K+
Hypokalemia - too little K+
Both disrupt electrical conduction in heart 
Sudden death

19. Regulation of Potassium Balance
K+ part of body's buffer system
H+ shifts in and out of cells in opposite direction of K+ to maintain cation balance, so
ECF K+ levels rise with acidosis
ECF K+ levels fall with alkalosis
Interferes with activity of excitable cells

20. Influence of Plasma Potassium Concentration
Most important factor affecting K+ secretion is its concentration in ECF
High K+ diet   K+ content of ECF  K+ entry into principal cells  K+ secretion
Low K+ diet or accelerated K+ loss reduces its secretion

21. Regulation of Calcium 99% of body's calcium in bones
Calcium phosphate salts
Ca2+ in ECF important for
Blood clotting
Cell membrane permeability
Secretory activities
Neuromuscular excitability - most important

22. Regulation of Calcium Hypocalcemia   excitability and muscle tetany
Hypercalcemia  inhibits neurons and muscle cells, may cause heart arrhythmias
Calcium balance controlled by parathyroid hormone (PTH) from parathyroid gland
Rarely deviates from normal limits

23. Regulation of Anions Cl– is major anion in ECF
Helps maintain osmotic pressure of blood
99% of Cl– is reabsorbed under normal pH conditions
When acidosis occurs, fewer chloride ions are reabsorbed
Other anions have transport maximums and excesses are excreted in urine

24. Acid-base Balance
pH affects all functional proteins and biochemical reactions, so closely regulated
Normal pH of body fluids
Arterial blood: pH 7.4
Venous blood and IF fluid: pH 7.35
ICF: pH 7.0
Alkalosis or alkalemia: arterial pH >7.45
Acidosis or acidemia: arterial pH <7.35

25. Acid-base Balance Most H+ produced by metabolism
Phosphorus-containing protein breakdown releases phosphoric acid into ECF
Lactic acid from anaerobic respiration of glucose
Fatty acids and ketone bodies from fat metabolism
H+ liberated when CO2 converted to HCO3– in blood

26. Acid-base Balance
Concentration of hydrogen ions regulated sequentially by
Chemical buffer systems: rapid; first line of defense
Brain stem respiratory centers: act within 1–3 min
Renal mechanisms: most potent, but require hours to days to effect pH changes

27. Acid-base Balance: Chemical Buffer Systems
Strong acids dissociate completely in water; can dramatically affect pH
Weak acids dissociate partially in water; are efficient at preventing pH changes
Strong bases dissociate easily in water; quickly tie up H+
Weak bases accept H+ more slowly

28. Dissociation of strong and weak acids in water.
A strong acid such as
HCI dissociates
completely into its ions.
A weak acid such as
H2CO3 does not
dissociate completely.

29. Chemical Buffer Systems
Chemical buffer: system of one or more compounds that act to resist pH changes when strong acid or base is added
Bind H+ if pH drops; release H+ if pH rises
Bicarbonate buffer system
Phosphate buffer system
Protein buffer system

30. Phosphate Buffer System
Action nearly identical to bicarbonate buffer
Components are sodium salts of:
Dihydrogen phosphate (H2PO4–), a weak acid
Monohydrogen phosphate (HPO42–), a weak base
Unimportant in buffering plasma
Effective buffer in urine and ICF, where phosphate concentrations are high

31. ORS
WHO and UNICEF jointly have developed official guidelines for the manufacture of oral rehydration solution and the oral rehydration salts used to make it (both often abbreviated as ORS). They also describe acceptable alternative preparations, depending on material availability. Commercial preparations are available as either pre-prepared fluids or packets of oral rehydration salts ready for mixing with water.
The formula for the current WHO oral rehydration solution (also known as low-osmolar ORS or reduced-osmolarity ORS) is 2.6 grams (0.092 oz) salt (NaCl), 2.9 grams (0.10 oz) trisodium citrate dihydrate (C6H5Na3O7⋅2H2O), 1.5 grams (0.053 oz) potassium chloride (KCl), 13.5 grams (0.48 oz) anhydrous glucose (C6H12O6) per litre of fluid.
A basic oral rehydration therapy solution can also be prepared when packets of oral rehydration salts are not available. It can be made using 6 level teaspoons (25.2 grams) of sugar and 0.5 teaspoon (2.1 grams) of salt in 1 litre of water.[16][17] The molar ratio of sugar to salt should be 1:1 and the solution should not be hyperosmolar.[18] The Rehydration Project states, "Making the mixture a little diluted (with more than 1 litre of clean water) is not harmful."[19]
The optimal fluid for preparing oral rehydration solution is clean water. However, if this is not available the usually available water should be used. Oral rehydration solution should not be withheld simply because the available water is potentially unsafe; rehydration takes precedence.[20]
When oral rehydration salts packets and suitable teaspoons for measuring sugar and salt are not available, WHO has recommended that home made gruels, soups, etc. may be considered to help maintain hydration.[21] A Lancet review in 2013 emphasized the need for more research on appropriate home made fluids to prevent dehydration.[22] Sports drinksare not optimal oral rehydration solutions, but they can be used if optimal choices are not available. They should not be withheld for lack of better options; rehydration takes precedence. But they are not replacements for oral rehydration solutions in nonemergency situations.[23]