1. Acid base balance
Dr. S. Parthasarathy MD., DA., DNB, MD (Acu), Dip. Diabetes Diploma in Software based statistics PhD ( physiology), IDRA , FICA
Certifícate in USGRA

2. A lot of confusion !! What is what ?
Sometimes anions are called bases ?
Sometimes called acids
E. g. bicarbonate , chloride
Know the definition !!

3. An acid is an hydrogen ion donor
Acid = H+ + base
H2CO3 = H+ + HCO3 –
H3PO4 = H + + H2PO4–
A base is an hydrogen ion acceptor

4. What is an alkali ! An alkali produces hydroxyl ions in solution
NaOH = Na + + OH-
Alkali is strong – more hydroxyl ions in solution while more hydrogen ions means strong acid

5. Sorenson !!
In 1909 , he found out that enzyme activity changes with minute or minimal changes of hydrogen ion concentration
mole pr liter of hydrogen ion
moles per liter
= moles per liter
Write like this – take the power and make it positive
4 and 6
Negative logarithm of hydrogen ion concentration in moles per liter

6. pH change and hydrogen ion change is never linear
Example: a solution with a pH of 4 has 10 times the hydrogen ion concentration of a solution with a pH of 5 and 100 times the hydrogen ion concentration of a solution with a pH of 6

7. What is neutral pH ??
Water dissociates into equal amounts of hydrogen ions and OH ions
In chemistry , the equilibrium has been found to be H OH- = 10-14
Water contains equal H and OH
Hence the neutral pH is 7

8. pH of blood ! Acids have more H+ ions and less pH than 7
Which is strong – or
Alkali more than 7
Blood is faintly alkaline
pH of 7 -- Oxygenation of Hb is impaired

9. Henderson hasselbach pH=pKa + log([k]/[HA])
lactic acid (pKa, = 3.9) is a stronger acid than carbonic acid (pKa, = 6.1)
because, at any given pH, lactic acid will be more dissociated and therefore will release more H+ than carbonic acid.

10. Replenished continuously hence able to have that pH

11. Our life is acidogenic

12. Approx 10 neq for 0.1 pH change
We need to have a pH between 7.36 – 7.44 approx
What happens if it changes
It is dangerous
then how it is avoided

13. Buffers !!
A buffer is a solution containing either a weak acid and its salt or a weak base and its salt, which is resistant to changes in pH.
Fast pH changes are not allowed

14. Water is great ! HCl + H2O ↔ H3O+ + Cl− NaOH + H2O ↔ Na+ + H2O + OH−
Alterations in this “balance” lead to significant cardiovascular problems caused by dysfunction of transcellular ion pumps

15. ECF
The body's chemical buffer system consists of three individual buffers out of which the carbonic acid bicarbonate buffer is the most important. ( EC water )
Phosphate buffer
Protein buffer

16. HCO3 + H2CO3
Strong alkali
NaOH + H2Co3 = NaHCO3 + H2O
Strong acid

17. carbonic acid bicarbonate buffer
pH = log HCO3/ H2CO3
6.1 + log 27/1.35
6.1 + log 20
= 7.4

18. Phosphate buffer system
Na2HPO4 and NaH2PO4
HCl + Na2HPO4 = NaH2PO4 + Nacl
NaOH +NaH2PO4 = Na2HPO4 + H2O
Kidney tubules and RBCs

19. Protein buffer system
Protein Buffers in Blood Plasma and Cells. Nearly all proteins can function as buffers. 
Proteins are made up of amino acids, which contain positively charged amino groups and negatively charged carboxyl groups.
The charged regions of these molecules can bind hydrogen and hydroxyl ions, and thus function as buffers.

20. Intracellular buffer with immediate ECF effect
Haemoglobin exists within the red cell as a weak acid (HHb) and its potassium salt (KHb)
Hemoglobin is a protein

22. Can we repeat ?? Or go ahead ?

23. Respiratory regulation
CNS receptors

24. RS - works how ?
Doubling the respiratory rate for less than 1 minute, removing “extra” CO2, would increase the blood pH by 0.2.
This situation is common if you are exercising strenuously over a period of time. To keep up the necessary energy production, you would produce excess CO2(and lactic acid if exercising beyond your aerobic threshold).
This helps to keep you from developing acidosis.

25. Physiology ! Medullary CNS receptors CO2 more permeable than HCO3
Ventilation increase
Peripheral carotid receptors – more hyoxemic insult

26. Upto 7 stimulation – hyperventilation
But below 7 – may not have the effect
Think of kussmaul respiration
Think of carbondioxide narcosis

27. If we give massive doses of bicarbonate For eg 27 meq to 54 meq/litre
Depression of respiration
PCO2 increase from 40 to 80
Carbonic acid content becomes 2.7
pH remains the same
pH = log HCO3/ H2CO3
6.1 + log 27/1.35
6.1 + log 20
= 7.4

28. Renal regulation
The kidneys control acid-base balance by excreting either acidic or basic urine
Excreting acidic urine reduces the amount of acid in extracellular fluid
Excreting basic urine removes base from the extracellular fluid

29. Three mechanisms Reabsorption of bicarbonate
Acidification of buffer salts
Secretion of ammonia

30. Normally 4000 meq of HCO3 reabsorbed /day

31. Acidification of buffer salts

32. Oxidation of glutamine

33. Urine pH may vary from 4.5 to 7.8
What is normal ??

34. Inter-relation of buffers
HC03- is a useful marker of metabolic acid changes but not in a linear fashion.
We expect the bicarb to decrease this much ?
But does this happen ?
Changes in HC03- are dependent upon respiratory acid-base variations.

35. ECF mechanisms are instantaneous
Respiratory may take a few hours
Kidneys may take hours to days
But mechanisms by the kidneys permanent

36. Thank you all