Physiological acid base balance

Pharmaceutical Inorganic Chemistry B.Pharmacy I yaer I sem Subject

1. Physiological acid base balance
•Mrs. Kulkarni DipaliM.
•Assistant Professor,
•Yash Institute of Pharmacy,
•Aurangabad

2. pH disturbances evaluated with reference to (HCO3
–
–
H2CO3) bicarbonate and carbonic acid
Physiological Acid Base Balance
Abnormalities of pH of body
•Acedemiaan abnormal decrease in pH
Alkalemiaan abnormal increase in pH
•Acidosis and alkalosis are clinical states .

3. Buffer
systems
Bicarbonate and carbonic
acid (HCO
3–
: H
2
CO
3
)
plasma and kidney
Monohydrogen
phosphate/dihyd
rogenphosphate
(HPO
4--
: H
2
PO
4-
)
cells kidney.
Hemoglobin
buffer
system in
RBC’s
Acids
1. Carbonic acid from carbon dioxide
2. Lactic acid from anaerobic metabolism
Constantly produced during metabolism
Metabolic reactions occur only within narrowpH range of
7.38-7.42

5. Bicarbonate –carbonic acid buffer system
Bicarbonate present more in extracellular fluid
than any other buffer component
Limitless supply of carbon dioxide
Extracellular pH function by controlling fluid
Works in conjunction with haemoglobin.

6. Reabsorption of bicarbonate

7. Each millimoleof oxygen that dissociates from hemoglobin
(Hb) 0.7 millimoleof H
+
are removed.
Hemoglobin buffer system
RBC’s have hemoglobin buffer system
Most effective single buffer system.
Buffers carbonic acid produced during
metabolism

8. CO
2
enters
the
erythrocytes
Rapidly forms
H
2
CO3by the
action of carbonic
anhydrase
Combines with Hb.
Carbonic anhydrase
CO
2
+ H
2
O H
2
CO
3
Carbon dioxide-acid anhydride of carbonic acid is produced in cells.
CO2diffuses into the plasma and reacts with water to form
carbonic acid
The increased carbonic acid is buffered by plasma proteins
The tendency to lower the pH of the erythrocytes due to increased
concentration of H
2
CO
3
is compensated by Hb.

9. Bicarbonate in plasma, along with the plasma carbonic acid
now acts as efficient buffer system
Chloride shift
The bicarbonate anion then diffuses out of erythrocytes
and chloride anion diffuses in.
H
2
CO
3
+ K
+
+HbO
2-
K
+
+ HCO
3-
+ HHb + O
2
Normal HCO
3-
/ H
2
CO
3
ratio is 27/1.35 meq/lt(20:1)
corresponding to pH 7.4

10. Lungs

11. By regulating breathing it is possible for the body to exert a partial
control on the HCO
3-
/H
2
CO
3
ratio.
Inlungs reversal of above process due to the large amount of
Oxygen O
2
present
Oxygen Oxygencombines with the protonateddeoxyhemoglobin
releasing proton
These combine with HCO
3-
forming H
2
CO
3
which then dissociates
to CO2 and water. carbon dioxide is exhaled by the lungs
O
2
+ HHb + K
+
+ HCO
3-
K
+
HbO
2-
+ H
2
CO
3
Carbonic anhydrase
CO
2
+ H
2
O

12. Phosphate buffer system
Effective in
maintaining
physiological pH.
At pH 7.4
HPO4
-2
/H
2
PO
4-
ratio is approx.
4:1.
In kidney, urine pH
drop to 4.5-4.8
corresponding to
HPO4
-2
/H
2
PO
4-
ratio of 1:99 to
1:100.
sodium salt of
mineral or
organic acids are
removed from
plasma by
glomerular
filtration
sodium hydrogen
exchange
Sodium is removed
from renal filtrate/
tubular fluid in
tubular cells..
Sodium bicarbonate
returns to plasma
(eventually being
removed in the lungs
as CO
2
) and protons
enter tubular fluid,
forming acids of
sodium anions

13. Phosphate buffer system

14. Factors altering the pH of Extra Cellular Fluid
1. Acidosis
Increase in either potential and/or nonvolatile hydrogen ion
(H
+
) content of body
Acedemia:Increase in H
+
ion concentration of plasma
It is manifested by fall in the pH of blood.
Compensated acidosis: no rise in H
+
concentration of plasma.
This state of acidosis (without acedemia)

15. Metabolic
•excess production of
proton in the body
•Acceleration of normal
metabolic process
•excessive catabolism e.g.
fever proton donor drug
e.g. salicylates,chlorides
•Loss of alkaline fluid from
intestine, eg. diarrhea
•large quantity of saline.
Renal
•Defective renal excretion of H+.
•Tubular disorders, Addisons
disease
•Drugs interfere with tubular
secretion of H+
•Eg. carbonic anhydrase
inhibitors
Respiratory
•increase retention of carbon
dioxide
•rise in plasma carbonic acid
content.
•occurs due to chronic lung
disease, respiratory muscle
paralysis
•drugs that depress respiratory
center.

16. 1.Sodium salts of bicarbonate, lactate, acetate and citrate.
4.They are degraded to carbon dioxide and water by TCA
cycle (Citric acid cycle or Krebs cycle).
3. Lactate, acetate and citrate ions are normal components of
metabolism
2.If bicarbonate is deficit, administration of bicarbonate
increases the HCO
3-
/H
2
CO
3
ratio.
Treatment of metabolic acidosis

17. 2. Alkalosis
Reduction in the total hydrogen ion content of the body
Alkalemia: reduction of hydrogen ion content in plasma
It is manifested by increase in the pH of blood.
Compensated alkalosis: no decrease in H
+
concentration of
plasma.
Thisstateof alkalosis (without alkalemia)

18. Metabolic
•Due to renal
damage
•alkali ingestion
•vomiting causes
loss of H+,Cl-ions
•treated with
ammonium salts.
•in kidney it retards
the Na
+
-H
+
exchange
Contraction
•Occurs with mercurial
diuretics which cause
excessive loss of Cl–
and sodium.
Respiratory
•caused by
hyperventilation
•washes large
amount of CO2
•Bicarbonate ion and
carbonic acid ratio
reduces
•Occurs due to high
altitude, fever,
encephalitis,
hypothalamic
tumor, drugs like
salicylate, hot bath

19. Oral Rehydration Salt
It contains not less than 90% and not
more than 110 % of Dextrose
Required electrolytes are sodium,
potassium, chloride ,citrate
It can be preferred when excess fluid
loss is there.
Ex vomiting ,diarrhea

20. It is dry homogenous powdered mixture of dextrose, sodium chloride.
potassium chloride along with sodium citrate or sodium bicarbonate
All are used for electrolyte replacement therapy.
After being dissolved in sufficient quantity of water
It may contain some flavoring agents, sweetening agents,
diluents to increase flow properties.
eg.Saccharin, aspartame
Oral Rehydration Salt

21. Thank you