Biochemistry Lectures 3

Front 1

First Line of defense against pH changes

Back 1

Chemical Buffer System:
Bicarbonate
Phosphate
Protein

Front 2

Second Line of Defense against pH changes

Back 2

Physiological Mechanisms:
Respiratory System (regulates PCO2)
Renal System (regulates HCO3)

Front 3

Renal response to Acidosis

Back 3

When pH falls, there is increased proton secretion in urine and urine becomes acidic and blood basic. Phosphate and ammonia buffers are used and excreted

Front 4

Renal Response to Alkalosis

Back 4

When pH decreases, there is increased HCO3- excretion, and urine becomes alkaline (basic) while blood becomes acidic.

Front 5

Normal Levels by acid base analyzers

Back 5

pH ; 7.36 -7.44
PCO2 : 38 - 42 mmHG
HCO3-: 22 - 25 mmol/L

Front 6

Respiratory Acid Base Disorders

Back 6

Due to dysfunction of the respiratory system and are result of changes in PCO2

Front 7

Metabolic Acid Base Disorders

Back 7

Due to metabolic or renal disorders and caused by changes in HCO3-

Front 8

Respiratory Acidosis

Back 8

Decreased rate of respiration/lung function or obstruction (hypoventilation)
-CO2 not wash out, increased in PCO2
Will cause a decrease in pH, elevated PCO2, with normal HCO3_

Front 9

Compensation for respiratory acidosis

Back 9

Compensation will by the renal system until primary disturbance is treated. pH will slightly increase to try to return to normal, PCO2 will stay elevated. HCO3 will increase by the renal system as the kidney tries excrete H+ ions to increase pH. Phosphate and ammonia will acidify the urine.

Front 10

Henderson-Hasselbalch Respiratory Acidosis

Back 10

Increase in PCO2 results in decrease in pH
Compensation by renal system, increases HCO3- and ratio of acid to base return almost to normal

Front 11

Cause of respiratory acidosis

Back 11

-Airway obstruction
-Opiod drugs - anesthetics
-Muscle diseases in chest wall
-Disease/injury of phrenic nerve (Gullian Barre syndrome)
-Lung disease, COP@, RDS, fibrosis of lung

Front 12

Respiratory Alkalosis

Back 12

Increase rate of respiration --> increase washout of CO2, resulting in low PCO2 ---> increasing pH
-pH is increased
-PCO2 is low
-HCO3 is normal

Front 13

Compensation of respiratory Alkalosis

Back 13

Compensation will be by the renal system as it tries to bring pH back to normal by not excreting H+, resulting in increased excretion of HCO3- in the urine (causing urine) to become alkaline.
pH increases closer to normal
PCO2 - remains low
HCO3 - decreases due to renal compensation

Front 14

Henderson-Hasselbalch Respiratory Alkalosis

Back 14

Decrease in PCO2 (due to hyperventilation) results in increased in pH
HCO3- decreases due to renal compensation and ratio of base/acid returns toward normal

Front 15

Causes of respiratory alkalosis

Back 15

Causes of hyperventilation:
-Anxiety, fever
-Hypoxia - high altitude stimulates increase rate of respiration

Front 16

Metabolic Acidosis

Back 16

Low HCO3- (base) results in low pH
HCO3- is low either due to increased nonvolatile acids (lost by buffering) or increases losses
-pH is decreased
-PCO2 is normal
-HCO3 is decreased

Front 17

Compensation of Metabolic Acidosis

Back 17

When plasma pH falls, stimulates respiration to washout CO2 and decreased PCO2-
If renal system is functioning it can compensate to increase H+ excretion
-pH is closer to normal
-PCO2 decreased due to compensatory hyperventilation
-HCO3- decreased

Front 18

Causes of Metabolic Acidosis

Back 18

Increased production of non-volatide acids
Increased loss of HCO3- (base)

Front 19

Diabetic Ketoacidosis

Back 19

Results in increased production of non-volatile ketone bodies

Front 20

Lactic Acidosis

Back 20

Results in increased production of non-volatile lactate

Front 21

Chronic Renal Failure

Back 21

Results in metabolic acidosis due to decreased excretion of sulfate and phosphate

Front 22

Renal tubular acidosis

Back 22

-Causes metabolic acidosis due to failure to secret h+ and reabsorb HCO3-

Front 23

Metabolic Alkalosis

Back 23

Results from increased HCO3- causing increase in pH.
-pH is increased
-HCO3 is increased
-PCO2 is normal

Front 24

Compensated metabolic alkalosis

Back 24

Increased pH inhibits respiratory center resulting in hypoventilation --> increases PCO2
-If renal system is function, can increase excretion of HCO3-
-pH comes closer to normal
-HCO3- is increased (primary abnormality)
-PCO2 is increased due to respiratory compensation

Front 25

Causes of Metabolic alkalosis

Back 25

Vomiting, pyloris stenosis
-results in loss of acidic contents of stomach
Nasogastric suction - draining stomach
Excess consumption of antacids

Front 26

Summary

Back 26