acid and base balance
Download
Skip this Video
Download Presentation
Acid and Base Balance

Loading in 2 Seconds...

play fullscreen
1 / 30

Acid and Base Balance - PowerPoint PPT Presentation


  • 111 Views
  • Uploaded on

Acid and Base Balance. Zhihong Li (李志红) Department of Biochemistry. The Body and pH. Homeostasis of pH is tightly controlled Extracellular fluid = 7.4 Blood = 7.35 – 7.45 < 7.35: Acidosis (acidemia) > 7.45: Alkalosis (alkalemia) < 6.8 or > 8.0: death occurs. CO 2. CO 2.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Acid and Base Balance' - natane


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
acid and base balance

Acid and Base Balance

Zhihong Li(李志红)

Department of Biochemistry

the body and ph
The Body and pH
  • Homeostasis of pH is tightly controlled
  • Extracellular fluid = 7.4
  • Blood = 7.35 – 7.45
  • < 7.35: Acidosis (acidemia)
  • > 7.45: Alkalosis (alkalemia)
  • < 6.8 or > 8.0: death occurs
the body produces more acids than bases

CO2

CO2

The body produces more acids than bases
  • Acids take in with foods.
  • Cellular metabolism produces CO2.
  • Acids produced by metabolism of lipids and proteins.

CO2

H2CO3

CO2+ H2O

Volatile acid

(H+ 15 –20 mol /d)

H2SO4 H3PO4

Uric acid

Lactic acid

Ketone body

(H+ < 0.05 –0.10 mol /d)

Fixed acid

maintenance of blood ph
Maintenance of blood pH
  • Three lines of defense to regulate the body’s acid-base balance
    • Blood buffers
    • Respiratory mechanism
    • Renal mechanism
buffer systems
Buffer systems
  • Take up H+ or release H+ as conditions change
  • Buffer pairs – weak acid and a base
  • Exchange a strong acid or base for a weak one
  • Results in a much smaller pH change
bicarbonate buffer

[HCO3-]

pH=pKa+lg

[H2CO3]

H2CO3 H+ + HCO3-

24

= 6.1+ lg

1.2

20

= 6.1+ lg

1

= 6.1+1.3 = 7.4

Bicarbonate buffer
  • Predominant buffer system
  • Sodium Bicarbonate (NaHCO3) and carbonic acid (H2CO3)
  • HCO3- : H2CO3: Maintain a 20:1 ratio
bicarbonate buffer1
Bicarbonate buffer
  • HCl + NaHCO3↔ H2CO3 + NaCl
  • NaOH + H2CO3 ↔ NaHCO3 + H2O
phosphate buffer
Phosphate buffer
  • Major intracellular buffer
  • NaH2PO4-Na2HPO4
  • H+ + HPO42-↔ H2PO4-
  • OH- + H2PO4- ↔ H2O + HPO42-
protein buffers
Protein Buffers
  • Include plasma proteins and hemoglobin
  • Carboxyl group gives up H+
  • Amino Group accepts H+
2 respiratory mechanisms

CO2

CO2

2. Respiratory mechanisms
  • Exhalation of CO2
  • Rapid, powerful, but only works with volatile acids
  • H+ + HCO3-↔ H2CO3 ↔ CO2 + H20
  • Doesn’t affect fixed acids like lactic acid
  • Body pH can be adjusted by changing rate and depth of breathing
3 kidney excretion
3. Kidney excretion
  • Most effective regulator of pH
  • The pH of urine is normally acidic (~6.0)
    • H+ ions generated in the body are eliminated by acidified urine.
  • Can eliminate large amounts of acid (→H+)
  • Reabsorption of bicarbonate (HCO3-) (←HCO3-)
  • Excretion of ammonium ions(NH4+) (→NH4+)
  • If kidneys fail, pH balance fails
rates of correction
Rates of correction
  • Buffers function: almost instantaneously
  • Respiratory mechanisms: take several minutes to hours
  • Renal mechanisms: may take several hours to days
acid base imbalances
Acid-Base Imbalances
  • pH< 7.35: acidosis
  • pH > 7.45: alkalosis
  • The body response to acid-base imbalance is called compensation
    • The body gears up its homeostatic mechanism and makes every attempt to restore the pH to normal level.
    • May be complete if brought back within normal limits
    • Partial compensation if range is still outside norms.
acid base imbalances1
Acid-Base Imbalances
  • Acidosis- a decline in blood pH ↓
    • Metabolic acidosis: due to a decrease in bicarbonate. ↓
    • Respiratory acidosis: due to an increase in carbonic acid. ↑
  • Alkalosis- a rise in blood pH ↑
    • Metabolic alkalosis: due to an increase in bicarbonate.↑
    • Respiratory alkalosis : due to a decrease in carbonic acid. ↓
slide19

pH

acidosis

alkalosis

metabolic

respiretory

metabolic

respiretory

[HCO3-]↓

PaCO2↑

[HCO3-]↑

PaCO2↓

HCO3-

compensation
Compensation
  • If underlying problem is metabolic, hyperventilation or hypoventilation can help: respiratory compensation.
  • If problem is respiratory, renal mechanisms can bring about metabolic compensation.
metabolic acidosis
Metabolic Acidosis
  • Bicarbonate deficit (↓)- blood concentrations of bicarb drop below 22mEq/L (milliequivalents / liter)
  • Causes:
    • Loss of bicarbonate through diarrhea or renal dysfunction
    • Accumulation of acids (lactic acid or ketones)
    • Failure of kidneys to excrete H+
  • Commonly seen in severe uncontrolled DM (ketoacidosis).
compensation for metabolic acidosis
Compensation for Metabolic Acidosis
  • Hyperventilation: increased ventilation
  • Renal excretion of H+ if possible
  • K+ exchanges with excess H+ in ECF
    • H+ into cells, K+ out of cells
respiratory acidosis
Respiratory Acidosis
  • Carbonic acid excesscaused by blood levels of CO2 above 45 mm Hg.
  • Hypercapnia – high levels of CO2 in blood
  • Causes:
    • Depression of respiratory center in brain that controls breathing rate – drugs or head trauma
    • Paralysis of respiratory or chest muscles
    • Emphysema
compensation for respiratory acidosis
Compensation for Respiratory Acidosis
  • Kidneys eliminate hydrogen ion (H+ and NH4+) and retain bicarbonate ion
metabolic alkalosis
Metabolic Alkalosis
  • Bicarbonate excess↑ - concentration in blood is greater than 26 mEq/L
  • Causes:
    • Excess vomiting = loss of stomach acid
    • Excessive use of alkaline drugs
    • Certain diuretics
    • Endocrine disorders: aldosterone ↑
    • Heavy ingestion of antacids
compensation for metabolic alkalosis
Compensation for Metabolic Alkalosis
  • Hypoventilation to retain CO2 (hence H2CO3↑)
  • Renal excretes more HCO3-, retain H+.
respiratory alkalosis
Respiratory Alkalosis
  • Carbonic acid deficit↓
  • pCO2 less than 35 mm Hg (hypocapnea)
  • Most common acid-base imbalance
  • Primary cause is hyperventilation
    • Hysteria, hypoxia, raised intracranial pressure, excessive artificial ventilation and the action of certain drugs (salicylate) that stimulate respiratory centre.
compensation of respiratory alkalosis
Compensation of Respiratory Alkalosis
  • Kidneys conserve hydrogen ion
  • Excrete bicarbonate ion
mixed acid base disorders
Mixed acid-base disorders
  • Sometimes, the patient may have two or more acid-base disturbances occurring simultaneously.
  • In such instances, both HCO3- and H2CO3 are altered.
points
Points
  • Blood = 7.35 – 7.45;
  • < 7.35: Acidosis, > 7.45: Alkalosis
  • Three lines of defense to regulate the body’s acid-base balance
    • Blood buffers:Bicarbonate buffer, Phosphate buffer, Protein Buffers
    • Respiratory mechanisms: Exhalation of CO2
    • Renal mechanism: eliminate acid, Reabsorption of HCO3-
  • Acidosis- blood pH ↓(Causes, Compensation)
    • Metabolic acidosis: bicarbonate ↓
    • Respiratory acidosis: carbonic acid ↑
  • Alkalosis- blood pH ↑ (Causes, Compensation)
    • Metabolic alkalosis: bicarbonate↑
    • Respiratory alkalosis : carbonic acid ↓
ad