Acid Base Balance
Acid Base Balance
Acid Base Balance
By:
Dr. Samraa Abdalwhab khider
Normal pH
- pH = - log [H] = 7.4 ± 0.05.
- [H+] = 40 nmol/L or 0.00004 mmol/L (in arterial
blood).
- pH less than 7.35 = Acidosis & more than 7.45 =
Alkalosis.
- pH above 7.7 or below 7.0 is incompatible with life
control)
The buffers
In the interstitium
–Bicarbonate
Inthe cells
–Proteins
–Phosphate
In urine
–Bicarbonate
–Ammonia
–Phosphate
The respiratory system
pH (in plasma)
o Central: Stimulated by high Pco2 & low pH (in CSF)
- Stimulation of the chemoreceptors (e.g. by the low
pH) results in stimulation of the respiratory center
which causes hyperventilation. This results in washout
of CO2 and correction of the low pH.
- On the other hand, high pH decreases stimulation of
- Causes:
o Failure to excrete acids (renal failure)
o Formation of high amounts of acids (diabetic
- Characterized by:
o Low pH & low bicarbonate
- Compensation:
o Buffers
o Respiratory system (hyperventilation)= low PCO2
2- Metabolic alkalosis
- Causes:
o Loss of gastric acid: (vomiting or naso-gastric tube suction)
o Ingestion of alkali
o Diuretics
- Characterized by:
o High pH & high bicarbonate
- Compensation:
o Buffers
o Renal system
3- Respiratory acidosis
- Causes:
o Respiratory center depression by drugs or trauma
o Paralysis of respiratory muscles
o Diseases of the lung
- Characterized by:
o Low pH & high PCO2
- Compensation:
o Buffers & renal system (the respiratory system is the
cause)
4- Respiratory alkalosis
- Causes:
o Hys (hyperventilation)
- Characterized by:
o High pH & low PCO2
- Compensation:
o Buffers & renal system (the respiratory system is the
cause)
EVALUATION OF ACID BASE STATUS
NR : arterial = 40
venous = 46
Momken n7seba by gehas esmo puls oximeter .
o HCO3-
[2] Measurement of the anion gap
bgme3o al + & - charge in the body wa bteaho
mgmo3 al – men mgmo3 al + charge eza al + akter
7ykon 3endana low anion gap wa eza al – akter 7ykon
3endana high anoin gap .