1. Acid – Base Imbalance Disorders
By
Dr KHALED ALGARIRI
February 2020

2. • Small changes in pH can produce major disturbances
Most enzymes function only with narrow pH ranges
Acid-base balance can also affect electrolytes (Na+, K+,
Cl-)
Can also affect hormones
Introduction

3. Introduction
Acid-base disorders are changes in arterial Pco2, serum
HCO3−and serum pH.
1. Acidemia is serum pH < 7.35.
2. Alkalemia is serum pH > 7.45.

4. Adults Neonates
pH 7.35-7.45 7.30-7.40
pCO2 (kPa)
4.7-6.0 3.5-5.4
Bicarbonate
(mmol/L) 22-28 15-25
pH = 6.1 + log ([HCO3 –] / ( pCO2 (a) × 0.23))
Henderson-Hasselbalch equation

5. Compensation for acid-base
disorders:
Compensation is a series of physiological responses that react to
acid- base imbalances, by returning blood pH to the normal range
(7.35 – 7.45).
the respiratory system compensates for metabolic disturbances
while metabolic mechanisms compensate for respiratory
disturbances.

6. In compensation, the kidneys attempt to compensate
for changes in blood CO2 by making a corresponding
adjustment in blood bicarbonate.
Normally, almost all the bicarbonate formed by the
kidneys are retained
The lungs attempt to compensate for abnormal changes
in blood bicarbonate by making corresponding
adjustment in blood CO2

7. Determine the extent of compensation
ABSENT: the value that does not match the acid-base
status of the pH is normal
PARTIAL: both the value that doesn’t match the acid-
base status of the pH and the pH itself are abnormal
COMPLETE: the value that doesn’t match the acid-base
status is abnormal but the pH is normal

8. Types of Acid-Base Disorders

9. Respiratory acidosis
• Defined as a pH less than 7.35 with a PCO2 greater than 45 mm Hg
 Acidosis is caused by an accumulation of CO2 which combines with water
in the body to produce carbonic acid, thus, lowering the pH of the blood
 Any condition that results in hypoventilation can cause respiratory
acidosis.
 Pco2 in the extracellular fluid is increased because CO2 cannot be
cleared off by the lungs.

10. Respiratory acidosis

11. Compensation:

12. Respiratory Alkalosis
• Defined as a pH greater than 7.45 with a PCO2 less than 35 mm Hg
 Any condition that causes hyperventilation can result in respiratory
alkalosis
 Causes of RespiratoryAlkalosis
1. Psychological responses (such as anxiety or fear)
2. Pain
3. Increased metabolic demands (e.g. fever, thyrotoxicosis,
pregnancy)
4. Medications (e.g. respiratory stimulants).
5. Central nervous system lesions

13. Respiratory Alkalosis

14. Compensation of Respiratory Alkalosis

15. Metabolic Acidosis
• Defined as a bicarbonate level of less than 22 mEq/L with a pH of
less than 7.35
 Metabolic acidosis is caused by either a deficit of base in the
bloodstream or an excess of acids, other than CO2.
 For example:
1. Loss of bicarbonate through diarrhea or renal dysfunction
2. Accumulation of acids (lactic acid or ketones) which may occur
in starvation or high fever.
3. Failure of kidneys to excrete H+
Kidneys

16. Metabolic Acidosis

17. Compensatory of metabolic acidosis

18. Metabolic alkalosis
The primary abnormality in metabolic alkalosis is the increased
plasma bicarbonate level. (HCO3-).
Causes:
Less common
1- Intake of a large amounts of alkali as sodium bicarbonate:
More common
2- Loss of H+ (acids) from the body:
1- From the kidneys (increased excretion of acids, H+ ions):
a- (aldosterone) excess
b- Severe potassium deficiency
2- From the GIT (increased loss acids, H+ ions): vomiting and
gastric wash

19. Metabolic alkalosis

20. Compensation of Metabolic alkalosis

21. Conditions pH Problem Compensation in progress
Lab Values if
compensating
Lab values if not
compensating
Respiratory
acidosis
Low High pCO2
Kidneys reabsorb HCO3 and
secrete H+
Blood pCO2 is high
Blood HCO3 levels will be
high
Blood pCO2 is high
Blood HCO3 is normal
Respiratory
alkalosis
High Low pCO2
Kidneys secrete HCO3 and
stop secreting H+
Blood pCO2 is low
Blood HCO3 levels will be
low
Blood pCO2 is low
Blood HCO3 is normal
Metabolic
acidosis
Low Low HCO3
Lungs hyperventilate
(Kussmaul breathing)
Kidneys reabsorb HCO3 and
secrete H+
Blood pCO2 is low
Blood HCO3 levels will be
high
Blood pCO2 is normal
Blood HCO3 is normal to
low
Metabolic
alkalosis
High High HCO3
Lungs increase pCO2
(hypoventilation)
Kidneys secrete HCO3 and
stop secreting H+
Blood pCO2 is high
Blood HCO3 levels will be
low
Blood pCO2 is normal
Blood HCO3 is normal to
high

22. Thank you