1. This document discusses acid-base disturbances and their classification, causes, clinical features, and treatment. It covers topics like metabolic acidosis, respiratory acidosis, metabolic alkalosis, and respiratory alkalosis. 2. Normal acid-base balance and electrolyte values are outlined. Case histories of patients with acid-base imbalances are presented, asking questions about identifying and explaining the nature of the disturbances. 3. Compensatory responses to primary acid-base disorders aim to restore pH balance. Anion gap and its role in identifying acid-base etiologies are explained. Causes, signs, and management of the main acid-base disorders are detailed.

1. Acid-Base Disturbances
Dr Neha Rani Verma
Assistant professor
Dept. of Biochemistry

2. ACID BASE BALANCE
 In normal life, the variation of plasma pH is very small.
 The pH of plasma is maintained within a narrow range of 7.38 to 7.42.
 The pH of the interstitial fluid is generally 0.5 units below that of the plasma.
 During metabolism Volatile acids produced are carbonic acid, is eliminated as CO2 AND
 Nonvolatile (fixed) acids produced are lactate, keto acids, sulfuric acid and phosphoric acid, are
buffered and excreted by the kidney.
Acidosis
If the pH is below 7.38
Acidosis leads to CNS depression
and coma.
Death occurs when pH is below
7.0.
Alkalosis
When the pH is more than 7.42
Alkalosis induces neuromuscular
hyperexcitability and tetany.
Death occurs when the pH is above
7.6.

3. Classification of Acid-Base Disturbances
 1. Acidosis (fall in pH)
a. Respiratory acidosis:
Primary excess of carbonic acid or INCREASE pCO2
b. Metabolic acidosis:
Primary deficit of bicarbonate (HCO3-).
 2. Alkalosis (Rise in pH)
a. Respiratory alkalosis:
Primary deficit of carbonic acid or DECREASE pCO2
b. Metabolic alkalosis:
Primary excess of bicarbonate (HCO3-).
 3. Compensatory responses
a. Uncompensated
b. Partially compensated
c. Fully compensated.

4. Compensatory Responses
 Primary disturbances will be followed by a secondary compensatory change in the
counteracting variable.

6. Anion Gap
 The sum of cations and anions in ECF is always equal, so as to maintain the electrical
neutrality.
 The unmeasured anions constitute the anion gap.
 Sodium and potassium together account for 95% of the cations whereas chloride and
bicarbonate account for only 86% of the anions.
K+ can be ignored if it is not significant in
second formula.

7. Metabolic Acidosis
 A fall in blood pH due to a decrease in bicarbonate levels of plasma is called
metabolic acidosis.
 Decrease in bicarbonate levels may be due to:
 Increased production of acids.
 In uncontrolled diabetes mellitus and starvation
 Excessive loss of bicarbonate
 In renal tubular dysfunction and from GI tract in severe diarrhoea.

8.  High Anion Gap Metabolic Acidosis (HAGMA)
 Accumulation of acid anions or, cations are decreased (hypokalemia, hypo-calcemia,
hypomagnesemia).
 Hypoalbuminemia (decrease in negatively charged protein),
 Hypergammaglobulinemia (increase in positively charged protein).
 Normal Anion Gap Metabolic Acidosis (NAGMA)
 When there is a loss of both anions and cations, the anion gap is normal, but acidosis
may prevail.
 Diarrhea
 Renal tubular acidosis,

9. Clinical Features of Metabolic Acidosis
 The respiratory response to metabolic acidosis is to hyperventilation. So there is marked
increase in respiratory rate and depth of respiration; this is called as Kussmaul respiration.
 The acidosis is dangerous when pH is <7.2 and serum bicarbonate is <10 mmol/L.
 Treatment-
 In ketoacidosis, give intravenous fluids, insulin and potassium replacement.
 Oxygen is given in patient with lactic acidosis.
 In all cases, potassium abnormalities should be carefully treated.
 Bicarbonate is given

10. Metabolic Alkalosis
 Rise in pH of plasma is called metabolic alkalosis.
 This is seen in the following conditions:
 Loss of gastric juice along with H+ ions in prolonged and severe vomiting.
 Therapeutic administration of large dose of alkali (as in peptic ulcer) or chronic
intake of excess antacids.
 Clinical Features of Metabolic Alkalosis
 The respiratory center is depressed leading to hypoventilation.
 The renal mechanism conserves H+ and excretes more HCO3
–.
 Increased neuromuscular activity when pH is above 7.55. Tetany results even in the
presence of normal serum calcium.

11. Respiratory Acidosis
 It results from an increase in concentration of carbonic acid (H2CO3) in plasma,
due to decrease in alveolar ventilation, and that leads to retention of CO2.
 Causes are:
 Obstruction to respiration: This may occur in pneumonia, emphysema, asthma,
Chronic obstructive lung disease etc.
 Depression of respiration: Administration of respiratory depressant toxic drugs, e.g.
morphine
 The ratio of bicarbonate to carbonic acid will be less than 20.

12. Respiratory Alkalosis
 A rise in blood pH due to lowered concentration of CO2 or H2CO3, due to
hyperventilation.
 This occurs in the following conditions:
• Anxiety or hysteria
• Fever
• Hot baths
• At high altitude
• Working at high temperature, etc.
 Clinically, hyperventilation, muscle cramps, tingling and paraesthesias are seen.

13. Normal Serum Electrolyte and Arterial Blood Gas
Values
 pH = 7.4
 Bicarbonate = 22–26 mmol/L
 Chloride = 96–106 mmol/L
 Potassium = 3.5–5 mmol/L
 Sodium = 136–145 mmol/L
 pO2 = 95 (85–100) mm Hg
 pCO2 = 40 (35–45) mm Hg

15. Case History 1
 A 38-year-old man reported in the emergency ward of a hospital emergency with complaints of persistent
vomiting for one week. He had generalized muscular cramps. On examination, he appeared dehydrated
and had shallow respiration. Blood sample was analyzed with the following results:
 pH = 7.8
 Bicarbonates = 35 mEq/L
 pCO2 = 50 mm Hg
 Na+= 145 mEq/L
 K+ = 2.9 mEq/L.
 Questions
1. Identify the nature of acid-base disorder.
2. What could be the cause of this acid-base disorder?
3. What is the cause of shallow respiration?
4. Give reason for development of muscle cramps.
Please answer in comment box of classroom.

16. Case History 2
 A 50-year-old male was admitted with a history of chronic obstructive airways
disease for many years. On examination, he was found cyanosed, and breathless.
Blood sample was analyzed with the following results:
 Blood pH = below normal
 pCO2 = markedly elevated
 (HCO3–) = markedly elevated.
 Questions
1. Identify the nature of acid-base disorder.
2. What could be the cause of elevated pCO2?
3. What could be the cause of elevated (HCO3–)?
Please answer in comment box of classroom.