Metabolic Alkalosis

Question 1

What is metabolic alkalosis?

Answer 1

• Loss of hydrogen ions (H⁺)
• Gain of bicarbonate ion (HCO₃^-)

Question 2

Which organs are involved mainly in metabolic alkalosis?

Answer 2

• Kidney OR
• GI tract

Question 3

ABG level in metabolic alkalosis (uncompensated)

Answer 3

• pH >>> High
• HCO₃ >>> High
• pCO₂ >>> Normal

Question 4

ABG level in metabolic alkalosis (partially compensated)

Answer 4

• pH: High
• HCO₃: High
• pCO₂: High

Question 5

ABG level in fully compensated metabolic alkalosis

Answer 5

• pH: Normal
• HCO₃: High
• pCO₂: High

Question 6

Metabolic alkalosis is compensated by -?

Answer 6

Respiratory system (CO2 goes high)

Question 7

Metabolic alkalosis >>> K level

Answer 7

Hypokalaemia

Question 8

Metabolic alkalosis: causes

Answer 8

All the following also have hypokalaemia >>>

• Vomiting >>> ECF depletion + hypokalaemia, hypochloraemia
  
  • ​​peptic ulcer >>> pyloric stenosis
  • Any cause of vomiting
• ​Aspiration >>> hypokalaemia, hypochloraemia
  
  • ​Nasogastric suction, gastric aspiration etc.
• ​Extra intake of >
  
  • ​Diuretics >>> ECF depletion + hypokalaemia + hypochloraemia
  • ​Liquorice >>> hypokalaemia
  • Carbenoxolone >>> hypokalaemia
• Diseases >
  
  • ​Hypokalaemia (due to any cause)
  • Primary hyperaldosteronism (Or Conn’s syndrome)
  • Cushing’s syndrome
  • Congenital or inherited >
    
    • CAH (Congenital Adrenal Hyperplasia) (AR)
    • Bartter’s syndrome (AR)

Question 9

Metabolic alkalosis: key factor of mechanism

Answer 9

Activation of RAA (Renin-Angiotensin II- Aldosterone) system

Question 10

Metabolic alkalosis: pathophysiology/ mechanism

Answer 10

Mainly high aldosterone, and low K (potassium)

• Key factor: Activation of the RAA (Renin-Angiotensin II-Aldosterone) system >>> High aldosterone
• High aldosterone >>> reabsorbs Na⁺ (in exchange of H⁺) in DCT >>> Low H in blood >>> Metabolic alkalosis
• ECF depletion (e.g. vomiting, diuretics) >>> Na⁺ and Cl^- loss >>> Activation of RAA system to preserve Na⁺ >>> High aldosterone level (>>> prev. mechanism)
• Hypokalaemia (e.g. vomiting, diuretics, any cause) = Low K in blood >>> So, K shifts from cells >>> Lack of (+)ve charge in cell >>> exchange of H⁺ into cell (to balance neutrality) >>> Low H⁺ in blood (Metabolic alkalosis)

Question 11

How does activation of RAA system cause metabolic alkalosis?

Answer 11

Activation of the RAA (Renin-Angiotensin II-Aldosterone) system >>> High aldosterone

• High aldosterone >>> reabsorbs Na+ (in exchange of H+) in DCT >>> Low H in blood >>> Metabolic alkalosis

Question 12

How does ECF depletion cause metabolic alkalosis?

Answer 12

ECF depletion (e.g. vomiting, diuretics) >>> Na+ and Cl- loss >>> Activation of RAA system to preserve Na+ >>> High aldosterone level >>> reabsorbs Na+ (in exchange of H+) in DCT >>> Low H in blood >>> Metabolic alkalosis

Question 13

Why is hypokalaemia associated with metabolic alkalosis?

Answer 13

Hypokalaemia (e.g. vomiting, diuretics, any cause) = Low K in blood >>> So, K shifts from cells >>> Lack of (+)ve charge in cell >>> exchange of H+ into cell (to balance neutrality) >>> Low H+ in blood (Metabolic alkalosis)