Acid Base Disturbances

Question 1

What happens to give rise to a respiratory acidosis?

Answer 1

Rise in CO2 levels due to alveolar hypoventilation

Question 2

What can happen in respiratory acidosis?

Answer 2

Renal compensation - leading to compensated respiratory acidosis

Question 3

Causes of respiratory acidosis

Answer 3

COPD
Decompensation in other resp conditions e.g. life threatening asthma / pulmonary oedema
Sedative drugs; benzodiazepines, opiates

Question 4

What happens in respiratory alkalosis?

Answer 4

Hyperventilation resulting in a loss of carbon dioxide, resulting in an increasing pH

Question 5

Causes of respiratory alkalosis

Answer 5

Psychogenic; anxiety leading to hyperventilation
Hypoxia causing a subsequent hyperventilation; PE, high altitude
Early salicylate poisonings
CNS stimulation; stroke, SAH, encephalitis
Pregnancy

Question 6

What is the most common surgical acid base disorder?

Answer 6

Metabolic acidosis

Question 7

What happens to result in metabolic acidosis?

Answer 7

Reduced bicarbonate levels

Question 8

Two possible mechanisms for metabolic acidosis

Answer 8

1. Gain of a strong acid e.g. DKA

2. Loss of a base (e.g. from bowel in diarrhoea)

Question 9

What is metabolic acidosis classified according to and how do you work this out?

Answer 9

Anion gap

Na+ + K+) - (Cl- + HCO3-

Question 10

What would be a clue in the question that you should work out the anion gap?

Answer 10

If the chloride value is given

Question 11

What is a normal anion gap also known as?

Answer 11

Hyperchloremic metabolic acidosis

Question 12

Causes of normal anion gap metabolic acidosis

Answer 12

GI bicarbonate loss 
Renal tubular acidosis
Drugs e.g. acetazolamide 
Ammonium chloride injection 
Addisons disease

Question 13

Causes of raised anion gap metabolic acidosis

Answer 13

Lactate; shock, hypoxia
Ketones; DKA, alcohol
Urate; renal failure
Acid poisoning; salicylates, methanol

Question 14

Two types of metabolic acidosis caused by high lactate levels

Answer 14

Type A

Type B

Question 15

Type A lactate causing metabolic acidosis is due to….

Answer 15

Perfusion disorders e.g. shock, hypoxia, burns

Question 16

Type B lactate causing metabolic acidosis is due to…

Answer 16

Metabolic e.g. metformin toxicity

Question 17

What is metabolic alkalosis usually due to?

Answer 17

Rise in bicarbonate levels

Question 18

What will a rise in bicarbonate over 24 lead to?

Answer 18

Renal excretion of excess bicarb

Question 19

Mechanisms of metabolic alkalosis

Answer 19

Loss of hydrogen ions

Gain of bicarbonate

Question 20

What is metabolic alkalosis mainly due to problems of?

Answer 20

Kidneys

GI tract

Question 21

Causes of metabolic alkalosis

Answer 21

Vomiting / aspiration 
Diuretics
Liquorece
Hypokalaemia
Primary hyperaldosteronism
Cushings
Bartters syndrome
CAH

Question 22

What does a high bicarbonate in the context of COPD suggest?

Answer 22

Background of chronic resp acidosis

Question 23

What does hyperventilation lead to?

Answer 23

Carbon dioxide being ‘blown off’, causing a resp alkalosis