Acid base balance

Question 1

What is the range of pH

Answer 1

7.35-7.45

Question 2

Write the henderson hasselback equation

Answer 2

CO2+H20 H2CO3 HCO3- + H+

Question 3

Which organs govern acid base balance

Answer 3

Kidneys and Lungs

Question 4

what is the role of the kidneys in acid base balance

Answer 4

 H+ ions buffered by HCO3-
 H+ ions are
excreted by the kidneys in order to help maintain
blood pH

Question 5

what is the role of the lungs in acid base balance

Answer 5

 CO2 levels are detected in the hypothalamus by chemoreceptors,
 Rate and depth of respiration is adjusted to normalise pH

Question 6

How do you work out the anion gap

Answer 6

[Na++K+] – (HCO3-+Cl-)

Question 7

What is the normal anion gap

Answer 7

 Normal anion gap 10-18 mmol/L

- it estimates the unmeasured plasma anions

Question 8

What is a normal anion gap caused by

Answer 8

Due to loss of bicarbonate or ingestion of an acid
- diarrhoea
- renal tubular acidosis
- drugs - acetazolamide
- Addisons disease
- pancreatic fistula
 Hyperchloraemic acidosis = Due to excessive chloride therapy

Question 9

What is a elevated anion gap caused by

Answer 9

Due to increase production or decreased excretion of fixed/organic acids
- bicarbonate falls to compensate and unmeasured anions associated with the acids accumulate
DUE TO:
- lactic acid
- urate = renal failure
- Ketones = DKA, alcohol
- Drugs/toxins - salicylates, biguanides, ethylene glycol, methanol

Question 10

How to interpret the ABG

Answer 10

Look at the pH
 If low – must be acidosis; if high, must be alkalosis

 Does the pCO2 explain the pH change?
- If pCO2 high, could be respiratory acidosis, – if pCO2
low, could be respiratory alkalosis

Does the Bicarbonate explain the pH change?
 bicarb low in metabolic acidosis; high in metabolic alkalosis, or compensation for respiratory acidosis

Is the pCO2 in the normal range?
 Or is it compensating for a metabolic problem – eg low in metabolic acidosis

Question 11

What causes respiratory acidosis

Answer 11

Hypoventilation = Type 2 respiratory failure
Due to:
- pulmonary disease - asthma, COPD, pneumonia, obstructive sleep apnoea
- Reduced respiratory drive - sedative drugs, CNS tumour or trauma
- Neuromuscular disease - cervical cord lesion, diaphragmatic paralysis, poliomyelitis, myasthenia gravis, Guillain-Barre syndrome
- Thoracic wall disease - flail chest, kyphoscoliosis, obesity, pneumothorax

Question 12

What causes respiratory alkalosis

Answer 12

Hyperventilation

• CNS causes - stroke, subarachnoid haemorrhage, meningitis
• Others - mild/moderate asthma, anxiety, altitude, fever, pregnancy, pulmonary emboli, drugs

Question 13

What causes compensated respiratory acidosis

Answer 13

• Long standing Type 2 respiratory failure

Question 14

What can cause metabolic alkalosis

Answer 14

• prolonged vomiting
• potassium depletion (diuretics)
• burns
• ingestion of base

Question 15

What does ROME mean

Answer 15

Respriatory Oppoiste

• pH high, PCO2 - low = alkalosis
• ph low, pco2 high = acidosis

Metabolic Equal

• pH high, Bicarb high = alkalosis
• pH low, Bicarb low = acidosis

Question 16

What is the anion gap helpful in determining

Answer 16

• it is helpful in determining the cause of metabolic acidosis

Question 17

What can cause a lactic acidosis

Answer 17

• Shock
• infection
• tissue ischemia