Lecture 4-5 (blood gas analysis)

Question 1

What are electrolytes

Answer 1

Charged ions which are in solution in all body fluids

Question 2

Main extracellular cation

Answer 2

Sodium (Na+)

Question 3

Main intracellular cation

Answer 3

Potassium (K+)

Question 4

Main intracellular anions

Answer 4

Protein

Phosphate

Question 5

Main extracellular anions

Answer 5

Chloride (Cl-)

Bicarbonate (HCO3-)

Question 6

Normal hydrogen ion concentration

Answer 6

35-45nmol/L

pH 7.35-7.45

Question 7

What is a buffer

Answer 7

A weak acid in solution with its conjugate base.

Can absorb H+ or OH- ions

Question 8

What is the most important buffer in the ECF

Answer 8

Bicarbonate

Question 9

In normal arterial blood what is the ratio of HCO3- concentration to H2CO3 (carbonic acid) concentration

Answer 9

20:1

Question 10

Where are hydrogen ions excreted from the body

Answer 10

in the kidneys

Question 11

Name 4 types of acid base disturbances

Answer 11

Metabolic acidosis (HCO3- affected, pH decreased)

Metabolic alkalosis (HC03- affected, pH increased)

Respiratory acidosis (H2CO3 affected, pH decreased)

Respiratory alkalosis (H2CO3 affected, pH increased)

Question 12

Anion gap calculation

Answer 12

= Na+ - (Cl- + HC03-)

Question 13

Reasons for reduced anion gap

Answer 13

Hypoalbuminemia
Bromide intoxication
Multiple myeloma
Lab error

Question 14

Reasons for metabolic acidosis with a normal anion gap

Answer 14

Administration of chloride containing acids
GIT bicarbonate loss
Inherited.acquired renal tubular defects

Question 15

Reasons for metabolic acidosis with an increased anion gap

Answer 15

Uremia 
Ketoacidosis 
Lactic acidosis 
Methanol toxicity 
Ethylene glycol toxicity 
Salicylate

Question 16

Causes of meatbolic alkalosis

Answer 16

Exogenous alkali ingestion
Chronic vomiting
Severe potassium depletion

Question 17

Causes of respiratory acidosis

Answer 17

Generalised disease of the lung
Malfunction of the thoracic cage
Depression of the respiratory centre

Question 18

Causes of respiratory alkalosis

Answer 18

Hysterical over breathing
Mechanical over-ventilation
Raised intracranial pressure

Question 19

Compensatory mechanism of metabolic acidosis

Answer 19

Lungs - hyperventilation
Kidneys - increases HC03- reabsorption
increases Na+ - H+ exchange
increases ammonia formation

Question 20

Compensatory mechanism of metabolic alkalosis

Answer 20

Lungs - hypoventilation
Kidneys - Decreases reabsorption of HCO3-
decrease Na+ - H+ exchange
decreases ammonia formation

Question 21

Compensatory mechanisms of respiratory acidosis

Answer 21

Kidneys increases reabsorption of HC03-
increase Na+ - H+ exchange
increases ammonia formation

Question 22

Compensatory mechanisms of respiratory alkalosis

Answer 22

Kidneys - decreases reabsorption of HCO3-
decrease Na+ - H+ exchange
decreases ammonia formation