Acid - base balance

Question 1

What are the 2 basic challenges that confront the body systems for maintenance of acid base balance?

Answer 1

CO2 production: oxidative metabolism

Acid production: dietary phosphoproteins and sulphur containing proteins

Question 2

What are the extracellular buffers to H+?

Answer 2

bicarbonate = buffer system in ECF and erythrocytes and plasma
phosphate and proteins = mainly in the ICF but proteins in ECF can also buffer

Question 3

How does bicarbonate act as a buffer to H+?

Answer 3

in the DCT the high levels of CO2 can be taken up by the cells and join with H20 and then break down into H+ and HCO3-
- the H+ can be excreted in the tubular fluid and the HCO3- can enter the peritubular plasma

Question 4

What is a simplified version of the henderson-hasselbalch equation?

Answer 4

pH= HCO3/PCO2

Question 5

How can acidosis arise?

Answer 5

fall in HCO3 with normal PCO2

rise in PCO2 with normal HCO3

Question 6

How can alkalosis arise?

Answer 6

rise in HCO3 with normal PCO2

fall in PCO2 with normal HCO3

Question 7

How long dose respiratory compensation for metabolic acidosis/alkalosis take?

Answer 7

12-24 hours

Question 8

How long does metabolic compensation for respiratory acidosis/alkalosis take?

Answer 8

2-4 days

Question 9

What factors cause metabolic acidosis?

Answer 9

increased H+ load
decreased H+ secretion
Loss of bicarbonate

Question 10

What are some causes of increased H+ load?

Answer 10

ketoacidosis 
lactic acidosis 
drugs: salicylates
methanol 
ethanol 
ethylene glycol

Question 11

What are some causes of reduced H+ secretion?

Answer 11

renal failure
RTA
mineralocorticoid deficiency

Question 12

What are some causes of loss of HCO3?

Answer 12

GIT: diarrhoea
Renal: RTA

Question 13

What factors cause metabolic alkalosis ?

Answer 13

loss of H+

excessive HCO3 intake

Question 14

What are the causes of loss of H+?

Answer 14

vomiting
mineralocorticoid excess (cushing's, conns) bartters, severe K deficiency

Question 15

What are the causes of excessive HCO3 intake?

Answer 15

oral or IV therapy

Question 16

What are some causes of respiratory acidosis?

Answer 16

Lung disease:
- emphysema 
- bronchitis
- asthma 
Neuromuscular:
- guillain barre syndrome 
Central NS
- trauma
- infection 
- tumours 
Drugs
- sedatives
- anaesthetics
Mechanical ventilation

Question 17

What are some causes of respiratory alkalosis?

Answer 17

hyperventilation
pulmonary= pneumonia, asthma, CCF, embolism, mechanical ventilation

central - trauma, infection, tumours, septicaemia, liver failure, drugs (salicylates), hysterical