Acid-base homeostasis

Question 1

What buffering systems exist within the human body?

Answer 1

Haemoglobin

Bicarbonate

Phosphate

Proteins

Ammonia

Misc organic acids

Question 2

What are the sites of acid-base metabolism?

Answer 2

Lungs

Kidneys

GI tract

Liver

Question 3

What would cause a right shift of the O2-Hb dissociation curve?

Answer 3

Increased 2,3 diPG

Acidosis H+

Temperature

Question 4

Where is bicarb reclaimed and generated?

Answer 4

Kidneys

Question 5

Where is the dominant site of lactate metabolism?

Answer 5

Liver

Question 6

Where is the only site of urea synthesis?

Answer 6

Liver

Question 7

Whydoes severe metabolic alkalosis occur in liver failure?

Answer 7

Liver can no longer metabolise NH4+ to urea. Build up of ammonia.

Question 8

What are the compensatory mechanisms for acid/base disturbances?

Answer 8

Respiratory

Renal bicarbonate regeneration

Hepatic shift between urea synthesis and ammonia excretion

Question 9

What are the mechanisms behindmetabolic acidosis?

Answer 9

Increased H+ formation

Acid ingestion

Reduced renal H+ excretion, orLoss of bicarbonate

H+ increases,pCO2 decreases and pO2 increases (due to compensatory hyperventilation)

Question 10

What is the mechanism behind metabolic alkalosis?

Answer 10

Generation of bicarb by gastric mucosa (e.g. vomiting), renal generation of HCO3- in hypokalaemia, administration of bicarb (e.g. antacid abuse)

H+ decreases, pCO2 increases and pO2 decreases as drive to breathe is depressed by loss of H+

Question 11

What is the mechanism behind respiratory acidosis?

Answer 11

H+ + HCO3–>H2CO3->CO2+ H2O

CO2 retention due to

1: inadequate ventilation
2: parenchymal lung disease
3: inadequate perfusionH+ increases, pCO2 increases and pO2 decreases

Question 12

What is the mechanism behind respiratory alkalosis?

Answer 12

H+ + HCO3- ->H2CO3 ->CO2 + H2O

Increased CO2 excretion due to excessive ventilation producing alkalosisH+ decreases, pCO2 decreases (being blown off) and pO2 increases

Question 13

What conditions may cause increased H+ formation?

Answer 13

ketoacidosis, diabetic or alcoholic

lactic acidosis

poisoning

inherited organic acidoses

Question 14

What are the two types of lactic acidosis?

Answer 14

type a shock

type b metabolic and toxic causes

Question 15

Why does acidosis occur in alcoholics?

Answer 15

NAD+ depletion (thiamine)

Thiamine deficiency (PDH co-factor)

enhanced glycolysis for ATP formation

keto-acids (b-HBD) 20 to counter-regulatory hormones

profuse vomiting!!