Acid-base homeostasis Flashcards Preview

EMS - Mechanisms of disease > Acid-base homeostasis > Flashcards

Flashcards in Acid-base homeostasis Deck (15):
1

What buffering systems exist within the human body?

Haemoglobin

Bicarbonate

Phosphate

Proteins

Ammonia

Misc organic acids

2

What are the sites of acid-base metabolism?

Lungs

Kidneys

GI tract

Liver

3

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

Increased 2,3 diPG

Acidosis H+

Temperature

4

Where is bicarb reclaimed and generated?

Kidneys

5

Where is the dominant site of lactate metabolism?

Liver

6

Where is the only site of urea synthesis?

Liver

7

Why does severe metabolic alkalosis occur in liver failure?

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

8

What are the compensatory mechanisms for acid/base disturbances?

Respiratory

Renal bicarbonate regeneration

Hepatic shift between urea synthesis and ammonia excretion

9

What are the mechanisms behind metabolic acidosis?

Increased H+ formation

Acid ingestion

Reduced renal H+ excretion, or Loss of bicarbonate

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

10

What is the mechanism behind metabolic alkalosis?

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+

11

What is the mechanism behind respiratory acidosis?

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

12

What is the mechanism behind respiratory alkalosis?

H+ + HCO3- -> H2CO3 -> CO2 + H2O

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

13

What conditions may cause increased H+ formation?

ketoacidosis,  diabetic or alcoholic

lactic acidosis

poisoning

inherited organic acidoses

14

What are the two types of lactic acidosis?

type a  shock

type b  metabolic and toxic causes

15

Why does acidosis occur in alcoholics?

NAD+ depletion (thiamine)

Thiamine deficiency (PDH co-factor)

enhanced glycolysis for ATP formation

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

profuse vomiting!!