Biochemistry Flashcards
Where is most of [H+] in our body excreted?
Via urine
Is urine acidic or alkaline?
Acidic
Is buffering of H+ a temporary measure?
Yes
Give the bicarbonate equation.
[H+] + HCO3 = H2CO3 = CO2 + H2O
What is carbonic acid (H2CO3) removed as?
CO2
What is the equation which underpins all acid-base stuff?
[H+] (alpha sign) (pCO2/[HCO3])
What is the solution for too much H+ or too much CO2?
Compensation
When you’ve got too much H+, what occurs as compensation?
Lungs blow off CO2
When you’ve got too much CO2, what occurs as compensation?
The kidneys get rid of [H+]
What is acidaemia?
Increased [H+]
What is alkalaemia?
Decreased [H+]
What does acidosis tend to cause?
Increased [H+]
What does alkalosis tend to cause?
Decreased [H+]
What is the respiratory component?
pCO2
What is the metabolic component?
HCO3
What is an increase in [H+], due to increase pCO2?
Respiratory acidosis
What is a decrease in [H+], due to decreased pCO2?
Respiratory alkalosis
What is increased [H+], due to decreased HCO3?
Metabolic acidosis
What is decreased [H+], due to increased HCO3?
Metabolic alkalosis
What is the respiratory compensation for metabolic acidosis?
Blow off CO2
What is the metabolic compensation for respiratory acidosis?
Excrete more H+
What is the compensatory response for increased pCO2 (respiratory acidosis)?
Increased HCO3
What is the compensatory response for decreased pCO2 (Respiratory alkalosis)?
Decreased HCO3
What is the compensatory response for decreased HCO3 (metabolic acidosis)?
Decreased pCO2
What is the compensatory response for increased HCO3 (metabolic alkalosis)?
Increased PCO2
What are the 4 arterial blood gases?
H+
pCO2
HCO3
pO2
Give three causes of respiratory acidosis?
Choking
Bronchopneumonia
COAD
Give three causes for respiratory alkalosis?
Hysterical over-breathing
Mechanical over-ventialtion
Raised intracranial pressure
Give three causes of metabolic acidosis?
Imparied [H+] excretion
Increased [H+] production or ingestion
Loss of HCO3
Give three causes of metabolic alkalosis?
Loss of [H+] in vomit
Alkali ingestion
Potassium deficiency
What is the normal range of pH?
7.35 - 7.45
What must PaO2 always be interpreted against?
The inspired O2
What is PaO2?
the partial pressure of oxygen in arterial blood
What is the normal range breathing air of PaO2?
9.3 - 13.3 kPa
What is the normal range for PaCO2?
4.7 - 6 kPa
The body tries to compensate for a metabolic alkalosis by raising PaCO2, what does the body do physically?
Hypoventilating
The body will try to compensate for a metabolic acidosis by lowering PaCO2, what does the body do physically?
Hyperventialte
What is the normal range of base excess?
-2 to +2 mmol/l
What is base escess?
The measure of how much base has to be removed or added to the system to correct the pH in standard conditions. It is a measure of metabolic acidosis or alkalosis.
What does a negative BE indicate?
Metabolic acidosis
What does a positive BE indicate?
Metabolic alkalosis
What does the kidney do to compensate for respiratory acidosis?
Creates a metabolic alkalosis by retaining bicarbonate
What does the kidney do to compensate for respiratory alkalosis?
Creates a metabolic acidosis by excreting bicarbonate
What does hypercapnic mean?
High pCO2
What is polydipsia?
Excessive thirst
If the patient has metabolic acidosis, and the pCO2 is normal, what does this indicate?
No respiratory compensation
What is hypoxia?
Lack of oxygen
What is hypoxaemia?
Low oxygen levels within the blood (pO2 and SaO2 combined)
Give four causes of tissue hypoxia
- Anaemic hypoxia
- Perfusional hypoxia
- Toxic hypoxia
- Hypoxaemic hypoxia
What causes anaemic hypoxia?
Lack of Hb
What causes perfusional hypoxia?
Poor CO
What causes toxic hypoxia?
Failure of release of O2 at tissue level
What causes hypoxaemic hypoxia?
Low pO2 and SaO2 - respiratory insufficiency
Name 4 buffers
- Haemoglobin
- Bicarbonate
- Ammonium
- Phosphate
Can overcompensation occur?
NO
Name three causes of respiratory acidosis with metabolic compensation
Chronic type 2 respiratory failure: COPD, DF, kyphoscoliosis
Name 3 causes of metabolic alkalosis with respiratory compensation?
Milk alkali syndrome
Vomiting
Severe hypokalaemia
Give 5 causes of metabolic acidosis with respiratory compensation?
Sepsis DKA Poisoning Drugs Lactate
What are general causes of respiratory alkalosis with metabolic compensation?
Chronic hyper-ventilatory states
What are 9 causes of high anion gap? (AMUDPILES)
A - alcohol (alcohol dissociates to become a weak acid)
M - methanol (causes blindness)
U - uraemia (failure to reabsorb HCO3 and excrete H+
D - DKA (ketones are dehydrogenated alcohols, and dissociate to acid)
P - paraquat (very nasty poison, universally lethal
I - infection (commonest, localised tissue hypoxia leads to…)
L - lactic acid (product of anaerobic respiration, and tissue necrosis)
E - erythlene gylcol (antifreeze)
S - salicylates (aspirin causes respiratory alkalosis, then metabolic acidosis
What can these 5 things occur as a result of? Addisons disease, high output fistulas, RTA I, II, IV, Acetazolamide therapy, diarrhoea?
Normal anion gap
Who were pink puffers traditionally though to be?
Emphysema patients
What to pink puffers react to hypoxaemia by doing?
Hyperventilating
Who were blue bloaters traditionally though to be?
Chronic bronchitis patients
What do blue bloaters not do?
React to hypoxia or hyperventilate
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In acid base balance, what is being regulated?
Hydrogen ion concentration ([H+], pH)