Acids, bases and buffers Flashcards
What’s an acid (in terms of protons)?
Proton donor
What’s a base (in terms of protons)?
Proton acceptor
What’s a buffer?
A weak acid or base that acts to maintain H+ concentration
What is pH (in terms of logs)?
-log[H+]
Normal blood pH?
7.35 - 7.45
What is acidosis?
pH too low
What is alkalosis?
pH too high
Write out the Henderson Hasselbalch equation.
[H+] x [HCO3-] = K x pCO2
What is the Hend-Hass equation used for?
Calculate blood pH
What is the equation that goes on inside the body?
CO2 + H2O H2CO3 HCO3- + H+
Catalysed by carbonic acid
What is acidaemia?
Abnormal acidity of blood
What is alkalaemia?
Abnormal alkalinity of blood
How does respiratory acidosis occur?
Insufficient ventilation
CO2 retained
More carbonic acid in blood > acidosis
CO2 + H2O H2CO3 HCO3- + H+
What causes resp acidosis?
COPD, asthsma
How does metabolic acidosis occur?
Low bicarbonate levels in blood
CO2 + H2O H2CO3 HCO3- + H+
What causes metabolic acidosis?
Bicarb losses due to diarrhoea, renal failure, diabetic ketoacidosis
How does respiratory alkalosis occur?
Blowing off too much CO2
CO2 + H2O H2CO3 HCO3- + H+
What causes respiratory alkalosis?
COPD (type 1 resp failure)
Anxiety, fever
How does metabolic alkalosis occur?
Loss of H+ or too much Bicarb (HCO3-)
What causes metabolic alkalosis?
Excess vomiting (losing H+ from stomach)
Pyloric stenosis
Anorexia nervosa
Ingestion of bicarb
What type of compensation occurs in metabolic acid/base disorders? Speed?
Rapid RESPIRATORY compensation
What type of compensation occurs in respiratory acid/base disorders? Speed?
Eventual METABOLIC compensation
What is an anion?
A negatively charged ion
What is meant by the anion gap?
The difference in concentration of measured cations and anions
Gives us the concentration of unmeasured ions
Give some examples of unmeasured anions (whose total concentration can be calculated by the anion gap)?
Lactate
Phosphate
Sulphate
Acetoacetate
Give the anion gap equation.
Gap = [Na+] + [K+] - [Cl-] - [HCO3-]
K+ has little effect
What conditions does a wide anion gap point to?
Excess of unmeasured anions
Ingestion of acid, ketoacidosis, renal failure
What conditions does a narrow anion gap point to?
High chloride
GI HCO3- loss
