L16- Acid-Base Homeostasis Flashcards
What buffering systems are in place to try to keep balance?
Haemoglobin
Bicarbonate
Phosphate
Proteins
Ammonia
Misc organic acids
Normal range of pH?
7.45- 7.35
What are the sites of Acid-base metabolism
Lungs
Kidneys
GI tract
Liver
What direction does the O2-Haemoglobin dissociation curve when there is increased 2,3 DPG
To the RIGHT
An increased concentration of BPG in red blood cells favours formation of the T, low-affinity state of hemoglobin and so the oxygen-binding curve will shift to the right.
What direction does the O2-Haemoglobin dissociation curve when there is increased temperature?
To the RIGHT
Increasing temperature will weaken and denature the bond between an oxygen and a hemoglobin which in turn decreases the concentration of the oxyhemoglobin
What direction does the O2-Haemoglobin dissociation curve when there is acidosis?
To the RIGHT
decrease in blood pH, will result in haemoglobin proteins releasing their load of oxygen
What are proteins catabolised to in the Liver?
proteins catabolised to NH4+ and HCO3 -
Why can Severe Liver Failure cause NH4+ toxicity
Because the liver uses it for the reaction:
NH4+ + CO2 –X–> Urea + H+
Therefore a build of NH4+ can cause metabolic alkalosis
Causes of Metabolic Acidosis
Increased H+ formation
Acid ingestion
Reduced renal H+ excretion
Loss of bicarbonate
Causes of Metabolic Alkalosis
Generation of bicarbonate by gastric mucosa
Renal generation of HCO3- in Hypokalaemia
Administration of bicarbonate
Consequences of Metabolic alkalosis
K+ —> Cells and Urine
PO4 —> Cells
Respiratory Suppression
Reasons for Respiratory Acidosis
1: inadequate ventilation
2: parenchymal lung disease
3: inadequate perfusion
Reasons for Respiratory Alkalosis
Increased CO2 excretion due to excessive ventilation producing alkalosis
What can lead to increase H+ formation
ketoacidosis, diabetic or alcoholic
lactic acidosis
poisoning
inherited organic acidoses
What is Diabetic keto-acidosis
hyperglycaemia
osmotic diuresis —> to pre-renal uraemia
hyperketonaemia
increased FFA
—> all lead to acidosis
What is Lactic acidosis ?
a form of metabolic acidosis due to the inadequate clearance of lactic acid from the blood
What is meant by a high anion gap?
metabolic acidosis
caused generally by the body producing too much acid or not producing enough bicarbonate
Process of acidosis in an alcoholic
There is NAD+ depletion (due to lack of thiamine)
Thiamine is pyruvate dehydrogenase co-factor
Inc Glycolysis for ATP production
(also another factor leading to acidosis is vomiting!)
Does high lactate = lactic acidosis ?
In alkalosis
1. increased glycolysis
- reduced O2 delivery due to shift in O2 dissociation curve
- Lactate induced vasoconstriction
impaired mitochondrial respiration
O2 debt due to # 2
1. further anaerobic lactate production
Hyperventilation
status asthmaticus
a severe condition in which asthma attacks follow one another without pause
What can be a cause of Reduced H+ excretion ?
renal tubular acidosis (kidneys fail to excrete acids into the urine, which causes a person’s blood to remain too acidic)
generalised renal failure
What can Renal Failure lead to (ions etc)?
Lead to REDUCED VOLUME OF NEPHRONS
Increased bicarbonate loss
Reduced NH4+ excretion
Therefore more NH4+ to liver for urea + H+ synthesis
