9 - Acid Base Balance Flashcards
What is the normal pH of blood?
- 35 - 7.45
- 5 - 35.5 nmol per litre H+
What is more dangerous, alkalemia or acidaemia?
Alkalaemia
What pH range causes high mortality in alkalosis and why?
Reduces solubility of Ca salts so more free Ca leaves the ECF to bind to bones and proteins. Hypocalcaemia leads to excitable nerves, paraesthesia and tetany
- Paraesthesia and tetany above 7.45
- 45% mortality at 7.5
- 80% mortality at 7.65
What pH range causes high mortality in acidosis and why?
High H+ affects enzyme function and leads to K+ movement out of cells so hyperkalaemia leading to arrythmias.
- Effects seen at 7.1
- Life threatening below 7
What is the main buffer system for pH in the ECF?
- Carbon Dioxide/Hydrogen carbonate system
- pCO2 determined by ventilation* so disturbed by respiratory disease
- HCO3- determined by kidneys* so disturbed by metabolic or kidney disease
![](https://s3.amazonaws.com/brainscape-prod/system/cm/291/305/051/a_image_thumb.jpeg?1571940053)
How do the kidneys maintain plasma pH in general terms?
- Variable recovery of HCO3- produced by RBC
- Secretion of H+
What parameters change to get the following outcomes in the blood:
- Respiratory acidosis
- Respiratory alkalosis
- Metabolic acidosis
- Metabolic alkalosis
- Resp acid: increased pCO2
- Resp alk: decrease pCO2
- Met acid: decreased HCO3- due to reaction with metabolic acids, e.g lactate and ketoacids
- Met alk: increased HCO3-
![](https://s3.amazonaws.com/brainscape-prod/system/cm/291/305/495/a_image_thumb.png?1571940262)
How does the body compensate for the following:
- Respiratory acidosis
- Respiratory alkalosis
- Metabolic acidosis
- Metabolic alkalosis
- Respiratory acidosis: kidneys retain more HCO3-
- Respiratory alkalosis: kidneys lose more HCO3-
- Metabolic acidosis: hyperventilation
- Metabolic alkalosis: limited by the hypoxia that comes with hypoventilation
How do we stop HCO3- depleting in the body when the body produces metabolic acids like lactate that react with HCO3- ?
- Kidneys recover all filtered HCO3- (80% PCT and 15% DCT in intercalated cells)
- PCT makes HCO3- from AA putting NH4+ onto urine
- DCT makes HCO3- from CO2 and H2O and the H+ is buffered by ammonia and phosphate
![](https://s3.amazonaws.com/brainscape-prod/system/cm/291/305/975/a_image_thumb.jpeg?1571943373)
How is HCO3- in the kidney produced?
- H+ ions actively secreted in the DCT
- H+ buffered by phosphate (titratable) and ammonia
![](https://s3.amazonaws.com/brainscape-prod/system/cm/291/310/108/a_image_thumb.jpeg?1571943464)
What is the major adaptive response of the kidney to an increased acid load?
- Production of NH3 from glutamate that moves throughout interstitiums
- H+ actively pumped into lumen of DCT and CT
- H+ reacts with NH3 to make NH4+ which is excreted in urine
- Allows HCO3- to be reabsorbed to buffer and loses H+
![](https://s3.amazonaws.com/brainscape-prod/system/cm/291/310/585/a_image_thumb.jpeg?1571944030)
What is the minimum pH of urine?
- 4.5
- All HCO3- has been recovered
- Some H+ in the urine buffered by ammonia to ammonium and phosphate to stop urinary tract being damaged
What can happen to potassium levels in alkalosis and acidosis?
Hyperkalaemia can cause metabolic acidosis or the acidosis can cause hyperkalaemia etc.
![](https://s3.amazonaws.com/brainscape-prod/system/cm/291/310/884/a_image_thumb.jpeg?1571944388)
Why does hyper/hypokalaemia lead to acidosis/alkalosis?
![](https://s3.amazonaws.com/brainscape-prod/system/cm/291/311/129/a_image_thumb.jpeg?1571944541)
What will the following blood parameters look like:
- Compensated respiratory acidosis
- Compensated respiratory alkalosis
- Compensated metabolic acidosis
- Comp Resp Acidosis: high pCO2, high HCO3-, normal pH
- Comp Resp Alkalosis: low pCO2, low HCO3-, normal pH
- Comp Met Acidosis: low HCO3-, low pCO2, normal pH