Acid Base Balance Flashcards
Name 4 complications with acid-base disturbance.
- protein structure
- neuron excitability
- potassium balance (electrochemical gradient)
- cardiac arrhythmias
Normal pH of arterial blood =
7.38-7.42
Aciodosis:
blood pH < 7.35
Alkalosis:
blood pH > 7.45
Name 4 sources of acid-base disturbances.
- respiratory acidosis
- metabolic acidosis
- respiratory alkalosis
- metabolic alkalosis
What is respiratory acidosis?
increased plasma CO2
What is the source of CO2 for respiratory alkalosis?
metabolism
What is used for compensation for respiratory alkalosis?
ventilation
What is metabolic acidosis?
decreased pH (not CO2)
How can you get metabolic acidosis?
- high protein diet
- high fat diet
- heavy exercise
- severe diarrhea (loss of bicarbonate)
- renal dysfunction
What is respiratory alkalosis?
decreased plasma CO2
What is metabolic alkalosis?
increased pH (not CO2)
How can you get metabolic alkalosis?
- excessive vomiting (H+)
- consumption
- renal dysfunction
What is bicarbonate loading?
a technique that some try to use to offset changes to acidity caused by exercise
Describe the benefits of bicarbonate loading.
generally, most people cannot tolerate the bicarbonate load and benefits are minimal
What are the 3 lines of defence mechanisms against acid base disturbances?
- buffering of hydrogen ions
- respiratory compensation
- renal compensation
What is the quickest defence against changes in pH? How long does it take?
- buffering
- seconds: limited only by time it takes to bind acid or release H+
What is the most important ECF buffer?
bicarbonate
HCO3– + H+ =
H2CO3
What are ICF buffers?
- Proteins: Protein– + H+ = HProtein
- Phosphates: HPO42– + H+ = H2PO4–
What is the second line of defence? How long does it take?
- respiratory compensation
- response is within minutes
How does respiratory compensation regulate pH?
by varying ventilation
In respiratory compensation, increased ventilation leads to …
decreased CO2
In respiratory compensation, decreased ventilation leads to …
increased CO2
Describe the mechanism by which decreases in plasma pH increases ventilation.
- dec. plasma pH (inc. acidity)
- detect and respond
- inc. ventilation
- dec. plasma P CO2
- inc. plasma pH
- neg. feedback
What is the third defence? How long does it take?
- renal compensation
- hours –> days
Renal compensation regulates:
- Excretion of H+ and HCO3-
- Synthesis of new HCO3-
What are the 3 effects of increased acidity?
- inc. secretion of H+
- inc. reabsorption of HCO3-
- inc. synthesis of new HCO3-
Describe renal handling of hydrogen and bicarbonate ions in the PCT.
bicarbonate reabsorption coupled to hydrogen
Describe renal handling of hydrogen and bicarbonate ions in the DCT and collecting duct.
secretion of hydrogen ions coupled to synthesis of new bicarbonate ions
Regulation of acids/bases by _____ usually sufficient.
kidneys
Severe acidosis:
- Glutamine metabolism produces new HCO3-
- Secretes H+ in the form of ammonium
What is the cause of respiratory acidosis?
hypoventilation
Respiratory acidosis = ______ CO2 = _______ H+
- increased
- increased
What is the compensation for respiratory acidosis?
- renal
- increased H+ secretion
- increased HCO3- reabsorption
What is the cause of respiratory alkalosis?
hyperventilation
Respiratory alkalosis = _____ CO2 = _____ H+
- decreased
- decreased
What is the compensation for respiratory alkalosis?
- renal
- decreased H+ secretion
- decreased HCO3- reabsorption
What is the compensation for metabolic acidosis?
respiratory and renal (unless renal problem)
What is respiratory compensation for metabolic acidosis?
increased ventilation –> decreased CO2
Acidosis ratio:
[HCO3–]/[CO2] < 20:1
Alkalosis ratio:
[HCO3–]/[CO2] > 20:1
______ regulate HCO3-.
kidneys
______ regulate CO2.
lungs
What is renal compensation for metabolic acidosis?
- inc. H+ secretion
- inc. HCO3- reabsorption
- inc. synthesis of new HCO3=
What is the compensation for metabolic alkalosis?
respiratory and renal (unless renal problem)
What is respiratory compensation for metabolic alkalosis?
dec. ventilation –> inc. CO2
What is renal compensation for metabolic alkalosis?
- dec. H+ secretion
- dec. HCO3- reabsorption
- dec. synthesis of new bicarbonate
What is RCP?
- respiratory compensation point
- boundary between heavy and severe intensity exercise
What is AT/GET?
the anaerobic threshold where lactate production exceeds removal and CO2 increases (ventilatory threshold) to buffer lactate: increases ventilation
What is GET?
the boundary between moderate and heavy intensity exercise
What is RCP (RC)?
- seen when acidaemia takes over from CO2 as the stimulus for ventilation
- typically occurs between 70-84% of VO2 peak
- VE increases at a greater rate than VCO2
The RCP graph:
- may be due to increased K+ in plasma and activation of peripheral chemoreceptors
- indicates a near maximal effort by the individual exercising
- critical power may occur within the same time frame (dependent on type of test)
- may be the boundary between heavy intensity and severe intensity exercise
