Acid/Base Balance & Disorders Flashcards
What is a volatile acid?
an acid that can vaporise or become gaseous
What is the only physiological volatile acid and why?
= H2CO3
- Volatile bc comes form CO2 in CO2 +H20 <-> H2CO3 <-> H+ + HCO3-
- The H+ makes it acidic
How does CO2 get eliminated?
At the tissues:
- there will be increased CO2
- bc of this equation shifts to right so CO2 +H2O -> H2CO3 -> H+ + HCO3-
- H+ + HCO3- gets transported in blood to the lungs
At the lungs:
- equation will shift back to the left
- H+ + HCO3- -> H2CO3 -> CO2 + H20
- CO2 then gets exhaled
What are Peripheral Chemoreceptors?
- they are sensitive to H+
- this means more CO2 because equation shifts to the left -> higher respiration rate to remove CO2 from body
What is the normal pH range of the body?
7.35 - 7.45
What are non-volatile acids?
all those except carbonic acid and cannot be handled by the lungs
How do buffers act to maintain acid/base balance?
buffers prevent rapid fluctuations of pH -> present in various forms in ICF and ECF
How does the resp system act to maintain acid/base balance?
- Resp compensation adjusts CO2 saturation -> this affects the equation and alters equilibrium of carbonic acid and H+
- this system acts rapidly and is most effective for volatile acids
How does renal system act to maintain acid/base balance?
-Kidneys allow excretion of H+ and generation of HCO3- \
- renal system acts slowly
What are the 4 basic types of Acid-base Disorders? and describe ph ranges and CO2 and HCO3 levels
- Resp Acidosis (pH < 7.35 & PaCO2 > 45mmHg)
- Resp Alkalosis (pH > 7.45 & Pa CO2 < 35mmHg)
- Metabolic Acidosis (pH < 7.35 & HCO3- < 22 mmol/L)
- Metabolic Alkalosis (pH > 7.45 & HCO3- > 26 mmol/L)
- Resp acidosis & alkalosis due to primary changes in plasma CO2 levels
- Metabolic acidosis & alkalosis due to primary changes in HCO3-
Acute vs Chronic Respiratory Acidosis
Acute:
- sudden elevation of PCO2 due to failed ventilation
- PCO2 is inversely proportional to Minute Volume (the amount of gas inhaled or exhaled from a person’s lungs in one minute)
Chronic:
- caused by chronic lung disease with restrictive lung disease with V/Q mismatch, obstructive diseases or chronic neuromuscular disease
describe Metabolic Acidosis. why it happens. what happens.
Metabolic Acidosis : pH < 7.35 & HCO3- < 22mmol/L
- key feature = always reduction in HCO3- (lost from the body)
- due to an increased use of HCO3- in buffering abnormal acid load
What is the equation for Anion gap?
Anion Gap = Na+ + K+ - (Cl- +HCO3-)
Describe the Anion Gap in Metabolic Acidosis
You can have either:
- Increased anion gap due to unmeasured anions
- or no change in anion gap but increased Cl- to maintain balance (Hypercholeremic Acidosis)
What are some causes of high anion gap metabolic acidosis and non-anion gap metabolic acidosis?
What are Compensatory Patterns? and describe examples of what happens in metabolic Acidosis and Alkalosis
Body’s attempt to return pH to normal
- focus on [HCO3-] : pCO2 ratio
For example:
In a patient w metabolic acidosis, there will be lower pH bc less [HCO3-]. To compensate for less [HCO3-] & to restore [HCO3-] : pCO2 ratio, patient needs to decrease pCO2. Chemoreceptors will respond to increased [H+] -> ventilation -> eliminate CO2 -> less CO2 -> [HCO3-] : pCO2 ratio is back to normal
Another example:
In a patient with metabolic alkalosis, there will be increased [HCO3-] so lower CO2 -> Depression of lungs to retain CO2 -> pCO2 increases to match [HCO3-] and return to normal ratio HOWEVER depression of resp can lead to side effects
What do the first 4 rules of the Boston Bedside rules cover?
Resp Alkalosis and Acidosis
Determine whether they have a secondary acid-base disorder using Rule 1
Determine whether they have a secondary acid-base disorder using Rule 2
What is rule 5 of the Boston Bedside rules?
Example of Rule 5 of Boston Bedside Rules
What is rule 6 of the Boston Bedside rules?
