Acid-Base Balance Flashcards
What is pH?
an expression of the hydrogen ion concentration
How do you measure pH?
-log([H]+)
Physiologically, what do acids and bases come from?
food and cellular metabolism
Pathologically, what do acids and bases come from?
metabolic disease, decreased ventilation, vomiting, diarrhea, and renal insufficiency
Define an acid.
something that donates a proton to a solution
Do strong acids or weak acids disassociate well?
strong acids
Do strong acids or weak acids have high concentrations of [H+]?
strong acids
Define a base.
something that accepts a proton from a solution
What is a buffer?
a mixture of a weak acid and its conjugate base that resists change in [H+]
Is water an acid or a base?
it depends, it can be both
What is the normal pH of blood?
7.35-7.45
At what pH does acidemia occur?
<7.35
At what pH does alkalemia occur?
> 7.45
What is acidosis?
all of the physical processes and chemical reactions that result in an abnormally low pH
What is acidemia?
low blood pH
You cannot have acidemia without what?
acidosis
What factors affect pH?
PCO2, strong ion difference, total weak non volatile acid
What is strong ion difference?
the difference between the sums of concentrations of the strong cations and strong anions
Is this alkalinizing or acidifying: increase in SID
alkalinizing
Is this alkalinizing or acidifying: decrease in SID
acidifying
An increase in total weak non volatile acid results in what (in relation to pH)?
metabolic acidosis
A decrease in total weak non volatile acid results in what (in relation to pH)?
metabolic alkalosis
Why is ventilation in charge of keeping the acid-base balance in check?
because the lungs are in charge of eliminating carbon dioxide which becomes bicarbonate acid in the lungs; we need to breath out the acid
What is the Henderson-Hassalbalch equation?
pH = pK + Log([HCO3]/(0.03 x PCO2))
pk is a constant, what is it?
6.1
In the Henderson-Hassalbalch equation, what is pH related to?
bicarbonate and PCO2
How do buffers work?
they exchange a strong acid or base for a weak one
What are the buffer systems in the body?
bicarbonate, phosphate, and protein
Why is the bicarbonate buffer system important?
it is important for extracellular fluid because CO2 and HCO3 can be independently regulated and still function at a pH of 6
Why is the phosphate buffer system important?
it is an important intracellular buffer because its pKa is 6.8 and can buffer tubular fluid effectively
Why is the protein buffer important?
because proteins, especially hemoglobin can either accept or donate H+
Is oxygenated or deoxygenated hemoglobin a better buffer for H+?
deoxygenated because its pKa is 8.2
What is the isohydric principle?
buffers buffer the buffer
What is the first line in defense to acid-base imbalance?
the chemical buffers: bicarbonate, phosphate, and protein buffer systems
What is the second line of defense to acid-base imbalance?
physiological buffers: lungs excreting CO2 and kidneys excreting H+
To change acid-base imbalance, what needs to be altered?
PCO2 or HCO3
In respiratory alkalosis, what happens to the pH and how is it compensated?
pH is increased, compensated by a decrease in renal H excretion and retention of HCO3
In respiratory acidosis, what happens to the pH and how is it compensated?
pH is decreased, compensated by a increase in renal H excretion and retention of HCO3
In metabolic acidosis, what happens to the pH and how is it compensated?
pH is decreased, compensated by decreasing PaCO2 and H+
In metabolic alkalosis, what happens to the pH and how is it compensated?
pH is increased, compensated by an increase in PaCO2 and in H+
