SM_159a: Acid Base Flashcards
What is the formula for pH?
pH = log (1 / H+) = – log [H+]
(as [H+] increases, pH decreases)
What are two common acidic groups?
What is an anion?
Conjugate base of an acid
What is a buffer?
A buffer is a combination of acid + conjugate base which minimizes changes in H+
What is pK?
pK = pH at which [acid] = [conjugate base]
Buffers are most effective at pK _____ pH unit(s)
Buffers are most effective at pK ± 1 pH unit
What is acidemia?
[H+] is elevated in blood and pH is decreased below normal (< 7.35)
What is alkalemia?
[H+] is decreased in blood and pH is elevated from normal (> 7.45)
What is acidosis?
Process tending to decrease pH or increase [H+]
Says nothing about the specific pH
What is alkalemia?
Process tending to increase pH or decrease [H+]
Says nothing about the specific pH
What is a respiratory process?
Process in which PaCO2 is changed
Respiratory acidosis is caused by ________
Respiratory acidosis is caused by hypoventilation
Respiratory alkalosis is caused by _______
Respiratory alkalosis is caused by hyperventilation
Metabolic acidosis is caused by ________ or ________
Metabolic acidosis is caused by the addition of nonvolatile (fixed) acid (e.g. lactic acid) or loss of base
Metabolic alkalosis is caused by ________ or ________
Metabolic alkalosis is caused by addition of bases (e.g. sodium bicarbonate) or loss of acid
What is a buffer?
A substance that reduces a change in pH or [H+] when an acid or base is added or subtravted
Describe the bicarbonate buffer system
- pK = 6.1 which is > 1 pH unit from pHa of 7.4 (effective because lungs continuously expire CO2)
- Buffers metabolic acids or bases
- Primary extracellular buffer
What is the isohydric principle?
- The bodies contains multiple buffer pairs (HA and A-) which are all in equilibrium with each other via their effect on [H+]
- Altering equilibrium of one buffer pair alters the [H+] and equilibrium for all buffer pairs
In the isohydric principle, _____ buffer pairs contribute to equilibrium pH
pH can be calculated from _______
In the isohydric principle, all buffer pairs contribute to equilibrium pH
pH can be calculated from knowledge of the ratio of any one of the buffer pairs
What is the Henderson-Hasselbach equation?
On the PCO2 – HCO3- diagram, slope ______ as pH increases
On the PCO2 – HCO3- diagram, slope increases as pH increases
On the Davenport idagram, slope _____ as PCO2 increases
On the Davenport idagram, slope increases as PCO2 increases
What happens when you give an HCl bolus to a ventilated patient?
Metabolic acidosis
- Shifts buffer equations: H+ + HCO3- -> CO2 + H2O such that there is a pronounced decrease in [HCO3-]
Uncomplicated metabolic acidosis is indicated by _____ pH and caused by ______ HCO3-
Uncomplicated metabolic acidosis is indicated by decreased pH and caused by decreased HCO3-
In metabolic acidosis, the nonbicarbonate buffer reaction ______ the decrease in [HCO3-]
In metabolic acidosis, the nonbicarbonate buffer reaction reduces the decrease in [HCO3-]
(isohydric buffering)
What happens when you give an NaOH bolus to an artificially ventilated subject?
Metabolic alkalosis
Uncomplicated metabolic alkalosis is indicated by _____ pH and caused by ______ HCO3-
Uncomplicated metabolic alkalosis is indicated by increased pH and caused by increased HCO3-
In metabolic alkalosis, the nonbicarbonate buffer reaction ______ [HCO3-]
In metabolic alkalosis, the nonbicarbonate buffer reaction increases [HCO3-]
Respiratory processes are buffered by __________
Respiratory processes are buffered by nonbicarbonate buffers only
In respiratory processes, _____ HCO3- is produced per H+ added
In respiratory processes, 1 HCO3- is produced per H+ added
In respiratory processes, many added H+ ions are bound to _________
In respiratory processes, many added H+ ions are bound to nonbicarbonate buffers
In respiratory acidosis, PCO2 _______
In respiratory acidosis, PCO2 increases
In respiratory alkalosis, PCO2 ________
In respiratory alkalosis, PCO2 decreases
What is the nonbicarbonate buffer value?
Nonbicarbonate buffer value = ∆[H+] / pH unit
On the graph, _______ is equal to the nonbicarbonate buffer value
On the graph, the slope of B-A-C is equal to the nonbicarbonate buffer value
Slope of the Davenport diagram ( [HCO3-] versus pH graph) is determined by ______________
Slope of the Davenport diagram ( [HCO3-] versus pH graph) is determined by the amount of nonbicarbonate buffer present
(larger amounts produce greater slope)
In respiratory acidosis, hypoventilation _________
In respiratory acidosis, hypoventilation increases PCO2
Describe the effect of nonbicarbonate buffers in respiratory acidosis
- Nonbicarbonate buffers remove some H+
- Reduces decrease in pH but favors additional hydration of CO2 and production of more HCO3- (and H+)
The greater the [Buff-], the more HCO3- formed and the smaller the change in pH
In respiratory acidosis, the greater the [Buff-], the _____ HCO3- is formed and the _____ the change in pH
In respiratory acidosis, the greater the [Buff-], the more HCO3- is formed and the smaller the change in pH
In respiratory alkalosis, hyperventilation ________
In respiratory alkalosis, hyperventilation decreases PCO2 and [HCO3-]
Describe the effect of nonbicarbonate buffers in respiratory alkalosis
- Decrease in H+
- Nonbicarbonate buffers contribute H+
- Increase in pH is reduced but additional reduction of HCO3- is promoted
- {HCO3-] is reduced
The greater the [HBuff], the more HCO3- is reduced
In respiratory alkalosis, the greater the [HBuff], the _____ HCO3- is reduced
In respiratory alkalosis, the greater the [HBuff], the more HCO3- is reduced
Question
Horizontal line
[HCO3-] is in units of mM while [H+] is in units of nM, so the buffer line appears to be horizontal
Increasing CO2 shifts the bicarbonate buffer reaction in favor of _________
Increasing CO2 shifts the bicarbonate buffer reaction in favor of producing H+ and HCO3- in equal amounts
BUT [HCO3-] is in units of mM on graph while ∆[HCO3-] is in units of nM, so the buffer line appears to be horizontal
