test 1 Flashcards
in a closed system, gas content
- cannot change
- no gas fluid interface
an increase in H+ concentration results in
-decrease in pH
a decrease in temperature results in
- increase in solubility
- decrease in PPg
- moves dissociation to the left
- increase in pH
pH of neutrality
-at specific temperatures there is a new pH of neutrality
Henry’s law
Dissolved = Solubility x Partial Pressure
Solubility of CO2 and O2
CO2 @ 37 degrees C = 0.06 mls CO2
/100 mls bld/mmHg
O2 @ 37 degrees C = 0.003 mls O2
/100 mls bld/mmHg
CO2 moved from the lungs to tissue (3)
Dissolved
Bound to hemoglobin
As HCO3- (majority of CO2)
-all three determine CO2 content
how to change the pH of blood in a closed system
1) Change total CO2 content – KEEP TEMP CONSTANT
2) Change temperature – keep total CO2 content constant
3) Change total CO2 content – change temperature
Option one: Increase total CO2 content by ADDING additional CO2
pCO2 will increase
pH will decrease
Option one: Decrease total CO2 content by REMOVING CO2
pCO2 will decrease
pH will increase
Option two: Increase temperature
Drive acid-base disassociation equilibrium to the right
[H+] will increase
pH will decrease
Option two: Decrease temperature
Drive acid-base disassociation equilibrium to the left
[H+] will decrease
pH will increase
Option three: Change total CO2 content and Change temperature
pCO2 will change producing an inverse change in pH
Disassociation equilibrium will change causing a
corresponding increase or decrease in [H+]
Temperature Increases: Gas solubility \_\_\_\_\_\_\_\_\_\_\_\_\_ Gas partial pressure \_\_\_\_\_\_\_\_\_\_\_\_\_ Therefore gas pressure is \_\_\_\_\_\_\_\_\_\_\_\_\_ than the starting gas pressure Equilibrium of the water dissociation shifts to the \_\_\_\_\_\_\_\_\_\_\_\_\_ Therefore, pH will \_\_\_\_\_\_\_\_\_\_\_\_\_
Gas solubility decrease
Gas partial pressure increase
Therefore gas pressure is higher than the
starting gas pressure
Equilibrium of the water dissociation shifts to the
right
Therefore, pH will decrease
Draw sample
Need: waste syringe, sample syringe, cup of ice (??)
Draw from patient
Draw from ECC
Remove all air from sample – Cap tightly – Place in cup of ice
Blood Gas Determination Via Lab
Blood from sample injected into analyzer
Analyzer WARMS sample to 37o C
Analyzer determines the pO2, pCO2, and pH at 37o C
uncorrected gases
Report gas values determined at 37oC
corrected gases
Report gas values measured at 37oC but corrected back to actual body temperature
Patient temp is 25o so analyzer will WARM the sample. pH, CO2, and O2 will be
pH will be lower than expected (0.0147 per degree)
CO2 will be higher than expected
O2 will be higher than expected
On bypass, you must look at the temperature corrected
blood gases to correctly treat the patient’s what
pO2
where does most of the acid-base buffering in the body happen
-in the blood
primary blood buffering system for maintaining a constant ratio of OH- to H+ (16:1) due to the changes in temp is
- Imidazole moiety of the amino acid histidine
- found on most blood born proteins
what is controled by alpha stat and pH stat management of blood gases
- pH and pCO2
- arterial pO2 MUST be temperature corrected
how do you increase pCO2
increase CO2 content
In a normal human, what stays constant
CO2 content
intracellular pH (7.0)
- much lower than the blood pH
- more water inside the cells
as temperature increases, what happens to pH
pH decreases
pH varies from organ to organ. Why?
-temperature of each organ is different therefore changing the pH form organ to organ
Advantages of keeping CO2 content constant
Maintains constant pH difference across cell membranes
Maintains constant ratio of negative to positive charges on proteins
Allows enzyme systems to work at optimal level regardless of temperature
what stays constant and what changes for pH stat
- constant- pH
- changes- temperature CO2 content
what stays constant and what changes for alpha stat
- constant- CO2 content
- changes- temperature and pH
consequences of hypothermia for pH stat
blood more acidic (b/c of increase in CO2 content)
hydrogen ion gradient across the cell membrane changes
acidity alters metabolic activity (metabolic rate goes down)
cells do not maintain electroneutrality
added CO2
influences blood flow regulation (increase CO2> increase vasodilation)
consequences of hypothermia for alpha stat
maintain constant charge on alpha-imidazole side chain
hydrogen ion gradient across cell does not change
cellular enzyme functions are maintained
cells maintain electroneutrality
auto-regulation of blood flow maintained (flow depends on metabolism)
alpha-stat for peripheral perfusion
-studies suggest improvement of peripheral
perfusion
alpha stat cerebral blood flow
-less than normal because it is based on metabolic need of tissue
pH stat cerebral blood flow and management
- greater than normal because pressure dependent
- go from metabolism controlling CBF to a change in pressure controlling CBF
- lose autoregulation
Cerebral blood flow normally autoregulated
flow tightly coupled to cerebral metabolism
flow independent of blood pressure
flow regulated by PCO2
luxury flow
- flow is greater than the metabolic rate
- as blood flow through a tissue goes up, potential for embolic injury goes up
lose autoregulation at what temp
20 decrees C
pH-stat uncouples flow and metabolism
greater blood flow – pressure dependent
improved cooling – more homogeneous
luxury flow – predispose to risk of embolic injury, high intracranial pressure, edema
Alpha-stat maintains autoregulation
lower blood flow – based on metabolism
predispose to adverse distribution of blood flow – risk of ischemic injury
kids are more susceptible to
-ischemic injury rather than embolic injury
adults more susceptible to
-embolic injury rather than ischemic injury
regular bypass adult strategy
With little or no hypothermia might not make any difference.
-With mild to moderate alpha-stat might be better
PROFOUND WITH ARREST ADULTS best strategy
Combination (cross-over) best approach – use pH stat while cooling to ensure maximal cerebral metabolic suppression – switch to alpha-stat to remove acidosis
INFANTS best strategy
Appears pH-stat may offer better outcomes (major cause of brain injury may relate more to hypoperfusion rather than emboli (might switch to alpha stat)
manage pH stat
- Always keep temperature corrected PCO2 at 40 mmHg
* Always keep temperature corrected pH at 7.40
You are on bypass and the patient is at 28o. Your last blood gas came back with the following temperature corrected values: PO2=98 mmHg; PCO2=30 mmHg; pH=7.53; bicarb=24; SvO2=74. Assuming you are practicing pH stat, which of the following best describes the patient’s total CO2
ontent?
Total CO2 content lower than it should be
You are on bypass and the patient is at 28o. Your last blood gas came back with the following temperature corrected values: PO2=98 mmHg; PCO2=30 mmHg; pH=7.53; bicarb=24; SvO2=74. Assuming you are practicing pH stat, how would you bring the CO2 content back to where it should be?
Add CO2 to the patient
You are on bypass and the patient is at 28o. Your last blood gas came back with the following temperature corrected values: PO2=98 mmHg; PCO2=30 mmHg; pH=7.53; bicarb=24; SvO2=74. Which of the following best describes how you would “fix” the PO2? [pH stat]
Increase FiO2
You are on bypass and the patient is at 28o. Your last blood gas came back with the following temperature corrected values: PO2=98 mmHg; PCO2=30 mmHg; pH=7.53; bicarb=24; SvO2=74. Which of the following best describes how you would “fix” the SvO2? [pH stat]
Make no change
You are on bypass and the patient is at 32o. Your last blood gas came back with the following temperature corrected values: PO2=350 mmHg; PCO2=60 mmHg; pH=7.15; bicarb=20; SvO2=60. Assuming you are practicing pH stat, which of the following best describes the patient’s total CO2 content?
Total CO2 content higher than it should be
You are on bypass and the patient is at 320. Your last blood gas came back with the following temperature corrected values: PO2=350 mmHg; PCO2=60 mmHg; pH=7.15; bicarb=20; SvO2=60. Assuming you are practicing pH stat, how would you bring the CO2 content back to where it should be?
Remove CO2 from the patient
You are on bypass and the patient is at 320. Your last blood gas came back with the following temperature corrected values: PO2=350 mmHg; PCO2=60 mmHg; pH=7.15; bicarb=20; SvO2=60. Which of the following best describes how you would “fix” the PO2? [pH stat]
Decrease FiO2
You are on bypass and the patient is at 320. Your last blood gas came back with the following temperature corrected values: PO2=350 mmHg; PCO2=60 mmHg; pH=7.15; bicarb=20; SvO2=60. Which of the following best describes how you would “fix” the PCO2? [pH stat]
Increase gas-to-blood flow ratio
You are on bypass and the patient is at 320. Your last blood gas came back with the following temperature corrected values: PO2=350 mmHg; PCO2=60 mmHg; pH=7.15; bicarb=20; SvO2=60. Which of the following best describes how you would “fix” the bicarb? [pH stat]
Add bicarb
You are on bypass and the patient is at 320. Your last blood gas came back with the following temperature corrected values: PO2=350 mmHg; PCO2=60 mmHg; pH=7.15; bicarb=20; SvO2=60. Which of the following best describes how you would “fix” the SvO2? [pH stat]
Increase cardiac index
You are on bypass at 300. You have just received the following blood gas results:
PO2 [@ 37 = 100; @ 30 = 91]
PCO2 [@ 37 = 40; @ 30 = 29.4]
pH [@ 37 = 7.40; @ 30 = 7.51]
You are using alpha stat. Which PO2 value do you use for your analysis?
91 mmHg
You are on bypass at 300. You have just received the following blood gas results:
PO2 [@ 37 = 100; @ 30 = 91]
PCO2 [@ 37 = 40; @ 30 = 29.4]
pH [@ 37 = 7.40; @ 30 = 7.51]
You are using alpha stat. Which PCO2 value do you use for your analysis?
40 mmHg
You are on bypass at 300. You have just received the following blood gas results:
PO2 [@ 37 = 100; @ 30 = 91]
PCO2 [@ 37 = 40; @ 30 = 29.4]
pH [@ 37 = 7.40; @ 30 = 7.51]
You are using alpha stat. Which pH value do you use for your analysis?
7.40
You are on bypass at 300. You have just received the following blood gas results:
PO2 [@ 37 = 100; @ 30 = 91]
PCO2 [@ 37 = 40; @ 30 = 29.4]
pH [@ 37 = 7.40; @ 30 = 7.51]
You are using alpha stat. Which of the following best describes the patient’s total CO2 content?
Total CO2 content where it should be
You are on bypass at 300. You have just received the following blood gas results:
PO2 [@ 37 = 100; @ 30 = 91]
PCO2 [@ 37 = 40; @ 30 = 29.4]
pH [@ 37 = 7.40; @ 30 = 7.51]
You are using alpha stat. Which of the following best describes how you would “fix” the PO2?
Increase FiO2
You are on bypass at 300. You have just received the following blood gas results:
PO2 [@ 37 = 100; @ 30 = 91]
PCO2 [@ 37 = 40; @ 30 = 29.4]
pH [@ 37 = 7.40; @ 30 = 7.51]
You are using alpha stat. Which of the following best describes how you would “fix” the PCO2?
Make no change
You are on bypass at 300. You have just received the following blood gas results:
PO2 [@ 37 = 100; @ 30 = 91]
PCO2 [@ 37 = 40; @ 30 = 29.4]
pH [@ 37 = 7.40; @ 30 = 7.51]
You are using alpha stat. Which of the following best describes how you would “fix” the pH?
Make no change
You are on bypass at 300. You have just received the following blood gas results:
PO2 [@ 37 = 100; @ 30 = 91]
PCO2 [@ 37 = 40; @ 30 = 29.4]
pH [@ 37 = 7.40; @ 30 = 7.51]
You are using pH stat. Which PO2 value do you use for your analysis?
91 mmHg
You are on bypass at 300. You have just received the following blood gas results:
PO2 [@ 37 = 100; @ 30 = 91]
PCO2 [@ 37 = 40; @ 30 = 29.4]
pH [@ 37 = 7.40; @ 30 = 7.51]
You are using pH stat. Which PCO2 value do you use for your analysis?
29.4 mmHg
You are on bypass at 300. You have just received the following blood gas results:
PO2 [@ 37 = 100; @ 30 = 91]
PCO2 [@ 37 = 40; @ 30 = 29.4]
pH [@ 37 = 7.40; @ 30 = 7.51]
You are using pH stat. Which pH value do you use for your analysis?
7.51
You are on bypass at 300. You have just received the following blood gas results:
PO2 [@ 37 = 100; @ 30 = 91]
PCO2 [@ 37 = 40; @ 30 = 29.4]
pH [@ 37 = 7.40; @ 30 = 7.51]
You are using pH stat. Which of the following best describes how you would “fix” the PO2?
Increase FiO2
You are on bypass at 300. You have just received the following blood gas results:
PO2 [@ 37 = 100; @ 30 = 91]
PCO2 [@ 37 = 40; @ 30 = 29.4]
pH [@ 37 = 7.40; @ 30 = 7.51]
You are using pH stat. Which of the following best describes how you would “fix” the PCO2?
Decrease gas-to-blood flow ratio
You are on bypass at 250. You have just received the following blood gas results:
PO2 [@ 37 = 275; @ 25 = 250]
PCO2 [@ 37 = 75; @ 25 = 55]
pH [@ 37 = 7.13; @ 25 = 7.23]
SvO2 = 65%
You are using pH stat. Which of the following values will you use for your PCO2 analysis?
55 mmHg
You are on bypass at 250. You have just received the following blood gas results:
PO2 [@ 37 = 275; @ 25 = 250]
PCO2 [@ 37 = 75; @ 25 = 55]
pH [@ 37 = 7.13; @ 25 = 7.23]
SvO2 = 65%
You are using pH stat. Which of the following best describes how you would “fix” the PO2?
Make no change
You are on bypass at 250. You have just received the following blood gas results:
PO2 [@ 37 = 275; @ 25 = 250]
PCO2 [@ 37 = 75; @ 25 = 55]
pH [@ 37 = 7.13; @ 25 = 7.23]
SvO2 = 65%
You are using pH stat. Which of the following best describes how you would “fix” the PCO2?
Increase gas-to-blood flow ratio
You are on bypass at 250. You have just received the following blood gas results:
PO2 [@ 37 = 275; @ 25 = 250]
PCO2 [@ 37 = 75; @ 25 = 55]
pH [@ 37 = 7.13; @ 25 = 7.23]
SvO2 = 65%
You are using pH stat. Which of the following best describes how you would “fix” the SvO2?
Increase cardiac index
You are on bypass at 250. You have just received the following blood gas results:
PO2 [@ 37 = 275; @ 25 = 250]
PCO2 [@ 37 = 75; @ 25 = 55]
pH [@ 37 = 7.13; @ 25 = 7.23]
SvO2 = 65%
You are using alpha stat. Which of the following values will you use for your PCO2 analysis?
75 mmHg
You are on bypass at 250. You have just received the following blood gas results:
PO2 [@ 37 = 275; @ 25 = 250]
PCO2 [@ 37 = 75; @ 25 = 55]
pH [@ 37 = 7.13; @ 25 = 7.23]
SvO2 = 65%
You are using alpha stat. Which of the following best describes how you would “fix” the PO2?
Make no change
You are on bypass at 250. You have just received the following blood gas results:
PO2 [@ 37 = 275; @ 25 = 250]
PCO2 [@ 37 = 75; @ 25 = 55]
pH [@ 37 = 7.13; @ 25 = 7.23]
SvO2 = 65%
You are using alpha stat. Which of the following best describes how you would “fix” the PCO2?
Increase gas-to-blood flow ratio
You are on bypass at 250. You have just received the following blood gas results:
PO2 [@ 37 = 275; @ 25 = 250]
PCO2 [@ 37 = 75; @ 25 = 55]
pH [@ 37 = 7.13; @ 25 = 7.23]
SvO2 = 65%
You are using alpha stat. Which of the following best describes how you would “fix” the SvO2?
Increase cardiac index
You are on bypass at 250. You have just received the following blood gas results:
PO2 [@ 37 = 275; @ 25 = 250]
PCO2 [@ 37 = 67.6; @ 25 = 40]
pH [@ 37 = 7.22; @ 25 = 7.40]
SvO2 = 84%
You used pH-stat to cool the patient. You now want to convert to alpha-stat. Which of the following best describes how you would adjust the pO2?
Make no change
You are on bypass at 250. You have just received the following blood gas results:
PO2 [@ 37 = 275; @ 25 = 250]
PCO2 [@ 37 = 67.6; @ 25 = 40]
pH [@ 37 = 7.22; @ 25 = 7.40]
SvO2 = 84%
You used pH-stat to cool the patient. You now want to convert to alpha-stat. Which of the following best describes how you would adjust the pCO2?
Increase gas-to-blood flow ratio