Dr. Sullivan: Acid-Base Interpretation Flashcards
What are the 4 main acids that can be found in the human body?
- carbonic acid
- lactic acid
- aspirin/methanol/ethanol
- uremia/DKA
Note: DKA is diabetic ketacidosis
Intracellular buffering comes from what? (2)
proteins
phosphates (bones)
Extracellular buffering comes from what? (2)
bicarbonate
ammonia
What are 2 major organ systems?
lungs
kidneys
Lungs can compensate in about ___ min whereas the kidneys compensate in _____ hours.
10
72
PCO2 in arterial blood is ______mmHg.
40 mmHg
PCO2 in venous blood is ______ mmHg.
45
What would you expect to change in a respiratory acid-base disturbance?
PaCO2
What would you expect to change in a metabolic acid-base disturbance?
HCO3-
When a stress is applied to a system, the balance is shifted in the direction to relieve that stress is known as what principle?
Le Chatlier’s Principle
What enzyme makes this reaction occur?
CO2 + H2O ⇔ H2CO3 ⇔ H+ + HCO3-
carbonic anhydrase
What is the most important buffering system?
HCO3 - CO2 buffering system
First questions to ask yourself during an ABG analysis: (4)
This is known as figuring out the primary disorder.
- Is there acidemia or alkalemia?
- Is the problem respiratory or metabolic?
- If respiratory, is it chronic or acute?
- If metabolic, IS THERE AN ANION GAP?
To determine if there is a secondary disorder, ask yourself this question:
Is there compensation?
If anion gap acidosis is present, what do you ask yourself?
Are there any other underlying metabolic disorders?
What is present if either the PaCO2 or the pH is outside the normal range?
acid base abnormality
A normal pH or a normal PaCO2 does not rule out the presence of an acid-base disturbance. True or false?
true
If both PaCO2 and pH change in the same direction then the disturbance is _______.
metabolic
If both paCO2 and pH change in opposite directions then the disturbance is ______.
respiratory
If there is a respiratory disturbance, what must you do?
calculate expected pH
What is the ∆pH equation for an acute respiratory change?
∆PaCO2 x 0.008
What is the ∆pH for a chronic change?
∆PaCO2 x 0.003
If there is an anion gap then there is an excess of proton donors. If there is not a gap, then there is a loss of proton acceptors. Normal AG is _____.
12 ± 4
What is the Anion Gap equation?
Na - Cl - HCO3
If anion gap is greater than 12, what do we conclude the patient has?
anion gap acidosis
If the patient has a metabolic issue, what is the factor to determine next?
We need to ask:
“Is this a anion gap or non-anion gap metabolic issue?”
If anion gap is less than 12, what can we safely conclude?
This is a non-anion gap acidosis.
Anion gap calculation is made to determine if a metabolic acidosis is due to an accumulation of _________ or a net loss of _________.
non-volatile acids
bicarbonate
Pearl:
If you have a normal pH and a PaCO2 that is out of range, what can you DEFINITELY conclude?
3rd disorder is present.
If pH or PaCO2 are normal, then what do you conclude?
There is a mixed metabolic and respiratory disturbance.
Rule 3: : If pH or PaCO2 are normal, there is a mixed metabolic and respiratory disturbance
If the pH is normal then the direction of change of the PaCO2 determines what?
respiratory disorder
Rule 3: If pH or PaCO2 are normal, there is a mixed metabolic and respiratory disturbance
If the PaCO2 is normal, the direction of change or the pH identifies what?
metabolic disorder
If a primary metabolic acidosis or alkalosis, use the measured serum bicarbonate concentration to identify the expected PaCO2.
If the measured and calculated PaCO2 are similar, then the disturbance is _______.
compensated
You cannot have both respiratory acidosis and alkalosis. True or false?
true
If a primary metabolic acidosis or alkalosis, use the measured serum bicarbonate concentration to identify the expected PaCO2.
If the measured and calculated PaCO2 are different, then the disturbance is _______.
not compensated
If there is a respiratory acidosis or alkalemia, then use the formulas to calculate the expected pH.
Compare the measured pH to the expected pH to determine if the condition is: (3)
acute, partially compensated, or fully compensated
Given Primary respiratory disorder calculate expected ___.
pH
Calculating compensation
Given Primary Metabolic disorder calculate expected _______.
PaCO2
Calculating compensation
What is the PaCO2 ACIDOSIS equation?
(1.5 x HCO3) + 8 (±2)
What is the PaCO2 ALKALOSIS equation?
(0.7 x HCO3) + 21 (±2)
For respiratory disorders
If the expected (calculated) pH is different than measured pH, there is a second disorder, which is _____.
metabolic
For metabolic disorders
If the expected (calculated) PaCO2 is different than measured PaCO2, there is a second disorder, which is ________.
respiratory
What are the cardiac consequences of acidemia? (4)
Impaired contractility
Vascular dysfunction
Reductions in blood flow
Arrhythmogenesis
What are the pulmonary consequences of acidemia? (2)
Increased MV
Decreased/Fatigued respiratory muscle function
What are the metabolic consequences of acidemia? (4)
Increased metabolic demands
Insulin resistance
Hyperkalemia
Increased catabolism
Overcompensation is common. True or false?
False.
It is rare.
Loss of bicarbonate may be due to:
MUDPILES
- methanol
- uremia
- DKA
- propylene glycol
- isoniazid
- lactic acidosis
- ethylene glycol
- salicylates
Hemodialysis is effective for lactate acidosis. True or false?
false
NOT effective
Diuretic therapy is the biggest cause of metabolic alkalosis. True or false?
True
Number 1 cause for respiratory alkalosis is:
pain/anxiety
