Acid Base Flashcards
what does the henderson-hasselbalch equation estimate and define?
– Estimates pH and base excess/deficit
– Defines magnitude of change but not the cause
A ____ CO2 will result in a _____ HCO3- and vice versa
high; high
what are normal values for pH, PaCO2 and HCO3-
pH 7.4
PaCO2 40 mm Hg
HCO-3 24 mEq/L
what are some contributions to H+
– H2CO3
– Inorganic acid
– Organic acid
– Lactic acid
– Ketoacid
what is the solubility of CO2
0.03
what is a base excess/deficit
– any difference that exists from the normal value for bicarbonate
– Reflects non volatile acid changes (metabolic)
what is a buffer and what are some examples
Buffer: substance that prevents extreme changes in the free concentration of H + within a solution
– Hemoglobin
– NaHCO3
– Phosphate
– Protein
what is an ion
Ion: dissociated solute
– Cation (+)
– Anion (-)
behaviour of an acid vs a base in terms of H+
- Acid: donates H + from solutions
- Base: removes H+ from solutions
what does electroneutrality establish
Establishes that there has to be equal
amounts of cations and anions
what are unmeasured anions
- There are anions that are not routinely measured- Unmeasured anions (UA)
– Phosphate, Sulphate, organic acids (lactic acid), ketoacids, ± proteins
what is happening:
-low pH
-low PaCO2
-low ABE
metabolic acidosis
what is happening:
-low pH
-high PaCO2
-normal ABE
respiratory acidosis
what is happening:
-high pH
-low PaCO2
-normal ABE
respiratory alkalosis
what is happening:
-high pH
-low PaCO2
-high ABE
metabolic alkalosis
what is the formula to calculate CO2 for metabolic acidosis
CO2 = 1.5 (HCO-3) + 8
what is the formula to calculate CO2 for metabolic alkalosis
CO2 = 0.9 (HCO-3) + 9
what is the formula to calculate CO2 for respiratory acidosis
For every 10 mmHg increase in CO2 = (HCO-3) increases 1.3 units
what is the formula to calculate CO2 for respiratory alkalosis
For every 10 mmHg decrease in CO2 =(HCO-3) decreases 2-3 units
what are the three independent variables for quantitative/stewarts method to determine blood pH
– PaCO 2
– SID; Strong ion difference
– Weak acids (Atot); Proteins in blood
what does a SID of <44 indicate
metabolic acidosis
what does a SID of >44 indicate
metabolic alkalosis
how do you calculate SID
(Na+ + K+ ) - Cl- = ?
how do you calculate anion gap
(Na+ + K+ ) – (Cl- + HCO -3) = ?
is anion gap useful as a stand alone parameter
no, it includes bicarb in the calculation which isnt reliable so we dont use AG alone
what do proteins affect
anion gap
what is the affect of hyper vs hypoproteinemia in terms of pH
– Hyperproteinemia = metabolic acidosis
– Hypoproteinemia = metabolic alkalosis
proteins act as ____ _____
weak acids
dissociation level of weak ions/buffers and examples
-only partially dissociated
-proteins and hemoglobin
what does the strong anion gap correct for and what does it allow us to determine
Corrects Anion gap for proteins
This calculation allows to determine the unmeasured anions (UA)
formula for SIG
SIG = AG – (Total proteins x 0.25)
what can happen to PCV when you are administering fluids and there is blood loss
it can become low
what value of PCV do we need to administer blood
PCV < 20-25%
what is the fluid rate for maintenance
2-4mL/kg/hour
