acid base disorders Flashcards
normal arterial pH
7.4
normal plasma HCO3
24
normal arterial pCO2
40
normal plasma H+
36-44
when HCO3 is lost, pH will…
decrease
when pCO2 is lost, pH will…
increase
when H+ is lost, pH will…
increase
when pCO2 is gained pH will…
decrease
the lungs manage ___ and ___
PCO2 and pH
the kidneys manage ___ and ___
pH and HCO3
in metabolic acidosis, pH goes ____ and HCO3 goes ___
down
down
how are acid-base disorders diagnosed?
arterial blood gas interpretation
what is the mechanism behind metabolic acidosis?
either gaining an acid (H+) or losing HCO3
causes of anion-gap metabolic acidosis
lactic acidosis
ketoacidosis
renal insufficiency
aspirin
causes of non-anion gap metabolic acidosis
renal tubular acidosis
GI loss of HCO3 (diarrhea)
excess saline infusion
metabolic alkalosis mechanism
direct gain of HCO3, loss of H+
causes of metabolic alkalosis
vomiting
hypovolemia
thiazide diuretics
increased renal production of HCO3
respiratory acidosis mechanism
alveolar hypoventilation leads to CO2 retention
in metabolic alkalosis, pH goes ____ and HCO3 goes ___
up
up
in respiratory acidosis, pH goes ____ and PCO2 goes ___
down
up
in respiratory alkalosis, pH goes ____ and PCO2 goes ___
up
down
causes of respiratory acidosis
airway obstruction
respiratory muscle weakness
CNS depression
(anything that would lead you not to breath fast or deeply enough)
respiratory alkalosis mechanism
hyperventilation leads to too much CO2 being lost
causes of respiratory alkalosis
pain panic attacks pregnancy pulmonary disease pills (drugs) problem with your brains
7.32/10/98/8
what is each number on the ABG?
pH/ CO2/ O2/ HCO3
7.32/10/98/8 acidosis or alkalosis?
acidosis (7.32)
7.32/10/98/8
metabolic or respiratory
metabolic acidosis
7.32 is acidic
CO2=10 is low, but low CO2 would cause alkalosis
HCO3=8 is low which is driving the pH down
7.32/10/98/8
appropriate compensation or not?
look at CO2- metabolic acidosis
(1.5 x 8) + 8 +/-2=
20 +/- 2 does not equal 10
so lungs are not compensating appropriately to try and increase pH
second disorder is low PCO2= respiratory alkalosis
what is winter’s formula used for?
for metabolic acidosis ONLY: what CO2 should be if lungs are compensating appropriately
winter’s formula
(1.5 x HCO3) + 8 +/-2
which has faster compensatory changes–metabolic or respiratory disorders?
(think!)
in metabolic disorders, PCO2 compensates faster because ventilation can change quickly
respiratory disorders take longer to change urinary pH in response
compensation mechanism in metabolic acidosis
low HCO3 leads to low pH
so respiratory rate increases to get rid of more CO2 and have an alkalotic effect and try to raise pH
use winters formula to see if there is appropriate compensation
compensation mechanism in metabolic alkalosis
high HCO3 leads to high pH, respiratory compensation by decreasing respiratory rate to increase PCO2 and increase pH
compensation mechanism in acute respiratory alkalosis or acidosis
trick question, there’s not really any compensation from the kidneys just that there may be some buffering of excess acid or base
compensation mechanism of chronic respiratory acidosis
chronic high pCO2 and low pH leads to increased HCO3 by kidneys to try and raise pH
final pH will not be as acidic
compensation mechanism of chronic respiratory alkalosis
chronic low CO2 and high pH leads to lower HCO3 by kidneys to compensate and try to lower pH
final pH will not be as alkalotic
what is the anion-gap
represents the difference between the concentration of unmeasured anions (Cl-, HCO3-) and the the concentration of unmeasured cations (Na+, K+)
what is a normal anion-gap
10-12
high anion gap metabolic acidosis
anion gap > 12 due to increased concentration of acids like ketoacidosis or lactic acidosis
formula to see if anion gap is high
2.5 x albumin (4)
what is the delta delta ratio and when is it used
it is a ratio using the anion gap and serum bicarbonate to see if there is a second metabolic disorder occurring during high anion gap metabolic acidosis
delta delta fomrula
measured- expected anion gap= number of bicarbs consumed to buffer anions
serum bicarb-anion gap= shows what bicarb should be and confirms presence of a secondary disorder
if delta delta predicted bicarbonate is lower than expected, the other disorder present is …
non-gap metabolic acidosis
if delta delta predicted bicarbonate is higher than expected, the other disorder present is …
metabolic alkalosis (or chronic respiratory acidosis)
7.22/34/98/17
non-gap metabolic acidosis with appropriate respiratory compensation
causes of non-gap metabolic acidosis
diarrhea, drugs, renal tubular acidosis
urine anion gap formula
[Na] + [K] - [Cl]
positive urine anion gap is due to
kidney problems-renal acidification
negative urine anion gap is due to
GI loss of bicarbonate (diarrhea)
how much should HCO3 change in chronic respiratory acidosis?
3.5 for every change of 10 in CO2 from normal
if CO2 is 60, it should be 40 so 2 changes of 10, 3.5 x2=7
how much should HCO3 change in chronic respiratory alkalosis?
5 for every change of 10 in CO2 from normal
diabetic ketoacidosis labs would present as…
high anion gap metabolic acidosis
high gap because of ketones
