B4.038 Acid Base Balance

Question 1

what is an acid base disorder

Answer 1

change in the normal value of extracellular pH that may result when renal or respiratory function is abnormal or when and acid or base load overwhelms excretory capacity

Question 2

what do you get from an ABG?

Answer 2

pH
pCO2
PO2

Question 3

what 2 molecules give indication of acid base disorder

Answer 3

CO2

HCO3-

Question 4

normal pH

Answer 4

7.35-7.45

Question 5

normal pCO2

Answer 5

36-44

Question 6

normal HCO3-

Answer 6

22-26

Question 7

acidosis

Answer 7

process that increases [H+] by increasing PCO2 or reducing [HCO3-]

Question 8

alkalosis

Answer 8

process that reduces [H+] by reducing PCO2 or by increasing [HCO3-]

Question 9

what is a mixed acid base disorder

Answer 9

more than one disorder present
pH may be normal or abnormal
if abnormal trends toward the dominant disorder

Question 10

what systems can provide compensation for acid base disorders

Answer 10

renal
respiratory
will not return pH to normal, just trend it the right way

Question 11

what is a metabolic disorder

Answer 11

primary disturbance of blood [HCO3-]
metabolic acidosis- too little bicarb
metabolic alkalosis- too much bicarb

Question 12

what are the 2 types of metabolic acidosis

Answer 12

anion gap

non anion gap

Question 13

what are compensatory mechanisms for metabolic disorders

Answer 13

via respiration

changes in ventilation mediated by chemoreceptors in carotid body and lower brainstem

Question 14

definition of metabolic alkalosis

Answer 14

HCO3- retention

HCO3- produced more than excreted

Question 15

sources of metabolic alkalosis

Answer 15

nasogastric suctioning
vomiting
diuretic therapy
hyperaldosteronism (addisons)
cushing syndrome (acth excess)
exogenous steroids
licorice ingestion
alkali ingestion

Question 16

definition of metabolic acidosis

Answer 16

HCO3- depletion
anion gap: HCO3- used as a buffer for acid
nonunion gap: lost through urine or bowel

Question 17

sources of anion gap metabolic acidosis

Answer 17

methanol
uremia (acute renal failure)
DKA
paraldehyde
INH/iron
lactic acidosis (sepsis)
ethylene glycol
salicylates

Question 18

sources of non anion gap metabolic acidosis

Answer 18

hyperaimentation
acetazolamide and other carbonic anhydrase inhibitors
renal tubular acidosis
diarrhea
ureteroenteric fistula
pancreaticoduodenal fistula

Question 19

what is winters formula

Answer 19

predicts expected pCO2 for any given HCO3- level

expected pCO2=(1.5*[HCO3-])+8 (plus or minus 2)

Question 20

if pCO2 is above expected w winters…

Answer 20

secondary resp acidosis

Question 21

if pCO2 is below expected w winters

Answer 21

secondary resp alkalosis

Question 22

what is a respiratory disorder

Answer 22

primary alteration in the pCO2

regulated through alveolar ventilation

Question 23

definition of respiratory acidosis

Answer 23

CO2 retention

decreased alveolar ventilation

Question 24

causes of respiratory acidosis

Answer 24

CNS depression, sedatives
neuromuscular disorders
thoracic cage limitations
acute obstruction
chronic obstruction
ventilator malfunction

Question 25

definition of respiratory alkalosis

Answer 25

CO2 depletion | increased alveolar ventilation

Question 26

causes of respiratory alkalosis

Answer 26

``` anxiety CNS disorders salicylates, analeptics fever, sepsis pregnancy liver insufficiency hyperthyroidism ```

Question 27

basic steps of acid base problems

Answer 27

1. look at pH 2. respiratory or metabolic? 3. if respiratory, acute or chronic? 4. if metabolic acidosis, is resp system compensating? (winters) 5. anion gap? 6. delta gap?

Question 28

acute respiratory acidosis

Answer 28

increase in pCO2 shifts equilibrium to increase HCO3, this occurs immediately

Question 29

acute respiratory acidosis equations

Answer 29

pH=7.4-0.008(pCO2-40) | HCO3=24+0.1(pCO2-40)

Question 30

chronic respiratory acidosis

Answer 30

kidneys retain HCO3 which takes a few days to fully occur

Question 31

chronic respiratory acidosis equations

Answer 31

pH=7.4-0.003(pCO2-40) | HCO3=24+0.4(pCO2-40)

Question 32

anion gap equation

Answer 32

``` gap = [Na] - ([Cl]+[HCO3]) normal = 12 ```

Question 33

when do you check delta gap?

Answer 33

if there is an anion gap metabolic acidosis present

Question 34

what is the delta gap equation

Answer 34

corrected HCO3 = measured HCO3 + (anion gap-12)

Question 35

how do you interpret results of the delta gap

Answer 35

if corrected HCO3 is less than normal, there is an additional metabolic acidosis present if corrected value of HCO3 is greater than 26, there is a co-existing metabolic alkalosis present

Question 36

chronic respiratory alkalosis equations

Answer 36

pH=7.4-0.003(pCO2-40) | HCO3=24+0.5(pCO2-40)

Question 37

acute respiratory alkalosis equations

Answer 37

pH=7.4-0.008(pCO2-40) | HCO3=24+0.2(pCO2-40)