Acidosis and Alkalosis Case Questions

Question 1

What is the first rule of evaluating acid base?

Answer 1

look at the pH on ABG.

Question 2

What is the second rule of acid base evaluation?

Answer 2

calculate the anion gap

Question 3

If the anion gap is elevated, what does that suggest?

Answer 3

most likely a primary metabolic acidosis

can also be a mixed acid base problem that includes an anion gap

Question 4

What is the thurd rule of acid base evaluation? Aka, what should you check if there is an anion gap?

Answer 4

Calculate the osmol gap

Question 5

How do you check an osmol gap?

Answer 5

you do measured osmolarity (by lab) - calcualted osmolarity

Question 6

How do you calculate osmolarity?

Answer 6

2(Na) + Glucose/18 + BUN/2.8

Question 7

What is a normal osmol gap and what does a high osmol gap suggest?

Answer 7

should be equal to or less than 10

over 10 suggests the person took in a volatile chemical like ethylene glycol or methanol

Question 8

What is rule 4?

Answer 8

If there’s an anion gap, you need to calular the excess anion gap (also called the delta gap) - this tells you whether the patient is compensating appropriately with bicarb

Question 9

How co you calcualate a delta gap?

Answer 9

Calculated anion gap minus 12 (the excess gap) added to the measured bicarb should euqal a normal bicarb level (24-26)

Question 10

If the delta gap is low, what does that suggest? If it’s high, what does that suggest?

Answer 10

low delta gap means there is also a non-anion gap acidosis going on (because the body isn’t compensating appropriately)

high delta gap means there is an underlying metabolic alkalosis as well

Question 11

What is rule 5 of acid base evaluation?

Answer 11

interpret using the clinical picture!!

Question 12

What do you have if the ABG is normal but you have an elevated anion gap?

Answer 12

you must have a mixed metabolic alkalosis and anion gap metabolic acidosis

Question 13

What is the primary disturbance in metabolic acidosis?

Answer 13

overproduction or retention of acid (with subsequent decrease in bicarb)

Question 14

What is the compensation for a metabolic cacidosis?

Answer 14

hyeprventilation to blow off CO2

Question 15

What’s an easy rule to see whether someone is compensating apropriately for a metabolic acidosis?

Answer 15

pCO2 should equal the last 2 digits of the pH

Question 16

What is the differential diagnosis for metabolic acidosis with a high anion gap?

Answer 16

MUDPILES
methanol
uremia - from kidney failure
DKA and AKA
Paraldahydre
Iron OD or Isoniazid use
Lactic acidosis
Ethylene glycol (and ethanol)
Salicylates

Question 17

What is a normal anion gap metabolic acidosis caused by?

Answer 17

It’s a loss of bicarb from GI or the kidney with an equal rise of Cl for the loss of bicarb

Question 18

What are some of the causes of GI/kidney bicarb loss with subsequent normal anion gap metabolic acidosis?

Answer 18

HARDUP
Hyperventilation/hyperalimentation
Acid ingestion
RTA (?)
Diarrhea
Ureteral and ileal diversion
Pancreatic fistulas

Question 19

What is the primary disturbance in metabolic alkalsois?

Answer 19

increased plasma HCO3 (with subsequent decrease in plasma H) - can happen vice bersa too though

Question 20

What is the compensation for metaoblic alkalsosis/

Answer 20

hypoventilation - so compensation is limited (you can’t stop breathing)

Question 21

If a metabolic alkalosis is accompnanied by a urine chloride less than 10, it’s chloride responsibe and will repsond to what treatment?

Answer 21

saline infusion

Question 22

What are some examples of chloride responsive metabolic alkaloses?

Answer 22

vomiting
diuretics
NG suction
dehydration from diarrhea with Cl wasting
villous adenoma

Question 23

If the metabolic alkalosis if chloride unresponsive, what is the general cause?

Answer 23

high aldosterone, which leads to icnreased H and K excretion in exchange for reabsorbing Na as sodium bicarb

Question 24

What are the common causes of chloride unresponsive metabolic alkalosis?

Answer 24

Cushings
Hyperaldosterone - including Barter’s
Secondary hyperaldosterone like CHF and CRF
bicarb ingestion

Question 25

What is the primary disturbance in respiratory acidosis?

Answer 25

hypoventilation leading to an increase in arterial CO2 (with subsequent increase in both bicarb and H+)

Question 26

How do you compensate for a respiratory acidosis?

Answer 26

kidneys excrete H+ and reabsorb bicarb

Question 27

FOr a respiratory acidosis, how can you figure out if the compensation is acute or chornic?

Answer 27

For every 10-point rise in pCO2, the bicarb will go up 1 point if acute and up 3 points if chronic

Question 28

What are the common causes of respiratory acidosis?

Answer 28

airway obstruction
COPD, Aasthma, pneumothroax, infections
CNS depression or respiration - sedatives, hypnotics, drugs, tumors
neuromuscular weakness

Question 29

What is the primary disturbance in respiratory alkalosis?

Answer 29

hyperventioation blowing off too much CO2, with subsequent decrease in both acid and bicarb

Question 30

What is the compensation in respiratory alkalosis?

Answer 30

kidney excretion of bicarb and reabsorbtion of acid (beta intercalated cells)

Question 31

In a respiratory alkalosis, how do you determine if the compensation is acute or chronic?

Answer 31

For every 10 increase of pCO2, bicarb will fall by 2 if acute and by 4 if chronic

Question 32

What are some common causes of respiratory alkalosis?

Answer 32

anxiety, aspirin, cocaine, progesterone,

any cause of tachypnea = sepsis, fever, PE, pneumonia, hypoxia
alcohol or narcotic withdrawal