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CRRAB II Week 3 > Evaluation of Acid Base Disorders > Flashcards

Evaluation of Acid Base Disorders Flashcards

1
Q

What is rule 1 in evaluating Acid Base Disorders?

A

Look at pH using Arterial Blood Gases!

-Whichever side of 7.40 is the primary abnormality (acidosis or alkalosis –> body never fully compensates)

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2
Q

What is normal pH?

A

7.40

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3
Q

What does a pH below 7.40 indicate?

A

Acidosis

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4
Q

What does a pH above 7.40 indicate?

A

Alkalosis

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5
Q

What is rule 2 in evaluating Acid Base Disorders?

A

Calculate the ion gap!

-If elevated, you need to explain it

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6
Q

What two things will include an anion gap?

A
  • Primary metabolic acidosis

- Mixed acid base problem (w/ ion gap)

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7
Q

What if pH is normal and you have an anion gap?

A

You have anion gap acidosis!!

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8
Q

What is rule 3 in evaluating Acid Base Disorders?

A

If there is an elevated anion gap, calculate the osmol gap

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9
Q

How do you calculate the osmol gap? What should it be?

A

Measured osmolarity - Calculated osms

–> Should be

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10
Q

How do you calculate osmolarity for the osmol gap?

A

2 (Na) + Glucose/18 + BUN/2.8 = calculated osms (usually 285 or so)

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11
Q

What is the normal anion gap?

A

About 12

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12
Q

In what clinical scenarios will you find osmol gaps?

A

Ingestions - like ethylene glycol, methanol, etc.

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13
Q

What is rule 4 in evaluating Acid Base Disorders?

A

Delta gap!!
Calculate the excess anion gap (calculated minus 12) and add to measured bicarb –> should equal normal bicarb level (24-26)

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14
Q

What if the delta gap is low?

A

There is also a non-anion gap acidosis.

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15
Q

What if the delta gap is high?

A

There is an underlying metabolic alkalosis

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16
Q

What other thing should you know about delta gap?

A

Normally, a change in gap of 1 will drop HCO3- by an equal amount –> if it doesn’t add up right, there is a second ongoing process

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17
Q

What is rule 5 in evaluating Acid Base Disorders?

A

Interpret using the clinical picture

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18
Q
  1. If ABG is normal, but you have an elevated ion gap. . .
A

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

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19
Q
  1. Mixed Metabolic Acidosis and Respiratory Alkalosis leads to. .
A

. . .PCO2 lower than predicted for the acidosis

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20
Q
  1. Mixed Metabolic Alkalosis and Respiratory Acidosis leads to . . .
A

. . .bicarb (HCO3-) higher than predicted for acidosis

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21
Q
  1. Mixed metabolic and respiratory alkalosis . . .
A

. . .get a higher HCO3- and lower PCO2 than predicted

22
Q

What is the primary disturbance in Metabolic Acidosis?

A

Retention of acid –> reflected by decrease of HCO3-

23
Q

What is the compensatory response in Metabolic Acidosis?

A

Increased ventilation and decreased PaCO2

24
Q

What are four mechanisms by which metabolic acidosis can be produced?

A
  1. Overproduction of acid
  2. Loss of alkali stores
  3. Failure of renal mech. to synthesize base
  4. Failure of renal mech. to excrete acid
25
Q

What do labs show with High Anion Gap Metabolic Acidosis?

A

pH

26
Q

What should you ALWAYS calculate with High Anion Gap Acidosis?

A

Osmol and delta gap!

27
Q

What does MUDPILES ddx stand for? What condition does it relate to?

A 
M - Methanol
U - Uremia
D - DKA/AKA
P - Paraldahyde
I - Iron or INH (Isoniazid - TB treatment)
L - Lactic acid
E - Ethylene Glycol (and ethanol)
S - Salicylates
28
Q

What does methanol cause?

A
  • Creates osm gap (methanols osm forces/3 = methanol level)

- See in alcoholics using other volatiles to get intoxicated

29
Q

What do you see in uremia?

A

High anion gap acidosis

-Generally over 5, BUN over 60, gap rarely over 20

30
Q

What do you see in DKA/AKA?

A

(diabetic or alcoholic ketoacidosis)

  • Acidosis is due to ketone production
  • Alcohol increase the osm gap
31
Q

What do you see in Lactic Acid High Anion gap Acidosis?

A

See with sepsis, hypotension, CO or cyanide poisoning, measure level

32
Q

What do you see with Ethylene Glycol (and ethanol)?

A
  • See ODs, antifreeze or windshield washer
  • Causes renal failure, oxalate urine crystals
  • Creates Osm gap, each mosm gap = 6mg% of ethylene glycol
  • Dialysis, alcohol or medical rx are treatments
33
Q

What do you see with Salicylates?

A

These can cause almost any acid base disorder (except metabolic acidosis)

  • Multiple presentations, can cause coagulopathy, seizures
  • Also tend to see a primary resp. alkalosis or acidosis with this
34
Q

What mechanism often causes Normal Anion Gap Acidosis (Hyperchloremic Metabolic Acidosis)?

A

Due to loss of HCO3- from kidney or GI is most common.

-See equal rise in Cl- for loss of HCO3-

35
Q

What lab values do you see in Normal Anion Gap Metabolic Acidosis?

A 
Low bicarb (HCO3-)
High Cl-
Low pH (acidosis)
36
Q

What clinical presentations are associated with Normal Anion Gap Metabolic Acidosis?

A

HARDUP

37
Q

What does HARDUP stand for?

A

H - Post hyperventilation, hyperalimentation
A - Acid ingestion (Carbonic Anhydrase Inhibitor, HCl)
R - RTA (renal tubular acidosis)
D - Diarrhea
U - Ureteral and ileal diversion
P - Pancreatic fistulas

38
Q

What is the primary disturbance in Metabolic Alkalosis?

A

Increased plasma bicarbonate (HCO3-)

39
Q

What is the compensatory mechanisms for Metabolic Alkalosis?

A

Hypoventilating (we have limited ability to do this!)

40
Q

What are Cl- responsive Metabolic Alkalosis?

A

Urine Cl-

41
Q

What is Cl- unresponsive Metabolic Alkalosis?

A

Due to high Aldo! –> causes inc. H+, K+ excretion –> inc. Na+, NaHCO3 reabsorption

42
Q

What conditions cause Cl- unresponsive Metabolic Alkalosis?

A
  • Cushings
  • Hyperaldo. including Barter’s
  • Secondary hyperaldo. (CHF, CRF)
  • Bicarb. ingestion
43
Q

What is the primary disturbance in respiratory acidosis?

A

Increase in arterial CO2

44
Q

What is the compensation for Respiratory Acidosis?

A

Elevating bicarb. by metabolic mechanisms

45
Q

What is acute and chronic compensation for respiratory Acidosis?

A 
Acute = HCO3- rises 1 mEq for each rise of 10 of pCO2
Chronic = HCO3- increases 3 for each rise of 10 of pCO2
46
Q

What do you see for lab values in respiratory acidosis?

A

High CO2
Low pH
High HCO3-

47
Q

What conditions cause respiratory acidosis?

A
  • Airway obstruction
  • Lung (COPD, Asthma, pneumothorax, infection, etc.)
  • CNS (Sedative/Hypnotics, drugs- heroin overdose, tremor)
  • Neuromuscular weakness (ALS, G-B syndrome)
48
Q

What is the primary disturbance in respiratory alkalosis?

A

Decrease in arterial CO2

49
Q

What is the compensation for respiratory alkalosis?

A

Decreasing HCO3-

50
Q

What is acute and chronic compensation for respiratory alkalosis?

A 
Acute = HCO3- falls by 2 mEq for each drop of 10 of pCO2
Chronic = HCO3- falls by 4 mEq for each drop of 10 of pCO2
51
Q

What conditions cause respiratory alkalosis?

A
  • Anxiety
  • Aspirin and other drugs; cocaine, progesterone
  • Any cause of tachypnea: sepsis, fever, PE, Pneumonia, hypoxia
  • Alcohol or narcotic withdrawal
  • Many others

CRRAB II Week 3 (10 decks)

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