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ICU > Acid Base > Flashcards

Acid Base Flashcards

1
Q

Normal HCO3? Normal pCO2?

A

24

40

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2
Q

Describe the pH change, primary change, and compensatory change in metabolic acidosis

A

pH: decrease

HCO3 decrease
pCO2 decrease

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3
Q

Describe the pH change, primary change, and compensatory change in respiratory acidosis

A

pH: decrease

pCO2: increase
HCO3: increase

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4
Q

Describe the pH change, primary change, and compensatory change in metabolic alkalosis

A

pH: increase

HCO3: increase
pCO2: increase

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5
Q

Describe the pH change, primary change, and compensatory change in respiratory alkalosis

A

pH: increase

pCO2: decrease
HCO3: decrease

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6
Q

When do you know you have a mixed acid base disorder?

A

HCO3 decrease + pCO2 increase

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7
Q

Steps when there is a primary metabolic acidosis?

A
  1. Gap or no gap?
  2. Respiratory compensation (Winter’s)

If gap:

  1. Delta/delta
  2. Osmolar gap

If no gap:
3. Urine anion gap

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8
Q

Anion gap = ?

A

Na - Cl - HCO3
Normal = 12

Correct for albumin:

For every 1 g below 4 g, the gap decreases by 2.5

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9
Q

Winter’s formula?

A

Expected pCO2 = 1.5(HCO3) + 8 +/- 2

Measured < expected - respiratory alkalosis

Measured > expected - respiratory acidosis

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10
Q

Delta/delta?

A

Assess for non-gap acidosis or metabolic alkalosis

Delta AG (actual - normal) - Delta HCO3 (normal - actual)

Normal = 0
Negative = non-gap acidosis
Positive = metabolic alkalosis
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11
Q

DDx - AG metabolic acidosis

A 
Glycols (ethylene, propylene)
Oxoproline (Tylenol)
L-lactic acidosis
   - A: shock
   - B: no shock
D-lactic acidosis (s/p bypass, presents w/neuro symptoms)

Methanol
Aspirin
Renal failure
Ketoacidosis

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12
Q

DDx - type B L-lactic acidosis

A

Increased lactate production (seizures, asthma, leukemia, lymphoma, propylene glycol toxicity)

Increased pyruvate production (epi, dobutamine, NRTIs)

Decreased lactate clearance (hepatic dysfunction, propofol infusion)

Unknown mechanism - metformin, linezolid, VPA OD

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13
Q

3 types of toxic alcohol ingestion + how to distinguish them?

A 
Ethylene glycol (antifreeze) -> oxalic acid -> urinary crystals + kidney injury
Methanol (moonshine, windshield wiper fluid) -> formic acid + vision loss
Isopropyl alcohol (rubbing alcohol) -> acetone -> CNS depression
  • All cause osmolar gap
  • EG + M cause increased AG
  • EG + M treated with fomepizole, ethanol, dialysis
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14
Q

Osm gap = ?

A

Measured - calculated gap

Calculated = 2Na + (Glu/18) + (BUN/28) + (EtOH/4.6)

Normal = 10-15

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15
Q

What happens in non-gap acidosis?

A

If the anion of the acid added to the plasma is Cl, AG will be normal.

Lower HCO3 is matched by an increase in Cl

If GI loss HCO3 - kidney retains NaCl

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16
Q

DDx - non-gap acidosis

A 
Renal (RTA, early renal insufficiency)
Acetazolamide, hyperAl (TPN)
GI (diarrhea, fistulas)
Endocrine (AI)
Saline (high volume resuscitation
17
Q

Purpose of checking urine anion gap?

A

GI vs. renal loss of HCO3

18
Q

Urine anion gap = ?

A

Na + K - Cl

Normal is 0 or slightly positive
Negative (-20 to -50) indicates GI loss

19
Q

Effects of acidemia?

A 
Increased CO
Decreased SVR
Coronary vasodilation
Increased MV (compensatory)
HyperK
Shifts O2-Hgb curve to left (gets rid of O2)
Decreased mental status
20
Q

Steps when there is a primary metabolic alkalosis?

A
  1. Check for respiratory compensation

2. Measure urine chloride

21
Q

DDx - metabolic alkalosis

A 
Volume contraction (vomiting, diuretics, dehydration)
NGT suction
Hypokalemia
Post-hypercapnia
Glucocorticoid excess
22
Q

Check for respiratory compensation in primary metabolic alkalosis?

A

CO2 should be >40 but <55

23
Q

DDx - urine chloride <20 vs. >20

A

<20: chloride responsive - vomiting, diuretics, dehydration, continuous NG suction

> 20: chloride unresponsive - pure hypokalemia, hyperaldosterone state

24
Q

Effects of alkalemia?

A 
Decreased coronary blood flow
Arrhythmias
Hypoventilation
Shifts O2-Hgb curve to left (holds onto O2)
Decreases cerebral blood flow
25
Q

Steps when there is a primary respiratory acidosis? Alkalosis?

A

Determine if acute or chronic

Acidosis:

  • Acute: for every 10 increase in pCO2, pH will decrease by 0.08 and bicarb will increase by 1
  • Chronic: for every 10 increase in pCO2, pH will decrease by 0.03 and bicarb will increase by 4

Alkalosis:

  • Acute: for every 10 decrease in pCO2, pH will increase by 0.08 and bicarb will decrease by 2
  • Chronic: for every 10 decrease in pCO2, pH will increase by 0.03 and bicarb will decrease by 5

If pH is lower than expected pH, there is an additional metabolic acidosis

If pH is higher than expected pH, metabolic alkalosis

26
Q

DDx - respiratory acidosis

A

Lung disease (expiratory flow limitation) - asthma, COPD
Depression of respiratory center (Drug OD, obesity hypoventilation)
Neuromuscular disorders

27
Q

DDx - respiratory alkalosis

A 
Sepsis
Hypoxia
Anxiety
Drugs (ASA OD, progesterone)
Pregnancy
Liver disease
Head injury

ICU (6 decks)

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