acid-base Flashcards

1
Q

ABG: where is blood drawn from

A
  • usually radial artery
    • can be brachial or femoral
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2
Q

what parameters are measured in ABG

A
  • pO2
  • O2 saturation
  • pH
  • pCO2
  • HCO3
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3
Q

normal pO2

A

80-100 mmHg

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4
Q

normal O2 saturation

A

> 95%

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5
Q

normal pH

A

7.35-7.45

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6
Q

normal pCO2 values

A

35-45 mmHg

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7
Q

normal HCO3 levels

A

22-26 mmol/L

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8
Q

what two system can have a primary effect on arterial PaCO2 and cause abnormality in pH

A
  • central nervous system
  • respiratory system
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9
Q

hyperventilation can cause

A

respiratory alkalosis

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10
Q

hypoventilation can cause

A

respiratory acidosis

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11
Q

which compensation method causes a rapid change

A

respiratory compensation

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12
Q

full metabolic compensation for a respiratory process can take

A

3-5 days

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13
Q

is the body able to fully compensate for primary acid-base disorders?

A

No

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14
Q

if serum bicarbonate and arterial PCO2 move in opposite direction, what is going on?

A

mixed disorder

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15
Q

clinical presentation

  • hyperventilation
  • ventricular arrhythmia
  • altered mental status
  • ABG: low pH, low bicarb, low PaCO2
A
  • metabolic acidosis
  • caused by: addition of H+ ions to serum or loss of bicarbonate
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16
Q

how can you quickly determine what the PCO2 should be based on pH

A
  • PCO2 same as decimal point of pH
    • pH=7.25 would have PCO2 = 25
17
Q

how is anion gap calculated? What is the normal range?

A
  • AG= (Na + K) - (Cl) - (HCO3)
  • normal = 8-12
18
Q

What are the conditions that can cause a high anion gap (AG >12)

A

MUDPILES

  • methanol
  • uremia (renal failure)
  • DKA
  • propylene glycol; paraldehyde
  • iron/isoniazide
  • lactic acidosis
  • ethanol/ethylene glycol
  • salicylate/starvation
19
Q

treatment of metabolic acidosis

A
  • reverse underlying cause
  • bicarbonate therapy
20
Q

What ion values maintains metabolic alkalosis

A
  • hypokalemia
  • hypocholemia
21
Q

clinical presentation

  • lightheadedness, paresthesia
  • orthostasis
  • weakness
  • polydypsia
  • polyuria
  • ABG: high pH, high bicarb, high PaCO2
A

metabolic alkalosis

22
Q

vomiting, nasogastic suction, thiazide and loop diuretics can cause what

A
  • metabolic alkalosis
    • hypovolemic hypochloremic
23
Q

COPD, PE, myasthenia gravis, CNS dysfunction, and drug induced hypoventilation can cause

A

respiratory acidosis

24
Q

metabolic encephalopathy can cause

A

respiratory acidosis

25
Q

every 10mmHg increase in PaCO2 leads to what change in HCO3

A

1 mEq/L increase

26
Q

how can ABG help distinguish between acute and chronic respiratory acidosis

A
  • acute: bicarb minimally changed
  • chronic: high bicarb
27
Q

anxiety, liver failure, gram negative sepsis, salicylate poisoning, pregnancy, and high altitude can lead to

A

respiratory alkalosis

28
Q

clinical presentation

  • lightheadedness
  • palpitations
  • circumoral paresthesias, acroparesthesias, carpopedal spasm
  • tachypnea
A

respiratory alkalosis

29
Q

every 10mmHg drop in PaCO2 causes what change in HCO3-

A

2 mEq/L drop in HCO3-

30
Q

what can you expect to see in chronic respiratory alkalosis

A
  • high pH, low PaCO2, low bicarb
  • hyperchloremia
    • body’s way of maintaining normal fluid volume in setting of bicarb loss
  • increased anion gap
31
Q

excessive vomiting with severe dehydration can cause

A
  • mixed metabolic alkalosis and acidosis
    • hypochloremic alkalosis
    • lactic acidosis
32
Q

every 10 mmHg increase in PaCO2 has what effect on pH

A

pH drops 0.08

  • ex: PaCO2 increased from 40->70
  • 70-40 = 30: 3 (10) -> 3 x 0.08 = .24 -> 7.4-.24 = 7.16
33
Q

winters formula to calculate expected PCO2 compensation in metabolic acidosis

A

(1.5 x HCO3 + 8) +/- 2

34
Q

why is it important to differentiate between acute and chronic respiratory acidosis

A
  • acute: may require emergent intubation and mechanical ventilation
  • chronic: often clinically stable (e.g. COPD)
35
Q

mineralocorticoid excess: primary aldosteronism, cushing, increased renin can cause

A

metabolic alkalosis

36
Q

to help determine cause of metabolic acidosis, look at

A

anion gap

37
Q

if the anion gap is > or = 20, what does this indicate

A
  • that a primary metabolic acidosis is present, regardless of pH or bicarb level
38
Q

if anion gap is increased, what should you calculate? What is it used for?

A
  • excess anion gap
    • excess = total AG - normal AG (12)
  • add excess AG to measured HCO3
    • if the sum of the excess AG + measured HCO3 > a normal HCO3- then an underlying metabolic alkalosis is present, regardless of pH or measured bicarb