Clin Lab: ABGs (done) Flashcards

1
Q

What is ABG used for?

A

assess O2 status & acid/base balance

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2
Q

Where is the blood drawn from for ABG test?

A

radial artery

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3
Q

Absolute contraindications for ABG test.

A
  • poor blood flow to the hand (via Allen test)
  • known vascular dz in the extremity
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4
Q

Relative contraindications for ABG

A
  • bleeding disorder or on blood thinner
  • low platelet count
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5
Q

Procedure for ABG test

A
  • Allen test
  • Wrist positioning
  • Needle insertion (self fills)
  • 5 min pressure after removal
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6
Q

Measurement components of an ABG

A
  • PaO2
  • SaO2
  • pH
  • PCO2
  • HCO3
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7
Q

Normal PaO2

A

80-100 mmHg
(some say 75-100)

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8
Q

Normal SaO2

A

94-100%

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9
Q

Normal pH

A

7.35 - 7.45

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10
Q

Normal PaCO2

A

35 - 45

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11
Q

Normal HCO3-

A

22 - 26

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12
Q

Acid-Base problems occur when there is…

A

too much or too little acid in relation to base

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13
Q

What happens once pH has large shifts?

A
  • proteins start to change shapes
  • enzymes start to denature
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14
Q

What two components of an ABG are important, but not part of acid/base balance?

A

PaO2 & SaO2

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15
Q

3 main regulators of pH

A
  1. Buffer Systems - primary
    2A. Lungs
    2B. Kidneys
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16
Q

What is the main driver of the principle buffer system?

A

bicarbonate

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17
Q

What are the other parts of the principle buffer system?

A
  • hemoglobin
  • phosphate
  • proteins
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18
Q

Role of hemoglobin.

A
  • can absorb or release acids
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19
Q

Role of phosphate

A
  • holding on or giving off H+
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20
Q

What info does the Henderson Hesslebach equation give us?

A

what the expected pH is going to be. (7.40)

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21
Q

What is the ratio for bicarbonate & carbonic acid?

A

20:1

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22
Q

Principles of acid/base regulation. Normal status (equation)

A

H+ + HCO3- <–> H2CO3 <-CA-> CO2 + H20

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23
Q

What is pKa?

A

acid dissociation constant specific to each acid

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24
Q

What is the biggest determiner of pH in our body?

A

bicarbonate balance

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25
Q

If HCO3- goes up to 40, what would the H2CO3 be?

A

2

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26
Q

If the HCO3- goes down to 10, what would the H2CO3 be?

A

.5

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27
Q

If buffer systems are not sufficient, what two system respond?

A

Lungs & kidneys

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28
Q

What short term fix kicks in if the buffer system isn’t sufficient?

A

the lungs

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29
Q

How do the lungs combat acid/base imbalances?

A

change levels of CO2 by increasing/decreasing rate of resp

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30
Q

What does increasing resp rate do to the acid/base balance?

A
  • more CO2 exhaled = decr CO2 in blood
  • Equilibrium shifts to right, reducing H+
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31
Q

What does decreasing resp rate do to the acid/base balance?

A
  • less CO2 exhaled = inc CO2 in the blood

Equilibrium shifts to left, increasing H+

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32
Q

How long does it take the lungs to respond to acid/base imbalance?

A

minutes

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33
Q

How do the kidneys participate in acid/base regulation?

A

regulate HCO3-

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34
Q

What do the kidneys do if pH is acidic?

A

reabsorb more HCO3- and excrete more H+

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35
Q

What do the kidneys do if the pH is alkaline?

A
  • excrete more HCO3- & reabsorb more H+
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36
Q

How long does it take the kidneys to respond to acid/base imbalance?

A

3-5 days

37
Q

If pH is too acidic, what do the kidneys do?

A

excrete H+ & reabsorb bicarb

38
Q

If pH is too basic, what do the kidneys do?

A

excrete bicarb & reabsorb H+

39
Q

What two possible main issues to cause acidosis?

A
  • resp acidosis
  • metabolic acidosis
40
Q

What is the cause to result in resp acidosis?

A
  • rate of ventilation of CO2 is decr (lungs aren’t working)
41
Q

What is the cause to result in metabolic acidosis?

A
  • ^ production of acid
  • ^ loss of bicarb
42
Q

What two possible main issues to cause alkalosis?

A
  • resp alkalosis
  • metabolic alkalosis
43
Q

What is the cause to result in resp alkalosis?

A
  • rate of ventilation ^^
44
Q

What is the cause to result in metabolic alkalosis?

A
  • ^^ bicarb
  • ^^ loss of acid
45
Q

A person who only has one type of acid-base disorder is considered…

A

simple

46
Q

What is it called when a pt. has more than one acid-base disorder at a time?

A

mixed

47
Q

Can you have 4 acid-base disorders?

A

NO

48
Q

Can you have resp acidosis & resp alkalosis?

A

NO

49
Q

Can you have resp acidosis, metabolic acidosis, & metabolic alkalosis at the same time?

A

YES

50
Q

Describe pCO2 & pH in Resp acidosis

A

^ pCO2 & v pH

51
Q

What can cause Resp acidosis? (w/examples)

A
  • decreased ventilation
    (obstruction, pneumo, pleural effusion, emphysema, COPD, stroke)
  • decreased perfusion
    (PE, cardiac arrest)

NM condition

52
Q

S/S of resp acidosis

A
  • HA
  • Tachycardia
  • CNS depression
  • Cardiac arrhythmia
  • Obtunded
53
Q

Therapy for resp acidosis?

A
  • CPAP, BiPAP
  • pneumonectomy
54
Q

Acute (no compensation) presents as…

A
  • CNS depression - drug OD, acute stroke
  • Acute airway obstruction
  • Severe pneumonia & pulm edema
55
Q

Chronic (compensation) presents as…

A
  • chronic lung disease
  • chronic NM disorder
  • chronic resp center depression
  • obesity
56
Q

Describe pCO2 & pH in resp alkalosis.

A

v pCO2 & ^ pH

57
Q

Causes of resp alkalosis (w/ examples)

A
  • hyperventilation
    (anxiety, stress, fear, CNS disease, drug uses, pregnancy, sepsis, liver dz, hypoxemia, low O2
58
Q

S/S of resp alkalosis

A
  • Lightheadedness
  • CNS irritability
  • Cardiac arrhythmias
59
Q

Therapy for resp Alkalosis

A
  • anti-anxiety meds
  • O2 if b/c of hypoxia
  • CO2 rebreathing
60
Q

Describe an aspirin OD

A

leads to hyperventilation early on–> resp alkalosis
aspirin continues to absorb –> leads to metabolic acidosis

61
Q

How does sepsis cause resp alkalosis?

A

usually from fever
fever will incr resp rate, & lead to akalosis

62
Q

Describe HCO3 & pH for Metabolic acidosis

A

v HCO3 & v pH

63
Q

Causes of Metabolic acidosis

A
  1. acid production (poisoning, abnormal metabolism, shock/low perfusion)
  2. loss of base (diarrhea, pancreatic fistula)
64
Q

S/S of metabolic acidosis
(HAC)

A
  • HA
  • CNS depression
  • altered mental status
65
Q

Therapy for Metabolic acidosis

A
  • correct underlysing causes
  • improve tissue oxygenation (lactic acid)
  • consider giving NaHCO3 if pH < 7
66
Q

Major cations in the blood?

A

Na+ & K+

67
Q

Major anions in blood

A

Cl-, HCO3-, phosphate (PO4-)

68
Q

Define an anion gap.

A

the difference b/t measured anions & measured cations

69
Q

Normal anion gap range

A

8 - 16

70
Q

In anion gap: there will always be more ___ things than ___ things.

A

positive; negative

71
Q

What causes a decreased anion gap & should we be worried?

A

-hypoalbuminemia or incr in unmeasured cation
NO

72
Q

Which type of anion gap are we most worried about? & what causes it?

A

increased gap =
retention of 1 or more unmeasured anions (weak base from acid accumulation)

Take home message–> incr gap = too much acid

73
Q

Which type of acid/base disorder deals w/ anion gaps?

A

metabolic acidosis

74
Q

Reasons for high anion gap metabolic acidosis (MUDPILES)

A
  • methanol/metformin
  • Uremia (high BUN)
  • DM ketoacidosis
  • Paraldehyde/phenformin
  • Iron/Isoniazid
  • Lactate
  • Ethylene glycol (antifreeze)
  • Salicylates (aspirin)
75
Q

HAGMA anion gap value

A

> 20

76
Q

Go study slide 30 in ABG lecture

A

Okay

77
Q

Acronym for reasons of high anion gap metabolic acidosis

A
  • M - Methanol/metformin
  • U - Uremia (high BUN)
  • D - Diabetic ketoacidosis
  • P - Paraldehyde/phenformin
  • I - Iron/Isoniazid
  • L - Lactate
  • E - Ethylene glycol (antifreeze)
  • S - Salicylates (aspirin)
78
Q

Describe HCO3- & pH for metabolic alkalosis.

A
  • ^ HCO3- & ^ pH
79
Q

Causes for metabolic alkalosis

A
  1. base accumulation (excessive antacids, blood transfusion)
  2. loss of acid (vomiting, gastric suction (NG tube), diuretic use
80
Q

S/S of metabolic alkalosis

A
  • CNS irritability
  • eventual CNA depression
81
Q

Therapy for Metabolic alkalosis

A
  • revere underlying causes (antacids, low Cl-, low K+, vomiting)
  • almost NEVER give HCl
82
Q

Which acid-base disorder has to do w/ the release of aldosterone?

A

metabolic alkalosis

83
Q

Describe Chloride responsive

A

Low Urine Cl- Level
- vomiting, nasogastric suction
- laxative abuse
- diuretic use

CAN FIX W/ FLUIDS (NaCl)
except w/ diuretic induced alkalosis has a result of CHF

84
Q

Describe chloride resistant

A

(something rare)
Normal or High Urine Cl- Level
- excess mineralocorticoid activity (Cushing’s syndrome, Conn’s syndrome, exogenous steriods, licorice ingestion, incr renin states)
- excess alkali admin

85
Q

Is normal or high Urine Cl- levels responsive or unresponsive

A

unresponsive: tx underlying cause

86
Q

Describe uncompensated.

A

pH is off
PCO2 or HCO3- is off & one is WNL

87
Q

Describe partially compensated.

A

pH, PCO2 & HCO3 are off

88
Q

Describe fully compensated.

A

PCO2 & HCO3 are off
pH is NORMAL