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KLowe Anesthesia Physiology 1: Respiratory > Lecture 9: One Lung Ventilation/Malignant Hyperthermia > Flashcards

Lecture 9: One Lung Ventilation/Malignant Hyperthermia Flashcards

1
Q

What is most often the position for thoracic surgery?

A

Lateral decubitus position

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2
Q

Dependent lung =

A

Lower lung

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3
Q

Nondependent lung =

A

Upper lung

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4
Q

___ of the upper lung provides access to the surgical field

A

Iatrogenic pneumothorax

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5
Q

Where is the axillary roll placed during thoracic surgery?

A

Placed on upper chest wall, NOT in the axilla

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6
Q

Why do you restrict IVFs to basic maintenance during thoracic surgery?

A

D/t risk of gravity dependent transudation of fluid to lower lung and edema of the collapsed lung

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7
Q

In the awake and lateral position, the ___ lung is better perfused (gravity) and ventilated

A

Dependent

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8
Q

With induction of anesthesia, there is a ___ in FRC, the upper lung ventilates ___, and there is a ___

A

Decrease in FRC, the upper lung ventilates more, V/Q mismatch

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9
Q

Positive pressure ventilation favors the ___ because it is more compliant

A

Upper lung

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10
Q

Muscle paralysis favors ventilation of the ___ due to abdominal contents pushing up more on the dependent hemidiaphragm

A

Upper lung

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11
Q

Open PTX of the upper lung ___ compliance, favoring ventilation of ___

A

Increases compliance, favoring ventilation of upper lung

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12
Q

The effect of anesthesia on lung compliance in the lateral decubitus position—the ___ lung assumes a more favorable position, while the ___ becomes less compliant

A

Upper lung, lower lung

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13
Q

Open pneumothorax—normal negative pleural pressure is ___, causing the lung to ___

A

Lost, causing the lung to recoil and collapse

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14
Q

Open pneumo is overcome by the use of ___ ventilation

A

Positive pressure

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15
Q

Intentional collapse of the ___ lung facilitates the thoracic procedure

A

Nondependent lunges

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16
Q

Upper lung during thoracic surgery is not ___ but is still ___ (although less than dependent lung); this causes a large ___ intrapulmonary shunt (20-30%)

A

Ventilated, but is still perfused; this causes a large right to left intrapulmonary shunt (20-30%)

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17
Q

Increased PA-a (alveolar to arterial) O2 gradient can lead to ___

A

Hypoxemia

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18
Q

Blood flow to the nonventilated/nondependent upper lung is ___ by HPV

A

Decreased by HPV—this improves the right to left shunt

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19
Q

What can also decrease blood flow to the upper lung?

A

Surgical compression, which improves the shunt

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20
Q

Factors that inhibit hypoxic pulmonary vasoconstriction (6):

A
  • Very high or very low pulmonary artery pressures
  • Hypocapnia***
  • High or very low mixed venous PO2
  • Vasodilators***
  • Pulmonary infections
  • Inhalation agents***
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21
Q

What vasodilators (4) inhibit hypoxic pulmonary vasoconstriction?

A
  • NTG
  • Nitroprusside (SNP)
  • B-adrenergic agonists (dobutamine)
  • Calcium channel blockers
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22
Q

What factors (5) decrease blood flow to dependent lung?

A
  • Worsens R to L shunt by sending more blood to the nondependent or collapsed lung
  • High mean airway pressures in ventilated lung from PEEP, hyperventilation, or increased PIP
  • Low FiO2 causes HPV in ventilated lung
  • Vasoconstrictors which may have a greater effect on norms ic vessels compared to hypoxic ones
  • Intrinsic PEEP which develops from inadequate expiratory times
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23
Q

CO2 elimination is usually ___ by one lung ventilation

A

NOT affected

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24
Q

CO2 elimination is not affected by one lung ventilation, provided what two things?

A

1) minute ventilation is unchanged

2) pre-existing CO2 retention was NOT present pre-op (COPD)

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25
Q

During one lung ventilation, tidal volumes are kept ___ as two lung ventilation

A

Roughly the same—around 10 cc/kg; may adjust d/t changes in PIP, RR altered to maintain normocapnia

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26
Q

FiO2 during one lung ventilation is usually kept ___

A

HIGH as a safety margin against hypoxia

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27
Q

What is apneic oxygenation?

A

Ventilation can be stopped for short periods, as long as O2 is supplied more than consumption (250-300 cc/min)

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28
Q

During apnea, PCO2 increases ___ for the first minute, and then ___ for each additional minute of apnea

A

5 mm Hg, then 3 mm Hg

Example: If PCO2 was 40, then after 10 minutes of apnea, the PCO2 will be 72

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29
Q

Progressive respiratory acidosis that occurs with apneic oxygenation limits the technique to ___ minutes

A

10-20 minutes

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30
Q

FiO2 of ___ to ___ during one lung ventilation

A

0.8 to 1.0

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31
Q

Tidal volumes during one lung ventilation

A

10 cc/kg

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32
Q

What is used to ensure proper ETT placement during one lung ventilation?

A

Fiber optic scope

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33
Q

One lung ventilation—adjust RR to keep PaCO2 at ___

A

40 mm Hg

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34
Q

Add ___ to nondependent lung—warn surgeon

A

5 cm H2O CPAP

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35
Q

Add ___ to dependent lung—treats __ but may increase ___

A

5 cm H2O PEEP, treats atelectasis but may increase vascular resistance

36
Q

Increase both CPAP and PEEP ___

A

Slowly

37
Q

Operability for pneumonectomy—clinical decision if patient can survive ___

A

Resection of one lung

38
Q

What is used to make the decision of operability for pneumonectomy?

A

PFTs

39
Q

Most common criterion for operability for pneumonectomy is a predicted post-op FEV1 of > ___

A

800 ccs

40
Q

Pre-op FEV1 for pneumonectomy should be > ___

A

2L

41
Q

High-risk patients for pneumonectomy—PaCO2 ___

A

> 45 mm Hg (on room air)

42
Q

High-risk patients for pneumonectomy—FEV1 ___

A

< 2 L

43
Q

High-risk patients for pneumonectomy—FEV1/FVC ___

A

< 50% of predicted

44
Q

High-risk patients for pneumonectomy—Maximum breathing capacity ___

A

< 50% of predicted

45
Q

Double lumen tubes come in ___ and ___ types

A

Left and right

46
Q

___ for most women

A

39 Fr

47
Q

___ for most men

A

41 Fr

48
Q

Double lumen ETT sizes

A

35, 37, 39, 41

49
Q

Bronchial lumen on double lumen ETT

A

Longer bronchial lumen with a blue cuff

50
Q

Tracheal lumen on double lumen ETT

A

Shorter tracheal lumen with a larger clear cuff

51
Q

Curve double lumen ETT at ___ to allow endobronchial placement

A

Tip

52
Q

Double lumen ETT allow for ___ and __ of each lung indepdently

A

Ventilating and suctioning

53
Q

Complications of double lumen ETT (4):

A
  • Traumatic laryngitis
  • Hypoxemia due to malpositioned tube
  • Bronchial trauma from over inflation of cuff
  • Inadvertent suturing of tube
54
Q

What is the most commonly used double lumen ETT?

A

Left double lumen tube—easier to place due to anatomic differences in the bronchi

55
Q

Bronchial lumen of left double lumen ETT is placed ___

A

Down left mainstem bronchus

56
Q

Symmetric cuff on left double lumen tube is inflated with ___ of air

A

1-2 ccs

57
Q

Tracheal lumen of left double lumen tube is located ___ and ventilates ___

A

Above the carina (with cuff up), ventilates the right lung

58
Q

More room to place left double lumen tube due to ___

A

Length of left mainstem

59
Q

Left double lumen ETT can be used for all thoracic cases except for ___

A

Surgery on left mainstem bronchus

60
Q

Right double lumen ETT is rarely used due to ___

A

Difficult placement

61
Q

Right double lumen ETT is indicated for ___

A

Left mainstem bronchus surgery

62
Q

Bronchial lumen of right double lumen tube is placed ___ and must align up with opening to the ___

A

To the right, must align up with the opening to the right upper lobe bronchus

63
Q

What kind of cuff is inflated on the right double lumen ETT?

A

An asymmetrical cuff with a slotted opening

64
Q

What blade gives better visualization for placement of double lumen ETT?

A

Mac blade

65
Q

Once you are past the cords, rotate tube ___ as you slowly advance, never forcing, until resistance is felt

A

90 degrees counter clockwise

66
Q

Average depth of double lumen tube is ___

A

29 cm at the teeth

67
Q

Inflate ___ cuff first

A

Tracheal; look for ETCO2, then inflate bronchial cuff gently, listen for breath sounds as each side is occluded

68
Q

Reconfirm position of double lumen tube with ___

A

Fiber optic scope

69
Q

MH triggers (top 2):

A
  • Depolarizing agent—succinylcholine

- Inhalational agents—halothane, isoflurane, sevoflurane, desflurane, enflurane

70
Q

First sign of MH/most sensitive =

A

Unexplained tachycardia

71
Q

Most specific sign of MH =

A

Increasing ETCO2

72
Q

ABG in MH—initial and then

A

Initially metabolic acidosis, then a combined metabolic and respiratory acidosis

73
Q

Treatment of MH

A

Dantrolene 2.5 mg/kg IV ASAP

74
Q

Max dose of dantrolene

A

10 mg/kg total

75
Q

In order to prevent recurrence of MH, continue dantrolene ___

A

1 mg/kg IV q6 hours for 72 hours

76
Q

What drug should not be given while on dantrolene and why?

A

Calcium channel blockers—d/t life-threatening hyperkalemia and myocardial depression that may occur

77
Q

How does dantrolene work?

A

It is a muscle relaxant that works directly on the ryanodine receptor to prevent the release of calcium

78
Q

Dantrolene directly interferes with muscle contraction by inhibiting ___

A

Ca release from the sarcoplasmic reticulum—intracellular dissociation of excitation-contraction coupling

79
Q

Side effects of dantrolene

A

Safe, may cause generalized muscle weakness which may lead to respiratory insufficiency or aspiration pneumonia; GI upset; thrombophlebitis

80
Q

Use dantrolene with extreme caution in what patient population?

A

Patients with pre-existing muscle disease—may cause significant muscle weakness

81
Q

Gold standard pre-op test for MH =

A

Muscle biopsy with halothane-caffeine contracture test—78% specific, 97% sensitive

82
Q

Halothane-caffeine contracture test—caffeine causes muscle to ___; halothane in the MH pt causes ___

A

Contract; more forceful contraction

83
Q

Prior uneventful general anesthetic does not rule out ___

A

The possibility of MH

84
Q

MH is more common in __

A

Children than adults

85
Q

Symptoms of MH usually develop within ___ after exposure to trigger substances

A

One hour; may even occur several hours later in rare instances

86
Q

MH does not occur with every exposure to ___

A

Triggering agents; susceptible patients may undergo multiple uneventful episodes of anesthesia before developing an episode of MH

87
Q

The only sure way to prevent MH is ___

A

Avoid the use of triggering agents in patients known or suspected of being susceptible to MH

KLowe Anesthesia Physiology 1: Respiratory (13 decks)

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