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Advanced Principles II > Vascular Surgery > Flashcards

Vascular Surgery Flashcards

1
Q

When does atherosclerosis become a significant health concern?

A

5th to 6th decade of life

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2
Q

What is thought to cause atherosclerosis?

A

Damage to the innermost layer of an artery , deposits lipids, cholesterol, platelets, cellular debris and decreases BF and oxygen delivery

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3
Q

What surgical procedures can treat atherosclerosis?

A 
Transluminal angioplasty
Endarterectomy
Thromnectomy
Endovascular stenting
Arterial bypass
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4
Q

What is the single most important factor in determining patient outcomes in patients with atherosclerosis?

A

Smoking

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5
Q

What three arteries branch off of the aortic arch?

A

Brachiocephalic
Left Common Carotid
Left Subclavian

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6
Q

What are the three layers of an artery?

A

Intima
Media
Adventitia

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7
Q

What is an aneurysm?

A

Dilation of all three layers of an artery that cause a decrease in diameter

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8
Q

When are most AAs found?

A

During diagnostic testing for other disorders

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9
Q

What symptoms are associated with a thoracic aortic aneurysms?

A

Hoarseness stretching RLN
Stridor compression of trachea
Dysphagia compression of esophagus
Dyspnea compression of the lungs

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10
Q

What is the law of leplace?

A 
T = P x r 
Tension = transmural pressure x radius
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11
Q

Why does increasing the size of the aneurysm increase the chance of rupture?

A

The vessel radius and wall tension are directly proportional so as the aneurysm increases in size so does the tension on the vessel wall

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12
Q

What is thought to be the reason why the incidence of AAA have increased over the last five decades?

A

Improved detection of asymptomatic aneurysms

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13
Q

What is thought to be the primary cause of AAA?

A

Atherosclerosis from proteolytic degradation of the extracellular matrix proteins elastin and collagen

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14
Q

What criteria place a patient at high risk for a AAA?

A 
Greater than 70 years old
Diabetes
Stroke
Renal disease
COPD/ emphysema/ dyspnea 
Hx MI, CHF, Angina
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15
Q

When is an open AAA indicated?

A

AAA greater than 5.5cm in diameter
Smaller AAA become symptomatic
AAA grows greater than 0.5cm in six months

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16
Q

What type of blood products should be available prior to AAA surgery?

A

4 units RBCs and have in the room prior to induction

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17
Q

What tool could be used as a sensitive indicator for cardiac function and ischemia?

A

TEE

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18
Q

When should a RSI be considered for a AAA procedure?

A

If the aneurysm is compressing abdominal contents up or if they have been bleeding into their abdomen

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19
Q

What type of fluid requirement do patients undergoing a AAA need?

A

High fluid requirements, due to large fluid shifts and high risk of bleeding
Do NOT over hydrate prior to cross clamping (avoid HTN)

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20
Q

When should heparin be given when bypass is indicated?

A

Prior to cross clamp

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21
Q

When should the ACT be checked after giving heparin?

A

Three minutes after heparin administration

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22
Q

What causes an increase in BP above the cross clamp?

A

Due to impedance of blood flow and systolic ventricular wall tension (after load)

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23
Q

Clamping in which location causes the largest increase in BP?

A

At or above the diaphragm, unless blood is shunted around the level of the clamp or vasodilators are used

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24
Q

What physiologic changes are seen above and below the level of the clamp on bypass?

A

HTN above the clamp

HoTN and ischemia below the clamp

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25
Q

Why hemodynamic changes occur when when the clamp is released?

A

Profound vasodilaton leading to HoTN, primarily due to reactive hyperemia and relative central hypovolemia

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26
Q

What drugs are used to vasodilate HTN above the clamp?

A

SNP

Nitroglycerine

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27
Q

What is the mechanism of action of SNP?

A

Non Selective
Releases cyanide and NO into the circulation, NO crosses the cellular membrane causing an increase in cGMP which inhibits Ca entry into the vascular smooth muscle

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28
Q

What is the mechanism of action of Nitroglycerine?

A

Acts on venous capacitance vessels and large coronary arteries
NO formed thought glutathione dependent pathway leading to vasodilation

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29
Q

What metabolic products are increased during an open AAA repair?

A 
Mixed venous O2 saturation
Epi and norepi
Lactic acid
Thromboxane A2
Cytokines/ inflammatory response
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30
Q

How are the kidneys affected by AAA repair?

A

Renal insufficiency and failure are not uncommon regardless of level of clamp

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31
Q

What is the most significant predictor of post op renal dysfunction in AAA repair?

A

Pre op renal function

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32
Q

What is the most effective renal protective mechanism in patients undergoing AAA repair?

A

Optimal systemic hemodynamics and maintenance of intravascular volume

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33
Q

What pharmacological interventions could potentially preserve renal blood flow in patients undergoing a AAA repair?

A

Mannitol
Dopamine
Statins

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34
Q

What factors determine the hemodynamic response to removal of cross clamp?

A

Level of clamp
Total clamp time
Use of diverting support
Intravascular volume

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35
Q

What should the provider do prior to removing the cross clamp in an open AAA procedure?

A

Assess and maximize intravascular volume
Reduce or discontinue vasodilators
Decrease volatile agent concentration (recall)

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36
Q

What agent should be given to combat heparin prior to emergence?

A

Protamine

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37
Q

What is the mechanism of action of Protamine?

A

Positively charged substance that neutralizes the negatively charged heparin

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38
Q

What can protamine cause pulmonary HTN?

A

Can cause release of thromboxane A2 and serotonin

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39
Q

What can be seen if protamine is given too quickly?

A

Histamine release causing facial flushing, tachycardia and HoTN

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40
Q

What population may develop an allergic reaction to protamine?

A

Allergic to fish or chronic exposure to NPH insulin

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41
Q

Why should the lower body be warmed during AAA?

A

May increase ischemic injury to tissues below the cross clamp due to increased metabolic demands

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42
Q

How are AAA repaired endovascularly?

A

A stent is placed in the aortic lumen with bilateral femoral arteries cannulated
Fluoroscopy used to position sheath at the site of the aneurysm

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43
Q

What type of anesthetic can be used for an EVAR?

A

Neuraxial anesthesia or GA

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44
Q

What size aneurysm is appropriate for EVAR?

A

Non ruptured aneurysm greater than 5cm but less than 24cm long

45
Q

What are hemodynamic advantages of an EVAR compared to a open AAA repair?

A

Less hemodynamic instability and blood loss

46
Q

What can occur with stent deployment in patients undergoing an EVAR?

A

HoTN and Bradycardia during deployment

47
Q

What should the provider always be prepared to do when taking care of a patient undergoing an EVAR?

A

Be prepared to convert to an open procedure

48
Q

What are the most common symptoms of a ruptured AAA?

A

Abdomina discomfort/back pain
Pulsatile abdominal mass
Decreased peripheral pulses
HoTN

49
Q

What are the primary goals of treatment of a ruptured AAA?

A

CV resuscitation and hemodynamic stability

50
Q

What is the greatest concern for a patient with a ruptured AAA?

A

Gaining control of the proximal aorta

51
Q

How many units of blood should be brought to the OR for a patient with a ruptured AAA?

A

10-12 units of O negative blood

52
Q

How should the provider induce a patient with a ruptured AAA?

A 
Minimal anesthesia (ketamine, vec and no gas) for induction, use Midaz liberally 
Place lines after the patient is asleep
53
Q

What drug should not be given to a ruptured AAA that would normally be given for repair cases?

A

Heparin, can induce DIC

54
Q

What is thought to be the reason that patients survive a ruptured AAA?

A

Tamponade of the bleeding, when opened will code almost immediately

55
Q

When does an aortic dissection occur?

A

With injury to the intima of the aorta, blood enters the media layer of the blood vessel via a tear in the intima

56
Q

What classification systems are used to describe aortic dissections?

A

Crawford and DeBakey

57
Q

What characteristics are used to classify an aortic aneurysm?

A

Size
Shape
Location

58
Q

What layers of the arterial wall are involved in an aneurysm?

A

A true aneurysm involves all three layers of the arterial wall

59
Q

What is considered a Crawford Type I aneurysm?

A

Descending thoracic and upper abdominal aorta

60
Q

What is considered a Crawford Type II aneurysm?

A

Descending thoracic and most of abdominal aorta

61
Q

What is considered a Crawford Type III aneurysm?

A

Lower thoracic and most of abdominal aorta

62
Q

What is considered a Crawford Type IV aneurysm?

A

Most of all of abdominal aorta

63
Q

What type of dissections are DeBakey I and II?

A

Proximal

64
Q

What percentage of dissections are DeBakey I?

A

60%

65
Q

What percentage of dissections are DeBakey II?

A

10-15%

66
Q

What type of dissection is a DeBakey III?

A

Distal

67
Q

What percentage of dissections are DeBakey III?

A

25-30%

68
Q

What drug can help reduce blood loss in an ascending aortic dissection?

A

Aprotinin (Amicar)

69
Q

What shout the ACT be with full heparinization?

A

Greater than 400

70
Q

What is a Bentall procedure?

A

Often involves aortic valve replacement/repair and coronary reimplantation with ascending aortic surgery

71
Q

What is done with a transverse aortic arch repair?

A 
Performed with mediansternotomy and CPB
Deep hypothermic (15degreesC) circulatory arrest
72
Q

What should the provider do for a transverse aortic arch repair?

A 
Pack head in ice
Maintain flat EEG
Methylprednisolone or dexamethasone 
Mannitol
Phenytoin
73
Q

Where does a descending thoracic aneurysm typically occur?

A

Occurs between left subclavian artery and aortic hiatus

74
Q

What type of ventilation is required for a descending thoracic aneurysm repair?

A

One-lung ventilation R DLT or Bronchial blocker

75
Q

Why should the provider place the arterial line of the right side with an aortic aneurysm repair?

A

Monitor blood flow to the innominate arteries and artery of adamkiewicz

76
Q

What is the most devastating complication for a descending thoracic aneurysm repair?

A

Paraplegia

77
Q

What are the components of intrinsic circulation to the spinal cord?

A

One anterior spinal artery (75% to 80% of blood flow, anterior cord)
Two posterior spinal arteries (20-25% blood flow, posterior cord)

78
Q

What are the components of extrinsic circulation to the spinal cord?

A

Radicular and medullary arteries

79
Q

What is another name for the great radicular artery or the arteria radicularis magna?

A

Artery of Adamkiewicz

80
Q

Where does the artery of Adamkiewicz enter circulation?

A

Enters intravertebral foramen in thoracolumbar region
• T9-T12 (75%)
• T5-T8 (15%)
• L1-L2 (10%)

81
Q

What is the importance of the artery of Adamkiewicz?

A

This artery is the main determinant of paraplegia because it provides most of the blood flow to the anterior spinal cords, or motor tracts of the spinal cord
Major source of blood flow to the lower 2/3 of the spinal cord

82
Q

What patient populations are at highest risk for spinal cord ischemia?

A 
Aortic dissection or rupture
Extensive aneurysm size
Prolonged aortic occlusion time
Patient age
CSF pressure
Perioperative hypotension
83
Q

What is the most important determinant of paraplegia and acute renal failure in aortic surgery?

A

Duration of aortic cross clamping

84
Q

What is considered a safe cross clamp time with almost no paraplegia?

A

20-30minutes

85
Q

What is considered the vulnerable time for paraplegia during cross clamping?

A

30-60 minutes of cross clamp time = 10-90% incidence of paraplegia, the likelihood of paraplegia increases with duration

86
Q

How does administering Intrathecal papaverine help in protecting the spinal cord from ischemia?

A
  • Dilates spinal arteries

* Oxygen free radical scavenger

87
Q

How do we determine spinal cord perfusion pressure?

A

Spinal cord perfusion pressure (SCPP) = Mean aortic pressure - CSF pressure

88
Q

What perfusion pressure are we concerned with causing paraplegia?

A

Distal perfusion pressure

89
Q

How is CSF pressure affected by cross clamping?

A

Normally, CSF pressure increases during cross clamp while arterial pressure decreases distal to the cross clamp.

90
Q

How can the perfusion pressure be manipulated during cross clamping?

A

Altering ABP and draining CSF through an intrathecal catheter

91
Q

What is the primary cause of carotid occlusive disease?

A

Atherosclerosis

92
Q

Where is the most common place to find carotid occlusive disease?

A

Carotid bifurcation

93
Q

What determines the degree of cerebral injury in patients with carotid occlusive disease?

A

Cerebral collateral flow due to the integrity of the Circle of Willis, duration of hypoperfusion, cerebrovascular vasoreactivity, plague morphology

94
Q

What are indications for a carotid endarterectomy?

A

TIA associated with ipsilateral severe carotid stenosis (>70%)
Severe ipsilateral stenosis with minor stroke
30-70% stenosis with ipsilateral symptoms
Asymptomatic but with significantly stenotic lesions
(>60%)

95
Q

What are the end effects of carotid artery occlusion?

A

Ischemia and ultimately loss of cerebral blood flow autoregulation

96
Q

Why is it important to have a fully awake patient at the end of a carotid endarterectomy?

A

To allow for comprehensive neurologic assessment

97
Q

What is a major benefit of regional anesthesia for awake endarterectomies?

A

Allows continuous assessment of an awake patient

98
Q

What dermatomes would need to be blocked for an awake endarterectomy?

A

Superficial and Deep cervical block C2-C4 dermatomes

99
Q

What are major disadvantages to using regional for an awake endarterectomy?

A

Inability to use pharmacologic tx for cerebral protection
Patient panic and loss of cooperation
Inadequate airway access
Phrenic nerve paralysis leading to potential for respiratory compromise
LA toxicity with high volumes of LA or intravascular
injection

100
Q

What are relative and absolute contraindications for regional anesthesia in patients undergoing an endarterectomy?

A 
Absolute:
– Patient refusal 
– Language barrier
Relative:
– Difficult anatomy
– Sever COPD or diaphragmatic dysfunction
101
Q

What is the most sensitive monitor of cerebral perfusion and ischemia during a CEA?

A

An awake patient

102
Q

What do carotid sum pressures measure?

A

Assess extent of collateral flow

103
Q

What does a carotid stump pressure less than 60mmHg suggest?

A

Hypoperfusion and need for shunt placement

104
Q

What is a good range to keep SBP when cross clamping is released?

A

SBP be kept 140-160mmHg to ensure adequate but not excessive cerebral perfusion

105
Q

What is a complication of CEA that can affect PaO2?

A

Blunted ventilatory response to hypoxemia by CAROTID CHEMORECEPTORS (primarily decreases in PaO2)*** - NOT CENTRAL

106
Q

What is post op cerebral hyper perfusion syndrome?

A

Increase in cerebral BF with loss of autoregulation in reperfused brain leading to a h/a, seizures, focal neurologic signs, edema and hemorrhage

107
Q

What population is at risk for cerebral hyper perfusion syndrome?

A

Patients with severe preop carotid stenosis and post-op HTN are at increased risk

108
Q

When are symptoms associated with cerebral hyper perfusion syndrome following a CEA typically seen?

A

Typically occurs several days following CEA

109
Q

What pathologies are known to cause respiratory compromise following a CEA?

A 
Hematoma
Bilateral RLN injury
Deficient Carotid Body function 
Vocal cord paralysis
Tension pneumo
Stroke or loss of consciousness

Advanced Principles II (8 decks)

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