Aortic Surgery- Exam 2 Flashcards
1
Q
What is the goal of aortic surgery?
A
Enable aortic repair while limiting ischemic injury to the CNS
2
Q
We utilize different perfusion strategies depending on what?
A
What portion of the aorta is affected
3
Q
What are the 4 portions of the aorta?
A
Ascending
Arch
Thoracic
Descending
4
Q
What are the two different types of aortic conditions?
A
Aneurysms
Dissections
5
Q
Ascending Aorta
A
Begins at the AV annulus and extends to the proximal innominate artery
6
Q
Transverse Arch
A
Where 3 brachiocephalic branches arise
7
Q
How does the treatment for ascending and transverse arch compare?
A
Very similar
8
Q
Descending Thoracic and Thoracoabdominal Aorta
A
Lies just beyond the subclavian to the aortoiliac bifurcation
9
Q
Dissection
A
Occurs when blood penetrates the intima of the aorta; creates an expanding hematoma between medial layers; true lumen is not usually dilated/compressed by dissection
10
Q
Are the branching vessels affected in a dissection?
A
May not be
11
Q
Aneurysm
A
Dilation of all 3 layers
12
Q
Incidence of Aortic Dissections
A
According to European Autopsy Study
Occurs in 3.2 dissections per 100,000 autopsies
13
Q
What occurs in more deaths: Aortic Dissection or Aneurysm rupture?
A
Aortic dissection
14
Q
Aortic Dissection risk factors
A
Hypertension (90% pts), advanced age (>60), male sex, Marfan’s Syndrome, Coarctation, bicuspid AV, pregnancy, toxins and diet
15
Q
Marfan’s Disease
A
Connective Tissue disorder
16
Q
Aortic Dissection Causes (Inciting Events)
A
Increased Physical Activity
Emotional Stress
Blunt Trauma
Can occur w/o any physical activity (i.e. cannulation for bypass)
17
Q
Aortic Dissection Mechanism
A
Intimal Tear; presence of a weakened aortic wall; areas experiencing greatest mechanism shear forces, points where the aorta is fixed, there is increased shear stress applied to the aortic wall
18
Q
What percent has intimal tear in ascending aorta?
A
61%
19
Q
What percent has intimal tear in descending aorta?
A
24%
20
Q
What percent has intimal tear in descending aorta; isthmus (distal to left subclavian)
A
16%
21
Q
What percent has intimal tear in arch?
A
9%
22
Q
What percent has intimal tear in abdominal?
A
3%
23
Q
What percent has intimal tear in other areas?
A
1%
24
Q
How fast does propagation occur?
A
Within seconds
25
What is propagation driven by?
Pulse pressure and ejection velocity
26
What may be involved in aortic dissections?
Origins of arteries; vessel occlusions can also occur due to compression by the false lumen
27
DeBakey Classification
3 types based upon location of intimal tear and which section of the aorta is involved; Type 1, 2, 3A, 3B
28
Debakey Classification: Type 1
Intimal Tear: Ascending Aorta
| Dissection: All parts of the thoracic Aorta (ascending, arch, and descending)
29
DeBakey Classification: Type 2
Intimal Tear : Ascending Aorta
Dissection: Ascending Aorta only
stops before innominate artery
30
DeBakey classificaiton: Type 3A
Intimal Tear: Descending Aorta
| Dissection: Descending Thoracic only distal to left subclavian, ends above diaphragm
31
DeBakey Classficiation: Type 3 B
Intimal Tear: Descending Aorta
| Dissection: below diaphragm
32
Whats the "easier" classification system?
Stanford (Daily) Classficiation; Type A and Type B
33
Stanford (Daily) Classification: Type A
Ascending Aorta
Any involvement regardless of where tear is
regardless of how far it propagates; usually emergent/urgent cases more virulent course
34
Stanford (Daily) Classification: Type B
Distal Aorta
| Any part of aorta distal to left subclavian
35
Prognosis for untreated ascending dissection
Dismal
2 day mortality- 50%
3 month mortality- 90%
36
What is the usual cause of death in aortic dissection?
Rupture of the false lumen into the pleural space or percardium
37
Lower incidence of death in what types of patients...
Debakey Type III
| Stanford B
38
Other causes of death
Progressive heart failure (AV involvement)
MI (Coronary involvement)
Stroke (Occlusion of cerebral vessels)
Bowel Gangrene (Mesenteric artery occlusion)
39
Surgical Mortality of Aortic Dissections
3-24%
Depends on affected section of aorta
Aortic arch- highest mortality
Descending Thoracic- lowest mortality
40
What is the incidence of Thoracic Aneurysms? What percent of hwat types?
```
European studies show 460/100,000 thoracic aneurysms
45% involved ascending aorta
10% involved arch
35% involved descending aorta
10% thoracoabdominal
```
41
Aneurysms Classification by shape
Fusiform
| Saccular
42
Fusiform
entire circumference of the aortic wall
43
Saccular
Involves only part of the circumference of the aortic wall
44
Arch aneurysms are typically what shape?
saccular
45
What type of classification is used to classify thoracoabdominal aortic anuerysms?
Crawford Classification
46
Crawford Classificiation
used to describe the extent of aorta requiring replacement
| Crawford Extents I-IV
47
Crawford Classificiation: Extent 1
involves most or all of the descending thoracic aorta and upper abdominal aorta
48
Crawford Classification: Extent 2
Involves most or all of descending thoracic aorta and extends into infrarenal abdominal aorta
49
Crawford Classification: Extent 3
Involves the distal 1/2 or less of descending thoracic aorta and varying portion of abdominal aorta
50
Crawford Classification: Extend 4
involves most of all abdominal aorta
51
Aneurysms: Natural Hx
Progessive dilation
52
What fraction of aortic aneurysms rupture?
more than 1/2
53
What is the untreated 5 year survival of the thoracoabdominal aortic aneurysm?
13-39%
54
What are other complications of aneurysms?
Mycotic infection
Atheroembolisation
Dissection (Rare)
55
What are some predictors of poor prognosis in aneurysm patients?
Larger size (less than 10 cm max transverse diameter)
Presence of other symptoms
Associated CV disease (CAD, MI, CVA)
56
When do the majoriy of thoracic artery tears occur?
After a trauma; involve a deceleration injury (MVA)
57
MVA
desceleration injury; large shear stress on points of aortic wall that are relatively immobile
58
What does thoracic artery tear lead to?
Immediate exsanguination and death
| 10-15 % are lucky and make it to the hospital (maintain integrity of the adventitial covering of the aortic lumen)
59
Where do most thoracic artery ruptures occur?
Most occur distal to the origin of the left subclavian artery; due to fixation at the point of the ligamentum arteriosum
60
What is the 2nd most common site of a thoracic artery rupture
ascending aorta just distal to the aortic valve
61
Aortic Dissection diagnosis
dramatic onset
62
Aneurysm Diagnosis
asymptomatic until late in course
| medical evaluation for unrelated problem or complication of aneurysm
63
Trauma Rupture Diagnosis
if they surivve trauma
| s/s similar to descending aortic aneurysm
64
Indications for Surgery: Ascending Aorta Dissection
Acute Type A
Virulent course
high mortality
65
Indications for Surgery: Ascending Aorta Aneurysm
```
Persistent pain despite small aneurysm
AV involvement creating MI
angina
rapidly expanding
greater than 5- 5.5 cm diameter
```
66
Indications for Surgery: Aortic Arch Dissection
acute, limited to arch (rare)
67
Indications for Surgery: Aortic Arch Anuerysm
repiar of arch aneurysm is more complicated
carries increased morbidity and mortality
persistent symptoms
greater than 5.5-6 cm
progressive expansion
68
Indications for Surgery: Descending Aorta Dissection
```
Medical management in acute phase
failure to control hypertension medically
continued pain
enlargement on CSR, CT, Angio
Neurologic Deficit
Renal/ GI ischemia
```
69
Indications for Surgery: Descending Aorta Aneurysm
Greater than 5-6 cm
Expanding
Leaking
Chronic, causing persistent pain
70
Perfusion: Aortic Surgery Considerations
```
Where is the aneurysm located?
Where do we need to cannulate?
Do we need to circ arrest?
Median sternotomy vs. Thoracotomy
Full CPB or Left heart bypass?
```
71
Very proximal aneurysms limited to what regions?
Aortic root or ascending aorta
72
CPB w/o Circ Arrest Cannulation
Ascending aorta or transverse aorta, and dual stage in RA or Bicaval
73
Where is the XC in CPB w/o circ arrest
proximal to the innominate artery
74
If patient is unstable prior to sternotomy, where do you cannulate?
Femoral to go on CPB prior to sternotomy
75
CPB w/o Circ arrest LV/PA Vent adn CPG
Normal LV/PA vent
| Normal cpg
76
DHCA
bloodless field
| uncluttered by clamps and cannulas
77
Does DHCA abate cerebral metabolic demands?
doesn't necessarily abate cerebral metabolic demands; significant cerebral metabolic activity occurs at temperatures at which DHCA is initiated; promotes brain ischemia; accumulation of metabolic wastes
78
When did RCP gain popularity?
90s
79
When was RCP first done? By who?
1980 by Milles and Oschner; treating massive air embolism
80
When was RCP used as neuroprotection?
1990
81
What are the benefits of RCP?
Homogeneous cerebral cooling
air bubble wash out
wash out of embolic debris
wash out of metabolic wastes
prevent cerebral blood cell micro aggregation
Delivery of oxygen and nutrients to the brain
82
ACP
older tehcnique
| maintained pre-DHCA jugular venous sats and cerebral oxygen extraction
83
Circ Arrest: Monitor Temps
Nasopharyngeal/Bladder
Arterial
Venous
Water
84
Circ Arrest: Monitor Brain
EEG- brain activity
| Electrocerebral silence dictates adequate cerebral cooling
85
Circ Arrest: Drugs
Mannitol (25g) and steroids
enhances cerebral protection
put in the pump prior to turning off the pump
86
Circ Arrest: Cannulation
Axillary Cannulation is preferred
artery is usually exposed prior to sternotomy
after heparin is given- 8mm graft is sewn to the artery
cannula is placed in the 8mm graft
87
Circ Arrest: Cannulation in an emergency
femoral artery is used; if its a dissection, make usre that the cannula is in the true lumen; venous cannula- RA, bicaval, femoral depends on need and access
88
Circ Arrest case: Cooling
10 degree C drop in temperature- reduces rate of oxygen consumption by 50%; as temperature decreases metabolic demand decreases; pump flows can be reduced to a CI of 1.6-1.8 L/min/m2
89
A 10 degree C decrease in temperature causes what percent increase in blood viscosity?
20-25%
90
Circ Arrest: Hemodilution to a hematocrit less than what percent?
25%
91
When doing a circ arrest case, how long do you keep cooling?
Keep cooling until EEG shows no cerebral electrical activity
Usually takes about 20-25 minutes
brain temp 18-20C
cool no lower than 15 C
92
When not using an EEG, cool for how long?
At least 25 minutes to a target core temp of 18-20 C
93
At EEG silence, give what drug?
Pentobarbital
| Circulate for 3 minutes
94
What position is a patient put in during a circ arrest case?
Trendelenburg position
95
Why would the head be packed in ice in a circ arrest case?
Facilitate Surface cooling
96
ACP is at how many ml/kg/min?
10 ml/kg/min
97
When the aorta is opened, you could get bleed back from what?
L Common Carotid and L Subclavian obscure field view; cardiotomy suction in distal arch; possible use of balloon occluder in both vessels
98
Circ Arrest Case: End of gRaft is sewn where?
Sewn to proximal descending thoracic aorta, transverse arch or distal ascending aorta; attach head vessels (island, branched graft)
99
Off pump: Want systolic BP of what?
100-120 mmHg
100
Off pump: MAP
70-90 mmHg
101
Off pump: HR
60-80 BPM
102
Off pump: CI
2.0-2.5 L/min/m2
103
Complications of Aortic Surgery and DHCA
```
Air Emboli
clots
LV dysfunction
MI (reimplanting coronaries)
renal failure
respiratory failure
coagulopathy
hemorrhage
```
104
Other procedures of Aortic Conditions
Endovascular REpair
| Left Heart Bypass
105
When was an endovascular repair 1st done?
1991 on abdominal aortic aneurysm
106
TEVAR
Thoracic Endovascular aortic repiar
107
Endovascular Repair required proximal "landing zone" of what lenght?
15mm
108
TEVAR Con
Side branches- possibility of occluding a vessel that branches off the aorta
109
TEVAR Considerations
Aortic Tortuosity, calcification, atherosclerosis
110
TEVAR Advantages
```
reduces mortality
reduces morbidity
less blood loss
quicker recovery
hemodynamic stability
pulmonary and cardiac comorbidities that may have not made them a candidate for open surgeries, allow them to have this option
```
111
TEVAR Complications
Conversion to open procedure (aortic rupture/dissection, malposition causing visceral ischemia)
bleeding
endoleak (blood flows back into the aneurysmal sac after the endovascular graft is placed; usually observe and hope it spontaneously resolves)
stroke
paraplegia
contrast nephropathy
112
Left Heart Bypass
shunt around the aneurysm/dissection; used on descending legions
113
Left Heart Bypass: ECC
```
tubling
centrifugal pump
noreservoir
n H/E
no bubble trap
exclusing those help minimize the heparinization required
```
114
Who gives volume in left heart bypass?
Anesthesia
115
What does connective tissue do?
Provides strength and support to tendons, ligaments, cartilage, blood vessel walls and heart valves
