Flashcards in Aortic Surgery- Exam 2 Deck (115):
What is the goal of aortic surgery?
Enable aortic repair while limiting ischemic injury to the CNS
We utilize different perfusion strategies depending on what?
What portion of the aorta is affected
What are the 4 portions of the aorta?
What are the two different types of aortic conditions?
Begins at the AV annulus and extends to the proximal innominate artery
Where 3 brachiocephalic branches arise
How does the treatment for ascending and transverse arch compare?
Descending Thoracic and Thoracoabdominal Aorta
Lies just beyond the subclavian to the aortoiliac bifurcation
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
Are the branching vessels affected in a dissection?
May not be
Dilation of all 3 layers
Incidence of Aortic Dissections
According to European Autopsy Study
Occurs in 3.2 dissections per 100,000 autopsies
What occurs in more deaths: Aortic Dissection or Aneurysm rupture?
Aortic Dissection risk factors
Hypertension (90% pts), advanced age (>60), male sex, Marfan's Syndrome, Coarctation, bicuspid AV, pregnancy, toxins and diet
Connective Tissue disorder
Aortic Dissection Causes (Inciting Events)
Increased Physical Activity
Can occur w/o any physical activity (i.e. cannulation for bypass)
Aortic Dissection Mechanism
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
What percent has intimal tear in ascending aorta?
What percent has intimal tear in descending aorta?
What percent has intimal tear in descending aorta; isthmus (distal to left subclavian)
What percent has intimal tear in arch?
What percent has intimal tear in abdominal?
What percent has intimal tear in other areas?
How fast does propagation occur?
What is propagation driven by?
Pulse pressure and ejection velocity
What may be involved in aortic dissections?
Origins of arteries; vessel occlusions can also occur due to compression by the false lumen
3 types based upon location of intimal tear and which section of the aorta is involved; Type 1, 2, 3A, 3B
Debakey Classification: Type 1
Intimal Tear: Ascending Aorta
Dissection: All parts of the thoracic Aorta (ascending, arch, and descending)
DeBakey Classification: Type 2
Intimal Tear : Ascending Aorta
Dissection: Ascending Aorta only
stops before innominate artery
DeBakey classificaiton: Type 3A
Intimal Tear: Descending Aorta
Dissection: Descending Thoracic only distal to left subclavian, ends above diaphragm
DeBakey Classficiation: Type 3 B
Intimal Tear: Descending Aorta
Dissection: below diaphragm
Whats the "easier" classification system?
Stanford (Daily) Classficiation; Type A and Type B
Stanford (Daily) Classification: Type A
Any involvement regardless of where tear is
regardless of how far it propagates; usually emergent/urgent cases more virulent course
Stanford (Daily) Classification: Type B
Any part of aorta distal to left subclavian
Prognosis for untreated ascending dissection
2 day mortality- 50%
3 month mortality- 90%
What is the usual cause of death in aortic dissection?
Rupture of the false lumen into the pleural space or percardium
Lower incidence of death in what types of patients...
Debakey Type III
Other causes of death
Progressive heart failure (AV involvement)
MI (Coronary involvement)
Stroke (Occlusion of cerebral vessels)
Bowel Gangrene (Mesenteric artery occlusion)
Surgical Mortality of Aortic Dissections
Depends on affected section of aorta
Aortic arch- highest mortality
Descending Thoracic- lowest mortality
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
Aneurysms Classification by shape
entire circumference of the aortic wall
Involves only part of the circumference of the aortic wall
Arch aneurysms are typically what shape?
What type of classification is used to classify thoracoabdominal aortic anuerysms?
used to describe the extent of aorta requiring replacement
Crawford Extents I-IV
Crawford Classificiation: Extent 1
involves most or all of the descending thoracic aorta and upper abdominal aorta
Crawford Classification: Extent 2
Involves most or all of descending thoracic aorta and extends into infrarenal abdominal aorta
Crawford Classification: Extent 3
Involves the distal 1/2 or less of descending thoracic aorta and varying portion of abdominal aorta
Crawford Classification: Extend 4
involves most of all abdominal aorta
Aneurysms: Natural Hx
What fraction of aortic aneurysms rupture?
more than 1/2
What is the untreated 5 year survival of the thoracoabdominal aortic aneurysm?
What are other complications of aneurysms?
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)
When do the majoriy of thoracic artery tears occur?
After a trauma; involve a deceleration injury (MVA)
desceleration injury; large shear stress on points of aortic wall that are relatively immobile
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)
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
What is the 2nd most common site of a thoracic artery rupture
ascending aorta just distal to the aortic valve
Aortic Dissection diagnosis
asymptomatic until late in course
medical evaluation for unrelated problem or complication of aneurysm
Trauma Rupture Diagnosis
if they surivve trauma
s/s similar to descending aortic aneurysm
Indications for Surgery: Ascending Aorta Dissection
Acute Type A
Indications for Surgery: Ascending Aorta Aneurysm
Persistent pain despite small aneurysm
AV involvement creating MI
greater than 5- 5.5 cm diameter
Indications for Surgery: Aortic Arch Dissection
acute, limited to arch (rare)
Indications for Surgery: Aortic Arch Anuerysm
repiar of arch aneurysm is more complicated
carries increased morbidity and mortality
greater than 5.5-6 cm
Indications for Surgery: Descending Aorta Dissection
Medical management in acute phase
failure to control hypertension medically
enlargement on CSR, CT, Angio
Renal/ GI ischemia
Indications for Surgery: Descending Aorta Aneurysm
Greater than 5-6 cm
Chronic, causing persistent pain
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?
Very proximal aneurysms limited to what regions?
Aortic root or ascending aorta
CPB w/o Circ Arrest Cannulation
Ascending aorta or transverse aorta, and dual stage in RA or Bicaval
Where is the XC in CPB w/o circ arrest
proximal to the innominate artery
If patient is unstable prior to sternotomy, where do you cannulate?
Femoral to go on CPB prior to sternotomy
CPB w/o Circ arrest LV/PA Vent adn CPG
Normal LV/PA vent
uncluttered by clamps and cannulas
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
When did RCP gain popularity?
When was RCP first done? By who?
1980 by Milles and Oschner; treating massive air embolism
When was RCP used as neuroprotection?
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
maintained pre-DHCA jugular venous sats and cerebral oxygen extraction
Circ Arrest: Monitor Temps
Circ Arrest: Monitor Brain
EEG- brain activity
Electrocerebral silence dictates adequate cerebral cooling
Circ Arrest: Drugs
Mannitol (25g) and steroids
enhances cerebral protection
put in the pump prior to turning off the pump
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
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
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
A 10 degree C decrease in temperature causes what percent increase in blood viscosity?
Circ Arrest: Hemodilution to a hematocrit less than what percent?
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
When not using an EEG, cool for how long?
At least 25 minutes to a target core temp of 18-20 C
At EEG silence, give what drug?
Circulate for 3 minutes
What position is a patient put in during a circ arrest case?
Why would the head be packed in ice in a circ arrest case?
Facilitate Surface cooling
ACP is at how many ml/kg/min?
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
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)
Off pump: Want systolic BP of what?
Off pump: MAP
Off pump: HR
Off pump: CI
Complications of Aortic Surgery and DHCA
MI (reimplanting coronaries)
Other procedures of Aortic Conditions
Left Heart Bypass
When was an endovascular repair 1st done?
1991 on abdominal aortic aneurysm
Thoracic Endovascular aortic repiar
Endovascular Repair required proximal "landing zone" of what lenght?
Side branches- possibility of occluding a vessel that branches off the aorta
Aortic Tortuosity, calcification, atherosclerosis
less blood loss
pulmonary and cardiac comorbidities that may have not made them a candidate for open surgeries, allow them to have this option
Conversion to open procedure (aortic rupture/dissection, malposition causing visceral ischemia)
endoleak (blood flows back into the aneurysmal sac after the endovascular graft is placed; usually observe and hope it spontaneously resolves)
Left Heart Bypass
shunt around the aneurysm/dissection; used on descending legions
Left Heart Bypass: ECC
no bubble trap
exclusing those help minimize the heparinization required
Who gives volume in left heart bypass?