Vascular Surgery & Hypertension Flashcards
What “branches” off of the ascending aorta?
Coronary arteries
What are the branches off of the aortic arch?
Innominate artery/brachiocephalic
Left common carotid
Left subclavian
What branches come off of the brachiocephalic?
Right subclavian
Right common carotid
Why should an arterial line always be placed in the right arm during a mediastinoscopy?
If the aorta is compressed during mediastinoscopy, the first vessel affected would be the innominate so monitoring a-line in the right arm would monitor perfusion
How is monitoring with an A-line in the right arm also a monitor of brain perfusion during a mediastinoscopy?
This also monitors perfusion to the brain because the right carotid comes off the innominate
What determines where the A-line is placed for an ascending aortic aneurysm?
Location of the surgeon’s cross-clamp
-surgeon may put in a femoral line
What can an asceding aortic aneurysm also affect?
The aortic valve
What diseases are aortic dissections associated with?
Marfan’s
Hypertension
Where are traumatic aortic dissections more common?
In the ascending aorta
Where are aortic aneurysms more common?
In the abdominal aorta
Where is aortic occlusive disease more common?
At aortic bifurcation
What medication is required with aortic cross clamping?
Heparinization
What besides blood can anesthesia give to prevent clot breakdown?
Antifibrolytics
What does an aortic cross clamp do to afterload?
Increases afterload
The increased afterload due to aortic cross clamping can have what negative effects on the heart?
Increases LV pressure required may > LV failure
Increases O2 demand > ischemia
What device is common to use during aortic cross clamping in order to monitor afterload and the heart’s response to this increase?
PA catheter
What vasodilator is used during aortic cross clamping in order to help decrease resistance?
NTG
Why is an arterial dilator (Nipride) not used in aortic cross clamping in order to decrease afterload?
May decrease spinal cord perfusion pressure by both decreasing distal aortic pressure and increasing CSF pressure
What does anesthesia want to give before cross clamp is removed? Why?
Volume
Because when the clamp is removed there is a sudden drop in afterload
What happens when the cross clamp is removed?
Sudden drop in afterload > hypotension
-turn NTG off
What is a risk with all surgeries that invovles aortic cross clamping?
Acute kidney injury
What increases the risk of kideny injury with aortic cross clamping?
longer cross clamping times
emergency surgery
pre-existing renal disease
What kidney injury prevention attempts have been tried, none of which are successful?
Mannitol
Furosemide
Fendolopam
Dopamine
What makes ascending aorta repairs more risky?
Disscetions or tears can extend back into valve
- surgery is similar to AVR but:
- longer surgery time
- more blood loss
What is circulatory arrest? When is it utilized?
Surgical technique that involves deep hypothermia and stopping circulation
Ascending aortic repairs
Why is circulatory arrest utilized in ascending aorta dissections or tears?
Perfusion is difficult even with CPB, profound hypothermia decreases metabolism and reduce risk of ischemia
What is unique about descending aorta incision and ansethesia?
Thoracolumar incision and one lung anesthesia
-sternotomy can be done if needed
Why is one lung ansethesia performed during descending aorta repair?
Makes more room for surgeon to work
Where are aoritc clamps placed during descending aortic repair?
Above and below the site
What does cross clamping above and below the descending aortic repair do to circulation?
Circulation is isolated into 2 separate systems
- femoral cannulation for CBP of lower body
- upper body perfusion via heart and lungs
What risk does double cross clamping the descending aorta carry?
Paraplegia due to inadequate spinal cord perfusion
Why is paraplegia a risk with descending aorta repair surgery?
The main radicular artery that perfuses the spinal cord is the Artery of Adamkiewicz, it’s location varies among the population, so it is unknown if it is affected by clamp until postop
What percetage of the population have the artery of adamkiewicz coming off T5-T8?
15%
What percetage of the population have the artery of adamkiewicz coming off T9-T12?
60%
What percetage of the population have the artery of adamkiewicz coming off L1-L2?
25%
How can anesthesia help protect the spinal cord during descending aorta repair?
Steroids Hypothermia Mannitol Lumbar CSF drainage Avoid excessive vasodilator administration with cross clamp afterload elevation
How does removing some lumbar CSF help protect the spinal cord?
Decreases CSF pressure > less tissue pressure for vascular to push against and get spinal cord perfused
Where is an infrarenal cross clamp of the aorta? Does this risk renal failure?
Below the kidneys
Yes
Where is a suprarenal cross clamp of the aorta? Does this risk renal failure?
Above the kidneys
Yes
What less invasive technique for repairing dissection or aneurysm removes the need for aortic cross clamping?
Endovascular stents
Where can endovascular stenting be used in aortic repairs?
Anywhere
What could be suspected in a person with peripheral vascular disease from plaque?
They are prone to plaque, so it is reasonable to suspect there may be plaque in the coronaries and/or carotids
Lower extremity peripheral vacular bypass graft procedures done with regional anesthesia have what benefits for the graft?
Increase graft flow and decrease graft thrombosis
Peripheral vascular surgeries for bypass
Femoral popliteal bypass
Femoral to femoral bypass
Aorta bi-femoral bypass
Hypertension does what to vascular tone?
Causes chronic vasoconstriction
What does this chronic vasoconstriction mean for volume status?
Chronic volume depletion due to less vascular space for fluid
What used to treat hypertension also affects chronic volume depletion?
Diuretics
What happens to the kidney with chronic volume depletion from volume depletion and/or chronic constriction of the renal vasculature?
Kidneys are under perfused
What response do the kidney have due to under perfusion?
Triggers renin, angiotensin, aldosterone
What overall effect does the trigger of RAAS have?
Retain fluid in an attempt to increase renal blood flow
What diseases are associated with hypertension?
CAD
PVD
Carotid disease
Renal dysfunction
How does hypertension affect autoregulation?
It shifts the autoregulation curve to the right
What does a right shift in the autoregulation curve mean?
The range for autoregulation function is higher
-patients needs a higher BP to maintain autoregulation
What are the advantages of continuing BP medications preop?
No rebound hypertension
-more stable BP, less labile
Less angina/ischemia
Lower morbidity and complications
What is the DBP “red flag” value for HTN and that May case should be postponed?
110 mmHg
-consider postponement if elective procedure
Why is continued preop use of ACE inhibitors and ARBs controversial?
Possible refractory hypotension under anesthesia when continued -only class that is sometimes held
What benefits does continuing beta blockers preop have?
Smoother induction
-consider additional dose
Should BB be given preop to those not on them?
Risks out weigh benefits
- Fewer MIs and arrhythmias
- More strokes and deaths
What do all calcium channel blockers cause?
Myocardial depression
-so does VA and BB
What can be given for a coronary vasospasm?
Calcium channel blocker
What happens in a HTN patient during induction (BP wise)?
Labile BP
- induction agent vasodilates them > hypotension
- stimulation > HTN
What makes lability of BP worse in HTN patients?
If they are volume depleted
With poor preop control of BP what are they at higher risk for?
Ischemia
What also increases the risk of ischemia?
Hypotension
-HTN is better than hypotension
What helps reduce the labile BP swings?
Fluid Induction-adequate depth -fentanyl -lidocaine Adjunct BB dose or sodium nitroprusside
What is the danger of hypotension in a HTN patient?
Poor organ perfusion
-autoregulated orgran now require higher BP to maintain perfusion
Why is hypertension a significant cause of congestive heart failure and cardiomyopathy?
Nagelhout
Because it causes increased afterload from chronic vasoconstriction
Hypertension increases the likelihood of the development of what?
Atherosclerosis
-and thus chronic and untreated HTN increases risk of MI, stroke and chronic kidney injury
What is essential hypertension?
AKA primary and idiopathic
- has no identifiable cause
- diagnosed on the basis of exclusion
What is remedial hypertension?
AKA secondary hypertension
-has an identifiable and potentially curable cause
What is concentric hypertrophy?
Hypertrophy that occurs in response to chronic increases in intracardiac pressures
- Chronic HTN and increased afterload > hypertrophy of LV
Does LV hypertrophy affect the O2 supply and demand balance?
Yes, it increases demand
All patients with chronic HTN should be suspected of having?
Some degree of coronary artery disease
What medications have been found to help with refractory hypotension from ACE inhibitors and ARBs?
Vasopressin and methylene blue
Patient with DBP great than what have a significantly increased risk of perioperative cardiac morbidity?
110 mmHg
-may be modified in patients with HTN in whom DBPs greater than 110 occur frequently despite aggressive antihypertensive therapy
Why may Etomidate offer some advantages in patients with cardiac pathology as compared to Propofol?
Etomidate preserves SV and CO
Intraluminal stent grafts have been approved for aneurysms of what size?
Co-existing
Above 5.5 cm
-as well as complicated type B dissections
Chronic impairment of blood flow to the extremities is most often due to what?
Atherosclerosis
Acute arterial occlusion is mostly likely from?
Embolism
What is an ankle-brachial index? (ABI)
The calculated ratio of SBP at the ankle to the SBP in the brachial artery
What does the ABI define?
An ABI of less than 0.9 is the most widely accepted definition of peripheral arterial insufficiency
Why does intermittent claudication occur with peripheral arterial disease?
When the metabolic requirement of exercising skeletal muscles exceeds oxygen delivery
Why does rest pain occur with peripheral artery disease?
The arterial blood supply does not even meet the minimal nutritional requirements of the affected extremity
What are the risk factors associated with development of peripheral atherosclerosis?
Older age Family Hx Smoking DM HTN Obesity Dyslipidemia
What are the most reliable physical findings associated with PAD?
Decreased or absent arterial pulses
-buits may indicate the anatomical site of arterial stenosis
Signs of chronic leg ischemia?
SQ atrophy Hair loss Coolness Pallor Cyanosis Dependent redness
Reduced lower extremity pulses may be the presenting sign of what (less commonly)?
Undiagnosed aortic coarctation
What is an aortic dissection?
M and M
An intimal tear that allows blood to track into the aortic wall (the media)
Who diseases put patient at risk of aortic dissection?
Marian syndrome and Ehlers-Danlos syndrome > cystic medial necrosis > aortic dissection
What aortic dissections are most common?
Proximal type involving the ascending aorta
Where do aortic aneurysms more commonly occur?
In the abdominal vs thoracic aorta
What is the most common cause of aortic aneurysms?
Atherosclerosis
What is a pseudoaneurysm?
When the intima and media are ruptured and only adventitia or blood clot forms the outer layer
When is elective treatment of aortic aneurysms generally performed?
With aneurysms 5 cm or greater
Where does atherosclerotic obliteration of the aorta (Occlusive disease of the aorta) most commonly occur?
Near the aortic bifurcation
-Leriche syndrome
What is coarctation of the aorta?
A congenital narrowing of the aorta
What is preductal (infantile) type coarctation of the aorta?
Lesion is proximal to the opening of the ductus arteriosis
-recognized in infancy because lower extremities are cyanotic
What is postductal coarctation of the aorta?
Lesion is after the ductus arteriosus
- may not be recognized until adulthood
- symptoms and hemodynamic significance depend on severity of narrowing and the extent of collateral circulation
- HTN in the upper body is usually present
- “rib notching” on CXR may be present d/t dilated collateral intercostal arteries
What aortic procedures are usually performed with median sternotomy, CPB and deep hypothermic circulatory arrest?
Surgery on the ascending aorta
Surgery on the aortic arch
This aortic surgery may be complicated by long aortic cross clamp times and large intraoperative blood loss?
Ascending aorta
What aortic surgery can be performed with a left thoracotomy with or without CPB?
Surgery involving the descending thoracic aorta
Surgery on the descending thoracic aorta involves cross clamping the aorta above and below the lesion, what does this do to BP?
Acute hypertension develops above the clamp and hypotension below (when there is no shunt or partial bypass)
During surgery involving the descending thoracic aorta, when is the period of greatest hemodynamic instability?
Following the release of the aortic cross clamp
-abrupt decrease in afterload together with bleeding and release of vasodilation acid metabolites from the ischemic lower body can precipitate severe hypotension
Spinal cord perfusion pressure =
MAP - CSF pressure
In general, the more distally the clamp is applied to the aorta what affect does this have on LV afterload
The more distally the clamp is placed the less effect on LV afterload
