Vascular Anesthesia Flashcards
3 layers of arterial wall structure
Intima (inner layer made of endothelial cells)
Media (contains muscular elastic fibers)
Adventitia (outer CT)
True aneurysm
Localized dilatation of an artery including all the layers of the wall
Aneurysm contained inside endothelium
Usually consequence of arterial wall congenital or acquired deficiency
WALL OF ARTERY FORMS ANEURYSM
at least 1 vessel layer is still intact
fusiform
circumferential, relatively uniform in shape
Saccular
pouch like with narrow net connecting bulge to one side of arterial wall
Aortic dissection
MEDICAL EMERGENCY- quickly leads to cardiac failure, rupture of aorta, death
tear in inner wall of the aorta causes blood to flow between the layers of the wall of the aorta, forcing the layers apart
Associated with: HTN, known thoracic aortic aneurysm, Marfan’s syndrome, Ehlers-Danlos syndrome, Loeys-Dietz syndrome
Severe chest or abdominal pain “tearing” inside aorta BF between levels = painful
vomiting, sweating, and lightheadedness may occur
quickly leads to death as a result of not enough BF to the heart or rupture of the aorta
Marfan Syndrome
genetic CT disorder Abe Lincoln appearance (elongation of face is a major clue) major CV abnormalities: -heart valves and aorta -lungs, eyes, dural sac, skeleton, hard palate prophylactic ABx
Thoracic Aortic Aneurysm 3 types
ascending aorta
transverse arch
descending aorta
ALL UP IN CHEST (THORACIC)
Thoracic Aortic Aneurysm symptoms
pain in jaw, neck, and/or upper back
pain in chest and/or back
wheeze, cough, SOB = pressure on trachea
hoarseness = pressure on vocal cords
difficulty swallowing due to pressure on esophagus
ascending aortic aneurysm
begins at LV and extends to aortic arch age/degenerative disease of aortic wall uncontrolled HTN long term tobacco use inflammation or swelling of aorta infxn Hx of CT disorders Trauma family Hx
typically also need an aortic valve replacement (aneurysm extends into valve and unseats it)
transverse aortic aneurysm
2:1 occurrence in male vs. female
50-75 y/o
etiology:
- degenerative disease
- atherosclerotic disease
- chronic dissection
associated conditions:
- aortic valve disease 30%
- CAD 15%
- COPD 20%
typically also need an aortic valve replacement (aneurysm extends into valve and unseats it)
Descending aortic aneurysm causes
atherosclerosis
HTN
traumatic injury
untreated infxn (salmonella and syphilis)
bicuspid aortic valve (2 leaflets instead of 3)
genetics (marfan, loeys-dietz, ehlers-danlos)
inflammatory conditions (giant cell arteritis, takayasu arteritis)
Descending aortic aneurysm symptoms
back pain or vague chest pain difficulty swallowing hoarseness difficulty breathing (compression on left mainstem bronchus) cough
DeBakey System
anatomical description of the aortic dissection
categorized based on where the original intimal tear is located and the extent of the dissection
TYPE 1 = aneurysm in ascending, propagates at least to the aortic arch and often beyond it distally. Most often seen in patients less than 65 yrs and most lethal
TYPE 2
TYPE 3
The Stanford Classification
A and B
is the ascending aorta involved?
if yes, type A =
if no, type B =
Abdominal aortic aneurysms (AAA)
M to F = 4:1
Non-Marfan age = 55-75 (Marfan 35-55)
primarily atherosclerotic or marfan
Pre-op considerations
check LVH and ischemia on EKG
50% have pulmonary insufficiency
CXR - distortion of trachea and left main bronchus
pre-treat with bronchodilators
cessation of smoking
incentive spirometry (generating some CPAP, pre and post)
8-14% need tracheostomy
will see atelectasis
spinal cord perfusion
entire blood supply of SC depends on 2 sets of branches from dorsal aorta
Loss of supply to posterior portion of cord - lose sensory
loss of supply to anterior portion of cord - lose motor
neurological considerations
incidence of SC ischemia 3.8% to 40%
depends on anatomic location, duration of cross-clamping, degree of dissection, rupture
sometimes done on bypass, get temp down from 37 to 22,
Ascending Aorta Recipe
EBL 300-400mL
Position = supine
incision = medial sternotomy
Special instrumentation = A-line, CPB
Surgical time = aortic cross clamp 40-120min, CPB 70-150min, total 2.5-5h
Closing considerations = aggressive management of coagulopathy
Ascending Aorta Recipe
EBL 300-400mL
Position = supine
incision = medial sternotomy
Special instrumentation = A-line, CPB
Surgical time = aortic cross clamp 40-120min, CPB 70-150min, total 2.5-5h
Closing considerations = aggressive management of coagulopathy
Post-op ICU intubated
Transverse Arch Recipe
EBL = 400-700mL
Position = supine
Incision = medial sternotomy
Special instrumentation = A-line, CPB, hypothermic measures (barbs/propofol, steroids)
Surgical time = aortic cross clamp75-120min, circulatory arrest 30-45 min, CPB 3-4.5min, total 4-6h
closing = aggressive management of coagulopathy
Post-op ICU intubated
Mortality 10-15%
Descending Aorta Recipe
Induction: prevent HTN with laryngoscopy, intro myocardial ischemia, Left DLT
Positioning: RLD, hips rotated posteriorly 45deg, left draped fwd, chest roll
Maintenance: varies at portions of cases refer to descending thoracic aneurysms
Pre-op considerations
renal - possible aneurysmal renal artery involvement; 6% of patients need post-op dialysis
GI - possible aneurysmal involvement of mesenteric arteries
hematologic (PT/PTT/INR/Plt/Hct)
Premeds (anx, emergent - full stomach)
high mortality (30-60%)
Intra-op considerations cross clamping hemodynamics
BV hasn’t changed but vascular space has changed
Blood below clamp back in venous side, valves, one way system
–> sudden relative hypervolemia
increasing pulm congestion and cardiac work bc extra volume
start NTG to vasodilator and encourage pooling of blood in legs and increase VR
build up lactic acid and metabolites below clamp
INCREASED PRE AND AFTER
increased aortic pressure proximal to clamp
decreased EF, CO, Renal BF
increased pulm. occlusion pressure, CVP, CorBF
Intra-op considerations cross clamping metabolic changes
no BF to lower part of body DECREASE tb oxygen consumption/extraction increase mvSaO2 decrease tb CO2 production metabolic acidosis epi and norepi resp alk
amrinone
can increase contractility? may not increase cardiac contractility in diseased myocardium
vasodilator
not sure if id use it here
beneficial intervention
depth anesthesia –> vasoDILATE
Renal protection
mannitol
fenoldopam
causes arterial vasodilation
rapid
decreases afterload
influences on success
level of clamp= greatest impact if patient survives successfully
higher it goes, worse off it will be (preload)
LV function
vasodilator therapy
volume status
duration of clamp
pt temp
AORTIC UNCLAMPING
decrease myocardium O2 supply and contractility
Decreased:
-ABP, CVP, PAP, VR, CO (sometimes up)
not usually hypovolemia but increased vascular space
AORTIC UNCLAMPING hemodynamic changes
decrease myocardium O2 supply and contractility
Decreased:
-ABP, CVP, PAP, VR, CO (sometimes up)
not usually hypovolemia but increased vascular space
AORTIC UNCLAMPING
re-perfusion
increase tb O2 consumption
decreased mvSaO2
AORTIC UNCLAMPING
re-perfusion increase tb O2 consumption decreased mvSaO2 increased prostaglandins decreased temp increased lactate metabolic acidosis
preemptive therapeutic interventions
TANKS when unclamp
insure adequate volume
-increase filling pressures, replace BL, increase fluid administration
DECREASE VA DECREASE vasodilators (NTG) increase vasoconstrictors
reapply cross clamp for severe hypotension
consider mannitol
consider NaBicarb (usually not)
Emergence
BP should be closely controlled to decrease bleeding from graft site
adequate pain control
regional???
Anesthesia for AAA
preserve myocardial, renal, pulm, CNS, visceral organ function
maintain adequate intravascular volume and CO
control BP so as to not cause rupture
anticipate surgical maneuvers that will effect BP and BV
Pre-op considerations AAA
resp: many have COPD CV: CAD most common co-ex, BP control Renal: know whether aneurysm is supra or infra renal hematologic: PT/PTT/INR/plt/Hct premed - anx and full stomach, reflux
intra-op considerations AAA
induction low and slow but adequate vasoactive drips ready patient may be very labile minimize stimulation of intubation
Maintenance
N2O ok but may cause bowel distention
GA with epidural offers good abdominal relaxation
warm patient, large incision but turn off bair hugger when cross clamped (could get 2nd degree burn)
Blood and fluids anticipate large BL IV 14ga or 7fr x2 rapid infuser, cell saver type and cross 8-10 PRBCs warm fluids and humidify gases maintain UO crystalloid and colloid use
aortic cross-clamping in general
increase preload
increase CVP, pulm occlusion pressure, LVEDP, LV wall tension, segmental wall motion abnormalities
decrease EF and CO
Increases afterload
increase ABP, increase filling pressure, CorBF
decreased perfusion to viscera below the clamp
negative inotropic agents should be used cautiously
check ABGs and electrolytes
ALL WARMING DEVICES BELOW LEVEL OF CROSS CLAMP SHOULD BE OFF DURING CLAMPING TO AVOID THERMAL INJURY
intra-op considerations aortic unclamping
relative hypovolemia
decreased afterload
lactate washout
surgeon can re-clamp
