Vascular Anesthesia Flashcards
1
Q
What is the primary process leading to CAD, stroke, extremity ischemia, and aneurysms?
A
Atherosclerosis
2
Q
What is the presumed progression of atherosclerosis?
A
Fatty streaks –> Fibrous plaques –> Complicated lesions
3
Q
What locations does atherosclerosis commonly form?
A
- Coronary arteries
- Carotid bifurcation
- Infrarenal abdominal aorta
- Iliac arteries
- Superficial femoral artery
4
Q
Risk factors for atherosclerosis (11)
A
- Hyperlipidemia
- Smoking
- Diabetes
- Hypertension
- Family history
- Male
- Advanced age
- Insulin resistance
- Physical inactivity
- Elevated C-reactive protein
- Elevated lipoprotein
5
Q
T/F Atherosclerosis is a slow gradual process
A
True
6
Q
3 causes of ultimate injury in atherosclerosis
A
- Plaque enlargement reducing blood flow
- Embolism of plaque-associated platelet thrombi or debris
- Complete occlusion of arteries by advanced plaque
7
Q
What three major vessels does arteriosclerosis occur in?
A
Infrarenal abdominal aorta
Thoracoabdominal aorta
Descending thoracic aorta
8
Q
What is cystic medial necrosis and where does it occur?
A
Degeneration of the aortic media
Occurs in ascending aorta
9
Q
When is elective repair of aortic aneurysm recomended?
(Hint: at what diameter?)
A
> 5 cm
10
Q
Mortality rate of elective AAA repair vs ruptured aneurysms
What about if it ruptures outside of the hospital?
A
Elective 1-11%
Ruptured 35-94% or ~75%
Pre-hospital mortaility combined 80-90%
11
Q
Mortality if aneurysm left untreated for 5 years?
10 years?
A
5 years: 81%
10 years: 100%
12
Q
How much do aneurysms grow per year?
A
approximately 4 mm/year
13
Q
complications of atherosclerosis (4)
A
- MI
- Cerebral infarct
- Gangrene of extremities
- Abdominal aortic aneurysm
14
Q
At what age do you begin to see fatty streaks in vessels?
A
20’s
15
Q
At what age do you begin to see atheroma in vessels?
A
30s
16
Q
At what age do you typically begin to see atheromas with complications?
What are the complications?
A
40’s
- Thrombosis
- Plaque rupture
- Hemorrhage
- Wall weakening
- Calcification
17
Q
Law of Laplace formula
A
T = P x r
T = wall tension
P = transmural pressure
r= vessel radius
18
Q
What happens as the radius of the vessel increases?
A
Wall tension increases
AKA the bigger the aneurysm the higher risk of rupture
19
Q
Which type of aneurysm is described?
Originates in proximal aorta and usually involves ascending aorta, arch and can go into abdominal aorta
A
Debakey Type 1
20
Q
Which type of aneurysm is described?
Confined to descending thoracic aorta
A
Debakey Type IIIA
21
Q
Which type of aneurysm is described?
Confined to ascending aorta
A
Debakey Type II
22
Q
Which type of aneurysm is described?
May extend into abdominal aorta and iliac arteries
A
Debakey Type IIIB
23
Q
Which type of aneurysm is described?
Descending thoracic aorta involved with or without proximal or distal extension
A
Stanford Type B
24
Q
Which type of aneurysm is described?
Ascending aorta is involved with or without the arch or descending aorta
A
Stanford Type A
25
Which type of aneurysm?
Debakey Type 1
26
Which type of aneurysm?
Debakey Type II
27
Which type of aneurysm?
Debakey Type IIIa
28
Which type of aneurysm?
Debakey Type IIIb
29
Which type of aneurysm?
Stanford Type A
30
Which type of aneurysm?
Stanford Type B
31
Where are the two places aneurysms most commonly occur?
Ascending thoracic aorta close to aortic valve
Descending thoracic aorta just distal to left subclavian artery
32
Why do aneurysms commonly occur in ascending thoracic aorta close to aortic valve?
Pressure is highest just outside the aortic valve
33
Why do aneurysms commonly occur in descending thoracic aorta just distal to left subclavian artery?
Right after the bifurctation, just past subclavian artery the stress of that pressure can cause a break in the intima that allows blood flow in between the layers of the artery
34
When doing an aneurysm repair, do we think that one operative vessels is the only diseased one in the whole body?
NO
prob have vascular/atherosclerotic disease other places
35
Major causes of M&M for aortic aneurysm repair patients
* MI
* Respiratory failure
* Renal failure
* Stroke
36
What percent of patients having AAA reconstruction have CAD?
What percent of deaths after repair attributed to MI?
50% have CAD
40-70% of deaths attributed to MI
37
What part of AAA repair puts patients at risk of MI and heart failure?
The cross clamping causes significant stress on heart potentially causing ischemia and heart failure
38
If a patient has hypertension, what do we also assume they have until proven otherwise?
CAD
Proven otherwise = clear heart cath
39
What 3 things determine hemodynamic effects of aortic cross clamping?
1. Site of clamp
2. Patient's pre-op cardiac reserve
3. Patient's intravascular volume
40
What is required due to stagnant blood flow when the aortic cross clamp is applied?
Heparinization
| (not to the degree of CPB)
41
3 considerations in heparinizing patient for aortic cross clamping
1. ensure good blood return in IV
2. hypotension may occur after heparin bolus
3. know exact minute and second you admin heparin to be able to tell surgeon when he can cross clamp (usually 2-3 minutes after heparin admin)
42
When the aorta is cross clamped, what happens to BP above and below level of the clamp?
Hypertension above clamp
Hypotension below clamp
43
Hemodynamic effects of aortic cross clamping:
What happens to afterload?
MAP and SVR?
HR?
CO?
LVEDP?
* Afterload increased
* MAP and SVR increase
* HR unchanged
* CO may decrease or remain unchanged
* LVEDP may increase or show no change
44
Why does HR remain unchanged in aortic cross clamping when you would think it woud decreased related to increased SVR and HTN?
Release of catcholamines offsets compensatory decrease
45
If a patient has poor cardiac reserve, what will you expect with cross clamping?
May have decreased ventricular function and myocardial ischemia
**Will** see an increase in LVEDP
46
How to assess patients cardiac reserve?
"How many flights of stairs can you climb"?
NO
Ask them what they do on a daily basis
If sedentary, expect poor cariac reserve
47
What causes increased preload in aortic cross clamping?
Active venoconstriction proximal and distal to clamp
48
Which will have more hemodynamic effects.. placing cross clamp more proximal or more distal?
Distal (infrarenal) has little effect of hemodynamics
Proximal (supraceliac) has major hemodynamic effects
49
Besides location of cross clamp, what other factor has major impact on hemodynamics?
Length of duration of cross clamping
Longer duration = greater increase in SVR and decrease in CO
50
What kind of pulmonary damage can occur related to cross clamping?
What contributes to this process?
**Pulmonary edema**
Related to:
* increased pulmonary vascular resistance (\>at unclamping)
* increased capillary membrane permeability
51
What worsens pulmonary edema r/t aortic cross clamping?
* Hypervolemia
* Junk AKA Prostaglandins, oxygen free radicals, activation of RAAS, and complement cascade
52
Effect of **infrarenal** aortic cross clamping on renal blood flow and renal vascular resistance
Decrased renal blood flow 40%
Increased renal vascular resistance 75%
53
Effect of **suprarenal and juxta-renal** aortic cross clamping on renal blood flow
Decreases renal blood flow as much as 80%
54
Renal failure is common post aortic surgery
What is the cause?
Acute tubular necrosis related to ischemic **reperfusion** injury
55
Why is spinal cord damage associated with aortic cross clamping?
Artery of Adamkiewics is occluded with no collateral flow to the anterior portion of cord
Anterior = motor
56
Greater risk of paraplegia when aortic clamp is more proximal or distal?
More proximal
57
Why is SSEP not good monitoring for spinal cord ischemia in aortic cross clamping?
SSEP looks at posterior
Does not provide good information about anterior which is what we are worried about
58
Incidence of anterior spinal syndrome with elective infrarenal vs rupture of descending aorta
Elective infrarenal 0.2%
Rupture of descending aorta 40%
59
Main blood supply to anterior spinal cord
Where does it originate?
Why is this problematic?
* Artery of Adamkiewicz
* Origin varies but somewhere between T5 and L2
* Almost always emerges from left side
* Variations among individuals make it hard to identify
60
Spinal cord perfusion formula
What two ways can we help with perfusion?
MAP - CSF pressure
Drainage of CSF has allowed best avoidance of ischemia
Limiting cross clamp time to 30 minutes
61
Preventative measures for anterior spinal syndrome
(Long list so sry)
* Shunt from left atruim to common femoral artery
* Maintenance of HTN during cross clamp
* Methylprednisone
* Moderate hypothermia (30-32 degrees C) below clamp
* Avoiding hyperglycemia
* Mannitol to lower CSF pressure by decreasing production
* Drainage of CSF
62
How may nipride increase risk of spinal cord ischemia?
Decreases pressure proximal to the clamp but also distal to clamp
63
S/s of anterior spinal syndrome
What is preserved?
S/S: Loss of motor function and pinpric sensation
Sense of vibration and proprioception are preserved because they are posterior
64
Major metabolic abnormality seen in cross clamping
Why may this not show up on ABG?
Metabolic acidosis because tissues distal to the clamp are hypoxic causing accumulation of metabolites including lactate
May not be seen on ABG because they are building up below level of clamp and ABG is drawn above level of clamp
May be seen on ABG after unclamping
65
What effect does aortic cross clamping have on oxygen consumption?
Total body extraction?
MvO2?
CO2 production?
Catecholamines?
* O2 consumption decreased due to portion of tissues not being perfused
* Total body oxygen extraction decreased
* Increased MvO2
* Decreased CO2 production = respiratory alkalosis
* Increased catecholamines
66
Major goals during aortic cross clamping
* Reduce afterload
* Reduce proload
* Renal protection
* Hypothermia below clamp
* Decrease minute ventilation
* Correct acidosis with bicarb
67
How to reduce afterload in aortic cross clamping?
* Nipride
* Inhalation agents
* Milrinone
* Shunt or aorta to fem bypass
68
How to reduce preload in aortic cross clamping?
* Nitroglycerine
* Atrial to fem bypass
69
How to provide renal protection in aortic cross clamping?
* Fluid
* Renal cold perfusion
* Pharmacologic (mannitol, renal dose dopamine?)
70
Effect of release of cross clamp and built up metabolites
Metabolites such as lactate are ciruclated causing vasodilation, increased EtCO2, and hypotension
71
how does aortic cross-clamp release affect:
* afterload/SVR?
* MAP?
* Preload?
* CO?
* PCWP?
* ETCO2 and PH?
* Temperature?
* Afterload and SVR decrease
* MAP decreases
* Preload decreases
* CO increases, or no change or increases
* PCWP decreases
* ETCO2 increases and pH decreases
* Temperature decreases
72
When releasing aortic cross clamp significant acidosis may occur requiring what drug?
Bicarb
73
When releasing aortic cross clamp, what potential lethal arrhythmia can result from profound hypothermia?
V fib
74
Why may CO increase when aortic cross clamp is released?
May increase if ventricle has nothing to pump against
(Major decrease in afterload)
75
What contributes to unclamping hypotension?
Blood shifting to periphery
Hypoxia related vasodilation below level of clamp
Release of vasoactive and myocardial depressant metabolites
76
How to minimize hypotensive effects of cross clamp release?
* Maintain or restore intravascular volume
* Replace blood loss
* Raise PCWP 3-4 mmHg above pre-clamp values just prior to release
* Lower site of clamping = less drastic change
* Release clamp gradually
77
What drug should you have ready before releasing cross clamp?
Phenylephrine
78
Interventions you can use during unclamping to decrease effects
* Decrease anesthetic depth (MACamnesia) to reduce vasodilation
* Decrease vasodilators
* Increase fluids
* Increase vasoconstrictors
* Consider mannitol to pull volume back intravascularly
* Nabicarb to correct acidosis
79
What can you ask the surgeon to do if you have tried everything to correct hypotension after unclamping?
Reapply cross clamp
80
What monitoring and equipment do you need for aortic aneurysm repair?
* 2 large gauge IVs, blood warmer, blood filter
* Radial art line
* PA catheter (to monitor left sided filling pressures and fluid)
* ECG- leads II and V5
* Esophageal stethoscope
* Foley
* TEE
81
Advantages of GA with inhalation agent for aortic aneurysm repair
* Rapid adjustment of level
* Rapid emergence
* Potentially early extubation
82
Advantages and disadvantages of GA with narcotics for aneurysm repair
* Advantages:
* Cardiac stability
* Excellent post-op analgesia
* Disadvantages:
* No amnesia
* Unreliable supression of autonomic stimulation
* Respiratory depression
83
Advantages of regional for aneurysm repair
* Decreased preload and afterload
* Preserved myocardial oxygenation
* Increased graft flow to lower extremities
84
Risks and considerations of regional for aortic aneurysm repair
* Requires 1600-2000 ml more IV fluids
* Potential for epidural hematoma
Study showed 20 patients out of 3164 epidurals had neurologic complications
Epidural placed before surgery due to use of heparin intra-op and then usually dosed at the end of the case
Want to check an INR before removing the catheter
85
Why is combined GA and regional good for aneurysm repair?
Benefits of regional plus amnesai and controlled ventilation
Epidural good for post-op pain relief
86
What places aneurysm repair patients at high risk for bleeding?
* Anticoagulation
* Back-bleeding after clamped and aneurysm is opened
87
What guides fluid volume replacement for aneurysm repairs?
Want to maintain pts normal cardiac filling pressures and normal CO
UOP goal of 1 ml/kg/hr
88
What reduces need for banked blood in aneurysm repair?
Cell saver
(75% less banked blood used)
80% of AAA done with only cell-saver and no banked blood
89
Drugs to improve CO if LV is struggling after cross clamp removed
Dopamine and dobutamine
90
What is the **best** prevention of renal failure in aortic aneurysm repair pts?
Prevention of hypovolemia
91
What drug may be administerd 20-30 minutes prior to cross clamping?
Mannitol (0.5 gm/kg)
(Surgeon may just assume you know he wants this so ask preceptor)
92
What is the renal dose of dopamine that is not necessarily proven effective?
3-5 mcg/kg/min
93
What 4 factors increase risk of renal failure after aortic aneurysm repair?
1. Emergency procedures
2. Long aortic cross clamp time
3. Prolonged hypotension
4. Pre-existing renal disease
94
3 cardiac goals for post-op care of aortic aneurysm repair
1. Avoid hypertension
2. Maintain intravascular volume
3. Maintain myocardial oxygenation
95
After aortic aneurysm repair we must evaluate need for post-op ventilation
Which particular types of these surgeries may need this?
Surgery involving:
* Ascending aorta
* Aortic arch
* Thoracic aorta
96
Renal goals after aneurysm repair
* Maintain UOP at 1 ml/kg/hr
* Maintain volume
* Maintain normotension
* Use dopamine if necessary
97
Symptoms of ruptured AAA
* Abdominal pain with pulsatile mass
* Back pain,
* Hypotension
98
Induciton for ruptured AAA is similar to induction for what type of patient
Trauma patient
Use scopolamine not midazolam
Goal is hemodynamic stability
"Saving their life is the goal, amnesia is just icing on the cake"
99
Considerations for fluid replacement in ruptured AAA
Give whatever you have on hand
You prob will only have crystalloids at first so give that dont want until you have colloid or blood, but you can give those once you have them
100
Hemodynamic and respiratory considerations of ruptured AAA
HD effects of cross-clamping will be more pronounced in these patients
Most will need post-op ventilation due to potential for lung injury related to blood products
101
mortality if AAA is ruptured or even just leaking prior to surgery
50%
102
Risk factors associated with increased risk of mortality in patients with AAA rupture
(Box 28.7)
* Increased age
* Female
* Non-white race
* Insurance status (higher for self-pay or Medicaid in US)
* Comorbid conditions
* CHF
* Renal failure
* Valvular heart disease
103
Post op considerations for patients having AAA repair (8)
(Box 28.5)
* Continue invasive HD monitoring
* Treat acute BP extremes and arrhythmias (a. fib)
* Assess for postop MI
* Provide ventilatory mgmt with weaning and extubation
* Assess for abdominal compartment syndrome
* Evaluate Hgb, Hct, coag status, and adequacy of volume replacement
* Assess BUN/creatinine and UOP
* Institute DVT prophylaxis per protocol
104
What is unique/more scary about surgical repair of ascending aorta?
Requires CPB
Anesthesia is similar to cardiac anesthesia and requires median sternotomy
105
What potentially futher complicates repair of ascending aorta?
* Aortic regurgition
* Large blood loss
* AV replacement
* Coronary reimplantation
106
Where should art line be placed in ascending aortic aneurysm repair?
Why?
Left radial
Because inominate artery may be clampled
107
What would you want to avoid in patient undergoing ascending aorta repair who also has aortic regurg?
Bradycardia
| (F,F,F bby)
108
What is unique about aortic arch repair?
May need circ arrest after CPB
* hypothermia 15-18 degress C allows arrest of 30-40 mins
* Ice to head, cooling on bypass, thiopental
* Long rewarming may increase blood loss
Need median sternotomy
109
What is unique about repairs of descending thoracic aorta?
* Require left thoracotomy so one-lung ventilation
* Does not require CPB
* Use of shunts with cross clamp
110
Risk of descending thoracic aneurysms compared to AAA
* Greater HD effects with cross clamping and clamp release
* Greater risk of spinal cord ischemia
* Greater risk of renal insufficience
All related to the clamp being placed higher in this procedure
111
What determines level of monitoring in peripheral vascular surgeries?
Co-existing disease in
* coronary arteries
* cerebral arteries
* renal arteries
112
Common anesthetic for peripheral vascular surgeries
Why?
Regional + sedation (dexmedetomidine or sedation dose propofol)
SNS blockade with regional increases peripheral blood flow, helps with postop pain
Good because these patients are sick sick so may not want to put them to sleep
113
Considerations with existing AV graft
Assess pre and post op
Protect graft (put BP cuff on other side, dont stick there)
114
Why are CEAs so important?
Becasue strokes are the 5th leading cause of death in the US
with 80% of them being ischemic and 20% being hemorrhagic
115
What is the most significant predictor of post op stroke incidence?
Pre-op neuro funciton
Document pre-op deficits
116
Incidence of perioperative strokes related neuro history
* Asymptomatic pts: 3%
* Symptomatic pts: 5%
* Existing strokes: 10%
117
Two common co-existing diseases in patients undergoing CEA
Significance?
* Hypertenison
* Diabetes
Hypertensive pateints autoregulation shifted higher so need to maintain higher CPP
118
Operative mortality of CEA?
Most common cause?
0.5-2.5%
Mostly due to MI
119
What factors increase risks in CEA? (6)
* Age greater than 75
* Symptomatic lesions
* Uncontrolled HTN
* Angina
* Carotid thrombus
* Occlusions near carotid siphon (really high up in 🧠 )
120
Major anesthetic goal in CEA
Balance cerebral and myocardial protection
Increasing pressure for cerebral perfusion causes increased myocardial oxygen consumption
121
Why do we want rapid awakening in CEA?
for neuro assessment
prefer to do this in the OR in case there are deficits that could be fixed
122
How to provide cerebral protection in CEA?
* Increasing collateral flow by maintaining good vertebral flow
* Decreasing CMRO2
* Barbiturates (pentothal decreases more but has hangover, propofol satisfactory)
* Passive hypothermia
123
When is autoregulation maintained?
Hypertension effect on curve
50-150 mm Hg
HTN shifts curve to right causing CBF decrease with hypotension
124
CPP formula
CPP = MAP - ICP
ICP shouldnt be elevated so CPP should = MAP
125
Monitoring for CEA
* Art line
* EtCO2 monitoring
* SSEP or EEG (but EEG is gold standard) – but the goldest standard is an awake pt
126
Indications of neurologic dysfunction on EEG
* Loss of beta-wave activity
* Loss of amplitude
* Emergence of slow-wave activity
127
How to determine if shunt placement is necessary in CEA?
Measure the carotid stump pressure distal to the clamp
Surgeon will hand us sterile pressure tubing to hook up to transducer
Need shunt if pressure \<50 mm Hg
128
Value of cerebral oximetry in CEA
Monitoring for a significant change
One single value doesnt really mean anything
??? someone indicate if this is right because we never used these
129
Regional technique for CEA
Infiltration of local or deep cervical plexus block (C2-C4)
Surgeon performed
130
Advantages and disadvantages of regional for CEA
* Advantages
* Shorter, less cardiopulmonary complications
* Directly assess neuro function (LOC, speech, grip on opposite side)
* Disadvantages
* Requires patient cooperation and acceptance
131
Advantages and disadvantages of GA for CEA
* Advantages
* Inhalation agents provide better HD stability and may benefit cerebral circulation
* muscle relaxants beneficial for low agent
* Disadvantages
* Narcotics can prolong wake-up
* Volatiles interfere with EEG and SSEP monitoring if \>1 MAC
132
Which is better for CEA: regional or GA?
No difference in M&M with either type
133
What HD changes should you be ready for with CEA?
Both hypertension and hypotension
Patients are hypertensive pre-op but can easily become hypotensive
134
How common is hypotension during CEA?
What is the cause?
How to treat?
* 10-20% of patients become hypotensive
* Carotid sinus baroreceptor stimulation
* Treatment:
* Ephedrine or phenylephrine infusion
* Atropine if bradycardic
* Surgeon can prevent with LA infiltration
135
How common is hypertension in CEA pts?
What is the cause?
Treatment?
* 10-66% will have HTN
* Caused by carotid sinus denervation
* Treatment/prevention:
* Have patient take antihypertensive pre-op
* Beta-blockers, hydralazine
* Nitroglycerine, nipride
136
What effect may carotid sinus denervation have on ventilation?
Decreases ventilation response to hypoxemia
137
BP goal after carotid is cleaned out
"normotension"
138
Why is it super easy to overshoot BP one way or the other in pts undergoing CEA?
* These patients have history of hypertension so they are baseline vasoconstricted and volume depleted
* Makes them have enhanced response to vasodilators and vasocontrictors
139
Postop complications of CEA (10)
* HD instability
* myocardial ischemia/infarction
* cerebral hypoperfusion syndrome
* Stroke
* respiratory insufficiency
* RLN/SLN damage
* Hematoma
* Carotid body dysfunction
* Tension pneumo
* Acute carotid occlusion
140
Implications of bleeding and hematoma after CEA
May cause airway obstruction
Requires emergency surgery
This is why surgeons do not cover the neck with a big dressing anymore these days
141
Effect of HTN (SBP \>180) after CEA
Associated with higher incidence of stroke or MI
Incidence of neuro deficits increased 3x in patients who become hypertensive postop
142
3 major things you want to evaluate and document when dropping you CEA off in the PACU
1. Do they MAE to command? is this the same as they could do pre-op?
2. Respiratory status- are they breathing on their own?
3. Responsiveness- should be awake and alert
143
When do CEAs usually go home?
The next day after surgery
144
What is mesenteric traction syndrome associated with?
Traction on the mesentery that is used to expose the aorta
145
S/S of mesenteric traction syndrome
Decrease in blood pressure and SVR
Tachycardia
Increased CO
Facial flushing
146
When does hemodynamic stability return after mesenteric traction syndrome?
As reperfusion occurs
147
what should you do with PCWP prior to cross clamp release? why?
raise 3-4 mmHg above pre-clamp value to prevent hypotension and decreased CO assoc. with clamp release
