Anesthesia for vascular surgery 3 Flashcards
EVAR technique is used for all types of
aortic diseases- traumatic injuries, ruptures, dissections, thoracic, and abdominal aneurysms
The EVAR technique is useful because it is
less invasive
reduced M&M
shorter hospital stay
Anesthesia technique for EVARs includes
MAC with local/regional vs. GA
-consider pt functional status (can they lay flat?), co-morbidities, aneurysm complexity, and surgical urgency (full stomach?)
Steering guiding sheaths for EVARS may require _________ arm arterial cut down**
left
Anesthesia considerations for EVARs includes
spinal cord-extensive collateral network hemodynamic management preservation of organ perfusion blood loss and intravascular volume temperature radiation safety
The artery of adamkiewicz is located at
T9-T12
The Preserve trial found that the two most important factors that contribute to CIN are the
contrast load and the preexisting kidney disease*******
limiting the contrast load & adequate hydration to decrease the viscosity of the iodine-based dyes
Early EVAR complications include
paraplegia, stroke, ARI, aneurysm rupture, pelvic hematoma
Late EVAR complication sinclude
endoleaks, aneurysm rupture, device migration, limb occlusion, graft infection
Endoleaks are normally treated by
balloon angioplasty of the proximal attachment site so that the desired seal is obtained through remodeling of the stent-graft
If endovascular treatment or endoleak fails or is not possible, then
open surgical treatment is indicated
Considerations for open abdominal aortic reconstruction includes
large incisions & extensive dissections
clamping & unclamping of the aorta or tis major branches
varying duration of organ ischemia- reperfusion
significant fluid shifts
temperature fluctuations
activation of neurohumoral and inflammatory responses
The two most common sites of chronic atherosclerosis include
the infrarenal aorta & the iliac arteries
Patients undergo surgery for aortoiliac occlusive disease only if
they are symptomatic
-claudication & limb-threatening ischemia
Management of aortoiliac occlusive disease includes
direct reconstruction- Gold-standard
extra anatomic or indirect bypass grafts
catheter based endoluminal techniques
The pathophysiology of aortic cross-clamping is complex & depends on the following factors:
level of the cross-clamp status of the left ventricle degree of periaortic collateralization intravascular blood volume & distribution, activation of the sympathetic nervous system anesthetic drugs & techniques heparinization monitor ACTs
The aortic cross clamp results in arterial __________ above the clamp and arterial ________ below the clamp
hypertension****
hypotension***
Common ischemic complications of aortic cross clamp include
renal failure hepatic ischemia coagulopathy bowel infarction paraplegia
Thoracic aortic cross clamping leads to an increase in
mean arterial pressure
central venous pressure
pulmonary wedge
and mean pulmonary arterial
Thoracic aortic cross clamp leads to a decrease in
EF
Cardiac index
no change in HR
A normal intact heart can withstand large increases in
volume without significant ventricular distension or dysfunction
An impaired heart with reduced myocardial contractility & coronary reserve may respond to an increase in volume conditions with
marked ventricular distension leading to acute left ventricular dysfunction & myocardial ischemia
_________ activation resulting from increased aortic pressure should depress the heart rate, contractility, and vascular tone
Baroreceptor
Cross-clamping of the thoracic aorta decreases ______ by approximately 50%
total-body O2
Blood flow through tissues & organs below the level of aortic occlusion is dependent on ________ and is independent of ________
perfusion pressure***
independent of cardiac output
_______ should be used when aortic cross clamp is applied to decrease afterload, wall stress, and myocardial oxygen demand
Vasodilators- nitroprusside, nitroglycerine, nicardipine, & clevidipine
Perfusion to distal organs is dependent on ________which originate _______ to the clamp or shunts
collaterals; proximal
Aortic cross clamp management includes
acute increase in SVR & decreased CO
avoid long-acting medications
the higher the clamp, the more significant impact on perfusion to vital organs thoracic> supraceliac> infrarenal
______ remains the strongest predictor of postoperative renal dysfunction
Preoperative renal insufficiency***
Renal failure after repair results from
preexisting renal dysfunction, ischemia during cross-clamping, thrombotic or embolic interruption of renal blood flow, hypovolemia and hypotension
Renal sympathetic blockade with epidural anesthesia to a T6 level does
not prevent or modify the severe impairment in renal perfusion and function
Renal protection may include
mannitol 12.5 g/70 kg
low-dose dopamine (1-3 mcg/kg/min)
can be injected directly into renal artery by surgeon
controversial- mannitol, loop diuretics, methylprednisolone & dopamine
Patients with _______ & _______ are most vulnerable to the stress imposed on the cardiovascular system by aortic cross-clamping
preexisting impaired ventricular function & reduced coronary reserve
Goals during cross clamping include
reduce afterload (nitroprusside or clevidipine) maintain normal preload (IV fluid) maintain cardiac output (inotropes, MAP goals)
Aortic unclamping may result in
hypotension
reactive hyperemia
washout of vasoactive & cardio-depressant mediators
pulmonary hypervolemia
The hemodynamic response to unclamping depends on many factors including the
level of aortic occlusion, total occlusion time, use of diverting support, and intravascular volume
If hypotension persists for more than a few minutes after removal of the cross clamp, consider
unrecognized bleeding or inadequate volume replacement
Therapeutic interventions for unclamping include
decrease inhaled anesthetics decrease vasodilators increase fluid administration give vasoconstrictors reapply cross-clamp for severe hypotension consider mannitol consider sodium bicarbonate
Techniques for open AAA include
GA/ETT, regional, combined, low volatile
propofol vs. etomidate
fentanyl or sufentanil
esmolol, nitroprusside, nitroglycerin, clevidipine, phenylephrine boluses ready
heparin IV 100-300 units/kg- monitor ACT; protamine
Monitors for open AAA include
TEE +/-
cerebral oximetry +/-
potential for rapid blood loss- central line, PIVs, a-line (awake?), PAC no longer recommended
cell saver, cross-matched blood
Describe temperature management for open AAA
forced warming upper body, fluid warmers
lower body should not be warmed during the cross-clamp period because doing so can increase metabolic demands
_______ should be avoided because acute stress on the aneurysm can cause rupture
HYPERTENSION
The heart rate* should be maintained at
or below baseline because myocardial ischemia is often related to the heart rate
_______ may be deferred until the aortic rupture is surgically controlled in the OR
Euvolemic resuscitation**
- the resultant increase in BP without surgical control of bleeding may lead to loss of retroperitoneal tamponade, further bleeding, hypotension, and death
Postoperative treatment of AAA include
aggressively control hypertension & tachycardia
LOS is variable
pain-epidural vs. PCA
__________ (3 things) must be maintained before extubation after AAA
hemodynamic, metabolic, and temeprature
Complications of AAA include
MI, pneumonia, sepsis, renal failure, decreased tissue perfusion, hypothermia
