Anesthesia for Surgery on the Aorta – Flashcards
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Where are lesions of the ascending aorta found?
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between AV and innominate artery
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Where are lesions of the aortic arch found?
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between innominate artery and left SCA
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where are lesions of the descending aorta found?
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distal to the left SCA but above the diaphragm
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where are lesions of the abdominal aorta found?
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below the diaphragm
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what is pathologic process is necessary for dissection of the aorta to occur?
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medial cystic necrosis, a primary degenerative process
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what are the two causes of aortic dissection?
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1. intimal tear allows blood to be forced into the aortic wall (media) 2. hemorrhage in the aortic media extends and disrupts the aortic intima
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what two hereditary connective tissue defects will develop medial cystic necrosis?
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Marfan syndrome and Ehlers-Danlos syndrome
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where aortic dissections most commonly occur?
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ascending aorta (AV to innominate artery)
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What are dissections of the ascending aorta classified as?
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Stanford type A De Bakey Type 1 or 2
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What are De Bakey type II dissections?
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intimal tear in ascending aorta. dissection does not extend beyond the innominate artery. they only involve the ascending aorta
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What are De Bakey type I dissections?
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intimal tear in the ascending aorta. dissection involves the ascending, arch, and descending aorta
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what are De Bakey type III dissections?
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Dissections that occur distal to the left SCA
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What is the difference between Stanford type A and B dissections?
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A involves the ascending aorta. it is a surgical emergency B does not involve the ascending aorta. it is not a surgical emergency
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what is the goal of SBP management of pt with aortic dissection?
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maintain SBP 90-120
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whay is Esmolol beneficial in aortic dissection?
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reduces the shear forces related to the rate of rise of aortic pressure (dP/dt)
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what drug given to lower SBP may increase dP/dt?
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nipride, by causing vasodilation and increasing flow out of the LV
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where are aortic aneurysms most commonly found?
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abdominal aorta
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what are the 2 main causes for aortic aneurysms?
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1. athlerosclerosis 2. medial cystic necrosis
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What may valve abnormality may be caused by aortic root dilation?
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aortic regurgitation
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what is a pseudoaneurysm?
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formed from rupture of the intima and media, with only the adventia or a blood clot forming the outer layer of the vessel
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what is the normal width of the aorta? when is there 50% chance of rupture? elective repair
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1. 2-3cm (wider going cephlad) 2. 50% rupture within 1 year in larger than 6cm 3. > 4cm
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what is Leriche's syndrome? Treatment?
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1. thromboembolic obliteration of aorta at aortic bifurcation. usually due to atherosclerosis 2. aortiobifemoral bypass with a synthetic graft
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what is the Bentall procedure?
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AV replacement and coronary reimplantation. Maybe done during surgery of ascending aorta
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where should A-line be placed during ascending aorta sx?
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in left radial or femoral arteries, d/t innominate artery compression
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where is arterial inflow cannula for CPB placed in aortic dissection repair?
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femoral arty
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when is deep hypothermic circulatory arrest used in aortic surgery?
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aortic arch repair
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what is the goal for hypothermic circ arrest? meds?
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1. reach 15C 2. thiopental to maintain flat EEG 3. solumedrol or decadron, mannitol and phenytoin are used commonly
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what is probably the cause of large intraoperative blood loss after CPB?
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the long rewarming period. Hypothermia interferes with clotting fuctioning
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how is the descending aorta usually accessed?
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through a left thoracotomy without CPB
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where is the aorta clamped with surgery to the descending aorta?
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above and below the lesion
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where should the Aline be placed in pt undergoing descending thoracic aorta repair?
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place in right radial, d/t possible clamping of the L SCA
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what occurs after aortic cross-clamp?
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there is an increase in LV afterload
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what pts are at increased risk of acute LV failure and myocardial ischemia with aortic cross clamping?
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pt with LV dysfunction or CAD
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what is used to prevent excessive increase in BP and decrease in CO after aortic cross clamp?
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Nipride. increasing anesthtic depth just prior to cross-clamping may be helpful in pt with good LV function
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what occurs when aortic cross clamp is released?
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Period of greatest HD instability, RELEASE HOTN
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what is the cause of "release HOTN"
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1. abrupt decrease in afterload coupled with bleeding and release of vasodilating acid metabolites from ischemic lower body
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what electrolyte abnormality may occur with "release HOTN"
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hyperkalemia, d/t acidotic metabolites released from unperfused lower extremities
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what may help avoid severe HOTN with aortic cross clamp release? 3
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1. decrease anesthetic depth 2. volume loading 3. partial or slow release of cross-clamp
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when is NaHCO3 given to acidotic pt?
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when pH is <7.2 and there is HOTN
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what should be given if large amounts of banked blood were given? y?
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give calcium chloride. this is because citrate binds with ionized calcium. replacing calcium will help increase contractility and vasoconstriction. both help with low CO and HOTN
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what increases risk of paraplegia after aortic cross clamping?
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1. > 30 minutes 2. extensive surgical dissection 3. emergency procedures
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what is anterior spinal artery syndrome?
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1. loss of motor function and pinprick sensation 2. preservation of vibration and proprioception
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how many arteries supply the spinal cord blood?
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2 posterior and one anterior
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what supplies the anterior and posterior arteries in the upper thoracic area segment of SC?
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the intercostal arteries
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what supplies the anterior artery blood in the lower thoracic and lumbar area of SC?
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thoracolumbar artery of Adamkiewicz
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where is the origin of the artery of Adamkiewicz ?
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Usually left side and arises from: T5-8 in 15% T9-12 in 60% L1-L2 in 25% of individuals
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how may nipride contribute to spinal cord ischemia in aortic cross clamp?
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it not only causes vasodilation above cross clamp, but also below the cross clamp when administered prior to cross clamping.
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what are 3 interventions to decrease risk of renal failure with aortic surgery?
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1. infusion of Mannitol 0.5g/kg prior to cross-clamping 2. Fenoldopam infusion to presereve RBF 3. Maintain adequate cardiac function (preload, contractility, and systemic perfusion pressure) is mandatory
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where is the cross-clamp placed in abdominal aortic surgery?
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depending on location of lesion, cross-clamp can be applied to supraceliac, suprarenal, or infrarenal aorta
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how does location of cross-clamp effect LV afterload?
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the more distal the less effect on LV afterload
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what are fluid requirements for large incision and extensive retroperitoneal surgical dissection in abdominal aortic sx?
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10-12ml/kg/hr maintenance plus blood loss
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when should pt having aortic surgery be extubated? y
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1. ascending, arch, and thoracic aorta repair should be intubated 2-24 hours post op. focus should be on HD stability and postop bleeding 2. abdominal aorta repair should be extubated at end of surgery
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at what rate do abdominal aortic aneurysms grow per year?
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4mm/year
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what law determines the likelihood of an aneurysm rupturing? explain
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Laplace law determines likelihood of rupturing. It says that as the radius increases so does the wall tension. T=P x r
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should aneurysms small than 4 to 5 cm be considered benign?
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no, they are able to rupture also. Aneurysms greater than 5cm usually require surgical intervention
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where is most aortic cross clamping for AAA repairs? level?
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Most aortic cross-clamping is done infrarenal, because most aneurysms appear below the level of the renal arteries. Renal arteries are at L1-L2
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what patients are unable to fully compensate for changes in afterload with aortic cross-clamping?
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Patients with ischemic heart disease or ventricular dysfunction. The increased wall stress may contribute to decreased global ventricular function and myocardial ischemia
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what may occur with traction of the mesentery when trying to expose the aorta? 5
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There is decreased blood pressure and SVR, tachycardia, increased cardiac output, and facial flushing.
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What is one of the most significant predictors of postoperative renal dysfunction?
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Preoperative renal dysfunction
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what is the cause of ischemia of the colon during abdominal aorta cross-clamping?
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manipulation of the inferior mesenteric artery blood supply to the left colon
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when should a high concentration inhalation anesthetic technique be avoided in vascular surgery?
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when there is a moderate to severe decreased ejection fraction
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what is the advantage of using a balanced technique for vascular surgery?
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high dose opioids provide cardiovascular stability and is beneficial in patients with ischemic heart disease and ventricular dysfunction1
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In anticipation of aortic cross-clamping release what can be done to avoid severe hypotension?
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Administration of IV fluids to increase the CVP 3 to 5 mmHg or PAOP 3-4 mmHg
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when performing an induction sequence on a patient with a ruptured AAA what is the expected routine?
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Induction of anesthesia should follow the principles of trauma anesthesia
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what is the initial focus for the anesthesiologist in emergent repair of a ruptured AAA?
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Initial focus should be on cardiovascular resuscitation until bleeding from the proximal aorta is controlled by surgical intervention
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what type of aneurysms are most common in the descending and distal thoracic aorta? in the ascending aorta?
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Descending and distal throacic aorta aneurysms are most commonly fusiform aneurysms. Ascending aorta aneurysms are most commonly saccular aneurysms
