TAAA Flashcards
What does it mean if the aorta has ectasia? What about aneurysm?
Ectasia: Dilation of the aorta <150% of normal diameter; Aneurysm: >150% of normal diameter (of all 3 layers of the aorta - intima, media, adventia)
What is the difference between an aneurysm and a pseudoaneurysm?
A pseudoaneurysm does NOT involve all 3 layers of the aorta (an aneurysm involves all 3)
What is the cause of dilation of the aorta?
Loss of elastic fibers and increased deposition of proteoglycans (i.e. due to atherosclerosis, fibroelastic diseases, or inflammation of the aorta)
What is the cause of Marfan’s syndrome?
Defect in the FBN1 gene
What system is used to classify aortic aneurysms?
Crawford Classification (different from DeBakey which is for dissections)
What are the various types in the Crawford Classification?
Type I = left subclavian to celiac axis (suprarenal); Type II = left subclavian to the aortic bifurcation (most extensive); Type III = 6th intercostal space to the iliac bifurcation; Type IV = Visceral abdomoinal aorta to the iliac bifurcation (no thoracic component); Type V = 6th intercostal space to above the renal arteries
How many landing zones are there of the aorta?
Eleven
What size aneurysm should you consider surgical intervention?
TAA with diameters >/= 5.5cm OR <5.5cm but risk of rupture OR if there is increased risk for perioperative morbidity and mortality regardless of size
What constitutes increased risk of rupture for TAAs?
Rapid growth >/= 0.5 cm/year + symptomatic aneurysm + connective tissue disease + saccular aneurysm + female + infectious aneurysm
Why is the spinal cord at risk of injury during TAA repairs?
Multifactorial: decreased blood flow due to restriction of segmental arterial inflow + increased tissue pressure from edema or increased ICP + increased venous pressure limiting outflow
What part of the spinal cord is more often damaged?
The anterior spinal cord (versus the posterior) because there is only one anterior spinal artery while there are two posterior spinal arteries
What do you see if you have anterior spinal cord injury?
Decreased motor function
What is the formula for spinal cord perfusion pressure?
SCPP = MAP - ICP; should be > 70mmHg
How far after can you have delayed paraplegia?
Delayed paraplegia can occur any time in the first 2 weeks after open repair (accounts for 60% of spinal cord injuries encountered)
What should you do to optimize spinal cord and end-organ perfusion after open aneurysm repair?
CDV for tachyarrhythmias + increase lumbar drain + increased MAP + transfusion Hbg > 10 g/dL + volume resuscitation
What is the leading cause of morbidity and mortality after TAAA repair?
Respiratory failure
What Crawford classification types require lung isolation?
Type I, Type II, and Type III
What can be damaged during TAAA repair that would affect respiratory function?
The left recurrent laryngeal nerve
What is the perioperative morbidity and mortality rate for an open TAAA repair?
10-15%
What intervention helps reduce postop renal insufficiency?
Delivery of cold crystalloid perfusate into the renal arteries during repair
In what situation are open repairs the recommended route over endovascular?
In patients with connective tissue disorders and aneurysms
What are risk factors for perioperative morbidity and mortality for open surgical repair?
Age >/= 65yo (worse if >/= 75yo) + preoperative renal insufficiency or hemodialysis use + COPD and FEV1 </= 50% predicted + previous stroke
What are risk factors for perioperative morbidity and mortality for TEVAR?
Functional dependence (frailty) + TAAA extent + pulmonary disease + need for iliac access + zone 1/2 landing for thoracic stent graft
What are the different types of endoleaks?
Type I = proximal/distal graft attachment site leaks; Type II = retrograde flow into the aneurysm sac from aortic side branches; Type III = Defect in the graft (i.e. fabric tear or disconnection of modular overlap); Type IV = graft wall porosity; Type V = No identifiable cause
What is left heart bypass?
Left atrium to left femoral bypass; cannulation for the LA done via pulmonary vein which is then sent to the FA (or other distal site)
What is usually done with left heart bypass in surgery to help reduce cardiac injury?
Sequential clamping of the aneurysm to allow for reimplantation of arteries
If you are on left heart bypass, where do you need to measure BPs?
Right radial artery = measures perfusion to the upper body + Femoral artery = measures perfusion to the lower body
When do you go on partial CPB for TAAA repairs?
When one-lung ventilation will not be tolerated with left heart bypass; allows for oxygenation
How do you go on partial CPB for TAAA repairs?
Usually via the left femoral vein + aorta (distal to the aortic clamp)
Why do you not go on full bypass for TAAA repairs? What if you do go on full CPB?
The heart still needs to eject in order for blood to go to the upper body since there is an aortic cross-clamp that prevents blood from going back up to the head vessels; if you go on full CPB, you need to perform deep hypothermic circulatory arrest
What are the risk factors for spinal cord injury during aortic surgery?
Extent of aorta replacement/coverage (extent II aneurysms and >20 cm endovascular coverage are highest risk) + replacement or coverage of aortic zone 5 (T9-T12 artery of Adamkiewicz) + urgent/emergent repairs + patient factors that predispose to atherosclerosis or poor O2 delivery
What is the blood supply to the spinal cord?
One anterior spinal artery + two posterior spinal arteries + collaterals from thoracic, lumbar, and pelvic intercostal arteries
What is the recommendation for neuromonitoring during aortic surgery?
Class IIb + level of evidence C; no large-scale studies demonstrate superiority
How do SSEPs work?
Stimulus in peripheral nerve -> dorsal column (posterior cord) -> somatosensory cortex
How do MEPs work?
Stimulus in motor cortex -> corticospinal tract (anterior cord) -> motor function
What are causes of false positives during neuromonitoring?
Peripheral nerve ischemia, extremity malperfusion, or acute intraoperative stroke
What are the interventions that one can do for spinal cord perfusion?
CSF drainage (best evidence and principal intervention) + MAP augmentation (>90mmHg) + increased Hg (10 g/dL) + hypothermia + steroids/mannitol/naloxone + neuromonitoring
Should you put in a spinal drain for TEVARs?
Smaller benefits when compared to open repairs and there may be a higher risk of morbidity due to CSF drain complications; only in high-risk TEVARs (extensive length + previous aortic coverage + compromised pelvic perfusion + occluded vertebral arteries + planned left-subclavian coverage)
What is the overall complication rates for lumbar drains?
~6.5%
What are minor complications for lumbar drains?
Puncture site bleeding + hypotension + CSF leak (not requiring intervention) + drain fracture left in place + occluded or dislodged catheter + bloody CSF
What are moderate complications for lumbar drains?
Spinal headache + CSF leak requiring intervention + drain fracture requiring surgical removal
What are severe complications for lumbar drains?
Epidural hematoma + intracranial hemorrhage (from over-drainage of CSF) + SAH + meningitis + catheter-related neurologic deficits
What do you do if you have a blood lumbar drain insertion for a patient who needs full CPB for TAAA repair?
Postpone surgery for 24 hours
What is bloody CSF associated with when doing a lumbar drain?
Intracranial hemorrhage
How much CSF can you remove at a time for lumbar drains?
Maximum of 15 cc/hour to minimize risk of intracranial hemorrhage
