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Troncone et al. Vessel Plus 2023;7:14 https://dx.doi.org/10.20517/2574-1209.2023.08 Page 9 of 15

Table 1. Advantages and disadvantages of deep hypothermic circulatory arrest in the repair of thoracoabdominal aortic aneurysms
Advantages Disadvantages
Deep hypothermic Non-clampable distal aortic arch or proximal descending thoracic aorta Full heparization for cardiopulmonary bypass
circulatory arrest due to large aneurysms, distorted anatomy, or need for fenestration in Coagulopathy associated with deep
aortic dissection hypothermia
Additional spinal and visceral protection associated with hypothermia Difficult to provide cerebral perfusion during
circulatory arrest
Potential for cardiac ischemia during ventricular
fibrillation associated with hypothermia
Pulmonary injury associated with coagulopathy,
pulmonary edema, and cardiopulmonary bypass

Utilization of CPB with brief periods of DHCA for the repair of DTAAs and TAAAs has numerous
advantages compared to other approaches, including “clamp-and-sew,” left heart bypass, and partial
cardiopulmonary bypass. The ability to operate in a bloodless surgical field can make crucial differences in
the expeditious performance of the procedure, particularly during more challenging moments such as the
creation of the proximal anastomosis . The elimination of the need for proximal aortic clamping is one of
[44]
the primary advantages of DHCA, which has multiple included benefits. Firstly, the amount of healthy
aortic tissue used for construction of a proximal anastomosis is often compromised by the requirement of a
cross-clamp, which may unnecessarily lead to changing the location of the anastomosis to a more proximal
location with more available tissue and increase surgical complexity and risk. Secondly, even after
identification of a suitable proximal anastomotic site and associated clamp site, more extensive periaortic
dissection is required for placement of a clamp than is necessary when using DHCA, which may increase
risk of bleeding, injury to the recurrent laryngeal or phrenic nerve, as well as increased aortic manipulation
[8]
which may lead to atheroembolic events . Lastly, the unparalleled endoluminal exposure of the proximal
aortic anastomosis site during DHCA allows for inspection of the quality of aortic tissue and optimal suture
placement, as well as debridement of intra-aortic debris which may serve to reduce the incidence of
thromboembolism .
[19]

An additional advantage of utilizing DHCA relates to the ability of having an open proximal aorta. During
the creation of the proximal anastomosis, ongoing low-flow lower body perfusion with partial occlusion of
venous drainage of the right heart leads to retrograde flow into the superior vena cava, resulting in gentle
flushing of the innominate and left carotid arteries, removing air and debris . Increasing lower body flows
[19]
and volume loading the patient can also be performed as well just prior to graft clamping and restoration of
circulation to flush the cerebral vasculature and proximal aorta to clear debris .
[19]
Regardless of the various strategies used to facilitate DTAA/TAAA repair, there is a necessary reduction of
blood flow to the spinal cord [the degree to which varies depending on the extent of the aneurysm, previous
surgical intervention, and adjunctive perfusion strategies] as well as periods of absolute ischemia to end-
organs requiring target vessel anastomosis to the aortic graft [renal and visceral vessels]. DHCA provides an
effective method to off-set the substantial risks of spinal cord and renovisceral ischemia during these
operations. Kouchoukos has published multiple results on the routine use of DHCA for the repair of DTAs
and TAAAs, with particular focus on spinal cord and visceral protection, noting adequate protection during
periods of circulatory arrest without the need for other adjuncts . Spinal cord ischemia and subsequent
[16]
postoperative paraplegia is arguably the most devastating complication following open repair of DTAs/
TAAAs. Based on multiple laboratory-based models and clinical imaging studies, spinal cord injury
following DTA/TAAA repair followed the pathophysiology of an ischemic-reperfusion model, wherein
temporary aortic cross-clamping induces hypoperfusion to the distal spinal cord vessels, and re-perfusion
further exacerbates this insult . Systemic hypothermia is one of the most reliable adjuncts for the
[45]
prevention of spinal cord ischemia as well as mitigating the deleterious effects of reperfusion and is thus