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Page 10 of 15 Troncone et al. Vessel Plus 2023;7:14 https://dx.doi.org/10.20517/2574-1209.2023.08

[4]
used by many surgeons during complex aortic intervention, providing uniform spinal cord cooling . When
DHCA is not used, other surgical adjuncts are frequently employed to accomplish similar reductions in
spinal ischemic time, such as epidural spinal cord cooling, perfusion catheters, partial CPB, or left heart
bypass [LHB]. Left heart bypass is an excellent technique at proximal aortic decompression and distal aortic
perfusion to maintain blood flow to vessels beyond the distal aortic cross-clamp, including intercostal,
lumbar, and hypogastric vessels, providing ongoing in-line flow to the spinal cord during occlusion of other
major inflow sources. It is widely reported that distal aortic perfusion pressure must be equal to or greater
than 60mmHg to minimize spinal cord injury, and this is readily accomplished with centrifugal pumps used
in LHB . However, when using LHB, one must accept the lack of venous reservoir, ability to efficiently
[46]
cool and rewarm the patient, and rely on intrinsic lung function for gas exchange which may be impaired
due to the necessity of single lung ventilation. Furthermore, if the extent of the aneurysm requires aortic
arch clamping proximal to the left subclavian artery for proximal anastomosis creation, this temporary
occlusion will affect anterior spinal cord artery perfusion, potentially compromising spinal cord blood
flow . To overcome these deficiencies, at the expense of higher doses of systemic heparinization, partial
[25]
CPB can be utilized, allowing for optimal control of oxygenation; this can be converted to full CPB for
cerebral and myocardial perfusion with well-oxygenated blood when there is additional right axillary
cannulation, and if necessary, cool the patient for a period of DHCA. In summary, utilization of DHCA
certainly offers a high degree of protection to the spinal cord simply by virtue of direct reduction of
metabolic demands. Its use removes the uncertainty and technical complexity associated with relying on
other protective strategies such as selective segmental artery perfusion with various balloon-tipped catheter
techniques. Assessment of the aorta during periods of DHCA minimizes the duration of time with back-
[18]
bleeding spinal arteries, which may reduce spinal cord steal phenomena . However, ligation of intercostal
or lumbar arteries prior to or after aneurysm sac opening can also be equally performed. Lastly, the use of
DHCA for the proximal anastomosis can be augmented, rather than replaced, by similar adjunctive
protection strategies for DTA/TAAA repair that rely on the use of a proximal cross-clamp and distal
perfusion. While the practice of sequential clamping with distal perfusion is mostly utilized with LHB, one
can equally cool the patient and utilize DHCA for an open proximal anastomosis, taking advantage of the
hypothermic protection on the spinal cord, as well as utilize a distal aortic clamp with lower femoral flow
rates to augment hypothermic flow to the spinal cord in a manner analogous to antegrade cerebral
perfusion during DHCA for arch repair.

Analogously, DHCA simplifies the management of renovisceral artery protection. DHCA alone provides
simple yet robust protection of the kidneys and abdominal viscera, however the operative time required to
perform the proximal anastomosis, along with spinal reimplantation, and subsequently incorporate the
renovisceral vessel anastomoses as either separate bypasses or a patch into the aortic graft substantially
increases the DHCA time, with its inherent risks. The benefits of DHCA on renovisceral protection
essentially lie within the degree of protection it affords during creation of the proximal anastomosis. In this
regard, DHCA has a more protective effect than other perfusion techniques particularly when organ
ischemic time approaches or exceeds 60 min . Once there is no longer a need for circulatory arrest,
[5]
resumption of circulation can be combined with the achieved level of deep hypothermia to provide ongoing
visceral protection while resuming perfusion to the brain and/or lower body, depending on cannulation
techniques.

DISADVANTAGES
Utilization of both CPB and periods of DHCA are necessarily accompanied by a much greater degree of
systemic heparinization, exposure to the cardiopulmonary bypass circuit, and deleterious physiologic effects
systemic hypothermia compared to many of the other modalities of organ protection for DTA and TAAA