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Page 14 of 21 Calafiore et al. Vessel Plus 2023;7:18 https://dx.doi.org/10.20517/2574-1209.2023.42

A strategy to overcome this metabolic deadlock was experimentally proposed by Ehrlich et al., who
[104]
suggested to start rewarming after a period of cold perfusion at 20 °C after DHCA . After circulatory
arrest, astrocytes cannot simultaneously supply neurons with lactate and maintain extracellular glutamate
levels low, as their glycogen reserves become exhausted. If the circulation resumes at a consistently low
temperature, astrocytes have the ability to replenish their glycogen stores by uptaking glucose from the
blood, during a period when neuronal metabolism remains unaffected by higher temperatures. Astrocytes
can then remove glutamate from the extracellular fluid, eliminating the danger of neuronal death, and send
lactate to neurons for their metabolic needs. When rewarming starts, glutamate in the extracellular fluid has
been removed and metabolic reserves restored. In general, all organs can benefit from a period of cold
perfusion before rewarming to re-establish their nutrient stores.

In a clinical setting, Di Mauro et al. found that DR (defined as 10-min cold reperfusion before rewarming)
after DHCA was able to maintain a low NEs prevalence (1.6%) if CA time was ≤ 40 min in a mixture of
[105]
surgery for acute (48%) or chronic (52%) aortic disease . Similar results were reported by Calafiore et al. in
elective patients operated on with straight DHCA and DR .
[106]
COMMENT
Many surgeons abandoned DHCA (with/out ACP or RCP) in favor of MHCA with ACP, showing better
results that are more related to increased experience than to better cerebral protection, but there is no doubt
that any technique, in experienced hands, can provide stable and good results. Moreover, the interpretation
of comparative studies between strategies used in different periods is not easy to perform, and often, the
degree of hypothermia is not a risk factor for postoperative NDs.

The advent of ACP allowed the diffusion of arch surgery outside specialized Centers. However, the
technique is not perfect. Surgically delivered ACP is not comparable to physiologic delivered flow to the
brain in the native state. The flow can be too high and unbalanced, such as when the innominate artery
alone is perfused, sometimes adding the LCCA, rarely the LSA. This non-physiologic blood flow can have
consequences, such as reduced focal metabolism and localized brain edema .
[107]

The rate of NDs after CA is the fruit of a compromise between the strategy of cerebral protection and the
manipulation of the arch or of the epiaortic vessels we must work with. However, it is clear that clinical
evidence is inconclusive, as brain imaging detects more events and neurocognitive tests, repeated at 6
months after surgery, provide us the possibility to better evaluate the damages related to the surgical
procedure. Svensson et al., in a prospective randomized trial including 121 patients who had total arch
replacement under DHCA with ACP or RCP, found that 29 patients (24%) experienced clinical NDs,
cortical infarcts or deep white or gray matter changes on brain imaging, or neurocognitive changes, without
difference between groups .
[108]
Another point of interest, not very clear in the literature, is how long a CA has to last, even for a complex
arch surgery. The STS database, which includes Centers with different volumes, showed that in 7,830
chronic cases, the median CA time was 25.8 min (16.0-30.0) and in acute cases 31 min (23.0-43.0) . Lau et
[5]
[6]
al., in 1,043 cases where DHCA + RCP was used, reported a mean CA time of 25.8 ± 11.4 min, 50 min or
[109]
longer in only 4.8% of the cases . Damberg et al. reported a CA time of 29.7 ± 8.8 min using straight
DHCA . Pearsall et al., in 307 patients who underwent hemiarch surgery, reported a median CA time of 11
[65]
min (9-15) . Calafiore et al. reported a median CA time of 24 min (19-32) in patients who had undergone
[110]
hemiarch (51%) and total arch (49%) replacement . All these data show that the great majority of arch
[106]
surgery is performed within 40 min of CA time and almost all procedures can be accomplished within