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SAN ANTONIO -- During aortic arch surgery, even short bouts of hypothermic circulatory arrest (HCA) were associated with neurocognitive and neuroimaging deficits after surgery regardless of the level of hypothermia applied, a GOT ICE substudy found.

Patients who underwent surgery with less than 20 minutes of HCA and adjunctive antegrade cerebral perfusion (ACP) showed an approximately 40% incidence of dichotomous cognitive deficit 4 weeks post-surgery. Notably, there was a nonsignificant trend toward increased frequency with people assigned to warmer HCA temperatures:

• Deep hypothermia (≤20.0 °C): 37.3%
• Low-moderate hypothermia (20.1-24.0 °C): 41.8%
• High-moderate hypothermia (24.1-28.0 °C): 42.9%

"Overall, findings contradict longstanding surgical dogma that HCA durations [under] 25-30 minutes are safe with regards to brain injury," reported G. Chad Hughes, MD, of Duke University Medical Center in Durham, North Carolina, at the Society of Thoracic Surgeons (STS) annual conference.

HCA is a surgical technique that takes body temperature down very low and stops blood circulation to presumably protect the brain during surgeries such as the removal of venous tumors, aortic arch repair, and operations on arteriovenous malformations in the neck or head.

Hughes noted that the safe duration of HCA has remained a matter of debate, with some data suggesting 25-30 minutes to be safe at deep hypothermia. Aortic surgery centers worldwide have also shifted toward lesser hypothermia paired with ACP, an adjunctive technique for brain protection, based on clinical safety data, he said.

The recently showed that low-moderate cooling was noninferior to deep hypothermia in terms of a composite global cognitive change score between baseline and 4 weeks postoperatively, though structured verbal memory was better preserved in the deep group. There was no significant difference between deep cooling and high-moderate temperature groups in the trial, either, with ACP in the picture.

STS session discussant T. Brett Reece, MD, MBA, of University of Colorado School of Medicine, Anschutz, raised the question of whether practice variations such as flow pulsatility and smaller volumes may affect the frequency of neurocognitive deficits after aortic arch repair.

Hughes was open to those possibilities and said the research in this area is just beginning.

He suggested that the short-term cognitive deficits logged in GOT ICE may be related to postoperative cognitive dysfunction, a common complication after surgery that has been documented more in the coronary artery bypass grafting (CABG) population.

In any case, it'll take 5 years or more to see if the present neurocognitive findings at 1 month translate to problems later on like they have been shown to do in CABG, Hughes said.

The GOT ICE substudy presented at STS included the 170 out of 282 participants who had HCA last under 20 minutes. Average age was 61 years, with under 20% women. White people accounted for the vast majority of the cohort.

Hughes reported fairly balanced patient demographic and clinical characteristics at baseline across the three randomly assigned temperature groups, except for a higher prevalence of diabetes in the deep cooling group and more previous cardiac surgery in the low-moderate group.

Due to the limited HCA time in these patients, surgeries were limited to hemi-arch repair instead of total arch repair, he noted.

The trial defined dichotomous cognitive deficit as a greater than 1 standard deviation decline from baseline in at least one of the five cognitive domains: executive functioning, memory, attention and concentration, processing speed, and psychomotor skills.

In a subset of patients from Duke (n=43), neuroimaging with high-resolution anatomical and resting state functional MRI identified an area of the frontal lobes -- the right anterior superior frontal gyrus region -- as particularly susceptible to the effects of even short HCA in the range of 8-17 minutes.

Hughes warned that the study does not prove causality, though it suggests the possibility that longer HCA duration preferentially affects this brain region known to be functionally connected with the brain's default mode network.

He told the audience that he personally avoids HCA nowadays. "I don't think it's necessary."

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