Prospective randomized neurocognitive and S-100 study of hypothermic circulatory arrest, retrograde brain perfusion, and antegrade brain perfusion for aortic arch operations

Optimization of Hypothermic Protocols for Neurocognitive Preservation in Aortic Arch Surgery: A Literature Review

Shifts from deep to moderate hypothermic circulatory arrest (HCA) in aortic arch surgery necessitate an examination of their differential impacts on neurocognitive functions, especially structured verbal memory, given its significance for patient recovery and quality of life. This study evaluates and synthesizes evidence on the effects of deep (≤20.0 °C), low-moderate (20.1-24.0 °C), and high-moderate (24.1-28.0 °C) hypothermic temperatures on structured verbal memory preservation and overall cognitive health in patients undergoing aortic arch surgery. We evaluated the latest literature from major medical databases such as PubMed and Scopus, focusing on research from 2020 to 2024, to gather comprehensive insights into the current landscape of temperature management during HCA. This comparative analysis highlights the viability of moderate hypothermia (20.1-28.0 °C), supported by recent trials and observational studies, as a method to achieve comparable neuroprotection with fewer complications than traditional deep hypothermia. Notably, low-moderate and high-moderate temperatures have been shown to support substantial survival rates, with impacts on structured verbal memory preservation that necessitate careful selection based on individual surgical risks and patient profiles. The findings advocate for a nuanced approach to selecting hypothermic protocols in aortic arch surgeries, emphasizing the importance of tailoring temperature management to optimize neurocognitive outcomes and patient recovery. This study fills a critical gap in the literature by providing evidence-based recommendations for temperature ranges during HCA, calling for ongoing updates to clinical guidelines and further research to refine these recommendations. The implications of temperature on survival rates, complications, and success rates underpin the necessity for evolving cardiopulmonary bypass techniques and cerebral perfusion strategies to enhance patient outcomes in complex cardiovascular procedures.

Optimal brain protection in aortic arch surgery

There is considerable debate with regard to the optimal cerebral protection strategy during aortic arch surgery. There are three contemporary techniques in use which include straight deep hypothermic circulatory arrest (DHCA), DHCA with retrograde cerebral perfusion (DHCA + RCP), and moderate hypothermic circulatory arrest with antegrade cerebral perfusion (MHCA + ACP). Appropriate application of these methods ensures appropriate cerebral, myocardial, and visceral protection. Each of these techniques has benefits and drawbacks and ensuring coordinated circulation management strategy is critical to safe performance of aortic arch surgery. In this report, we will review various cannulation strategies, review logistics of hypothermia, and review the relevant literature to outline the strengths and weaknesses of these various cerebral protection strategies.

Modified Technique for Retrograde Cerebral Perfusion during Hemiarch Aortic Replacement

Background  Uncertainty remains regarding the optimal method of brain protection for procedures that require repair or replacement of the aortic arch. We examined the early outcomes of a technique for brain protection in patients undergoing partial aortic arch (hemiarch) replacement that involves deep hypothermic circulatory arrest (DHCA) and retrograde cerebral perfusion (RCP) of cold blood from the superior vena cava toward the end of the arrest interval.

Methods  During a recent 15-year interval, 520 patients underwent elective or urgent/emergent ascending aortic and hemiarch replacement as an isolated (47 patients) or combined (473 patients) procedure employing DHCA (mean nasopharyngeal temperature at circulatory arrest, 17.1°C and mean duration, 19.3 minutes) supplemented with RCP of cold blood from the superior vena cava toward the end of the arrest interval (mean, 6.7 minutes). The mean age of the patients was 59.5 years, and 65% were male.

Results  The in-hospital and 30-day mortality rates were 1.2% (six patients). Seven patients (1.4%) sustained a stroke and 19 patients (3.7%) had transient neurologic dysfunction that completely resolved by the time of hospital discharge. Four patients (0.77%) developed postoperative renal failure requiring dialysis. Twenty-one patients (4%) required ventilator support for >48 hours and five patients (0.96%) required a tracheostomy. The median hospital length of stay was 6 days.

Conclusion  DHCA with a brief interval of RCP is a safe and effective technique for brain protection during hemiarch aortic replacement. RCP reduces the duration of brain ischemia and permits removal of particulate matter and air from the arterial circulation.

Analysis of risk factors of cerebral complications after Stanford type A aortic dissection involving arch surgery

OBJECTIVE

To explore the risk factors of cerebral neurological complications after surgery for Stanford type A aortic arch surgery.

METHODS

One hundred sixteen patients who received Stanford type A aortic dissection from January 2012 to December 2019 were recruited. All patients received surgery under deep hypothermic circulatory arrest (DHCA) and general anesthesia. They were grouped by degree of postoperative cerebral neurological complication. The related factors of cerebral neurological complications were analyzed by single-factor analysis and multi-factor logistic regression.

RESULTS

Postoperative neurological complications were observed in 31 cases (26.72 %). Two groups were identified: permanent neurological dysfunction (PND) was observed in seven cases, and temporary neurological dysfunction (TND) was observed in 24 cases. In-hospital mortality was 9.48 % (11/116), with six in the cerebral complication groups and five in the non-complication group. Single-factor analysis showed the associated factors were age, stroke history, carotid plaque or stenosis, emergency surgery, renal dysfunction, hypotension, aortic clamping time, deep hypothermic circulatory arrest time, postoperative hypoxemia, postoperative low cardiac output and plasma transfusion >800 ml, and erythrocyte suspension transfusion >6 U. Multi-factor logistic analysis showed the independent predictive factors were DHCA time >40 min, plasma transfusion >800 ml, erythrocyte suspension transfusion >6 U, history of stroke, and carotid plaque or stenosis.

CONCLUSION

The factors independently associated with neurological complications are DHCA time >40 min, plasma transfusion >800 ml, erythrocyte suspension transfusion >6 U, history of stroke, and carotid plaque or stenosis. Our findings suggest that patients with these risk factors should receive intervention during treatment to reduce cerebral neurological complications.

Hybrid repair versus conventional open repair for thoracic aortic arch aneurysms

BACKGROUND

Thoracic aortic arch aneurysms (TAAs) can be a life-threatening condition due to the potential risk of rupture. Treatment is recommended when the risk of rupture is greater than the risk of surgical complications. Depending on the cause, size and growth rate of the TAA, treatment may vary from close observation to emergency surgery. Aneurysms of the thoracic aorta can be managed by a number of surgical techniques. Open surgical repair (OSR) of aneurysms involves either partial or total replacement of the aorta, which is dependent on the extent of the diseased segment of the aorta. During OSR, the aneurysm is replaced with a synthetic graft. Hybrid repair (HR) involves a combination of open surgery with endovascular aortic stent graft placement. Hybrid repair requires varying degrees of invasiveness, depending on the number of supra-aortic branches that require debranching. The hybrid technique that combines supra-aortic vascular debranching with stent grafting of the aortic arch has been introduced as a therapeutic alternative. However, the short- and long-term outcomes of HR remain unclear, due to technical difficulties and complications as a result of the angulation of the aortic arch as well as handling of the arch during surgery.

OBJECTIVES

To assess the effectiveness and safety of HR versus conventional OSR for the treatment of TAAs.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the Cochrane Vascular Specialised Register, CENTRAL, MEDLINE, Embase, CINAHL and AMED databases and World Health Organization International Clinical Trials Registry Platform and ClinicalTrials.gov trials registers to 22 March 2021. We also searched references of relevant articles retrieved from the electronic search for additional citations.

SELECTION CRITERIA

We considered for inclusion in the review all published and unpublished randomised controlled trials (RCTs) and controlled clinical trials (CCTs) comparing HR to OSR for TAAs.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened all titles and abstracts obtained from the literature search to identify those that met the inclusion criteria. We retrieved the full text of studies deemed as potentially relevant by at least one review author. The same review authors screened the full-text articles independently for inclusion or exclusion.

MAIN RESULTS

No RCTs or CCTs met the inclusion criteria for this review.

AUTHORS' CONCLUSIONS

Due to the lack of RCTs or CCTs, we were unable to determine the safety and effectiveness of HR compared to OSR in people with TAAs, and we are unable to provide high-certainty evidence on the optimal surgical intervention for this cohort of patients. High-quality RCTs or CCTs are necessary, addressing the objective of this review.

Open aortic arch surgery: the gold standard method

Aortic arch pathologies are complex and treating them requires close team collaboration and technical skills to provide safe outcomes with low morbidity and mortality rates. Such challenges are facing both aortic and vascular surgeons. Open aortic arch repair has been the standard method of practice in all cases of aortic arch pathologies for the last four decades since the very first successful published case series by Griepp et al. during 1975. However, since then, repair of multi-segmented thoracic aortic pathologies has been explored through endovascular techniques; this is with or without open repair as a one-stage procedure especially in high-risk and elderly patients. Although the role of endovascular techniques in thoracoabdominal aorta is well established, its utilization as solo technique in aortic arch pathologies remains debatable. In this review, we highlight current evidences behind using open, endovascular, and hybrid procedures in aortic arch surgery.

Intermittent upper and lower body perfusion during circulatory arrest is safe for aortic repair

Introduction:

We report our initial surgical experience of intermittent upper and lower body retrograde perfusion during aortic repair under circulatory arrest.

Methods:

Between 2007 and 2015, 148 consecutive patients underwent surgical aortic repair using moderate hypothermic circulatory arrest with intermittent upper and lower body retrograde perfusion.

Results:

All patients underwent ascending aorta replacement; eight had hemiarch replacement (5.4%) and 92 had aortic root surgery (62.2%). Twenty-nine patients (19.6%) had re-operations and 60 patients (40.5%) had concomitant procedures. The mean duration of circulatory arrest was 23.2 ± 5.4 minutes (range 13-48 minutes). Hospital length of stay was 11.3 ± 16.9 days (median 7.0 days; interquartile range [IQR] 6 days). Complications included death in 0.7%, stroke in 3.4%, respiratory failure in 12.8%, renal replacement therapy in 2.0% and re-exploration for bleeding in 0.7%. Peak renal and hepatic biomarkers were: creatinine 1.2 ± 0.3 mg/dL, aspartate aminotransferase (AST) 291 ± 1112 U/L (IQR 91.8 U/L), alanine aminotransferase (ALT) 212 ± 924 U/L (IQR 43.0 U/L) and total bilirubin 1.2 ± 0.9 mg/dL. Peak lactate was 5.0 ± 3.3 mmol/L (IQR 3.3 mmol/L) and the mean time to normalization (<2 mmol/L) was 14.3 ± 14.0 hours.

Conclusions:

Intermittent upper and lower body retrograde perfusion during circulatory arrest is safe for aortic repair, resulting in low morbidity and mortality. There were only modest rises in hepatic and renal injury biomarkers as well as the rapid clearance of lactate. These findings support the continued study of this technique to reduce end-organ dysfunction during circulatory arrest, including expansion to patients with longer circulatory arrest duration and a direct comparison with conventional circulatory arrest without retrograde upper and lower body perfusion.

Deep chronic microvascular white matter ischemic change as an independent predictor of acute brain infarction after thoracic aortic replacement

BACKGROUND

Postoperative brain injury is a cause of mortality and morbidity in patients who undergo thoracic aortic replacement. Chronic microvascular white matter ischemic change (WMIC) has been shown to be associated with acute brain infarction in the general population. WMIC has also been shown to be an independent predictor of non-focal neurocognitive changes, generalized seizures, and temporary neurologic dysfunction in patients who undergo thoracic aortic replacement. The aim of this study is to determine if WMIC is a risk factor for acute brain infarction in patients who undergo thoracic aortic replacement.

METHODS

A case-control study of patients who underwent thoracic aortic replacement between 2001 and 2014 were reviewed for neurological changes after surgery and acute brain infarction on postoperative diffusion-weighted imaging (DWI) magnetic resonance imaging (MRI). Patients with neurological changes were matched with control patients who underwent thoracic aortic replacement and had postoperative neurological symptoms without acute brain infarctions. Acute infarction was re-assessed by reviewing DWI sequences on postoperative MRI. WMIC was assessed on FLAIR and T2WI sequences on both preoperative and postoperative MRI. Logistic regression was performed assessing the relationship of WMIC and acute ischemic infarction.

RESULTS

5171 patients underwent thoracic aortic replacement; 179 had postoperative neurological changes, and of those 53 patients had acute brain infarction on postoperative DWI. Patients with deep WMIC were more likely to have acute DWI infarctions after thoracic aortic replacement (P = 0.023).

CONCLUSION

Our matched retrospective case-controlled study shows deep WMIC to be a predictor of acute brain infarction on DWI after thoracic aortic replacement.

Neuroprotective Strategies in Repair and Replacement of the Aortic Arch

Aortic arch surgery is a technical challenge, and cerebral protection during distal anastomosis is a continued topic of controversy and discussion. The physiologic effects of hypothermic arrest and adjunctive cerebral perfusion have yet to be fully defined, and the optimal strategies are still undetermined. This review highlights the historical context, physiological rationale, and clinical efficacy of various neuroprotective strategies during arch operations.

Protecting the brain and spinal cord in aortic arch surgery

Protection of the central nervous system-either the brain or the spinal cord-during aortic surgery has been the subject of intense research over the past several decades. While it took some 30 years to prove that some of the techniques first practiced in animals are valuable, surgeons can now take courage from 50 years of research that has resulted in superb outcomes, particularly when compared with historical results. Complex total arch operations and descending aortic operations can now be performed with less than a 2% rate of stroke, spinal cord injury, or death. Thoracoabdominal aortic operations and endovascular procedures have also become considerably safer with excellent results reported. The following review will discuss some of the historical outcomes, innovations, iterations, current techniques, and outcomes.

Varying Evidence on Deep Hypothermic Circulatory Arrest in Thoracic Aortic Aneurysm Surgery

Cardiovascular surgeons have long debated the safe duration of deep hypothermic circulatory arrest during thoracic aortic aneurysm surgery. The rationale for using adjunctive cerebral perfusion (or not) is to achieve the best technical aortic repair with the lowest risk of morbidity and death. In this literature review, we highlight the debates surrounding these issues, evaluate the disparate findings on deep hypothermic circulatory arrest durations and temperatures, and consider the usefulness of adjunctive perfusion.

Brain protection in aortic arch aneurysm: antegrade or retrograde?

During open aortic arch repair, there is an interruption of cerebral perfusion and to prevent neurological sequelae, the hypothermic circulatory arrest has been established to provide sufficient brain protection coupled with adjuncts including retrograde and antegrade cerebral perfusion. To date, brain protection during open aortic arch repair is a contested topic as to which provides superior brain protection with little evidence existing to suggest supremacy of one modality over the other. This article reviews current literature reflecting on key and emerging studies in brain protection and their associated outcomes in patients undergoing open aortic arch surgery.

Aortic Surgery and Deep-Hypothermic Circulatory Arrest: Anesthetic Update

Aortic arch surgery has become increasingly complex, and novel surgical approaches have been utilized. Efforts aimed at improving neurological outcomes in this patient population have been numerous, with varying degrees of success. This article summarizes the anesthetic considerations for procedures on the aortic arch, including evidence-based outcomes with respect to temperature management, perfusion strategies, hemodynamic goals, adjunct agents, and neuromonitoring.

Comparison between antegrade and retrograde cerebral perfusion or profound hypothermia as brain protection strategies during repair of type A aortic dissection

BACKGROUND

The goal of this study was to compare early postoperative outcomes and actuarial-free survival between patients who underwent repair of acute type A aortic dissection by the method of cerebral perfusion used.

METHODS

A total of 324 patients from five academic medical centers underwent repair of acute type A aortic dissection between January 2000 and December 2010. Of those, antegrade cerebral perfusion (ACP) was used for 84 patients, retrograde cerebral perfusion (RCP) was used for 55 patients, and deep hypothermic circulatory arrest (DHCA) was used for 184 patients during repair. Major morbidity, operative mortality, and 5-year actuarial survival were compared between groups. Multivariate logistic regression was used to determine predictors of operative mortality and Cox Regression hazard ratios were calculated to determine the predictors of long term mortality.

RESULTS

Operative mortality was not influenced by the type of cerebral protection (19% for ACP, 14.5% for RCP and 19.1% for DHCA, P=0.729). In multivariable logistic regression analysis, hemodynamic instability [odds ratio (OR) =19.6, 95% confidence intervals (CI), 0.102-0.414, P<0.001] and CPB time >200 min(OR =4.7, 95% CI, 1.962-1.072, P=0.029) emerged as independent predictors of operative mortality. Actuarial 5-year survival was unchanged by cerebral protection modality (48.8% for ACP, 61.8% for RCP and 66.8% for no cerebral protection, log-rank P=0.844).

CONCLUSIONS

During surgical repair of type A aortic dissection, ACP, RCP or DHCA are safe strategies for cerebral protection in selected patients with type A aortic dissection.

Deep Hypothermia and Circulatory Arrest in Adults

Brain protection during cardiopulmonary bypass has been the subject of intense research. Deep hypothermic circulatory arrest (DHCA) continues to be used for that goal during complex aortic arch and large intracranial aneurysm surgeries. The anesthetic management for adult patients undergoing these types of procedures requires specific knowledge and expertise. Based on our experience and review of the current literature, the authors highlight the key areas of the anesthetic plan, discussing the risk factors associated with adverse neurologic outcome as well as the rationale for decisions regarding specific monitors and medications. In the conclusion an anesthetic protocol for adult patients undergoing DHCA is suggested.

Evaluating the Quality of Trials of Hypothermic Circulatory Arrest Aortic Surgery

The quality of level 1 evidence in reports on deep hypothermic circulatory arrest was assessed, and the confounding factors in surgical management and study design that can prevent meta-analysis formulation were determined. A systematic search of the literature was conducted using categorized nomenclature for randomized controlled trials in adult patients undergoing deep hypothermic circulatory arrest in the last 40 years. Twelve randomized controlled trials (2.3%) were found among 504 publications on deep hypothermic circulatory arrest listed on Medline from 1960; only 4 of them related to adults. One adequately powered study demonstrated reduced blood loss in deep hypothermic circulatory arrest using aprotinin. Three studies comparing retrograde and antegrade perfusion were underpowered. The median CONSORT score was 14 (range, 13–15). There were no consistent measures of similar outcomes (neuropsychometric, neurocognitive). No explanation was provided for the difference in reported ranges of neurological deficits in nonrandomized (5%–70%) and randomized (3%–9%) studies. Existing studies of deep hypothermic circulatory arrest are insufficient and inconsistent in the outcome measured, which explains the lack of a meta-analysis. Neurological injury remains high, and an appropriately powered study of interventions that can optimize cerebral perfusion is necessary.

Risk Factors Associated with Cognitive Decline after Cardiac Surgery: A Systematic Review

Modern day cardiac surgery evolved upon the advent of cardiopulmonary bypass machines (CPB) in the 1950s. Following this development, cardiac surgery in recent years has improved significantly. Despite such advances and the introduction of new technologies, neurological sequelae after cardiac surgery still exist. Ischaemic stroke, delirium, and cognitive impairment cause significant morbidity and mortality and unfortunately remain common complications. Postoperative cognitive decline (POCD) is believed to be associated with the presence of new ischaemic lesions originating from emboli entering the cerebral circulation during surgery. Cardiopulmonary bypass was thought to be the reason of POCD, but randomised controlled trials comparing with off-pump surgery show contradictory results. Attention has now turned to the growing evidence that perioperative risk factors, as well as patient-related risk factors, play an important role in early and late POCD. Clearly, identifying the mechanism of POCD is challenging. The purpose of this systematic review is to discuss the literature that has investigated patient and perioperative risk factors to better understand the magnitude of the risk factors associated with POCD after cardiac surgery.

Implications from neurologic assessment of brain protection for total arch replacement from a randomized trial

OBJECTIVE

The study objective was to perform a randomized trial of brain protection during total aortic arch replacement and identify the best way to assess brain injury.

METHODS

From June 2003 to January 2010, 121 evaluable patients were randomized to retrograde (n = 60) or antegrade (n = 61) brain perfusion during hypothermic circulatory arrest. We assessed the sensitivity of clinical neurologic evaluation, brain imaging, and neurocognitive testing performed preoperatively and 4 to 6 months postoperatively to detect brain injury.

RESULTS

A total of 29 patients (24%) experienced neurologic events. Clinical stroke was evident in 1 patient (0.8%), and visual changes were evident in 2 patients; all had brain imaging changes. A total of 14 of 95 patients (15%) undergoing both preoperative and postoperative brain imaging had evidence of new white or gray matter changes; 10 of the 14 patients had neurocognitive testing, but only 2 patients experienced decline. A total of 17 of 96 patients (18%) undergoing both preoperative and postoperative neurocognitive testing manifested declines of 2 or more reliable change indexes; of these 17, 11 had neither imaging changes nor clinical events. Thirty-day mortality was 0.8% (1/121), with no neurologic deaths and a similar prevalence of neurologic events after retrograde and antegrade brain perfusion (22/60, 37% and 15/61, 25%, respectively; P = .2).

CONCLUSIONS

Although this randomized clinical trial revealed similar neurologic outcomes after retrograde or antegrade brain perfusion for total aortic arch replacement, clinical examination for postprocedural neurologic events is insensitive, brain imaging detects more events, and neurocognitive testing detects even more. Future neurologic assessments for cardiovascular procedures should include not only clinical examination but also brain imaging studies, neurocognitive testing, and long-term assessment.

The History of Deep Hypothermic Circulatory Arrest in Thoracic Aortic Surgery

Depending on the extent of aortic disease and surgical repair required, thoracic aortic surgery often involves periods of reduced cerebral perfusion. Historically, this resulted in detrimental neurological dysfunction, and high risk of mortality and morbidity. Over the last half century, rapid improvements have revolutionized aortic surgery. Among these, deep hypothermic circulatory arrest (DHCA) has drastically reduced the risk of mortality and morbidity following surgery on the thoracic aorta. This progress was facilitated by experimental pioneers such as Bigelow, who studied reduced oxygen expenditure consequent on induction of hypothermia in dogs. These encouraging findings led to trials in human cardiac surgery by Lewis in 1952 and further made possible the first successful aortic arch replacement by Denton Cooley and Michael De Bakey. Modern day surgery has come a long way from the use of immersion of the patient in ice baths and other primitive techniques previously described. This paper explores the development of deep hypothermic circulatory arrest from its origins to the present.

Antegrade versus retrograde cerebral perfusion for hemiarch replacement with deep hypothermic circulatory arrest: does it matter? A propensity-matched analysis

OBJECTIVE

The choice of cerebral perfusion strategy for aortic arch surgery has been debated, and the superiority of antegrade (ACP) or retrograde (RCP) cerebral perfusion has not been shown. We examined the early and late outcomes for ACP versus RCP in proximal (hemi-) arch replacement using deep hypothermic circulatory arrest (DHCA).

METHODS

A retrospective analysis of a prospectively maintained database was performed for all patients undergoing elective and nonelective hemiarch replacement at a single referral institution from June 2005 to February 2013. Total arch cases were excluded to limit the analysis to shorter DHCA times and a more uniform patient population for whom clinical equipoise regarding ACP versus RCP exists. A total of 440 procedures were identified, with 360 (82%) using ACP and 80 (18%) using RCP. The endpoints included 30-day/in-hospital and late outcomes. A propensity score with 1:1 matching of 40 pre- and intraoperative variables was used to adjust for differences between the 2 groups.

RESULTS

All 80 RCP patients were propensity matched to a cohort of 80 similar ACP patients. The pre- and intraoperative characteristics were not significantly different between the 2 groups after matching. No differences were found in 30-day/in-hospital mortality or morbidity outcomes. The only significant difference between the 2 groups was a shorter mean operative time in the RCP cohort (P = .01). No significant differences were noted in late survival (P = .90).

CONCLUSIONS

In proximal arch operations using DHCA, equivalent early and late outcomes can be achieved with RCP and ACP, although the mean operative time is significantly less with RCP, likely owing to avoidance of axillary cannulation. Questions remain regarding comparative outcomes with straight DHCA and lesser degrees of hypothermia.

"Open" approach to aortic arch aneurysm repair

Aortic arch aneurysm is a relatively rare entity in cardiac surgery. Repair of such aneurysms, either in isolation or combined with other cardiac procedures, remains a challenging task. The need to produce a relatively bloodless surgical field with circulatory arrest, while at the same time protecting the brain, is the hallmark of this challenge. However, a clear understanding of the topic allows a better and less morbid approach to such a complex surgery. Literature has shown the advantage of selective cerebral perfusion techniques in comparison with only circulatory arrest. Ability to perfuse the brain has allowed circulatory arrest temperatures at moderate hypothermia without the need for deep hypothermia. Even though cannulation site selection appears to be a minor issue, literature has shown that the subclavian/axillary route has the best outcomes and that femoral cannulation should only be reserved for no access patients. Although different techniques for arch anastomosis have been described, we routinely perform the distal first technique as we find it to be less cumbersome and easiest to reproduce. In this review our aim is to outline a systematic approach to aortic arch surgery. Starting with indications for intervention and proceeding with approaches on site of cannulation, approaches to brain protection with hypothermia and selective cerebral perfusion and finally surgical steps in performing the distal and arch vessels anastomosis.

Deep hypothermic circulatory arrest

Effective cerebral protection remains the principle concern during aortic arch surgery. Hypothermic circulatory arrest (HCA) is entrenched as the primary neuroprotection mechanism since the 70s, as it slows injury-inducing pathways by limiting cerebral metabolism. However, increases in HCA duration has been associated with poorer neurological outcomes, necessitating the adjunctive use of antegrade (ACP) and retrograde cerebral perfusion (RCP). ACP has superseded RCP as the preferred perfusion strategy as it most closely mimic physiological perfusion, although there exists uncertainty regarding several technical details, such as unilateral versus bilateral perfusion, flow rate and temperature, perfusion site, undue trauma to head vessels, and risks of embolization. Nevertheless, we believe that the convenience, simplicity and effectiveness of straight DHCA justifies its use in the majority of elective and emergency cases. The following perspective offers a historical and clinical comparison of the DHCA with other techniques of cerebral protection.

A meta-analysis of deep hypothermic circulatory arrest alone versus with adjunctive selective antegrade cerebral perfusion

INTRODUCTION

Recognizing the importance of neuroprotection in aortic arch surgery, deep hypothermic circulatory arrest (DHCA) now underpins operative practice as it minimizes cerebral metabolic activity. When prolonged periods of circulatory arrest are required, selective antegrade cerebral perfusion (SACP) is supplemented as an adjunct. However, concerns exist over the risks of SACP in introducing embolism and hypo- and hyper-perfusing the brain. The present meta-analysis aims to compare postoperative outcomes in arch surgery using DHCA alone or DHCA + SACP as neuroprotection strategies.

METHODS

Electronic searches were performed using six databases from their inception to January 2013. Two reviewers independently identified all relevant studies comparing DHCA alone with DHCA + SACP. Data were extracted and meta-analyzed according to pre-defined clinical endpoints.

RESULTS

Nine comparative studies were identified in the present meta-analysis, with 648 patients employing DHCA alone and 370 utilizing DHCA + SACP. No significant differences in temporary or permanent neurological outcomes were identified. DHCA + SACP was associated with significantly better survival outcomes (P=0.008, I(2)=0%), despite longer cardiopulmonary bypass time. Infrequent and inconsistent reporting of other clinical results precluded analysis of systemic outcomes.

CONCLUSIONS

The present meta-analysis indicate the superiority of DHCA + SACP in terms of mortality outcomes.

A reappraisal of retrograde cerebral perfusion

Brain protection during aortic arch surgery by perfusing cold oxygenated blood into the superior vena cava was first reported by Lemole et al. In 1990 Ueda and associates first described the routine use of continuous retrograde cerebral perfusion (RCP) in thoracic aortic surgery for the purpose of cerebral protection during the interval of obligatory interruption of anterograde cerebral flow. The beneficial effects of RCP may be its ability to sustain brain hypothermia during hypothermic circulatory arrest (HCA) and removal of embolic material from the arterial circulation of the brain. RCP can offer effective brain protection during HCA for about 40 to 60 minutes. Animal experiments revealed that RCP provided inadequate cerebral perfusion and that neurological recovery was improved with selective antegrade cerebral perfusion (ACP), however, both RCP and ACP provide comparable clinical outcomes regarding both the mortality and stroke rates by risk-adjusted and case-matched comparative study. RCP still remains a valuable adjunct for brain protection during aortic arch repair in particular pathologies and patients.

Total aortic arch replacement using hypothermic circulatory arrest with antegrade selective cerebral perfusion: are there cerebral deficits other than frank stroke?

BACKGROUND

It is controversial whether cerebral deficits other than frank stroke develop after total aortic arch replacement using hypothermic circulatory arrest (HCA) with antegrade selective cerebral perfusion (SCP).

OBJECTIVES

We investigated neuropsychological functions in patients who received total aortic arch replacement using deep HCA with SCP.

METHODS

Eleven patients who underwent elective total arch replacement using deep HCA with antegrade SCP were included. Cognitive functions of the patients were evaluated at baseline, and 3 weeks and 6 months after the aortic arch surgery.

RESULTS

The performance of cognitive tests did not change 3 weeks after surgery, except for the attention/calculation task of the Mini-Mental State Examination (MMSE). Six months after surgery, the decline in score for the attention/calculation task in the MMSE had reversed and the score for this task as well as for all other tests had returned to baseline levels.

CONCLUSION

Long-lasting cognitive deficits other than frank stroke may not develop after total arch replacement surgery using deep HCA with SCP.

Risk-adjusted and case-matched comparative study between antegrade and retrograde cerebral perfusion during aortic arch surgery: based on the Japan Adult Cardiovascular Surgery Database : the Japan Cardiovascular Surgery Database Organization

PURPOSE

Antegrade cerebral perfusion (ACP) and retrograde cerebral perfusion (RCP) are two major types of brain protection for aortic arch surgery. A large-scale clinical study of RCP and ACP is important to clarify the respective characteristics for major adverse events. We conducted a comparative study to evaluate up-to-date clinical outcomes in Japan based on the Japan Adult Cardiovascular Surgery Database (JACVSD).

METHODS

The subjects were confined to cases undergone electively with ACP or RCP for nondissection aneurysms in the ascending aorta and aortic arch between 2005 and 2008 from 13 467 aortic surgeries. There were 2209 ACP cases and 583 RCP cases. A risk-adjusted comparison based on 30-day mortality, operative mortality, and major morbidity was assessed by a multivariable logistic regression analysis. A conditional logistic regression analysis was also conducted in 499 propensity matched-pairs with ACP and RCP.

RESULTS

A risk-adjusted analysis showed no significant differences between the ACP and RCP groups regarding 30-day mortality (3.5% vs. 2.6%), operative mortality (5.3% vs. 4.1%), or stroke (6.8% vs. 3.1%). Propensity-matched pairs also revealed no significant differences between ACP and RCP regarding 30-day mortality (3.4% vs. 2.4%), operative mortality (3.8% vs. 3.4%), or stroke rate (5.0% vs. 3.0%); however, RCP resulted in a significantly higher rate of transient neurological dysfunction (3.0% vs. 5.8%) and need for dialysis (1.6% vs. 4.2%).

CONCLUSION

Both RCP and ACP provide comparable clinical outcomes regarding both the mortality and stroke rates. RCP resulted in a higher incidence only in patients demonstrating transient neurological dysfunction and the need for dialysis.

Brief review on systematic hypothermia for the protection of central nervous system during aortic arch surgery: a double-sword tool?

Antegrade selective cerebral perfusion in conjunction with hypothermia attenuate postoperative neurological injury, which in turn still remains the main cause of mortality and morbidity following aortic arch surgery. Hypothermic circulatory arrest however could be a useful tool during arch surgery, surgery for chronic thromboembolic disease, air on the arterial line during CPB, during cavotomy for extraction of renal cell carcinoma with level IV extension, or when dealing with difficult trauma to the SVC or IVC. Cerebral protective effects with hypothermic procedures including inhibition of neuron excitation, and discharge of excitable amino acids, and thereby, prevention of an increase in intercellular calcium ions, hyperoxidation of lipids in cell membranes, and free radical production.The authors are briefly discussing the fundamental principles of using hypothermia as an adjunct tool of the cardiothoracic surgeon's practice. The relationship between temperature, flow, metabolic requirements and adverse effects is addressed.

State of the art in neuroprotection during acute type A aortic dissection repair

Temporary (TND) or permanent neurologic dysfunctions (PND) represent the main neurological complications following acute aortic dissection repair. The aim of our experimental and clinical research was the improvement and update of the most common neuroprotective strategies which are in present use.

Hypothermic circulatory arrest (HCA): Cerebral metabolic suppression at the clinically most used temperatures (18-22°C) is less complete than had been assumed previously. If used as a ‘stand-alone’ neuroprotective strategy, cooling to 15-20°C with a jugular SO2 ≥ 95% is needed to provide sufficient metabolic suppression. Regardless of the depth of cooling, the HCA interval should not exceed 25 min. After 40 min of HCA, the incidence of TND and PND increases, after 60 min, the mortality rate increases.

Antegrade selective cerebral perfusion (ASCP): At moderate hypothermia (25-28°C), ASCP should be performed at a pump flow rate of 10ml/kg/min, targeting a cerebral perfusion pressure of 50-60mmHg. Experimental data revealed that these conditions offer an optimal regional blood flow in the cortex (80±27ml/min/100g), the cerebellum (77±32ml/min/100g), the pons (89±5ml/min/100g) and the hippocampus (55±16ml/min/100g) for 25 minutes. If prolonged, does ASCP at 32°C provide the same neuroprotective effect?

Cannulation strategy: Direct axillary artery cannulation ensures the advantage of performing both systemic cooling and ASCP through the same cannula, preventing additional manipulation with the attendant embolic risk. An additional cannulation of the left carotid artery ensures a bi-hemispheric perfusion, with a neurologic outcome of only 6% TND and 1% PND.

Neuromonitoring: Near-infrared spectroscopy and evoked potentials may prove the effectiveness of the neuroprotective strategy used, especially if the trend goes to less radical cooling.

Conclusion: A short interval of HCA (5 min) followed by a more extended period of ASCP (25 min) at moderate hypothermia (28°C), with a pump flow rate of 10ml/kg/min and a cerebral perfusion pressure of 50 mmHg, represents safe conditions for open arch surgery.