Hemiarch Replacement at 28°C: An Analysis of Mild and Moderate Hypothermia in 500 Patients

Hypothermic circulatory arrest at 20 ℃ does not deteriorate coagulopathy compared to 28 ℃ in a pig model

It is believed that a lower temperature setting of hypothermic circulatory arrest (HCA) in thoracic aortic surgery causes coagulopathy, resulting in excessive bleeding. However, experimental studies that eliminate clinical factors are lacking. The objective of this study is to investigate the influence of the temperature setting of HCA on coagulation in a pig model. Ten pigs were divided into the following two groups: moderate temperature at 28 °C (group M, n = 5) or lower temperature at 20 °C (group L, n = 5). Two hours of HCA during a total of 4 h of cardiopulmonary bypass (CPB) were performed. Blood samples were obtained at the beginning (T1) and the end (T2) of the surgery, and coagulation capability was analyzed through standard laboratory tests (SLTs) and rotational thromboelastometry (ROTEM). In SLTs, hemoglobin, fibrinogen, platelet count, prothrombin time, and activated partial thromboplastin time were analyzed. In ROTEM analyses, clotting time and clot formation time of EXTEM, maximum clot firmness (MCF), and maximum clot elasticity (MCE) of EXTEM and FIBTEM were analyzed. Fibrinogen decreased significantly in both groups (group M, p = 0.008; group L, p = 0.0175) at T2, and FIBTEM MCF and MCE also decreased at T2. There were no differences regarding changes in parameters of SLTs and ROTEM between groups. CPB decreases coagulation capacity, contributed by fibrinogen. However, a lower temperature setting of HCA at 20 °C for 2 h did not significantly affect coagulopathy compared to that of HCA at 28 °C after re-warming to 37 °C.

Clinical outcomes of mild versus moderate hypothermic circulatory arrest with antegrade cerebral perfusion in adult aortic arch surgery: A systematic review and meta-analysis

OBJECTIVES

In adult aortic arch surgery, moderate hypothermic circulatory arrest (HCA) with selective antegrade cerebral perfusion (SACP) (MoHACP) is widely used, but the application of mild HCA with SACP (MiHACP) is still controversial. This meta-analysis aimed to compare clinical outcomes using MiHACP or MoHACP.

METHODS

Studies comparing outcomes of MiHACP or MoHACP in adult aortic arch surgery were searched from four databases from inception through April 2022. Primary outcomes were postoperative permanent neurological deficit (PND), temporary neurological deficit (TND), and mortality. Secondary outcomes included other common complications. Meta-analysis was conducted using a random-effects model in all cases.

RESULTS

Eleven comparative studies were included, with 1555 patients in MiHACP group and 1499 patients in MoHACP group, and the mean HCA temperature were 29.4°C and 24.8°C, respectively. Postoperative PND, TND, mortality, paraplegia, dialysis, tracheotomy, reexploration for bleeding, and chest tube drainage volume were comparable in the two groups (p > 0.05). Ventilator time, intensive care unit and in-hospital length of stay were shorter in MiHACP group (p < 0.05). Outcomes were also comparable or had some benefits in MiHACP group when subgroup analyses were conducted according to hemiarch or total arch replacement, unilateral or bilateral SACP, HCA time, emergency aortic dissection surgery, and concomitant procedure.

CONCLUSION

The present meta-analysis showed acceptability of MiHACP in adult aortic arch surgery. Results need to be taken with caution as moderate risk of bias and very low quality of evidence were observed in this meta-analysis. Randomized controlled trials are needed for further analysis.

Cardiopulmonary bypass for total aortic arch replacement surgery: A review of three techniques

One treatment for acute type A aortic dissection is to replace the ascending aorta and aortic arch with a graft during circulatory arrest of the lower body, but this is associated with high mortality and morbidity. Maintaining the balance between oxygen supply and demand during circulatory arrest is the key to reducing morbidity and is the primary challenge during body perfusion. The aim of this review is to summarize current knowledge of body perfusion techniques and to predict future development of this field. We present three perfusion techniques based on deep hypothermic circulatory arrest (DHCA): DHCA alone, DHCA with selective cerebral perfusion, and DHCA with total body perfusion. DHCA was first developed to provide a clear surgical field, but it may contribute to stroke in 4%–15% of patients. Antegrade or retrograde cerebral perfusion can provide blood flow for the brain during circulatory arrest, and it is associated with much lower stroke incidence of 3%–9%. Antegrade cerebral perfusion may be better than retrograde perfusion during longer arrest. In theory, blood flow can be provided to all vital organs through total body perfusion, which can be implemented via either arterial or venous systems, or by combining retrograde inferior vena caval perfusion with antegrade cerebral perfusion. However, whether total body perfusion is better than other techniques require further investigation in large, multicenter studies. Current techniques for perfusion during circulatory arrest remain imperfect, and a technique that effectively perfuses the upper and lower body effectively during circulatory arrest is missing. Total body perfusion should be systematically compared against selective cerebral perfusion for improving outcomes after circulatory arrest.

Cerebral Protection Strategies and Stroke in Surgery for Acute Type A Aortic Dissection

Background: Perioperative stroke remains a devastating complication in the operative treatment of acute type A aortic dissection. To reduce the risk of perioperative stroke, different perfusion techniques can be applied. A consensus on the preferred cerebral protection strategy does not exist. Methods: To provide an overview about the different cerebral protection strategies, literature research on Medline/PubMed was performed. All available original articles reporting on cerebral protection in surgery for acute type A aortic dissection and neurologic outcomes since 2010 were included. Results: Antegrade and retrograde cerebral perfusion may provide similar neurological outcomes while outperforming deep hypothermic circulatory arrest. The choice of arterial cannulation site and chosen level of hypothermia are influencing factors for perioperative stroke. Conclusions: Deep hypothermic circulatory arrest is not recommended as the sole cerebral protection technique. Antegrade and retrograde cerebral perfusion are today’s standard to provide cerebral protection during aortic surgery. Bilateral antegrade cerebral perfusion potentially leads to superior outcomes during prolonged circulatory arrest times between 30 and 50 min. Arterial cannulation sites with antegrade perfusion (axillary, central or carotid artery) in combination with moderate hypothermia seem to be advantageous. Every concept should be complemented by adequate intraoperative neuromonitoring.

Neuroprotection during Open Aortic Arch Surgery: Cerebral Perfusion Methods and Temperature

Neuroprotection is important in open aortic arch surgery because of the dependence of brain tissues on cerebral perfusion. Therefore, several techniques have been developed to reduce cerebral ischemia and improve outcomes in open aortic arch surgery. In this review, I describe various neuroprotective strategies, such as profound and deep hypothermic circulatory arrest, selective antegrade cerebral perfusion, retrograde cerebral perfusion, and lower body circulatory arrest; compare their advantages and disadvantages, and discuss their evolution and current status by reviewing relevant literature.

Systematic review and network meta-analysis of various nadir temperature strategies for hypothermic circulatory arrest for aortic arch surgery

BACKGROUND

The optimal nadir temperature for hypothermic circulatory arrest during aortic arch surgery remains unclear. We aimed to assess and compare clinical outcomes of all three temperature strategies (deep, moderate, and mild hypothermia) using a network meta-analysis.

METHODS

After literature search with MEDLINE and EMBASE through December 2021, studies comparing clinical outcomes with deep (<20°C), moderate (20-28°C), or mild (>28°C) hypothermic circulatory arrest were included. The outcomes of interest were perioperative mortality, stroke, transient ischemia attack (TIA), acute kidney injury (AKI), postoperative bleeding, operative time, and length of hospital stay.

RESULTS

Twenty-four comparative studies were identified, including 6018 patients undergoing aortic arch surgery using hypothermic circulatory arrest (deep: 2,978, moderate: 2,525, and mild: 515). Compared to deep hypothermia, mild and moderate hypothermia were associated with lower mortality (mild vs. deep: odds ratio [OR] 0.50; 95% confidence interval (CI) 0.29-0.87, moderate vs. deep: OR 0.68; 95% CI 0.54-0.86). In addition, mild hypothermia was associated with lower stroke (OR 0.50; 95% CI 0.28-0.89), AKI (OR 0.36; 95% CI 0.15-0.88) and postoperative bleeding (OR 0.55; 95% CI 0.31-0.97) compared to deep hypothermia. There was no significant difference between mild and moderate hypothermia in mortality, AKI or bleeding occurrence, while mild hypothermia was associated with shorter operative time and hospital stay. There was no significant difference in TIA rate among three groups.

CONCLUSIONS

Mild hypothermia was associated with overall more favorable clinical outcomes with comparable neurological complications compared to deep hypothermia. Furthermore, considering the shorter operative time and hospital stay compared with moderate hypothermia, mild hypothermia may be warranted when appropriate adjunctive cerebral perfusion is employed.

Hypothermic circulatory arrest does not induce coagulopathy in vitro

Hypothermic circulatory arrest (HCA) is an essential procedure during aortic surgery to protect organs; however, hypothermia is believed to cause coagulopathy, which is a major fatal complication. This study aimed to clarify the impact of hypothermia on coagulation by eliminating clinical biases in vitro. In the hypothermic storage study, blood samples from five healthy volunteers were stored at 37 ℃ (group N) for 3 h or at 20 ℃ for 2 h, followed by 1 h of rewarming at 37 ℃ (group H). Thromboelastography was performed before and after 3 h of storage. In the mock circulation loop (MCL) study, blood samples were placed in the MCL and (a) maintained at 37 ℃ for 4 h (group N, n = 5), or (b) cooled to 20 ℃ to simulate HCA with a 0.1 L/min flow rate for 3 h and then rewarmed to 37 ℃ (group H, n = 5). The total MCL duration was 4 h, and the flow rate was maintained at 1 L/min, except during HCA. Blood samples collected 15 min after the beginning and end of MCL were subjected to standard laboratory tests and rotational thromboelastometry analyses. Hypothermia had no impact on coagulation in both the hypothermic storage and MCL studies. MCL significantly decreased the platelet counts and clot elasticity in the INTEM and EXTEM assays; however, there was no effect on fibrinogen contribution measured by FIBTEM. Hypothermia does not cause irreversible coagulopathy in vitro; however, MCL decreases coagulation due to the deterioration of platelets.

Optimal circulatory arrest temperature for aortic hemiarch replacement with antegrade brain perfusion

OBJECTIVE

This study sought to identify the optimal temperature for moderate hypothermic circulatory arrest in patients undergoing elective hemiarch replacement with antegrade brain perfusion.

METHODS

The Society of Thoracic Surgeons adult cardiac surgery database was queried for elective hemiarch replacements using antegrade brain perfusion for aneurysmal disease (2014-2019). Generalized estimating equations and restricted cubic splines were used to determine the risk-adjusted relationships between temperature as a continuous variable and outcomes.

RESULTS

Elective hemiarch replacement with antegrade brain perfusion occurred in 3898 patients at 374 centers with a median nadir temperature of 24.9 °C (first quartile, third quartile = 22.0 °C, 27.5 °C) and median circulatory arrest time of 19 minutes (first quartile, third quartile = 14.0 minutes, 27.0 minutes). After adjustment for comorbidities, circulatory arrest time, and individual surgeon, patients cooled between 25 and 28 °C had an early survival advantage compared with 24 °C, whereas those cooled between 21 and 23 °C had higher risks of mortality compared with 24 °C. A nadir temperature of 27 °C was associated with the lowest risk-adjusted odds of mortality (odds ratio, 0.62; 95% confidence interval, 0.42-0.91). A nadir temperature of 21 °C had the highest risk of mortality (odds ratio, 1.4; 95% confidence interval, 1.13-1.73). Risk of experiencing a major morbidity was elevated in patients cooled between 21 and 23 °C, with the highest risk occurring in patients cooled to 21 °C (odds ratio, 1.12; 95% confidence interval, 1.01-1.24).

CONCLUSIONS

For patients with aneurysmal disease undergoing elective hemiarch with antegrade brain perfusion, circulatory arrest with a nadir temperature of 27 °C confers the greatest early survival benefit and smallest risk of postoperative morbidity.

Temperatur- und Perfusionsmanagement bei akuter Typ-A-Aortendissektion

Die chirurgische Versorgung der akuten Typ-A-Aortendissektion erfuhr in den letzten Jahrzehnten v. a. im Hinblick auf das Perfusions- und Temperaturmanagement eine ständige Entwicklung. Neurologische Komplikationen sind die Hauptursache der postoperativen Morbidität und Mortalität. Die Verwendung einer Herz-Lungen-Maschine, des Kreislaufstillstands in tiefer Hypothermie, die temporäre Unterbrechung der zerebralen Perfusion oder Hypoperfusion des Gehirns und die Manipulation an der Aorta können zu neurologischen Schäden führen. Der Kreislaufstillstand in tiefer Hypothermie ermöglicht Eingriffe an der thorakalen Aorta, die für die Sanierung einer akuten Dissektion notwendig sein können. Dies hat allerdings Limitationen: Einerseits ist die Eingriffszeit begrenzt, andererseits führt die tiefe Hypothermie selbst zu Schäden. Experimentelle und klinische Studien konnten zeigen, dass der Grad der Hypothermie einen Einfluss auf die Komplikationsrate hat. Auch über den Nutzen der retrograden Hirnperfusion besteht noch Uneinigkeit. Das Konzept des Kreislaufstillstands mit zusätzlicher Hirnperfusion, besonders wenn der Grad der Hypothermie entsprechend der erwarteten Kreislaufstillstandzeit angepasst wird, erwies sich als sichere Methode. Es ermöglicht komplexe Eingriffe an der Aorta bei geringen Komplikationsraten und wird zunehmend als Standardverfahren bei der Versorgung der akuten Typ-A-Dissektion angewandt.

Aortic arch surgery at 32°C: mild hypothermia and unilateral antegrade cerebral perfusion

OBJECTIVES

With development of antegrade cerebral perfusion, the necessity of deep hypothermic circulatory arrest (CA) in aortic arch surgery has been called into question. To minimize the adverse effects of hypothermia, surgeons now perform these procedures closer to normothermia. This study examined postoperative outcomes of hemiarch replacement patients using unilateral selective antegrade cerebral perfusion and mild hypothermic CA.

METHODS

Single-centre retrospective review of 66 patients undergoing hemiarch replacement with mild hypothermic CA (32°C) and unilateral selective antegrade cerebral perfusion between 2011 and 2018. Antegrade cerebral perfusion was delivered using right axillary artery cannulation. Postoperative data included death, neurological dysfunction, acute kidney injury and renal failure requiring new dialysis. Additional intraoperative metabolic data and blood transfusions were obtained.

RESULTS

Eighty-six percent of patients underwent elective surgery. Mean age was 67 ± 3 years. Lowest mean core body temperature was 32 ± 2°C. Average CA was 17 ± 5 min. No intraoperative or 30-day mortality occurred. Survival was 97% at 1 year, 91% at 3 years and 88% at 5 years. Permanent and temporary neurological dysfunction occurred in 1 (2%) and 2 (3%) patients, respectively. Only 3 (5%) patients suffered postoperative stage 3 acute kidney injury requiring new dialysis. Intraoperative transfusions occurred in 44% of patients and no major metabolic derangements were observed.

CONCLUSIONS

In patients undergoing hemiarch surgery, mild hypothermia (32°C) with unilateral selective antegrade cerebral perfusion via right axillary cannulation is associated with low mortality and morbidity, offering adequate neurological and renal protection. These findings require validation in larger, prospective clinical trials.

COMMENCE trial (Comparing hypOtherMic teMperaturEs duriNg hemiarCh surgEry): a randomized controlled trial of mild vs moderate hypothermia on patient outcomes in aortic hemiarch surgery with anterograde cerebral perfusion

Background

Aortic arch surgery remains the only viable life-saving treatment for aortic arch disease. However, the necessity for cessation of systemic blood flow with hypothermic cardiac arrest carries substantial risk of morbidity and mortality, including poor neurological outcomes and kidney failure. While uncontrolled studies have suggested the safety of operating at warmer temperatures, significant variables remain un-investigated, supporting the need for a randomized clinical trial (RCT) to produce evidence-based guidelines for perfusion strategies in aortic surgery. This study proposes a multi-center RCT in order to compare outcomes of warmer hypothermic strategies during aortic hemiarch surgery on a composite endpoint of neurologic and acute kidney injury (AKI).

Methods/design

This is a prospective multi-center, single-blind two-arm RCT comparing mild (32 °C) versus moderate (26 °C) hypothermic cardiac arrest in patients (n = 282) undergoing hemiarch surgery with antegrade cerebral perfusion (ACP). The primary endpoint is a composite of neurological injury (incidence of transient ischemic attack and/or stroke) and Kidney Disease Improving Global Outcomes (KDIGO) stage 1 or higher AKI. Secondary outcomes include death, cardiopulmonary bypass time, bleeding, transfusion rates, prolonged mechanical ventilation, myocardial infarction, length of stay, and quality of life measures.

Patients will undergo 1:1 block randomization to each treatment arm on day of surgery. Sequence of operation will be at the surgeon’s discretion with mandatory guidelines for temperature and ACP administration. Perioperative management will occur as per enrolling center standard of care. Neurocognitive function will be assessed for neurological injury using validated neurological screening tests: NIHSS, MOCA, BI, and MRS throughout patient follow-up. Diagnosis and classification of AKI will be based on rising creatinine values as per the KDIGO criteria. Study duration for each patient will be 60 ± 14 days.

Discussion

It is hoped that performing hemiarch surgery using mild hypothermia (32 °C) and selective ACP will result in a 15% absolute risk reduction in the composite outcomes. The potential of this risk reduction will translate into improved patient outcomes, survival, and long-term financial savings to the health care system. In addition, the results of this trial will be used to create the first-ever guidelines for temperature management strategy during aortic surgery.

Trial registration

This trial is registered on ClinicalTrials.gov with the registration number NCT02860364. Registration date August 9th, 2016.

Aortic balloon occlusion technique versus moderate hypothermic circulatory arrest with antegrade cerebral perfusion in total arch replacement and frozen elephant trunk for acute type A aortic dissection

BACKGROUND

Moderate hypothermic circulatory arrest (MHCA) with antegrade cerebral perfusion (ACP) is safe and efficient in total arch replacement (TAR) and frozen elephant trunk (FET) for acute type A aortic dissection (ATAAD). Complications related to hypothermia and ischemia are inevitable, however. The aortic balloon occlusion (ABO) technique is performed to elevate the lowest nasopharyngeal temperature to 28°C and shorten the circulatory arrest time. In this study, we aimed to evaluate the efficacy of this new technique.

METHODS

We reviewed the clinical data of patients with ATAAD who underwent TAR and FET, including 79 who underwent ABO and 109 who underwent MHCA/ACP.

RESULTS

Circulatory arrest time was significantly lower in the ABO group compared with the MHCA/ACP group (mean, 4.8 ± 1.2 minutes vs 18.4 ± 3.1 minutes; P < .001). The composite endpoint was comparable in the 2 groups (11.4% for ABO vs 13.8% for MHCA/ACP; P = .631). Fewer patients in the ABO group developed high-grade acute kidney injury (AKI) according to a modified RIFLE criterion (22.8% vs 36.7%; P = .041), and the rate of hepatic dysfunction was lower in the ABO group (11.4% vs 28.4%; P = .005). Multivariable logistic analysis showed that the ABO technique is protective against duration of ventilation >24 hours (odds ratio [OR], 0.455; 95% confidence interval [CI], 0.234-0.887; P = .021), hepatic dysfunction (OR, 0.218; 95% CI, 0.084-0.561; P = .002), and grade II-III AKI (OR, 0.432; 95% CI, 0.204-0.915; P = .028).

CONCLUSIONS

The ABO technique significantly shortens the circulatory arrest time in TAR and FET. Available clinical data suggest that it has a certain protective effect on the liver and kidney. Future large-sample studies are warranted to thoroughly evaluate this new technique.

Temperature Selection in Antegrade Cerebral Perfusion for Aortic Arch Surgery: A Meta-Analysis

BACKGROUND

The increasing use of antegrade cerebral perfusion (ACP) during aortic arch surgery has corresponded with a trend toward warmer target temperatures for hypothermic circulatory arrest. This meta-analysis examined the clinical outcomes using colder or warmer circulatory arrest targets with ACP.

METHODS

Electronic searches were performed using four databases from their inception to February 2017. Comparative studies of adult patients who underwent aortic arch operations using ACP at different circulatory arrest temperatures were included. Data were extracted by 2 independent researchers and analyzed according to predefined end points using a random-effects model.

RESULTS

The literature search identified 18 comparative studies, with 1,215 patients in the "cold" cohort and 1,417 in the "warm" cohort. Mean hypothermic circulatory arrest temperatures were 20.3°C and 26.5°C in the cold and warm groups, respectively. A trend existed for increased permanent neurologic deficit overall when colder targets were used (odds ratio, 1.45; 95% confidence interval, 0.98 to 2.13; p = 0.06); this became significant when adjusted estimates were aggregated (odds ratio, 1.65; 95% confidence interval, 1.06 to 2.55; p = 0.03). No difference in the mortality rate was seen when adjusted effects were aggregated. Temporary neurologic deficit, postoperative dialysis, ventilator time, and intensive care unit stay were significantly reduced in the warm cohort overall. No significant differences in reexploration for bleeding were found.

CONCLUSIONS

ACP with warmer circulatory arrest temperatures may reduce the incidence of permanent neurologic deficit as well as potentially other clinical outcomes. Further studies are required to determine the safe circulatory arrest durations for visceral organs at warmer temperatures.

Role of Moderate Hypothermia and Antegrade Cerebral Perfusion during Repair of Type A Aortic Dissection

The goal of this study was to compare early postoperative outcomes and actuarial survival between patients who underwent repair of acute type A aortic dissection with deep or moderate hypothermia. A total of 132 consecutive patients from a single academic medical center underwent repair of acute type A aortic dissection between January 2000 and June 2014. Of those, 105 patients were repaired under deep hypothermia (< 24 C°), while 27 patients were repaired under moderate hypothermia (≥24 C°). Median ages were 62 years (range: 27-86) and 59 years (range: 35-83) for patients repaired under deep hypothermia compared with patients repaired under moderate hypothermia, respectively ( p  = 0.451). Major morbidity, operative mortality, and 10-year actuarial survival were compared between groups. Operative mortality was 17.1 and 7.4% in the deep and moderate hypothermia groups, respectively ( p  = 0.208). Incidence of permanent stroke was 12.4% in the deep hypothermic circulatory arrest group and 0% in the moderate hypothermia group ( p  = 0.054). Actuarial 5- and 10-year survival demonstrated a trend for lower long-term mortality with moderate hypothermia compared with deep hypothermia (69% 5-year and 54% 10-year for deep hypothermia vs. 79% 5-year and 10-year for moderate hypothermia, log-rank p  = 0.161). Moderate hypothermia is a safe and efficient alternative to deep hypothermia and may have protective benefits. Stroke rate was lower with moderate hypothermia.

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.

Low preoperative fibrinogen level is risk factor for neurological complications in acute aortic dissection

Aortic arch surgery in patients with acute aortic dissection is frequently complicated by neurological complications and coagulopathy. However, the relationship between the coagulation system and neurological complications in patients with acute aortic dissection has not been clarified. Thus, the aim of this study was to investigate the relationship between the coagulation system and neurological complications in patients with acute aortic dissection.From September 2014 to January 2016, a total of 126 patients with acute type A aortic dissection were enrolled. Perioperative characteristics and standard laboratory tests upon admission were analyzed using univariate and multivariate logistic regression analysis in this study. The primary outcome was the correlation between the coagulation system and neurological complications.Univariate logistic regression analysis showed that the neurological complications (+) group underwent more serious and complicated postoperative outcomes. Multivariable logistic regression analysis revealed serum creatinine level (OR, 1.049; 95% CI, 1.011-1.089; P = .01), white blood cell counts (OR, 1.581; 95% CI, 1.216-2.057; P = .001) and fibrinogen concentration upon admission (OR, 0.189; 95% CI, 0.060-0.596; P = .004) as predictors of neurological complications. However, we found that there was no association between the coagulation system and in-hospital mortality.Low preoperative fibrinogen level is the preferred marker for predicting clinical neurological complications in patients with acute type A aortic dissection treated with surgical repair.

Predictors of Outcomes after Correction of Acute Type A Aortic Dissection under Moderate Hypothermic Circulatory Arrest and Antegrade Cerebral Perfusion

INTRODUCTION

Hypothermic circulatory arrest is widely used for correction of acute type A aortic dissection pathology. We present our experience of 45 consecutive patients operated in our unit with bilateral antegrade cerebral perfusion and moderate hypothermic circulatory arrest.

METHODS

Between January 2011 and April 2015, 45 consecutive patients were admitted for acute type A aortic dissection and operated emergently under moderate hypothermic circulatory arrest and bilateral antegrade cerebral perfusion.

RESULTS

Mean age was 58±11.4 years old. Median circulatory arrest time was 41.5 (30-54) minutes while the 30-day mortality and postoperative permanent neurological deficits rates were 6.7% and 13.3%, respectively. Unadjusted analysis revealed that the factors associated with 30-day mortality were: preoperative hemodynamic instability (OR: 14.8, 95% CI: 2.41, 90.6, P=0.004); and postoperative requirement for open sternum management (OR: 5.0, 95% CI: 1.041, 24.02, P=0.044) while preoperative hemodynamic instability (OR: 8.8, 95% CI: 1.41, 54.9, P=0.02) and postoperative sepsis or multiple organ dysfunction (OR: 13.6, 95% CI: 2.1, 89.9, P=0.007) were correlated with neurological dysfunction. By multivariable logistic regression analysis, postoperative sepsis and multiple organ dysfunction independently predicted (OR: 15.9, 95% CI: 1.05, 96.4, P=0.045) the incidence of severe postoperative neurological complication. During median follow-up of 6 (2-12) months, the survival rate was 86.7%.

CONCLUSION

Bilateral antegrade cerebral perfusion and direct carotid perfusion for cardiopulmonary bypass, in the surgical treatment for correction of acute aortic dissection type A, is a valuable technique with low 30-day mortality rate. However, postoperative severe neurological dysfunctions remain an issue that warrants further research.

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.

Hypothermia inhibits the proliferation of bone marrow-derived mesenchymal stem cells and increases tolerance to hypoxia by enhancing SUMOylation

Hypothermia therapy has a positive effect on patients with severe brain injury. Recent studies have shown that mild hypothermia increases the survival of bone marrow-derived mesenchymal stem cells (BMSCs) in a hypoxic environment; however, the underlying mechanisms are not yet fully understood. Small ubiquitin-like modifiers (SUMOs) are sensitive to temperature stress reactions and are considered to exert a protective effect. In this study, we examined the protective effects of hypothermia on BMSCs in terms of SUMO protein modification. First, we found that mild hypothermia inhibited the proliferation and differentiation of BMSCs and increased cell tolerance to a hypoxic environment. Second, hypothermia significantly increased the levels of SUMO modification of multiple proteins in BMSCs. The knockdown of SUMO1/2/3 induced the rapid aging of the BMSCs, while the inhibition of the SUMO-conjugating enzyme, Ubc9, reduced cell proliferation and increased the proportion of BMSCs differentiating into nerve cells. Moreover, the tolerance of BMSCs to the hypoxic environment was significantly decreased. Lastly, we investigated 4 reported SUMO target proteins, anti-proliferating cell nuclear antigen, octamer-binding transcription factor 4, p53 and hypoxia-inducible factor-1α, to confirm that SUMO modification was indeed involved in maintaining the proliferation, inhibiting differentiation and enhancing the resistance of BMSCs against adverse conditions. Taken together, our results indicate that the SUMO pathway is involved in the response to hypothermic stress, and that SUMOylation may be an important protective mechanism against hypothermia for the survival of BMSCs under unfavorable conditions.

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.

The History of Cardiothoracic Surgery at Emory University

Over the past 50 years, the Emory Cardiothoracic Surgical Program has become one of the premier training programs in the United States. During this time, the Emory program has been sequentially led by Drs Osler Abbott, Charles Hatcher, and Robert Guyton. The program has grown from single faculty member to 25, and the culture of team collaboration, clinical excellence, research, and teaching established by Dr Hatcher has continued under the leadership of Dr Guyton for the past 26 years.

Hemiarch: The Real Operation for Ascending Aortic Aneurysm

The extent and technique of resection for ascending aortopathies remains debated. The 2 main camps are divided into those who believe in the hemiarch resection utilizing hypothermic circulatory arrest and those who feel that the same goal can be accomplished with just an ascending aortic resection with an aortic cross clamp. While this debate continues to happen within groups and in some cases even in the same hospital, it certainly has not happened in the literature. There are no studies directly comparing the safety and efficacy of these 2 ideologies. The aim of this review is to present the little data that do exist and to ultimately show that the hemiarch technique is superior after careful deliberation.

Temperature Management for Aortic Arch Surgery

Surgical treatment of aortic arch disease is a technically challenging procedure that requires complex circulation management strategies involving the use of hypothermic circulatory arrest. The definition of hypothermia has evolved with comfort and surgical adjuncts. This review describes the various circulation and temperature management strategies used during hemiarch and total arch replacement.

Neurophysiological Intraoperative Monitoring During Aortic Arch Surgery

Circulatory management during replacement of the aortic arch is complex and involves a period of circulatory arrest to provide a bloodless field during arch vessel anastomosis. To guard against ischemic brain injury, tissue metabolic demand is reduced by systemically cooling the patient prior to circulatory arrest. Neurophysiological intraoperative monitoring (NIOM) is often used during the course of these procedures to provide contemporaneous assessment of brain status to help direct circulatory management decisions and detect brain ischemia. In this review, we discuss the characteristics of electrocerebral activity through the process of cooling, circulatory arrest, and rewarming as depicted through commonly used NIOM modalities, including electroencephalography and peripheral nerve somatosensory-evoked potentials. Attention is directed toward the role NIOM has traditionally played during deep hypothermic circulatory arrest, where it is used to define the point of electrocerebral inactivity or maximal cerebral metabolic suppression prior to initiating circulatory arrest while also discussing the evolving utility of NIOM when systemic circulatory arrest is initiated at more moderate degrees of hypothermia in conjunction with regional brain perfusion. The use of cerebral tissue oximetry by near-infrared spectroscopy as an alternative NIOM modality during surgery of the aortic arch is addressed as well. Finally, special considerations for NIOM and the detection of spinal cord ischemia during hybrid aortic arch repair and emerging operative techniques are also discussed.

Does moderate hypothermia really carry less bleeding risk than deep hypothermia for circulatory arrest? A propensity-matched comparison in hemiarch replacement

BACKGROUND

Moderate (MHCA) versus deep (DHCA) hypothermia for circulatory arrest in aortic arch surgery has been purported to reduce coagulopathy and bleeding complications, although there are limited data supporting this claim. This study aimed to compare bleeding-related events after aortic hemiarch replacement with MHCA versus DHCA.

METHODS

Patients who underwent hemiarch replacement at a single institution from July 2005 to August 2014 were stratified into DHCA and MHCA groups (minimum systemic temperature ≤20°C and >20°C, respectively) and compared. Then, 1:1 propensity matching was performed to adjust for baseline differences.

RESULTS

During the study period, 571 patients underwent hemiarch replacement: 401 (70.2%) with DHCA and 170 (29.8%) with MHCA. After propensity matching, 155 patients remained in each group. There were no significant differences between matched groups with regard to the proportion transfused with red blood cells, plasma, platelet concentrates, or cryoprecipitate on the operative day, the rate of reoperation for bleeding, or postoperative hematologic laboratory values. Among patients who received plasma, the median transfusion volume was statistically greater in the DHCA group (6 vs 5 units, P = .01). MHCA also resulted in a slight reduction in median volume of blood returned via cell saver (500 vs 472 mL, P < .01) and 12-hour postoperative chest tube output (440 vs 350, P < .01). Thirty-day mortality and morbidity did not differ significantly between groups.

CONCLUSIONS

MHCA compared with DHCA during hermiarch replacement may slightly reduce perioperative blood-loss and plasma transfusion requirement, although these differences do not translate into reduced reoperation for bleeding or postoperative mortality and morbidity.

Optimal temperature management in aortic arch operations

Hypothermic circulatory arrest is a critical component of aortic arch procedures, without which these operations could not be safely performed. Despite the use of hypothermia as a protective adjunct for organ preservation, aortic arch surgery remains complex and is associated with numerous complications despite years of surgical advancement. Deep hypothermic circulatory arrest affords the surgeon a safe period of time to perform the arch reconstruction, but this interruption of perfusion comes at a high clinical cost: stroke, paraplegia, and organ dysfunction are all potential-associated complications. Retrograde cerebral perfusion was subsequently developed as a technique to improve upon the rates of neurologic dysfunction, but was done with only modest success. Selective antegrade cerebral perfusion, on the other hand, has consistently been shown to be an effective form of cerebral protection over deep hypothermia alone, even during extended periods of circulatory arrest. A primary disadvantage of using deep hypothermic circulatory arrest is the prolonged bypass times required for cooling and rewarming which adds significantly to the morbidity associated with these procedures, especially coagulopathic bleeding and organ dysfunction. In an effort to mitigate this problem, the degree of hypothermia at the time of the initial circulatory arrest has more recently been reduced in multiple centers across the globe. This technique of moderate hypothermic circulatory arrest in combination with adjunctive brain perfusion techniques has been shown to be safe when performing aortic arch operations. In this review, we will discuss the evolution of these protection strategies as well as their relative strengths and weaknesses.

Moderate hypothermic circulatory arrest in total arch repair for acute type A aortic dissection: clinical safety and efficacy

BACKGROUND

Continued debates exist regarding the optimal temperature during hypothermic circulatory arrest (HCA) in aortic arch repair for patients with type A aortic dissection (TAAD). This study seeks to examine whether the use of moderate HCA in emergency aortic arch surgery provides comparable operative outcomes to deep HCA for patients with acute TAAD.

METHODS

We prospectively enrolled 74 consecutive patients (mean age 47.7±9.8 years, 54 males) with acute TAAD, who underwent emergency total arch replacement and frozen elephant trunk implantation under HCA (18-28 °C) with unilateral selective antegrade cerebral perfusion (uSACP). Patients were divided into two groups based on the nasopharyngeal temperature at the initiation of HCA: deep HCA (DHCA, <20 °C) in 35 (47.3%) and moderate HCA (MHCA, 20-28 °C) in 39 (52.7%). Operative outcomes including mortality, morbidity and visceral organ functions were compared between the two groups.

RESULTS

The mean times of cardiopulmonary bypass (CPB) and aortic cross-clamp were 211±54 and 238±62 minutes (P=0.053) and 118±27 and 142±45 minutes (P=0.005) in the MHCA and DHCA groups, respectively. Operative mortality did not differ between two groups (10.2% in MHCA vs. 14.3% in DHCA groups, P=0.862). Nor did the incidence of morbidities differ between the two groups (P>0.05). The temporal trend in the changes of postoperative levels of creatinine, aspartate aminotransferase, total bilirubin and lactate did not differ between two groups (P>0.05). Multivariate analysis found that the temperature during HCA (MHCA vs. DHCA) did not affect operative mortality, morbidities and neurologic complications. Instead, CPB time (in minutes) was the risk factor for operative mortality (odds ratio, 1.032; 95% confidence interval, 1.004-1.061; P=0.023).

CONCLUSIONS

Moderate HCA is associated with equivalent operative mortality and morbidity and visceral organ functions compared to deep HCA in patients with acute TAAD undergoing total arch replacement under uSACP. This study implies the clinical safety and efficacy of moderate HCA in emergency aortic arch repair for such patients, which provides equivalent cerebral and visceral organ protection while decreasing CPB and cross-clamp times without increasing the risk of operative mortality and morbidity.

Antegrade or Retrograde Cerebral Perfusion in Ascending Aorta and Hemiarch Surgery? A Propensity-Matched Analysis

BACKGROUND

Over the years, numerous options have been proposed for surgical management of ascending aorta and aortic arch pathology in an attempt to minimize postoperative morbidity and probability of death. We present a propensity score-matching analysis of 259 patients from a single unit who were operated on under deep hypothermic arrest with retrograde cerebral perfusion (DHCA/RCP) or moderate hypothermic circulatory arrest with selective antegrade cerebral perfusion (via common carotid artery) (MHCA/ACP).

METHODS

Between 2006 and 2014 a total of 259 consecutive patients underwent ascending aorta and hemiarch correction under HCA. DHCA/RCP and MHCA/ACP were performed on 207 and 52 patients, respectively. Baseline patient characteristics accounted for in the propensity matching were age, sex, acute aortic dissection, emergency operation, re-operation, preoperative hemodynamic instability, preoperative kidney injury, and CA time. After propensity scoring 40 pairs (80 patients) were successfully matched (p = 0.732). Outcomes were defined as the incidence of postoperative neurologic complications, 30-day mortality, and all-cause midterm mortality.

RESULTS

Surgical procedure that involved the MHCA/ACP technique was associated with 76.5% decreased risk (risk ratio, 0.235; 95% CI, 0.079 to 0.699) of postoperative neurologic complications (p = 0.009). In addition to MHCA/ACP in surgical procedure for acute aortic dissection a relevant trend was established for 30-day mortality (risk ratio, 0.333; 95% CI, 0.09 to 1.23). For midterm all-cause mortality, MHCA/ACP modestly decreased the number of deaths (p = 0.0456) in comparison with the DHCA/RCP technique.

CONCLUSIONS

MHCA/ACP in aortic arch surgical procedure is associated with a decreased risk of all types of neurologic complications and a trend toward decreased 30-day and midterm mortality in comparison with DHCA/RCP.

How to Perfuse: Concepts of Cerebral Protection during Arch Replacement

Arch surgery remains undoubtedly among the most technically and strategically challenging endeavors in cardiovascular surgery. Surgical interventions of thoracic aneurysms involving the aortic arch require complete circulatory arrest in deep hypothermia (DHCA) or elaborate cerebral perfusion strategies with varying degrees of hypothermia to achieve satisfactory protection of the brain from ischemic insults, that is, unilateral/bilateral antegrade cerebral perfusion (ACP) and retrograde cerebral perfusion (RCP). Despite sophisticated and increasingly individualized surgical approaches for complex aortic pathologies, there remains a lack of consensus regarding the optimal method of cerebral protection and circulatory management during the time of arch exclusion. Many recent studies argue in favor of ACP with various degrees of hypothermic arrest during arch reconstruction and its advantages have been widely demonstrated. In fact ACP with more moderate degrees of hypothermia represents a paradigm shift in the cardiac surgery community and is widely adopted as an emergent strategy; however, many centers continue to report good results using other perfusion strategies. Amidst this important discussion we review currently available surgical strategies of cerebral protection management and compare the results of recent European multicenter and single-center data.

Electroencephalography During Hemiarch Replacement With Moderate Hypothermic Circulatory Arrest

BACKGROUND

This study aimed to characterize intraoperative electroencephalography (EEG) during moderate hypothermic circulatory arrest (MHCA) with selective antegrade cerebral perfusion (SACP), which has not been described previously.

METHODS

This was a single-institution retrospective study of patients undergoing aortic hemiarch replacement using MHCA (temperatures <28°C at circulatory arrest [CA]) and unilateral SACP with EEG monitoring from July 1, 2013 to November 1, 2014. The EEG pattern was determined before and immediately after CA, as well as after establishment of SACP. Patient and procedural characteristics and outcomes were determined and compared after stratification by the presence of ischemic EEG changes.

RESULTS

The study included 71 patients. Before CA, 47 patients (66%) demonstrated a continuous EEG pattern, with or without periodic complexes, and 24 (34%) had a burst suppression EEG pattern. Immediately after CA, abrupt loss of electrocerebral activity occurred in 32 patients (45%), suggestive of cerebral ischemia. Establishment of unilateral SACP rapidly restored electrocerebral activity in all but 2 patients. One patient had persistent loss of left-sided activity, which resolved after transition to bilateral SACP. Another patient had persistent global loss of activity and was placed back on cardiopulmonary bypass for further cooling before reinitiation of CA. No significant differences in characteristics or outcomes were assessed between patients with and without loss of EEG activity.

CONCLUSIONS

Nearly half of patients undergoing hemiarch replacement with MHCA/SACP experience abrupt loss of electrocerebral activity after CA is initiated. Although unilateral SACP usually restores prearrest electrocerebral activity, intraoperative EEG may be particularly valuable for the identification of patients with persistent cerebral ischemia even after SACP.

Knowledge, attitudes, and practice preferences of Canadian cardiac surgeons toward the management of acute type A aortic dissection

OBJECTIVES

The complexity of surgical treatment for acute type A dissection contributes to the variability in patient management. This study was designed to elucidate the contemporary practice preferences of cardiac surgeons regarding different phases of management of acute type A aortic dissection.

METHODS

A 34-item questionnaire was distributed to all Canadian adult cardiac surgeons addressing the preoperative, intraoperative, and postoperative management of acute type A dissection. A total of 100 responses were obtained (82% of active surgeons in Canada). Outcomes were compared between high- and low-volume aortic surgeons.

RESULTS

Seventy-six percent of respondents favored axillary artery cannulation. High-volume surgeons (>150 cases) were more likely to indicate a target lowest nasopharyngeal temperature more than 20 °C (53% vs 25%, P = .02). The majority of surgeons (65%) recommended using selective antegrade cerebral perfusion, with a significantly greater proportion for higher-volume aortic surgeons (P = .03). In addition, high-volume aortic surgeons were more likely to recommend aortic root replacement at smaller diameters (73% vs 55%, P = .02), to recommend more extensive distal aortic resection with routine open hemiarch anastomosis (85% vs 65%, P = .04), and to more commonly perform total arch reconstruction when needed (93% vs 77%, P = .04). In the follow-up period, frequency of serial imaging of the residual aorta was significantly higher for high-volume aortic surgeons (P = .04).

CONCLUSIONS

This study identified some commonalities in practice preferences among Canadian cardiac surgeons for the management of acute type A aortic dissection. However, it also highlighted significant differences in temperature management, cerebral protection strategies, and extent of resection between high-volume and low-volume aortic surgeons.

Optimal protective hypothermia in arrested mammalian hearts

Many therapeutic hypothermia recommendations have been reported, but the information supporting them is sparse, and reveals a need for the data of target therapeutic hypothermia (TTH) from well-controlled experiments. The core temperature ≤35°C is considered as hypothermia, and 29°C is a cooling injury threshold in pig heart in vivo. Thus, an optimal protective hypothermia (OPH) should be in the range 29-35°C. This study was conducted with a pig cardiopulmonary bypass preparation to decrease the core temperature to 29-35°C range at 20 minutes before and 60 minutes during heart arrest. The left ventricular (LV) developed pressure, maximum of the first derivative of LV (dP/dtmax), cardiac power, heart rate, cardiac output, and myocardial velocity (Vmax) were recorded continuously via an LV pressure catheter and an aortic flow probe. At 20 minutes of off-pump during reperfusion after 60 minutes arrest, 17 hypothermic hearts showed that the recovery of Vmax and dP/dtmax established sigmoid curves that consisted of two plateaus: a good recovery plateau at 29-30.5°C, the function recovered to baseline level (BL) (Vmax=118.4%±3.9% of BL, LV dP/dtmax=120.7%±3.1% of BL, n=6); another poor recovery plateau at 34-35°C (Vmax=60.2%±2.8% of BL, LV dP/dtmax=28.0%±5.9% of BL, p<0.05, n=6; ), which are similar to the four normothermia arrest (37°C) hearts (Vmax=55.9%±4.8% of BL, LV dP/dtmax=24.5%±2.1% of BL, n=4). The 32-32.5°C arrest hearts showed moderate recovery (n=5). A point of inflection (around 30.5-31°C) existed at the edge of a good recovery plateau followed by a steep slope. The point presented an OPH that should be the TTH. The results are concordant with data in the mammalian hearts, suggesting that the TTH should be initiated to cool core temperature at 31°C.

Type A intramural hematoma in the setting of acute type B aortic dissection

Type A intramural hematoma (IMH) is an uncommon entity, the pathophysiology of which is thought to be related to a contained hemorrhage within the medial layer of the aorta as a result of either rupture of the vasa vasorum or an atherosclerotic plaque. We present a case of type A IMH in the setting of acute type B aortic dissection with suspicion for malperfusion syndrome and discuss the treatment algorithm of this uncommon entity.

Aortic arch surgery using moderate hypothermia and unilateral selective antegrade cerebral perfusion

BACKGROUND

Cerebral protection and circulatory management remains a controversial issue in aortic arch surgery. The present study reported surgical outcomes of arch repair using moderate hypothermic circulatory arrest (MHCA) and unilateral selective antegrade perfusion (uSACP).

METHODS

From January 2004 and December 2012, 500 patients underwent hemiarch repair (HARCH) and 124 underwent total arch replacement (TARCH) utilizing moderate hypothermic circulatory arrest with unilateral selective antegrade cerebral perfusion of the right axillary artery. Emergent surgery was required in 142 (28.4%) of HARCH patients and 18 (14.5%) of TARCH patients. Mean arrest temperature ranged from 25.6-27.2 °C for elective and emergent operations in both groups. Mean circulatory arrest was 26.8 minutes for hemiarch repairs and 54.2 minutes for total arch replacement.

RESULTS

Overall mortality was 6.6% for hemiarch repairs and 9.7% for total arch replacements. Hospital mortality was 4.5% (16/358) and 10.4% (11/106) in elective cases, and 12% (17/142) and 5.6% (1/18) in elective cases, for hemiarch and total arch replacements respectively. Permanent neurological deficit (PND) occurred in 3 total arch replacement cases (2.4%). Multivariate analysis demonstrated that temperature was not found to be an independent risk factor during hemiarch or total arch replacements for mortality, permanent or neurological deficits, or renal failure.

CONCLUSIONS

Our approach for hemiarch and total arch repair utilizing MHCA and uSACP via the right axillary artery was associated excellent neurological and survival outcomes. Moderate hypothermia did not adversely impact cerebral or visceral organ protection.

Modified hypothermic circulatory arrest for emergent repair of acute aortic dissection type a: a single-center experience

Background

Deep hypothermic circulatory arrest (DHCA) with antegrade cerebral perfusion has been historically preferred for organ protection during surgical repair of the acute aortic dissection type A. However, in the past decades, different perfusion-specific strategies with a growing trend to increase the body temperature at circulatory arrest emerged. In this study, we retrospectively analyzed the clinical results of our modified protocol for cardiopulmonary bypass and hypothermia management.

Methods

Between February 2007 and September 2012, 54 consecutive patients suffering from acute aortic dissection type A underwent emergent surgery. All patients received hypothermic circulatory arrest in combination with antegrade cerebral perfusion. The patients were divided into two subsets according to the degree of hypothermia and perfusion strategies: namely the DHCA group and the group of modified hypothermic circulatory arrest (MHCA).

Results

The overall 30-day mortality was 27.8% and was not significantly different between groups (DHCA, 33.3%, MHCA, 19%; p=0.253). The requirement for blood product transfusion in MHCA patients was significantly less as as compared with the patients in the DHCA group. No difference occurred in the incidence of temporary neurologic dysfunction, dialysis-dependent renal failure, or reexploration for bleeding between two groups of patients. The use of MHCA was identified as a protective factor against the postoperative composite complications (OR, 0.78; CI, 0.52 to 0.98; p=0.04) and the prolonged intensive care unit stay (OR, 0.8; 95% CI, 0.56 to 0.98; p=0.04).

Conclusions

Moderate hypothermia in combination with selective brain perfusion and systemic retrograde perfusion is associated with adequate cerebral and visceral protection, reduced postoperative complications and shortened intensive care unit stay in our series. This modified perfusion strategy may help in improving perioperative outcomes in this particular group of patients.