Hypothermic Circulatory Arrest in Adult Aortic Arch Surgery: A Review of Hypothermic Circulatory Arrest and its Anesthetic Implications

Diseases affecting the aortic arch often require surgical intervention. Hypothermic circulatory arrest (HCA) enables a safe approach during open aortic arch surgeries. Additionally, HCA provides neuroprotection by reducing cerebral metabolism and oxygen requirements. However, HCA comes with significant risks (eg, neurologic dysfunction, stroke, and coagulopathy), and the cardiac anesthesiologist must completely understand the surgical techniques, possible complications, and management strategies.

Neurologic complications after cardiopulmonary bypass - A narrative review

Neurologic complications, associated with cardiac surgery and cardiopulmonary bypass (CPB) in adults, are common and can be devastating in some cases. This comprehensive review will not only consider the broad categories of stroke and neurocognitive dysfunction, but it also summarises other neurological complications associated with CPB, and it provides an update about risks, prevention and treatment. Where appropriate, we consider the impact of off-pump techniques upon our understanding of the contribution of CPB to adverse outcomes.

Piglet cardiopulmonary bypass induces intestinal dysbiosis and barrier dysfunction associated with systemic inflammation

The intestinal microbiome is essential to human health and homeostasis, and is implicated in the pathophysiology of disease, including congenital heart disease and cardiac surgery. Improving the microbiome and reducing inflammatory metabolites may reduce systemic inflammation following cardiac surgery with cardiopulmonary bypass (CPB) to expedite recovery post-operatively. Limited research exists in this area and identifying animal models that can replicate changes in the human intestinal microbiome after CPB is necessary. We used a piglet model of CPB with two groups, CPB (n=5) and a control group with mechanical ventilation (n=7), to evaluate changes to the microbiome, intestinal barrier dysfunction and intestinal metabolites with inflammation after CPB. We identified significant changes to the microbiome, barrier dysfunction, intestinal short-chain fatty acids and eicosanoids, and elevated cytokines in the CPB/deep hypothermic circulatory arrest group compared to the control group at just 4 h after intervention. This piglet model of CPB replicates known human changes to intestinal flora and metabolite profiles, and can be used to evaluate gut interventions aimed at reducing downstream inflammation after cardiac surgery with CPB.

The use of blood and blood products in aortic surgery is associated with adverse outcomes

OBJECTIVE

To report long-term outcomes after deep hypothermic circulatory arrest (DHCA) with or without perioperative blood or blood products.

METHODS

All patients who underwent proximal aortic surgery with DHCA from 2011 to 2018 were propensity matched according to baseline characteristics. Primary outcomes included short- and long-term mortality. Stratified Cox regression analysis was performed for significant associations with survival.

RESULTS

A total of 824 patients underwent aortic replacement requiring circulatory arrest. After matching, there were 224 patients in each arm (transfusion and no transfusion). All baseline characteristics were well matched, with a standardized mean difference (SMD) <0.1. Preoperative hematocrit (41.0 vs 40.6; SMD = 0.05) and ejection fraction (57.5% vs 57.0%; SMD = 0.08) were similar between the no transfusion and blood product transfusion cohorts. Rate of aortic dissection (42.9% vs 45.1%; SMD = 0.05), hemiarch replacement (70.1% vs 70.1%; SMD = 0.00), and total arch replacement (21.9% vs 23.2%; SMD = 0.03) were not statistically different. Cardiopulmonary bypass and cross-clamp time were higher in the blood product transfusion cohort (P < .001). Operative mortality (9.4% vs 2.7%; P = .003), stroke (7.6% vs 1.3%; P = .001), reoperation rate, pneumonia, prolonged ventilation, and dialysis requirements were significantly higher in the transfusion cohort (P < .001). In stratified Cox regression, transfusion was an independent predictor of mortality (hazard ratio, 2.62 [confidence interval, 1.47-4.67]; P = .001). One- and 5-year survival were significantly reduced for the transfusion cohort (P < .001).

CONCLUSIONS

In patients who underwent aortic surgery with DHCA, perioperative transfusions were associated with poor outcomes despite matching for preoperative baseline characteristics.

Temperature analysis of aortic repair with hypothermic circulatory arrest to quantify the injury by cooling

OBJECTIVES

We analyzed the temperature in proximal aortic repair with moderate hypothermic circulatory arrest (HCA) and evaluated the effect of the cooling status on postoperative outcomes.

METHODS

A total of 340 patients who underwent elective ascending aortic replacement or total arch replacement with moderate HCA from December 2006 to January 2021 were studied. The change in body temperature trends recorded during surgery was shown graphically. Several parameters, such as the nadir temperature, cooling speed and the degree of cooling (cooling area), which was the area under curve of inverted temperature trends from cooling to rewarming as calculated by the integral method, were analyzed. The relationships between these variables and a major adverse outcome (MAO) postoperatively defined as prolonged ventilation (>72 h), acute renal failure, stroke, reoperation for bleeding, deep sternal wound infection or in-hospital death were evaluated.

RESULTS

An MAO was observed in 68 patients (20%). The cooling area was larger in the MAO group than in the non-MAO group (1668.7 vs 1383.2°C min; P < 0.0001). A multivariate logistic model showed that old myocardial infarction, peripheral vascular disease, chronic renal dysfunction, cardiopulmonary bypass time and the cooling area were independent risk factors for an MAO (odds ratio = 1.1 per 100°C min; P < 0.001).

CONCLUSIONS

The cooling area, which indicates the degree of cooling, shows a significant relationship with an MAO after aortic repair. This finding indicates that the cooling status with HCA can affect clinical outcomes.

Duration of deep hypothermic circulatory arrest for aortic arch surgery: is it a myth, fiction, or scientific leap?

INTRODUCTION

The use of deep hypothermic circulatory arrest (DHCA) to provide aortic surgeons with a bloodless operative field while simultaneously protecting the brain and peripheries from ischemic damage revolutionized cardiac and aortic surgery, and is currently used in specialist centers across the globe. However, it is associated with manifold adverse outcomes, including neurocognitive dysfunction and mortality. This review seeks to analyze the relationship between DHCA duration and clinical outcome, and evaluate the controversies and limitations surrounding its use.

EVIDENCE ACQUISITION

We performed a review of available literature with statistical analysis to evaluate the relationship between DHCA duration (<40 min and >40 min) and key clinical outcomes, including mortality, permanent and temporary neurological deficit, renal damage, admission length, and reintervention rate. The controversies surrounding DHCA use and future directions for care are also explored.

EVIDENCE SYNTHESIS

Statistical analysis revealed no significant association (P>0.05) between DHCA duration and clinical outcomes (early and late mortality rates, neurological deficit, admission length, and reintervention rate), both with and without adjunctive perfusion techniques.

CONCLUSIONS

Available literature suggests that the relationships between DHCA duration (with and without adjunctive perfusion) and clinical outcomes are unclear, and at present not statistically significant. Alternative surgical and endovascular techniques have been identified as promising novel approaches not requiring DHCA, as have the use of biomarkers to enable early diagnosis and intervention for aortic pathologies.

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.

Surgery for renal cell carcinoma extending to the right atrium in Japanese institutions: Focusing on cardiopulmonary bypass with or without deep hypothermic circulatory arrest

OBJECTIVES

To evaluate the outcomes of Japanese patients with renal cell carcinoma undergoing surgery for tumor thrombus invading the right atrium.

METHODS

We retrospectively evaluated 23 patients who underwent extracorporeal circulation-assisted surgery at two institutions. Perioperative outcomes and survival rates were evaluated and compared between two groups of patients, which were set according to the use or not of deep hypothermic circulatory arrest. Data on systemic treatments were assessed.

RESULTS

The median age was 64 years; the majority of patients were fit according to the Charlson Comorbidity Index. Five (21.7%) patients had at least one distant metastasis, and 17 (73.9%) received systemic therapy. A total of 16 (69.6%) patients underwent deep hypothermic circulatory arrest. Baseline characteristics were comparable between groups. Patients who underwent deep hypothermic circulatory arrest had a non-significant reduction in blood loss compared with those who did not undergo this procedure (1866.0 vs 3513.0 mL, P = 0.102). The complication rate, both of any grade (43.8% vs 71.4%, P = 0.215) and grade ≥3 (6.3% vs 28.6%, P = 0.162), tended to be lower in patients who underwent deep hypothermic circulatory arrest. The mean 90-day mortality rate was 8.7%, with no difference among groups (6.3% vs 14.3%, respectively; P = 0.545). The overall median cancer-specific and overall survival were both 64.4 months, and did not differ between groups.

CONCLUSIONS

Renal cell carcinoma patients undergoing extracorporeal circulation-assisted surgery and systemic therapy for right atrial tumor thrombus have acceptable long-term survival rates. Outcomes are comparable regardless of the use of deep hypothermic circulatory arrest.

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.

Emerging hemorrhage control and resuscitation strategies in trauma: Endovascular to extracorporeal

This article reviews four emerging endovascular hemorrhage control and extracorporeal perfusion techniques for management of trauma patients with profound hemorrhagic shock including hemorrhage-induced traumatic cardiac arrest: resuscitative endovascular balloon occlusion of the aorta, selective aortic arch perfusion, extracorporeal life support, and emergency preservation and resuscitation. The preclinical and clinical studies underpinning each of these techniques are summarized. We also present an integrated conceptual framework for how these emerging technologies may be used in the future care of trauma patients in both resource-rich and austere environments.

Total circulatory arrest as a support modality in congenital heart surgery: review and current evidence

The use of total circulatory arrest (TCA)/deep hypothermic circulatory arrest (DHCA) as a support modality in congenital heart surgery is a time-tested strategy. However, with technological advances, the widespread use of this technique has decreased. Adjunctive cerebral perfusion with continuous cardiopulmonary bypass (CPB) gradually has become more popular with a view to reduce the complications related to DHCA. In addition, better neuromonitoring and neuroprotective strategies have made DHCA much safer. However, the level of evidence to support the best way to protect the brain during congenital heart surgery is insufficient. This review analyzes the history, physiology, techniques of DHCA, as well as other alternative strategies like selective cerebral perfusion and presents the current available evidence.

Anticipating Postoperative Delirium During Burst Suppression Using Electroencephalography

OBJECTIVE

This study develops an electro-encephalography-based method for predicting postoperative delirium early during cardiac surgeries involving deep hypothermia circulatory arrest (DHCA), potentially providing an opportunity to intervene and minimize poor surgical outcome. DHCA is a surgical technique used during cardiac surgeries to facilitate repairs. Deep hypothermia is induced and supplemented by perfusion techniques to protect the brain during circulatory arrest, but concern for cerebral injury still remains.

METHODS

This research studies whether or not monitoring burst suppression, an electrophysiological phenomenon observed during patient cooling and warming, helps in predicting postoperative delirium, a correlate of poor prognosis. A metric called the burst suppression duty cycle (BSDC), akin to burst suppression ratio, is formulated to characterize this electrophysiological activity.

RESULTS

Assuming no complications occur prior to circulatory arrest, delirium diagnoses are correlated with the time elapsed until suppression activity ceases since resuming cardiopulmonary bypass. By comparing against a benchmark the times when BSDC reaches 100%, 15 of 16 cases can be correctly predicted. Similar accuracy can be achieved when querying BSDC progress earlier during warming.

CONCLUSION

Our results show that our BSDC metric is a promising candidate for early detection of postoperative delirium, and motivates further analysis of the causal relationship between postoperative delirium and the procedure transitioning out of circulatory arrest.

SIGNIFICANCE

The developed methodology anticipates incidences of postoperative delirium during rewarming, which potentially provides an opportunity to intervene and avert it.

PSP-like syndrome after aortic surgery in adults (Mokri syndrome)

Background

A rare progressive supranuclear palsy-like syndrome seemingly triggered by aortic surgery was first described in 2004. This largest case series to date describes the features of this syndrome.

Methods

We searched the Mayo Clinic electronic medical records using the advanced cohort explorer search engine for patients evaluated for neurologic symptoms after cardiac-aortic surgery in the past 30 years. Data were extracted to Microsoft Excel from the identified patients and included clinical and neuroimaging features and outcomes.

Results

Twenty-five patients met the inclusion criteria. All surgeries were performed under thoracic aortic bypass and deep hypothermia. Surgery included aortic aneurysm, aortic valve repair, and/or aortic dissection repair. Surgical records were unavailable, although surgery was documented in the Mayo record as uncomplicated in 60% of cases. In the remaining cases, no particular intraoperative or postoperative complications were documented at a high frequency. A typical triad was documented: supranuclear gaze palsy (SNGP; 100%), gait imbalance (80%), and dysarthria (96%). Part or all of the triad was observed before hospital discharge and stabilized over the course of days-weeks. A second phase of symptom worsening plus new symptoms developed up to a year later; this decline continued for up to several years before stabilization. Delayed epileptic seizures occurred in 32% of patients. Brain MRI revealed only nonspecific findings.

Conclusion

This syndrome following adult thoracic aortic bypass surgery with deep hypothermia remains unexplained. It follows a biphasic course and is characterized by the triad of SNGP, unsteady gait, and a predominantly ataxic dysarthria.

A Comprehensive Update of Current Anesthesia Perspectives on Therapeutic Hypothermia

Normal thermal regulation is a result of the integration of afferent sensory, central control, and efferent responses to temperature change. Therapeutic hypothermia (TH) is a technique utilized during surgery to protect vital organs from ischemia; however, in doing so leads to other physiological changes. Indications for inducing hypothermia have been described for neuroprotection, coronary artery bypass graft (CABG) surgery, surgical repair of thoracoabdominal and intracranial aneurysms, pulmonary thromboendarterectomy, and arterial switch operations in neonates. Initially it was thought that induced hypothermia worked exclusively by a temperature-dependent reduction in metabolism causing a decreased demand for oxygen and glucose. Induced hypothermia exerts its neuroprotective effects through multiple underlying mechanisms including preservation of the integrity and survival of neurons through a reduction of extracellular levels of excitatory neurotransmitters dopamine and glutamate, therefore reducing central nervous system hyperexcitability. Risks of hypothermia include increased infection risk, altered drug pharmacokinetics, and systemic cardiovascular changes. Indications for TH include ischemia-inducing surgeries and diseases. Two commonly used methods are used to induce TH, surface cooling and endovascular cooling. Core body temperature monitoring is essential during induction of TH and rewarming, with central venous temperature as the gold standard. The aim of this review is to highlight current literature discussing perioperative considerations of TH including risks, benefits, indications, methods, and monitoring.

Critical Care of Patients After Pulmonary Thromboendarterectomy

Pulmonary thromboendarterectomy (PTE) remains the only curative surgery for patients with chronic thromboembolic pulmonary hypertension (CTEPH). Postoperative intensive care unit care challenges providers with unique disease physiology, operative sequelae, and the potential for detrimental complications. Central concerns in patients with CTEPH immediately after PTE relate to neurologic, pulmonary, hemodynamic, and hematologic aspects. Institutional experience in critical care for the CTEPH population, a multidisciplinary team approach, patient risk assessment, and integration of current concepts in critical care determine outcomes after PTE surgery. In this review, the authors will focus on specific aspects unique to this population, with integration of current available evidence and future directions. The goal of this review is to provide the cardiac anesthesiologist and intensivist with a comprehensive understanding of postoperative physiology, potential complications, and contemporary intensive care unit management immediately after pulmonary endarterectomy.

Neuroprotection against stroke and encephalopathy after cardiac surgery

Cerebral ischemia in the perioperative period is a major risk factor for stroke, encephalopathy, and cognitive decline after cardiothoracic surgery. After coronary artery bypass grafting, both stroke and encephalopathy can result in poor patient outcomes and increased mortality. Neuroprotection aims to lessen the severity and occurrence of further injury mediated by stroke and encephalopathy and to aid the recovery of conditions already present. Several pharmacological and non-pharmacological methods of neuroprotection have been investigated in experimental studies and in animal models, and, although some have shown effectiveness in protection of the central nervous system, for most, clinical research is lacking or did not show the expected results. This review summarizes the value and need for neuroprotection in the context of cardiothoracic surgery and examines the use and effectiveness of several agents and methods with an emphasis on clinical trials and clinically relevant neuroprotectants.

A Review of Goal-Directed Cardiopulmonary Bypass Management in Pediatric Cardiac Surgery

Cardiopulmonary bypass perfusion management significantly affects postoperative outcomes. In recent years, the principles of goal-directed therapy have been applied to the field of cardiothoracic surgery to improve patient outcomes. Goal-directed therapy involves continuous peri- and postoperative monitoring of vital clinical parameters to tailor perfusion to each patient's specific needs. Closely measured parameters include fibrinogen, platelet count, lactate, venous oxygen saturation, central venous oxygen saturation, mean arterial pressure, perfusion flow rate, and perfusion pulsatility. These parameters have been shown to influence postoperative fresh frozen plasma transfusion rate, coagulation state, end-organ perfusion, and mortality. In this review, we discuss the recent paradigm shift in pediatric perfusion management toward goal-directed perfusion.

Evaluation of a novel in-line point-of-care blood gas analyser

Point-of-care testing is becoming increasingly relevant to the practice of anaesthesia and critical care medicine, especially in terms of minimisation of sample volumes and decreased time to decision making. We performed a prospective observational study to evaluate a novel, in-line blood gas analysis device against a conventional benchtop model, and assessed it while placing the enrolled patients under extreme physiological conditions, specifically deep hypothermic circulatory arrest. Eight patients were studied, and had between seven and 11 samples analysed for seven variables (pH, pCO2 , pO2 , HCO3 (-) , base excess [BE], K(+) and haematocrit [Hct]), using the device during the process of cooling to 20 °C on cardiopulmonary bypass, and subsequent rewarming to normothermia. After Passing-Bablok analysis, the variables were evaluated for bias, limits of agreement and percentage error at above and below 30 °C. Of the measured variables, only pH (percentage error 2.4%) and potassium (19.8%) demonstrated acceptable (< 30%) percentage error over the full range of temperatures measured. Carbon dioxide, when stratified by temperature, was acceptable (< 30 °C percentage error 24.6%, > 30 °C percentage error 9.9%), but the overall percentage error of the dataset (45.8%) was excessively high. Bicarbonate and haematocrit both had an acceptable percentage error above 30 °C (25.2% and 18.5%, respectively), but similar to carbon dioxide, percentage error for the full range of temperatures exceeded 30%. These data differ from previous work examining this device, and highlights the difference between derived measures using different apparatuses when exposed to extreme physiological conditions.

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.

Cerebral Glucose Metabolism and Sedation in Brain-injured Patients: A Microdialysis Study

BACKGROUND

Disturbed brain metabolism is a signature of primary damage and/or precipitates secondary injury processes after severe brain injury. Sedatives and analgesics target electrophysiological functioning and are as such well-known modulators of brain energy metabolism. Still unclear, however, is how sedatives impact glucose metabolism and whether they differentially influence brain metabolism in normally active, healthy brain and critically impaired, injured brain. We therefore examined and compared the effects of anesthetic drugs under both critical (<1 mmol/L) and noncritical (>1 mmol/L) extracellular brain glucose levels.

METHODS

We performed an explorative, retrospective analysis of anesthetic drug administration and brain glucose concentrations, obtained by bedside microdialysis, in 19 brain-injured patients.

RESULT

Our investigations revealed an inverse linear correlation between brain glucose and both the concentration of extracellular glutamate (Pearson r=-0.58, P=0.01) and the lactate/glucose ratio (Pearson r=-0.55, P=0.01). For noncritical brain glucose levels, we observed a positive linear correlation between midazolam dose and brain glucose (P<0.05). For critical brain glucose levels, extracellular brain glucose was unaffected by any type of sedative.

CONCLUSIONS

These findings suggest that the use of anesthetic drugs may be of limited value in attempts to influence brain glucose metabolism in injured brain tissue.

Therapeutic hypothermia applicable to cardiac surgery

OBJECTIVE

To review the beneficial and adverse effects of therapeutic hypothermia (TH) applicable to cardiac surgery with cardiopulmonary bypass (CPB) in the contexts of various temperature levels and techniques for achieving TH.

DATABASES USED

Multiple electronic literature searches were performed using PubMed and Google for articles published from June 2012 to December 2014. Relevant terms (e.g. 'hypothermia', 'cardiopulmonary bypass', 'cardiac surgery', 'neuroprotection') were used to search for original articles, letters and reviews without species limitation. Reviews were included despite potential publication bias. References from the studies identified were also searched to find other potentially relevant citations. Abstracts, case reports, conference presentations, editorials and expert opinions were excluded.

CONCLUSIONS

Therapeutic hypothermia is an essential measure of neuroprotection during cardiac surgery that may be achieved most effectively by intravascular cooling using hypothermic CPB. For most cardiac surgical procedures, mild to modest (32-36 °C) TH will be sufficient to assure neuroprotection and will avoid most of the adverse effects of hypothermia that occur at lower body core temperatures.