Brain protection in cardiac surgery

The Rationalisation of Intra-Operative Imaging During Cardiac Surgery: A Systematic Review

INTRODUCTION

One critical complication of cardiac surgery is cerebrovascular accidents (CVAs). Ascending aorta atherosclerosis poses a significant risk of embolisation to distal vessels and to cerebral arteries. Epi-aortic ultrasonography (EUS) is thought to offer a safe, high-quality accurate visualisation of the diseased aorta to guide the surgeon on the best surgical approach to the planned procedure and potentially improve neurological outcomes post-cardiac surgery.

METHOD

The authors conducted a comprehensive search of PubMed, Scopus and Embase. Studies that reported on epi-aortic ultrasound use in cardiac surgery were included. Major exclusion criteria were: (1) abstracts, conference presentations, editorials, literature reviews; (2) case series with <5 participants; (3) epi-aortic ultrasound in trauma or other surgeries.

RESULTS

A total of 59 studies and 48,255 patients were included in this review. Out of the studies that reported patient co-morbidities prior to cardiac surgery, 31.6% had diabetes, 59.5% had hyperlipidaemia and 66.1% had a diagnosis of hypertension. Of those that reported significant ascending aorta atherosclerosis found on EUS, this ranged from 8.3% of patients to 95.2% with a mean percentage of 37.8%. Hospital mortality ranged from 7% to 13%; four studies reported zero deaths. Long-term mortality and stroke rate varied significantly with hospital duration.

CONCLUSION

Current data have shown EUS to have superiority over manual palpation and transoesophageal echocardiography in the prevention of CVAs following cardiac surgery. Yet, EUS has not been implemented as a routine standard of care. Extensive adoption of EUS in clinical practice is warranted to aid large, randomised trials before making prospective conclusions on the efficacy of this screening method.

Oleocanthal protects against neuronal inflammation and cardiopulmonary bypass surgery-induced brain injury in rats by regulating the NLRP3 pathway

BACKGROUND

Open heart surgery is performed with the aid of cardiopulmonary bypass (CPB) techniques that may cause neuronal injuries.

OBJECTIVE

This study investigated the potential protective effect of oleocanthal pre-treatment against CPB-induced cerebral injury.

METHODS

Oleocanthal 30 mg/kg i.p. was administered 3 h before CPB induction in the treated group. Behavioral neurological scores and cerebral injury were assessed to determine the effects of oleocanthal, based on oxidative stress and serum mediators of inflammation by enzyme-linked immunosorbent assay (ELISA). Quantitative Polymerase Chain Reaction (qRT-PCR) was used to estimate the mRNA expression of Toll-like receptor 4 (TLR4) and Interleukin 1 Receptor Associated Kinase 4 (IRAK4) proteins in the cerebral tissue of rats CPB-induced injury. Western blot assay and histopathology were also performed.

RESULTS

The findings suggest that pre-treatment with oleocanthal reduced neurological dysfunction and cerebral injury. Parameters of oxidative stress and cytokine levels were reduced in the serum of the oleocanthal treated group compared with the CPB-only group. Pre-treatment with oleocanthal ameliorated the expression of TLR-4, IRAK4, and Zonula occludens-1 (ZO-1) proteins in the cerebral tissue of the CPB-injured rats.

CONCLUSIONS

The results revealed that treatment with oleocanthal protected against cerebral damage by controlling microglia inflammation through the TLR-4 pathway.

Trends in Utilization and Safety of In-Hospital Coronary Artery Bypass Grafting During a Non-ST-Segment Elevation Myocardial Infarction

Up to 10% of non-ST-segment elevation myocardial infarction (NSTEMI) patients require coronary artery bypass graft (CABG) surgery during their hospitalization. Contemporary, real-world, data regarding CABG utilization and safety in NSTEMI patients are lacking. Our objectives were to investigate the contemporary trends in utilization and outcomes of CABG in patients admitted for NSTEMI. Using the 2003 to 2015 National Inpatient Sample data, we identified hospitalizations for NSTEMI, during which a CABG was performed. Patients' sociodemographic and clinical characteristics, incidence of surgical complications, length of stay, and mortality were analyzed. Multivariate analyses were performed to identify predictors of in-hospital complications and mortality. An estimated total of 440,371 CABG surgeries, during a hospitalization for NSTEMI, were analyzed. The utilization of CABG was steady over the years. The data show increasing prevalence of individual co-morbidities as well as cases with Deyo Co-morbidity Index ≥2 (p <0.001). High, 26.4%, complication rate was driven mainly by cardiac and pulmonary complications. The mortality rate declined from 3.6% in 2003 to an average of 2.4% during 2010 to 2015. Older age, female gender, heart failure, and delayed CABG timing were independent predictors of adverse outcomes. In conclusion, utilization of in-hospital CABG as the primary revascularization strategy in patients with NSTEMI remained steady over the years. These data reveal the raising prevalence of co-morbidities during the study. High complication rate was recorded; however, the mortality declined over the years to about 2.4%. Delaying CABG was associated with small but statistically significant worsening in outcomes.

Neuroprotective Effect of Low Mean Arterial Pressure on Postoperative Cognitive Deficit Attenuated by Prolonged Coronary Artery Bypass Time: A Meta-Analysis

Introduction

The true influence of the low mean arterial pressure (low MAP) during coronary artery bypass grafting (CABG) on the development of postoperative cognitive deficit (POCD) remains controversial. We aimed to perform a meta-analysis and meta-regression to determine the effect of low MAP on POCD, as well as moderator variables between low MAP and POCD.

Methods

The Web of Science, PubMed database, Scopus and the Cochrane Library database (up to June 2018) were searched and retrieved articles systematically reviewed. Only randomized controlled trials (RCTs) comparing maintenance of low MAP (<80 mmHg) and high MAP (>80 mmHg) during cardiopulmonary bypass (CPB) were included in our final review. Statistical analysis of the risk ratio (RR) and corresponding 95% confidence interval (CI) was used to report the overall effect. The overall effect and meta-regression analysis were done using Mantel-Haenszel risk ratio (MHRR) and the corresponding 95% confidence interval (CI).

Results

A total of 731 patients in three RCTs were included in this study. POCD occurred in 6.4% of all cases. Maintenance of low MAP did not reduce the occurrence of POCD (MHRR 1.012 [95% CI 0.277-3.688]; Z=0.018; P=0.986; I²=66%). Shorter CPB time reduced the occurrence of POCD regardless of group assignment (MH log risk ratio -0.519 [95% CI -0.949 - -0.089]; Z= -2.367; P=0.017).

Conclusion

POCD is a common event among CABG patients. The neuroprotective effect of low MAP on POCD was attenuated by the prolonged CPB time.

Selective brain hypothermia: feasibility and safety study of a novel method in five patients

BACKGROUND/OBJECTIVE

Reduction of brain temperature remains the most common method of neuroprotection against ischemic injury employed during cardiac surgery. However, cooling delivered via the cardiopulmonary bypass circuit is brief and cooling the body core along with the brain has been associated with a variety of unwanted effects. This study investigated the feasibility and safety of a novel selective brain cooling approach to induce rapid, brain-targeted hypothermia independent of the cardiopulmonary bypass circuit.

METHODS

This first-in-human feasibility study enrolled five adults undergoing aortic valve replacement with cardiopulmonary bypass support. During surgery, the NeuroSave system circulated chilled saline within the pharynx and upper esophagus. Brain and body core temperature were continuously monitored. Adverse effects, cardiopulmonary function, and device function were noted.

RESULTS

Patient 1 received cooling fluid for an insignificant period, and Patients 2-5 successfully underwent the cooling procedure using the NeuroSave system for 56-89 minutes. Cooling fluid was 12°C for Patients 1-3, 6°C for Patient 4, and 2°C for Patient 5. There were no NeuroSave-related adverse events and no alterations in cardiopulmonary function during NeuroSave use. Brain temperature decreased by 3°C within 15 minutes and remained at least 3.5°C colder than the body core. During a brief episode of hypotension in one patient, the brain cooled an additional 4°C in 2 minutes, briefly reaching 27.4°C.

CONCLUSION

The NeuroSave system can induce rapid brain-targeted hypothermia and simultaneously maintain a favorable body-brain temperature gradient, even during hypotension. Further studies are required to evaluate the function of the system during longer periods of use.

Custodiol-N™ cardioplegia lowers cerebral inflammation and activation of hypoxia-inducible factor-1α

OBJECTIVES

Cardioplegic solutions induce cardiac arrest and protect cardiac tissue from ischaemia-reperfusion injury. However, the effects on the brain, which is vulnerable to cardiopulmonary bypass (CPB) surgery and ischaemia-reperfusion injury, mostly remain unknown. We investigated if cardioplegic solutions differ in their effects in altered oxygen conditions and in their ability to induce cerebral inflammation.

METHODS

Thirty pigs were subjected to a midline sternotomy and CPB at 34°C with 90 min cardiac arrest followed by 120 min reperfusion. Following randomization on a 1:1:1 basis, they received either a single shot of histidine-tryptophan-α-ketoglutarate (HTK)-Bretschneider solution (n = 10), histidine-tryptophan-α-ketoglutarate-N (HTK-N; n = 10) or HTK plus 1.2 mg/l cyclosporine A (HTK/CsA; n = 10). Brain regions of interest (frontal cortex, cerebellum, brain stem, diencephalon, colliculus superior) were analysed by real time quantitative reverse transcriptase polymerase chain reaction for hypoxia-inducible factor-1α (HIF-1α), tumour necrosis factor-α, interleukin (IL)-10, IL-1β and IL-1β receptor as well as by immunohistochemical analysis for HIF-1α. Blood gas and electrolyte analyses were performed.

RESULTS

Comparisons between baseline and reperfusion period levels revealed that HTK-N cardioplegia induced a smaller reduction of the haemoglobin content and blood calcium concentrations (hbbaseline: 5.97 ± 0.63 mmol/l; hbreperfusion: 6.16 ± 0.66 mmol/l; P = 0.428; Cabaseline2+: 1.36 ± 0.05 mmol/l; Careperfusion2+: 1.28 ± 0.05 mmol/l; P < 0.001) compared to HTK (hbbaseline: 5.93 ± 0.45 mmol/l; hbreperfusion: 4.72 ± 0.79 mmol/l; P = 0.001; Cabaseline2+: 1.34 ± 0.07 mmol/l; Careperfusion2+: 1.24 ± 0.06 mmol/l; P = 0.004) and HTK/CsA cardioplegia (hbbaseline: 5.88 ± 0.44 mmol/l; hbreperfusion: 5.14 ± 0.87 mmol/l; P = 0.040; Cabaseline2+: 1.38 ± 0.04 mmol/l; Careperfusion2+: 1.20 ± 0.14 mmol/l; P = 0.001). Brain region-specific regulation of the HIF-1α expression, no general HIF-1α activation and a lower tumour necrosis factor-α expression (pto HTK = 0.050, pto HTK/CsA = 0.013) were documented for HTK-N cardioplegia.

CONCLUSIONS

HTK-N (Custodiol-N) induced fewer cerebral effects and less inflammation during CPB surgery than HTK and HTK/CsA cardioplegia. These data suggest that HTK-N exerts brain protective effects during and after CPB surgery.

Successful Management of Massive Air Embolism During Cardiopulmonary Bypass Using Multimodal Neuroprotection Strategies

Complications and critical events during cardiopulmonary bypass (CPB) are very challenging, difficult to manage, and in some instances have the potential to lead to fatal outcomes. Massive cerebral air embolism is undoubtedly a feared complication during CPB. If not diagnosed and managed early, its effects are devastating and even fatal. It is a catastrophic complication and its early diagnosis and intraoperative management are still controversial. This is why the decision-making process during a massive cerebral air embolism represents a challenge for the entire surgical, anesthetic, and perfusion team. All caregivers involved in this event must synchronize their responses quickly, harmoniously, and in such a way that all interventions lead to minimizing the impact of this complication. Its occurrence leaves important lessons to the surgical team that faces it. The best management strategy for a complication of this type is prevention. Nevertheless, a surgical team may ultimately be confronted with such an occurrence at some point despite all the prevention strategies, as was the case with our patient. That is why, in each institution, no effort should be spared to establish cost-effective strategies for early detection and a clear and concise management protocol to guide actions once this complication is detected. It is the duty of each surgical team to determine and clearly organize which strategies will be followed. The purpose of this case study was to demonstrate that a massive air embolism can be rapidly detected using near-infrared spectroscopy monitoring and can be successfully corrected with a multimodal neuroprotection strategy.

Does Tetralogy of Fallot affect brain aging? A proof-of-concept study

The impact of congenital heart disease on brain aging has not been extensively investigated. We evaluated cerebral microbleeds and white matter hyperintensities on brain magnetic resonance imaging in adult patients with tetralogy of Fallot (ToF). Ten ToF patients (6 women, 4 men; aged 21–58 years; New York Heart Association [NYHA] class 1–2) were prospectively enrolled and underwent a T1-weighted, a T2-weighted dark fluid, and a T2*-weighted scans. Ten age- and sex-matched controls were prospectively recruited and subjected to the same acquisition protocol. Cerebral microbleeds (CMBs) were manually counted while white matter hyperintensities (WMHs) were segmented using ITK-Snap. Wilcoxon signed-rank test, Spearman correlation, and Bland-Altman statistics were used. The median (interquartile range [IQR]) age was 45.0 (30.5–49.5) years in ToF patients and 46.0 (30.5–49.8) years in controls. The median (IQR) of the number of CMBs was 6.0 (4.0–7.8) in ToF patients and 0 (0.0–0.0) in controls (p = 0.002). The WMHs burden was 2,506 (1,557–2,900) mm³ for ToF patients and 2,212 (1,860–2,586) mm³ for controls (p = 0.160). Moreover, a positive significant correlation was found between the WMHs burden and the NYHA class (ρ = 0.80, p = 0.005). Inter-operator concordance rate for the presence/absence of CMBs was 90%; the reproducibility for the WMHs burden was 77%. In conclusion, we found more cerebral microbleeds and a higher WMHs burden in adult ToF patients than in controls. This preliminary comparison supports the hypothesis of an early brain aging in ToF patients. Larger studies are warranted.

The protective role of sex hormones in females and exercise prehabilitation in males on sternotomy-induced cranial hypoperfusion in aortic banded mini-swine

During cardiac surgery, specifically sternotomy, cranial hypoperfusion is linked to cerebral ischemia, increased risk of perioperative watershed stroke, and other neurocognitive complications. The purpose of this study was to retrospectively examine the effect of sex hormones in females and exercise prehabilitation in males on median sternotomy-induced changes in cranial perfusion in a large animal model of heart failure. Cranial blood flow (CBF) before and 10 and 60 min poststernotomy was analyzed in eight groups of Yucatan mini-swine: female control, aortic banded, ovariectomized, and ovariectomized + aortic banded; male control, aortic banded, aortic banded + continuous exercise trained, and aortic banded + interval exercise trained. A median sternotomy decreased cranial perfusion during surgery in all pigs (~24 ± 2% relative to baseline; P ≤ 0.05). CBF was 30 ± 7% lower across all time points in all females vs. all males (P ≤ 0.05) and sternotomy decreased cranial perfusion (P ≤ 0.05) independent of sex (females = 34 ± 3% and males = 14 ± 3%) and aortic banding (intact control = 31 ± 5% and intact aortic banded = 31 ± 4%). CBF recovery at 60 min tended to be better in females vs. males (relative to 10 min poststernotomy, females = 23 ± 13% vs. males = -1 ± 5%) and intact aortic banded vs. control pigs (relative to 10 min poststernotomy, aortic banded = 43 ± 20% vs. control = 6 ± 16%; P ≤ 0.05) at 60 min poststernotomy. Ovariectomy impaired CBF recovery during cranial reperfusion 60 min following sternotomy (relative to baseline, all intact females = -1 ± 9% vs. all ovariectomized females = -15 ± 4%; P ≤ 0.05). Chronic exercise training completely prevented significant sternotomy-induced cranial hypoperfusion independent of aortic banding (sternotomy-induced deficit, all sedentary males = -24 ± 6% vs. all exercise-trained males = -7 ± 3%; P ≤ 0.05). Female sex hormones protected against impaired CBF recovery during reperfusion, while chronic exercise training prevented sternotomy-induced cranial hypoperfusion despite cardiac pressure overload.NEW & NOTEWORTHY Our findings suggest a median sternotomy may predispose patients, possibly postmenopausal women and sedentary men, to perioperative cerebral ischemia, an increased risk of cardiac surgery-related stroke, and resulting neurocognitive impairments. Specifically, data from this common surgical procedure show: 1) median sternotomy independently decreases cranial perfusion; 2) female sex hormones improve cranial blood flow recovery following sternotomy; and 3) exercise prehabilitation prevents sternotomy-induced cranial hypoperfusion. Exercise prehabilitation before cardiac surgery may be advantageous for capable patients.

Effect of preoperative statin therapy on early postoperative memory impairment after off-pump coronary artery bypass surgery

Context:

Frequent incidence of early postoperative memory impairment (POMI) after cardiac surgery remains a concern because of associated morbidity, impaired quality of life, and increased health care cost.

Aim:

To assess the effect of preoperative statin therapy on POMI in patients undergoing off-pump coronary artery bypass (OPCAB) surgery.

Setting and Design:

Prospective observational study in a tertiary level hospital.

Methods:

Sixty patients aged 45–65 years undergoing OPCAB surgery were allocated into two groups of 30 each. Group A patients were receiving statin and Group B patients were not receiving statins. All patients underwent memory function assessment preoperatively after admission to hospital and on the 6^th postoperative day using postgraduate institute memory scale.

Statistical Analysis:

Appropriate tests were applied with SPSS 20 to compare both groups. The value P < 0.05 was considered statistically significant. Multiple regression analysis was performed with confounding factors to determine the effect on memory impairment.

Results:

Patients in Group A showed significant postoperative deterioration in 6 of the 10 functions and in Group B showed deterioration in 9 of 10 functions tested compared to preoperative scores. Intergroup comparison detected less POMI in Group A compared to Group B and was statistically significant in 8 memory functions. Multiple regression analysis detected statin as an independent factor in preventing memory impairment.

Conclusions:

Preoperative statin therapy attenuates the early POMI in patients undergoing OPCAB. Future long-term studies will define the efficacy of statin on POMI.

Embolic Protection Devices in Transcatheter Aortic Valve Replacement

The initially reported periprocedural neurological events rates associated with transcatheter aortic valve replacement raised concerns that ultimately led to the development and to the clinical research of novel embolic protection devices. Although the reduction of clinical stroke is a desired goal, the current research design of embolic protection devices focuses on surrogate markers of the clinical disease, primarily on silent central nervous system lesions observed in postprocedural diffuse-weighted magnetic resonance imaging and cognitive function testing. As the mere presence of particulate debris in brain matter may not correlate with the extent of brain injury, cognitive function, or quality of life, the clinical significance of embolic protection devices has yet to be determined, and interpretation of study results with regard to real-life clinical use should be viewed accordingly. The purpose of this article is to provide an overview of the updated ongoing clinical research on embolic protection devices and present its major caveats.

Axillary artery cannulation provides balanced cerebral oxygenation

Deterioration of cerebral performance remains a major problem after cardiac surgery. Axillary artery cannulation can improve clinical outcome, but some experimental series show a malperfusion of the right hemisphere. The aim of our clinical study was to analyze the intraoperative investigation of cerebral oxygenation in two different arterial cannulation sites by use of near-infrared spectroscopic oximetry (NIRO). We compared retrospectively the cerebral saturation of 20 patients with aortic cannulation (group AoC) and 20 patients with right axillary artery cannulation (group AxC) during either valve, coronary artery bypass graft (CABG), combined procedures, or aortic surgery. Patients were monitored with bihemispheric NIRO (NIRO-200, Hamamatsu, Herrsching, Germany). The oxygenation data were calculated as tissue oxygenation index (TOI). And the cardiopulmonary bypass time was considered with special regard to potentially dangerous phases for cerebral desaturation like the starting of the extracorporeal circulation (ECC), cross-clamping, rewarming phase, aortic declamping, and stopping of ECC. Patients were then postoperatively evaluated by a standardized neurological examination. During the entire CPB time and the specific phases potentially at risk for cerebral desaturation, no statistically significant drop of cerebral oxygenation (>20 % for >60 s) was detected after aortic and right axillary artery cannulation, respectively. Furthermore, no significant difference in TOI was found comparing the left and right hemisphere in each group. Postoperatively 2 transient confusional syndromes (CS) were observed after aortic and 3 CS after axillary artery cannulation. Right axillary artery cannulation provides balanced cerebral oxygenation in both hemispheres during extracorporeal circulation and its specific phases potentially at risk for cerebral malperfusion. It might therefore reduce the risk of neurological injury by reduction of solid embolization and maintenance of balanced cerebral oxygenation.

Brain damage in cardiac surgery patients

Neuropsychological disorders and brain injury are still a serious problem in cardiac surgery patients. Owing to multifactorial mechanism of brain injury during extracorporeal circulation, the effective and safe protection is extremely difficult. Despite several studies, the ideal neuroprotective treatment has not been found. Based on literature we analysed the main mechanisms of brain injury and new methods of brain protection.

Avoiding stroke during cardiac surgery

The life saving benefits of cardiac surgery are frequently accompanied by negative side effects such as stroke, that occurs with an incidence of 2%-13% dependent to type of surgery. The etiology is most likely multifactorial with embolic events considered as main contributor. Although stroke presents a common complication, no guidelines for any routine use of pharmacological substances or non-pharmacological strategies exist to date. Non-pharmacological strategies include monitoring of brain oxygenation and perfusion with devices such as near infrared spectroscopy and Transcranial Doppler help. Epiaortic and transesophageal echocardiography visualize aorta pathology, enabling the surgeon to sidestep atheromatous segments. Additionally can the use of specially designed aortic cannulae and filters help to reduce embolization. Brain perfusion can be improved by using antero- or retrograde cerebral perfusion during deep hypothermic circulatory arrest, by tightly monitoring mean arterial blood pressure and hemodilution. Controlling perioperative temperature and glucose levels may additionally help to ameliorate secondary damage. Many pharmacological compounds have been shown to be neuroprotective in preclinical models, but clinical studies failed to confirm these results so far. Remacemide, an NMDA-receptor-antagonist showed a significant drug-based neuroprotection during cardiac surgery. Other substances currently assessed in clinical trials whose results are still pending are acadesine, an adenosine-regulating substance, the free radical scavenger edaravone and the local anesthetic lidocaine. Stroke remains as significant complication after cardiac surgery. Non-pharmacological strategies allow perioperative caregivers to detect injurious events and to ameliorate stroke and its sequelae. Considering the multi-factorial etiology though, stroke prevention will likely have to be addressed with an individualistic combination of different strategies and substances.

Role of surgical factors in strokes after cardiac surgery

Deficient neurological disorders after heart surgery are destructive and affect vital prognosis. They concern between 3% to 9% of patients and are related mainly to embolic episodes or brain perfusion defects. The causes of these mechanisms are numerous, but surgical procedures and cardiopulmonary bypass optimization reduce their occurrence significantly.