Is Selective Antegrade Cerebral Perfusion Superior to Retrograde Cerebral Perfusion for Brain Protection During Deep Hypothermic Circulatory Arrest? Metabolic Evidence From Microdialysis:

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.

Correlation of Cerebral Microdialysis with Non-Invasive Diffuse Optical Cerebral Hemodynamic Monitoring during Deep Hypothermic Cardiopulmonary Bypass

Neonates undergoing cardiac surgery involving aortic arch reconstruction are at an increased risk for hypoxic-ischemic brain injury. Deep hypothermia is utilized to help mitigate this risk when periods of circulatory arrest are needed for surgical repair. Here, we investigate correlations between non-invasive optical neuromonitoring of cerebral hemodynamics, which has recently shown promise for the prediction of postoperative white matter injury in this patient population, and invasive cerebral microdialysis biomarkers. We compared cerebral tissue oxygen saturation (StO₂), relative total hemoglobin concentration (rTHC), and relative cerebral blood flow (rCBF) measured by optics against the microdialysis biomarkers of metabolic stress and injury (lactate–pyruvate ratio (LPR) and glycerol) in neonatal swine models of deep hypothermic cardiopulmonary bypass (DHCPB), selective antegrade cerebral perfusion (SACP), and deep hypothermic circulatory arrest (DHCA). All three optical parameters were negatively correlated with LPR and glycerol in DHCA animals. Elevation of LPR was found to precede the elevation of glycerol by 30–60 min. From these data, thresholds for the detection of hypoxic-ischemia-associated cerebral metabolic distress and neurological injury are suggested. In total, this work provides insight into the timing and mechanisms of neurological injury following hypoxic-ischemia and reports a quantitative relationship between hypoxic-ischemia severity and neurological injury that may inform DHCA management.

Does supply meet demand? A comparison of perfusion strategies on cerebral metabolism in a neonatal swine model

OBJECTIVE

We aimed to determine the effects of selective antegrade cerebral perfusion compared with other perfusion strategies on indices of cerebral blood flow, oxygenation, cellular stress, and mitochondrial function.

METHODS

One-week-old piglets (n = 41) were assigned to 5 treatment groups. Thirty-eight were placed on cardiopulmonary bypass. Of these, 30 were cooled to 18°C and underwent deep hypothermic circulatory arrest (n = 10), underwent selective antegrade cerebral perfusion at 10 mL/kg/min (n = 10), or remained on continuous cardiopulmonary bypass (deep hypothermic cardiopulmonary bypass, n = 10) for 40 minutes. Other subjects remained on normothermic cardiopulmonary bypass (n = 8) or underwent sham surgery (n = 3). Novel, noninvasive optical measurements recorded cerebral blood flow, cerebral tissue oxyhemoglobin concentration, oxygen extraction fraction, total hemoglobin concentration, and cerebral metabolic rate of oxygen. Invasive measurements of cerebral microdialysis and cerebral blood flow were recorded. Cerebral mitochondrial respiration and reactive oxygen species generation were assessed after the piglets were killed.

RESULTS

During hypothermia, deep hypothermic circulatory arrest piglets experienced increases in oxygen extraction fraction (P < .001), indicating inadequate matching of oxygen supply and demand. Deep hypothermic cardiopulmonary bypass had higher cerebral blood flow (P = .046), oxyhemoglobin concentration (P = .019), and total hemoglobin concentration (P = .070) than selective antegrade cerebral perfusion, indicating greater oxygen delivery. Deep hypothermic circulatory arrest demonstrated worse mitochondrial function (P < .05), increased reactive oxygen species generation (P < .01), and increased markers of cellular stress (P < .01). Reactive oxygen species generation was increased in deep hypothermic cardiopulmonary bypass compared with selective antegrade cerebral perfusion (P < .05), but without significant microdialysis evidence of cerebral cellular stress.

CONCLUSIONS

Selective antegrade cerebral perfusion meets cerebral metabolic demand and mitigates cerebral mitochondrial reactive oxygen species generation. Excess oxygen delivery during deep hypothermia may have deleterious effects on cerebral mitochondria that may contribute to adverse neurologic outcomes. We describe noninvasive measurements that may help guide perfusion strategies.

Mesenchymal Stem Cell-derived Exosomes Rescue Oxygen-Glucose Deprivation-induced Injury in Endothelial Cells

OBJECTIVE

The effects of mesenchymal stem cell (MSC)-derived exosomes on brain microvascular endothelial cells under oxygen-glucose deprivation (OGD), which mimic cells in deep hypothermic circulatory arrest (DHCA) in vitro, are yet to be studied.

METHODS

MSCs were co-cultured with primary rat brain endothelial cells, which were then exposed to OGD. Cell viability, apoptosis, the inflammatory factors (IL-1β, IL-6, and TNF-α), and the activation of inflammation-associated TLR4-mediated pyroptosis and the NF-κB signaling pathway were determined. Furthermore, exosomes derived from MSCs were isolated and incubated with endothelial cells to investigate whether the effect of MSCs is associated with MSCderived exosomes. Apoptosis, cell viability, and the inflammatory response were also analyzed in OGD-induced endothelial cells incubated with MSC-derived exosomes.

RESULTS

OGD treatment promoted endothelial cell apoptosis, induced the release of inflammatory factors IL-1β, IL-6, and TNF-α, and inhibited cell viability. Western blot analysis showed that OGD treatment-induced TLR4, and NF-κB p65 subunit phosphorylation and caspase-1 upregulation, while co-culture with MSCs could reduce the effect of OGD treatment on endothelial cells. As expected, the effect of MSC-derived exosomes on OGD-treated endothelial cells was similar to that of MSCs. MSC-derived exosomes alleviated the OGD-induced decrease in the viability of endothelial cells, and increased levels of apoptosis, inflammatory factors, and the activation of inflammatory and inflammatory focal pathways.

CONCLUSION

Both MSCs and MSC-derived exosomes attenuated OGD-induced rat primary brain endothelial cell injury. These findings suggest that MSC-derived exosomes mediate at least some of the protective effects of MSCs on endothelial cells.

MHCA with SACP versus DHCA in Pediatric Aortic Arch Surgery: A Comparative Study

The safety and efficacy of selective antegrade cerebral perfusion (SACP) in children undergoing aortic arch surgery are unclear. In this retrospective analysis, we compared moderate hypothermic circulatory arrest (MHCA; n = 61) plus SACP vs deep hypothermic circulatory arrest (DHCA; n = 53) in children undergoing aortic arch surgery during a period from January 2008 to December 2017. Demographic characteristics and the underlying anomalies were comparable between the two groups. The MHCA + SACP group had shorter cardiopulmonary bypass (CPB) time (146.9 ± 40.6 vs 189.6 ± 41.2 min for DHCA; p < 0.05) and higher nasopharyngeal temperature (26.0 ± 2.1 vs 18.9 ± 1.6 °C; p < 0.01). The MHCA + SACP group had lower rate of neurologic complications (3/61 vs 10/53 for DHCA; p < 0.05) but not complications in other organ systems. The MHCA + SACP group also had less 24-hour chest drainage (median, interquartile rage: 28.9, 12.6–150.0 vs 47.4, 15.2–145.0 ml/kg for DHCA; p < 0.05), shorter duration of postoperative mechanical ventilation (35.0, 15.4–80.3 vs 94.0, 42.0–144.0 h; p < 0.01), and shorter stay in intensive care unit (3.9, 3.0–7.0 vs 7.7, 5.0–15.0 d; p < 0.05). In regression analysis, in-hospital mortality was associated with longer CPB time. In conclusion, MHCA + SACP is associated with better short-term outcomes in children receiving aortic arch surgery under CPB.

Cerebral mitochondrial dysfunction associated with deep hypothermic circulatory arrest in neonatal swine

OBJECTIVES

Controversy remains regarding the use of deep hypothermic circulatory arrest (DHCA) in neonatal cardiac surgery. Alterations in cerebral mitochondrial bioenergetics are thought to contribute to ischaemia-reperfusion injury in DHCA. The purpose of this study was to compare cerebral mitochondrial bioenergetics for DHCA with deep hypothermic continuous perfusion using a neonatal swine model.

METHODS

Twenty-four piglets (mean weight 3.8 kg) were placed on cardiopulmonary bypass (CPB): 10 underwent 40-min DHCA, following cooling to 18°C, 10 underwent 40 min DHCA and 10 remained at deep hypothermia for 40 min; animals were subsequently rewarmed to normothermia. 4 remained on normothermic CPB throughout. Fresh brain tissue was harvested while on CPB and assessed for mitochondrial respiration and reactive oxygen species generation. Cerebral microdialysis samples were collected throughout the analysis.

RESULTS

DHCA animals had significantly decreased mitochondrial complex I respiration, maximal oxidative phosphorylation, respiratory control ratio and significantly increased mitochondrial reactive oxygen species (P < 0.05 for all). DHCA animals also had significantly increased cerebral microdialysis indicators of cerebral ischaemia (lactate/pyruvate ratio) and neuronal death (glycerol) during and after rewarming.

CONCLUSIONS

DHCA is associated with disruption of mitochondrial bioenergetics compared with deep hypothermic continuous perfusion. Preserving mitochondrial health may mitigate brain injury in cardiac surgical patients. Further studies are needed to better understand the mechanisms of neurological injury in neonatal cardiac surgery and correlate mitochondrial dysfunction with neurological outcomes.

Neuroprotective effect of selective antegrade cerebral perfusion during prolonged deep hypothermic circulatory arrest: Cerebral metabolism evidence in a pig model

Objective:

The aim of this study was to elucidate the mechanism of cerebral injury and to evaluate selective antegrade cerebral perfusion (SACP) as a superior neuroprotective strategy for prolonged deep hypothermic circulatory arrest (DHCA).

Methods:

Twelve pigs (6–8-week old) were randomly assigned to DHCA alone (n=6) and DHCA with SACP (n=6) at 18°C for 80 min groups. Serum S100 was determined using an immunoassay analyzer. The concentrations of cerebral dialysate glucose, lactate, pyruvate, glycerol, and glutamate were measured using a microdialysis analyzer.

Results:

Compared with a peak at T4 (after 60 min of rewarming) in the DHCA group, the serum S100 in the SACP group was significantly lower throughout the study. The DHCA group was susceptible to significant increases in the levels of lactate, glycerol, and glutamate and the ratio of lactate/pyruvate as well as decreases in the level of glucose. These microdialysis variables showed only minor changes in the SACP group. There was a positive correlation between cerebral lactate and intracranial pressure during reperfusion in the DHCA group. However, the apoptosis index and C-FOS protein levels were lower in the SACP group.

Conclusion:

Metabolic dysfunction is involved in the mechanism of cerebral injury. SACP is a superior neuroprotective strategy for both mild and prolonged DHCA.

International survey on the perioperative management of pulmonary endarterectomy: the perfusion perspective

Introduction:

Pulmonary endarterectomy (PEA) is the most effective treatment available for chronic thromboembolic pulmonary hypertension (CTEPH). Patient selection, surgical technique and perioperative management have improved patient outcomes, which are traditionally linked to surgical and center experience. However, optimal perfusion care has not been well defined. The goal of the international survey was to better characterize the contemporary perfusion management of PEA and highlight similarities and controversies.

Method:

The combined caseload of 15 participating centers was 5,066 cases. Topics queried included materials and types of cardiopulmonary bypass (CPB) equipment, choice of prime, fluid management, deep hypothermia strategy, temperature management, treatment of acid-base abnormalities and intraoperative hematocrit as well as anticoagulation management for heparin-induced thrombocytopenia.

Conclusion:

Our assessment could provide a base for further advancement and may help design future studies to elucidate the impact of perfusion in this challenging field.

Cerebral Metabolic Profiling of Hypothermic Circulatory Arrest with and Without Antegrade Selective Cerebral Perfusion: Evidence from Nontargeted Tissue Metabolomics in a Rabbit Model

Background:

Antegrade selective cerebral perfusion (ASCP) is regarded to perform cerebral protection during the thoracic aorta surgery as an adjunctive technique to deep hypothermic circulatory arrest (DHCA). However, brain metabolism profile after ASCP has not been systematically investigated by metabolomics technology.

Methods:

To clarify the metabolomics profiling of ASCP, 12 New Zealand white rabbits were randomly assigned into 60 min DHCA with (DHCA+ASCP [DA] group, n = 6) and without (DHCA [D] group, n = 6) ASCP according to the random number table. ASCP was conducted by cannulation on the right subclavian artery and cross-clamping of the innominate artery. Rabbits were sacrificed 60 min after weaning off cardiopulmonary bypass. The metabolic features of the cerebral cortex were analyzed by a nontargeted metabolic profiling strategy based on gas chromatography-mass spectrometry. Variable importance projection values exceeding 1.0 were selected as potentially changed metabolites, and then Student's t-test was applied to test for statistical significance between the two groups.

Results:

Metabolic profiling of brain was distinctive significantly between the two groups (Q²Y = 0.88 for partial least squares-DA model). In comparing to group D, 62 definable metabolites were varied significantly after ASCP, which were mainly related to amino acid metabolism, carbohydrate metabolism, and lipid metabolism. Kyoto Encyclopedia of Genes and Genomes analysis revealed that metabolic pathways after DHCA with ASCP were mainly involved in the activated glycolytic pathway, subdued anaerobic metabolism, and oxidative stress. In addition, L-kynurenine (P = 0.0019), 5-methoxyindole-3-acetic acid (P = 0.0499), and 5-hydroxyindole-3-acetic acid (P = 0.0495) in tryptophan metabolism pathways were decreased, and citrulline (P = 0.0158) in urea cycle was increased in group DA comparing to group D.

Conclusions:

The present study applied metabolomics analysis to identify the cerebral metabolic profiling in rabbits with ASCP, and the results may shed new lights that cerebral metabolism is better preserved by ASCP compared with DHCA alone.

Moderate Hypothermia Provides Better Protection of the Intestinal Barrier than Deep Hypothermia during Circulatory Arrest in a Piglet Model: A Microdialysis Study

INTRODUCTION

This study aimed to assess the effects of different temperature settings of hypothermic circulatory arrest (HCA) on intestinal barrier function in a piglet model.

METHODS

Twenty Wuzhishan piglets were randomly assigned to 40 min of HCA at 18°C (DHCA group, n = 5), 40 min of HCA at 24°C (MHCA group, n = 5), normothermic cardiopulmonary bypass (CPB group, n = 5) or sham operation (SO group, n = 5). Serum D-lactate (SDL) and lipopolysaccharide (LPS) levels were determined. Microdialysis parameters (glucose, lactate, pyruvate and glycerol) in the intestinal dialysate were measured. After 180 min of reperfusion, intestinal samples were harvested for real-time polymerase chain reaction and western blotting measurements for E-cadherin and Claudin-1.

RESULTS

Higher levels of SDL and LPS were detected in the DHCA group than in the MHCA group (P < 0.001). Both MHCA and DHCA groups exhibited lower glucose levels, higher lactate and glycerol levels and a higher lactate to pyruvate (L/P) ratio compared with the CPB group (p<0.05); the DHCA group had higher lactate and glycerol levels and a higher L/P ratio (p<0.05) but similar glucose levels compared to the MHCA group. No significant differences in E-cadherin mRNA or protein levels were noted. Upregulation of claudin-1 mRNA levels was detected in both the DHCA and MHCA animals' intestines (P < 0.01), but only the DHCA group exhibited a decrease in claudin-1 protein expression (P < 0.01).

CONCLUSION

HCA altered the energy metabolism and expression of epithelial junctions in the intestine. Moderate hypothermia (24°C) was less detrimental to the markers of normal functioning of the intestinal barrier than deep hypothermia (18°C).

The protective effects of a phosphodiesterase 5 inhibitor, sildenafil, on postresuscitation cardiac dysfunction of cardiac arrest: metabolic evidence from microdialysis

INTRODUCTION

Recent experimental and clinical studies have indicated the cardioprotective role of sildenafil during ischemia/reperfusion injury. The aim of this study was to determine, by obtaining metabolic evidence from microdialysis, if sildenafil could reduce the severity of postresuscitation myocardial dysfunction and lead to cardioprotection through beneficial effects on energy metabolism.

METHODS

Twenty-four male piglets were randomly divided into three groups: sildenafil (n = 8), saline (SA; n = 8) and sham operation (n = 8). Sildenafil pretreatment consisted of 0.5 mg/kg sildenafil administered once intraperitoneally 30 minutes prior to ventricular fibrillation (VF). The myocardial interstitial fluid (ISF) concentrations of glucose, lactate, pyruvate, glutamate and glycerol were determined by microdialysis before VF. Afterward, the piglets were subjected to 8 minutes of untreated VF followed by 15 minutes of open-chest cardiopulmonary resuscitation. ISF was collected continuously, and the experiment was terminated 24 hours after resuscitation.

RESULTS

After 8 minutes of untreated VF, the sildenafil group exhibited higher glucose and pyruvate concentrations of ISF and lower lactate and glutamate levels in comparison with the SA group, and these data reached statistical significance (P < 0.05). Advanced cardiac life support was delivered to both groups, with a 24-hour survival rate showing a promising trend in the sildenafil group (7 of 8 versus 3 of 8 survivors, P < 0.05). Compared with the SA group, the sildenafil group had a better outcome in terms of hemodynamic and oxygen metabolism parameters (P < 0.05). Myocardial tissue analysis revealed a dramatic increase in the contents of ATP, ADP and phosphocreatine in the sildenafil group versus the SA group at 24 hours after return of spontaneous circulation (ROSC; P = 0.03, P = 0.02 and P = 0.02, respectively). Furthermore, 24 hours after ROSC, the sildenafil group had marked elevations in activity of left ventricular Na(+)-K(+)-ATPase and Ca(2+)-ATPase compared with the SA group (P = 0.03, P = 0.04, respectively).

CONCLUSIONS

Sildenafil could reduce the severity of postresuscitation myocardial dysfunction, and it produced better clearance of metabolic waste in the ISF. This work might provide insights into the development of a novel strategy to treat postresuscitation myocardial dysfunction.