Hypoxia-Induced Piglet Model of Cardiac Arrest with Assisted Resuscitation by Extracorporeal Membrane Oxygenation.

The mortality rate of newborns with severe congenital heart disease (CHD) has significantly decreased over the past few decades. However, many of these children experience neurological impairments, particularly following a hypoxic cardiac arrest. The use of extracorporeal membrane oxygenation (ECMO) has been considered an effective treatment for severe hypoxia in CHD cases. Various clinical studies have examined the use of ECMO for resuscitation after hypoxic cardiac arrest, but the results have been contradictory, showing a significant incidence of both mortality and morbidity in some studies while others report good outcome. In order to investigate the mechanisms behind brain injury associated with extracorporeal circulation, we have developed a neonatal porcine model of hypoxia-induced cardiac arrest followed by veno-arterial ECMO therapy.

Early Outcomes of Pulmonary Valve Replacement With the Edwards Inspiris Resilia Pericardial Bioprosthesis.

BACKGROUND: Controversy regarding the optimal pulmonary valve substitute remains, with no approved surgical valve for pulmonary valve replacement (PVR). Furthermore, unfavorable anatomy often precludes transcatheter PVR in patients with congenital heart disease. We therefore sought to evaluate the feasibility of the Edwards Inspiris pericardial aortic bioprosthesis in the pulmonary position in pediatric and adult patients requiring PVR. METHODS: Data from consecutive patients who underwent PVR from February 2019 to February 2021 at our institution were retrospectively reviewed. Postoperative adverse events included paravalvular or transvalvular leak, endocarditis, explant, thromboembolism, valve thrombosis, valve-related bleeding, hemolysis, and structural valve degeneration. Progression of valve gradients was assessed from discharge to 30 days and one year. RESULTS: Of 24 patients with median age of 26 years (interquartile range [IQR]: 17-33; range: 4-60 years), 22 (91.7%) patients had previously undergone tetralogy of Fallot repair and 2 (8.3%) patients had undergone double-outlet right ventricle repair in the neonatal period or infancy. All patients had at least mild right ventricular (RV) dilatation (median RV end-diastolic volume index 161.4, IQR: 152.3-183.5 mL/m2) and at least moderate pulmonary insufficiency (95.8%) or stenosis (8.3%). Median cardiopulmonary bypass and cross-clamp times were 71 (IQR: 63-101) min and 66 (IQR: 60-114) min, respectively. At a median postoperative follow-up of 2.5 years (IQR: 1.4-2.6; range: 1.0-3.0 years), there were no mortalities, valve-related reoperations, or adverse events. Postoperative valve gradients and the severity of pulmonary regurgitation did not change significantly over time. CONCLUSIONS: At short-term follow-up, the bioprosthesis in this study demonstrated excellent safety and effectiveness for PVR. Further studies with longer follow-up are warranted.

Surgical Repair of a Left Main Coronary Artery to Right Ventricle Fistula in a Neonate.

We describe the case of a newborn male with a large fistula from the left main coronary artery to the right ventricle. This case illustrates a rare congenital coronary artery fistula and its successful surgical management in the neonatal period.

Pericardiectomy for Successful Treatment of Constrictive Pericarditis in a Pediatric Patient.

A 15-year-old girl with history of asthma and obesity presented with recurrent anasarca without systolic heart failure or significant renal disease. She was diagnosed with constrictive pericarditis and successfully underwent pericardiectomy with pericardial stripping and a waffle procedure. (Level of Difficulty: Advanced.).

Acid ceramidase gene therapy ameliorates pulmonary arterial hypertension with right heart dysfunction.

BACKGROUND: Up-regulation of ceramides in pulmonary hypertension (PH), contributing to perturbations in sphingolipid homeostasis and the transition of cells to a senescence state. We assessed the safety, feasibility, and efficiency of acid ceramidase gene transfer in a rodent PH model. METHODS: A model of PH was established by the combination of left pneumonectomy and injection of Sugen toxin. Magnetic resonance imaging and right heart catheterization confirmed development of PH. Animals were subjected to intratracheal administration of synthetic adeno-associated viral vector (Anc80L65) carrying the acid ceramidase (Anc80L65.AC), an empty capsid vector, or saline. Therapeutic efficacy was evaluated 8 weeks after gene delivery. RESULTS: Hemodynamic assessment 4 weeks after PH model the development demonstrated an increase in the mean pulmonary artery pressure to 30.4 ± 2.13 mmHg versus 10.4 ± 1.65 mmHg in sham (p < 0.001), which was consistent with the definition of PH. We documented a significant increase in pulmonary vascular resistance in the saline-treated (6.79 ± 0.85 mm Hg) and empty capsid (6.94 ± 0.47 mm Hg) groups, but not in animals receiving Anc80L65.AC (4.44 ± 0.71 mm Hg, p < 0.001). Morphometric analysis demonstrated an increase in medial wall thickness in control groups in comparison to those treated with acid ceramidase. After acid ceramidase gene delivery, a significant decrease of pro-inflammatory factors, interleukins, and senescence markers was observed. CONCLUSION: Gene delivery of acid ceramidase provided tropism to pulmonary tissue and ameliorated vascular remodeling with right ventricular dysfunction in pulmonary hypertension.

Surgical Methods for Cardiac Gene Delivery in Large Animals.

This chapter describes main strategies of surgical gene delivery in large animals. Existing methods of cardiac gene transfer can be classified by the site of injection, interventional approach, and type of cardiac circulation at the time of transfer. Randomized clinical trials have suggested that the therapeutic benefits of gene therapy are not as substantial as expected from animal studies. This discordance in results is largely due to gene delivery methods that may be effective in small animals but are not scalable to larger species and, therefore, cannot transduce a sufficient fraction of myocytes to establish long-term clinical efficacy. Ideally, an optimized gene transfer should incorporate the following: a closed-loop recirculation for extended transgene residence time; vector washout form the vascular system after transfer to prevent collateral expression; use of methods to increase myocardial transcapillary gradient for viral particles for a better transduction, probably retrograde route of gene delivery through the coronary venous system; and myocardial ischemic preconditioning.

microRNA Expression Levels Change in Neonatal Patients During and After Exposure to Cardiopulmonary Bypass.

Background The systemic inflammation that occurs after exposure to cardiopulmonary bypass (CPB), which is especially severe in neonatal patients, is associated with poorer outcomes and is not well understood. In order to gain deeper insight into how exposure to bypass activates inflammatory responses in circulating leukocytes, we studied changes in microRNA (miRNA) expression during and after exposure to bypass. miRNAs are small noncoding RNAs that have important roles in modulating protein levels and function of cells. Methods and Results We performed miRNA-sequencing on leukocytes isolated from neonatal patients with CPB (n=5) at 7 time points during the process of CPB, including before the initiation of bypass, during bypass, and at 3 time points during the first 24 hours after weaning from bypass. We identified significant differentially expressed miRNAs using generalized linear regression models, and miRNAs were defined as statistically significant using a false discovery rate-adjusted P<0.05. We identified gene targets of these miRNAs using the TargetScan database and identified significantly enriched biological pathways for these gene targets. We identified 54 miRNAs with differential expression during and after CPB. These miRNAs clustered into 3 groups, including miRNAs that were increased during and after CPB (3 miRNAs), miRNAs that decreased during and after CPB (10 miRNAs), and miRNAs that decreased during CPB but then increased 8 to 24 hours after CPB. A total of 38.9% of the target genes of these miRNAs were significantly differentially expressed in our previous study. miRNAs with altered expression levels are predicted to significantly modulate pathways related to inflammation and signal transduction. Conclusions The unbiased profiling of the miRNA changes that occur in the circulating leukocytes of patients with bypass provides deeper insight into the mechanisms that underpin the systemic inflammatory response that occurs in patients after exposure to CPB. These data will help the development of novel treatments and biomarkers for bypass-associated inflammation.

Staged repair of truncus arteriosus with double aortic arch, tracheoesophageal fistula, and choanal atresia via a multi-disciplinary approach: a case report.

The previously unreported case of a child with an exceedingly rare amalgamation of complex defects, including truncus arteriosus (TA), double aortic arch (DAA), tracheoesophageal fistula, and choanal atresia is presented. First, on day-of-life (DOL) 2, with a joint effort involving Pediatric Cardiac Surgery, General Surgery, and Otolaryngology, division of tracheoesophageal fistula and repair of esophageal atresia, along with choanal atresia repair, was carried out. Via a right thoracotomy, the tracheoesophageal fistula, located medial to the azygous vein, was skeletonized and ligated. The proximal esophagus was then mobilized up to the thoracic inlet as it coursed through the vascular ring. This enabled esophageal anastomosis with preservation of both aortas. Next, on DOL 11, the child underwent TA repair. Following a standard midline sternotomy and cooling to moderate hypothermia, the left aortic arch was divided and oversewn. The aorta was then transected anteriorly, and the main pulmonary artery (MPA) exiting the posterior aorta was harvested as a single button. The aortic defect from the pulmonary artery button was repaired with autologous pericardium. Next, through a right ventriculotomy, the previously seen conoventricular septal defect was identified and closed. Finally, a 10-mm pulmonary homograft was anastomosed to the pulmonary artery bifurcation to complete the repair. The patient was discharged on DOL 78 and was noted to be doing well at 1-year follow-up. This case validates the feasibility of fistula repair complicated by DAA through a right thoracotomy, the durability of staged, complete repair of TA and DAA, and the advantages of a holistic, team-based approach that optimizes timing of all repairs based upon a careful consideration of the exponential, rather than additive, effects of multi-organ disease on post-cardiac surgery outcomes in neonates.

Shear stress associated with cardiopulmonary bypass induces expression of inflammatory cytokines and necroptosis in monocytes.

Cardiopulmonary bypass (CPB) is required during most cardiac surgeries. CBP drives systemic inflammation and multiorgan dysfunction that is especially severe in neonatal patients. Limited understanding of molecular mechanisms underlying CPB-associated inflammation presents a significant barrier to improve clinical outcomes. To better understand these clinical issues, we performed mRNA sequencing on total circulating leukocytes from neonatal patients undergoing CPB. Our data identify myeloid cells, particularly monocytes, as the major cell type driving transcriptional responses to CPB. Furthermore, IL-8 and TNF-α were inflammatory cytokines robustly upregulated in leukocytes from both patients and piglets exposed to CPB. To delineate the molecular mechanism, we exposed THP-1 human monocytic cells to CPB-like conditions, including artificial surfaces, high shear stress, and cooling/rewarming. Shear stress was found to drive cytokine upregulation via calcium-dependent signaling pathways. We also observed that a subpopulation of THP-1 cells died via TNF-α-mediated necroptosis, which we hypothesize contributes to post-CPB inflammation. Our study identifies a shear stress-modulated molecular mechanism that drives systemic inflammation in pediatric CPB patients. These are also the first data to our knowledge to demonstrate that shear stress causes necroptosis. Finally, we observe that calcium and TNF-α signaling are potentially novel targets to ameliorate post-CPB inflammation.

Transcriptome profiling reveals activation of inflammation and apoptosis in the neonatal striatum after deep hypothermic circulatory arrest.

OBJECTIVES: Brain injury, leading to long-term neurodevelopmental deficits, is a major complication in neonates undergoing cardiac surgeries. Because the striatum is one of the most vulnerable brain regions, we used mRNA sequencing to unbiasedly identify transcriptional changes in the striatum after cardiopulmonary bypass and associated deep hypothermic circulatory arrest. METHODS: Piglets were subjected to cardiopulmonary bypass with deep hypothermic circulatory arrest at 18°C for 30 minutes and then recovered for 6 hours. mRNA sequencing was performed to compare changes in gene expression between the striatums of sham control and deep hypothermic circulatory arrest brains. RESULTS: We found 124 significantly upregulated genes and 74 significantly downregulated genes in the striatums of the deep hypothermic circulatory arrest group compared with the sham controls. Pathway enrichment analysis demonstrated that inflammation and apoptosis were the strongest pathways activated after surgery. Chemokines CXCL9, CXCL10, and CCL2 were the top upregulated genes with 32.4-fold, 22.2-fold, and 17.6-fold increased expression, respectively, in the deep hypothermic circulatory arrest group compared with sham controls. Concomitantly, genes involved in cell proliferation, cell-cell adhesion, and structural integrity were significantly downregulated in the deep hypothermic circulatory arrest group. Analysis of promoter regions of all upregulated genes revealed over-representation of nuclear factor-kB transcription factor binding sites. CONCLUSIONS: Our study provides a comprehensive view of global transcriptional changes in the striatum after deep hypothermic circulatory arrest and found strong activation of both inflammatory and apoptotic signaling pathways in the deep hypothermic circulatory arrest group. Nuclear factor-kB, a key driver of inflammation, appears to be an upstream regulator of the majority of the upregulated genes; hence, nuclear factor-kB inhibitors could potentially be tested for beneficial effects on neurologic outcome.

Whole Body Periodic Acceleration (pGz) as a non-invasive preconditioning strategy for pediatric cardiac surgery.

We hypothesized that pGz has cardio and neuroprotective effects due to upregulation of pathways which include eNOS, anti-apoptotic, and anti-inflammatory pathways. We analyze protein expression of these pathways in the brain of neonatal piglets, as well as report on the myocardial function after Deep Hypothermic Circulatory Arrest (DHCA) and pGz preconditioning. Animal data affirms both a cardio and neuroprotective role for pGz. These findings suggest that pGz can be a simple, non-invasive cardio and neuroprotective strategy preconditioning strategy in children requiring surgical intervention.

Granulocyte colony-stimulating factor significantly decreases density of hippocampal caspase 3-positive nuclei, thus ameliorating apoptosis-mediated damage, in a model of ischaemic neonatal brain injury.

OBJECTIVES: Ischaemic brain injury is a major complication in patients undergoing surgery for congenital heart disease, with the hippocampus being a particularly vulnerable region. We hypothesized that neuronal injury resulting from cardiopulmonary bypass and associated circulatory arrest is ameliorated by pretreatment with granulocyte colony-stimulating factor (G-CSF), a cytokine and an anti-apoptotic neurotrophic factor. METHODS: In a model of ischaemic brain injury, 4 male newborn piglets were anaesthetized and subjected to deep hypothermic circulatory arrest (DHCA) (cooled to 18°C, DHCA maintained for 60 min, rewarmed and recovered for 8-9 h), while 4 animals received G-CSF (34 µg/kg, intravenously) 2 h prior to the DHCA procedure. At the end of each experiment, the animals were perfused with a fixative, the hippocampus was extracted, cryoprotected, cut and the brain sections were immunoprocessed for activated caspase 3, a pro-apoptotic factor. Immunopositive neuronal nuclei were counted in multiple counting boxes (440 × 330 µm) centred on the CA1 or CA3 hippocampal regions and their mean numbers compared between the different treatment groups and regions. RESULTS: G-CSF pretreatment resulted in significantly lower counts of caspase 3-positive nuclei per counting box in both the CA1 [52.2 ± 9.3 (SD) vs 61.6 ± 8.4, P < 0.001] and CA3 (41.2 ± 6.9 vs 60.4 ± 16.4, P < 0.00002) regions of the hippocampus as compared to DHCA groups. The effects of G-CSF were significant for pyramidal cells of both regions and for interneurons in the CA3 region. CONCLUSIONS: In an animal model of ischaemic brain injury, G-CSF reduces neuronal injury in the hippocampus, thus potentially having beneficial effect on neurologic outcomes.

A Rare Case of Vascular Ring and Coarctation of the Aorta in Association with CHARGE Syndrome.

A male neonate presented with CHARGE syndrome, a multiorgan genetic disorder involving the Coloboma of the eyes, congenital Heart defects, nasal choanal Atresia, growth and development Retardation, Genitourinary disorders, and Ear anomalies and deafness. Moreover, he had a rare case of vascular ring-consisting of a right aortic arch with retroesophageal brachiocephalic artery-combined with coarctation of the mid-aortic arch. He underwent both vascular ring and aortic arch repair at our institution. To our knowledge, this is the 4th documented case of this exceedingly rare type of aortic arch anomaly combined with aortic arch obstruction. Moreover, it is the first confirmed case of these combined disorders occurring in CHARGE syndrome. This report describes a truly rare case and reveals the limitations of echocardiography in detecting complex aortic arch anomalies while illustrating the benefits of advanced imaging prior to surgical intervention.

Granulocyte colony stimulating factor reduces brain injury in a cardiopulmonary bypass-circulatory arrest model of ischemia in a newborn piglet.

Ischemic brain injury continues to be of major concern in patients undergoing cardiopulmonary bypass (CPB) surgery for congenital heart disease. Striatum and hippocampus are particularly vulnerable to injury during these processes. Our hypothesis is that the neuronal injury resulting from CPB and the associated circulatory arrest can be at least partly ameliorated by pre-treatment with granulocyte colony stimulating factor (G-CSF). Fourteen male newborn piglets were assigned to three groups: deep hypothermic circulatory arrest (DHCA), DHCA with G-CSF, and sham-operated. The first two groups were placed on CPB, cooled to 18 °C, subjected to 60 min of DHCA, re-warmed and recovered for 8-9 h. At the end of experiment, the brains were perfused, fixed and cut into 10 µm transverse sections. Apoptotic cells were visualized by in situ DNA fragmentation assay (TUNEL), with the density of injured cells expressed as a mean number ± SD per mm(2). The number of injured cells in the striatum and CA1 and CA3 regions of the hippocampus increased significantly following DHCA. In the striatum, the increase was from 0.46 ± 0.37 to 3.67 ± 1.57 (p = 0.002); in the CA1, from 0.11 ± 0.19 to 5.16 ± 1.57 (p = 0.001), and in the CA3, from 0.28 ± 0.25 to 2.98 ± 1.82 (p = 0.040). Injection of G-CSF prior to bypass significantly reduced the number of injured cells in the striatum and CA1 region, by 51 and 37 %, respectively. In the CA3 region, injured cell density did not differ between the G-CSF and control group. In a model of hypoxic brain insult associated with CPB, G-CSF significantly reduces neuronal injury in brain regions important for cognitive functions, suggesting it can significantly improve neurological outcomes from procedures requiring DHCA.

Bicuspid aortic valves experience increased strain as compared to tricuspid aortic valves.

OBJECTIVE: To determine whether the leaflets of bicuspid aortic valve (BAV) experience increased strain when compared to tricuspid aortic valve (TAV) leaflets. BACKGROUND: The population at highest risk of aortic valve calcification (AVC) are individuals with BAVs. Currently, efforts to medically treat AVC are hampered by a limited understanding of the biomechanical forces involved in the molecular pathogenesis of AVC. METHODS: Surgically created BAVs and control TAVs were placed into a left heart simulator. Strains were calculated by comparing the distances between points on the aortic valve (AoV) leaflet during various time points during a simulated cardiac cycle. RESULTS: The fused leaflets of BAVs experience significantly more strain during systole when compared to TAVs. Specifically, BAVs experience 24% strain (P < .0001) in the radial direction, parallel to the direction of blood flow, as compared to TAVs. There was peak difference of 4% (P < .001) in the circumferential direction. DISCUSSION: Based upon the data presented here, we are in the process of identifying how increased strain activates calcification-associated pathways in AoV cells. Future studies will examine whether these stretch responsive pathways can be blocked to inhibit calcification of BAVs.

Effect of granulocyte-colony stimulating factor on expression of selected proteins involved in regulation of apoptosis in the brain of newborn piglets after cardiopulmonary bypass and deep hypothermic circulatory arrest.

OBJECTIVE: The study objective was to investigate the effect of granulocyte-colony stimulating factor on the expression of proteins that regulate apoptosis in newborn piglet brain after cardiopulmonary bypass and deep hypothermic circulatory arrest. METHODS: The newborn piglets were assigned to 3 groups: (1) deep hypothermic circulatory arrest (30 minutes of deep hypothermic circulatory arrest, 1 hour of low-flow cardiopulmonary bypass); (2) deep hypothermic circulatory arrest with prior injection of granulocyte-colony stimulating factor (17 µg/kg 2 hours before cardiopulmonary bypass); and (3) sham-operated. After 2 hours of post-bypass recovery, the frontal cortex, striatum, and hippocampus were dissected. The expression of proteins was measured by gel electrophoresis or protein arrays. Data are presented in arbitrary units. Statistical analysis was performed using 1-way analysis of variance. RESULTS: In the frontal cortex, only Fas ligand expression was significantly lower in the granulocyte-colony stimulating factor group when compared with the deep hypothermic circulatory arrest group. In the hippocampus, granulocyte-colony stimulating factor increased Bcl-2 (54.3 ± 6.4 vs 32.3 ± 2.2, P = .001) and serine/threonine-specific protein kinase (141.4 ± 19 vs 95.9 ± 21.1, P = .047) when compared with deep hypothermic circulatory arrest group. Caspase-3, Bax, Fas, Fas ligand, death receptor 6, and Janus protein tyrosine kinase 2 levels were unchanged. The Bcl-2/Bax ratio was 0.33 for deep hypothermic circulatory arrest group and 0.93 for the granulocyte-colony stimulating factor group (P = .02). In the striatum, when compared with the deep hypothermic circulatory arrest group, the granulocyte-colony stimulating factor group had higher levels of Bcl-2 (50.3 ± 7.4 vs 31.8 ± 3.8, P = .01), serine/threonine-specific protein kinase (132.7 ± 12.3 vs 14 ± 1.34, P = 2.3 × 10(6)), and Janus protein tyrosine kinase 2 (126 ± 17.4 vs 77.9 ± 13.6, P = .011), and lower levels of caspase-3 (12.8 ± 5.0 vs 32.2 ± 11.5, P = .033), Fas (390 ± 31 vs 581 ± 74, P = .038), Fas ligand (20.5 ± 11.5 vs 57.8 ± 15.6, P = .04), and death receptor 6 (57.4 ± 4.4 vs 108.8 ± 13.4, P = .007). The Bcl-2/Bax ratio was 0.25 for deep hypothermic circulatory arrest and 0.44 for the granulocyte-colony stimulating factor groups (P = .046). CONCLUSIONS: In the piglet model of hypoxic brain injury, granulocyte-colony stimulating factor decreases proapoptotic signaling, particularly in the striatum.

The hybrid procedure for the borderline left ventricle.

UNLABELLED: IntroductionIn patients with varying degrees of left heart hypoplasia, it is often difficult to determine whether the left heart structures are adequate in size to support biventricular circulation. Historically, the decision to pursue a single ventricle or biventricular repair needed to be made early and was often irreversible. The hybrid procedure may be a better initial approach for patients with borderline left ventricles. METHODS: We describe a series of four patients with various congenital cardiac malformations, all of whom had borderline left ventricles. Based on pre-operative echocardiograms, several scoring systems and left ventricle volumes were used to predict the optimal type of repair. A left ventricular volume of 20 millilitres per square metre was used as the minimum cut-off value for adequacy of biventricular repair. RESULTS: The left ventricular volumes for the patients were 17.1, 23.7, 25.4, and 25.8 millilitres per square metre. In none of the four patients were the calculations unanimous in the recommendation to pursue either type of repair. All patients underwent the hybrid procedure and then eventual single ventricle palliation (two patients) or biventricular repair (two patients). All survived with a mean follow-up of 18 plus or minus 3.9 months. CONCLUSIONS: The hybrid procedure may be the best option in patients with a borderline left ventricle. It can serve as a bridge to a more definitive repair when patients are older, larger, and for whom the decision between single ventricle and biventricular repair can be more easily made.

Effect of deep hypothermic circulatory arrest followed by low-flow cardiopulmonary bypass on brain metabolism in newborn piglets: comparison of pH-stat and α-stat management.

OBJECTIVE: To compare the effects of pH-stat and α-stat management before deep hypothermic circulatory arrest followed by a period of low-flow (two rates) cardiopulmonary bypass on cortical oxygenation and selected regulatory proteins: Bax, Bcl-2, Caspase-3, and phospho-Akt. DESIGN: Piglets were placed on cardiopulmonary bypass, cooled with pH-stat or α-stat management to 18 °C over 30 mins, subjected to 30-min deep hypothermic circulatory arrest and 1-hr low flow at 20 mL/kg/min (LF-20) or 50 mL/kg/min (LF-50), rewarmed to 37 °C, separated from cardiopulmonary bypass, and recovered for 6 hrs. SUBJECTS: Newborn piglets, 2-5 days old, assigned randomly to experimental groups. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Cortical oxygen was measured by oxygen-dependent quenching of phosphorescence; proteins were measured by Western blots. The means from six experiments ± sem are presented as % of α-stat. Significance was determined by Student's t test. For LF-20, cortical oxygenation was similar for α-stat and pH-stat, whereas for LF-50, it was significantly better using pH-stat. For LF-20, the measured proteins were not different except for Bax in the cortex (214 ± 24%, p = .006) and hippocampus (118 ± 6%, p = .024) and Caspase 3 in striatum (126% ± 7%, p = .019). For LF-50, in pH-stat group: In cortex, Bax and Caspase-3 were lower (72 ± 8%, p = .001 and 72 ± 10%, p = .004, respectively) and pAkt was higher (138 ± 12%, p = .049). In hippocampus, Bcl-2 and Bax were not different but pAkt was higher (212 ± 37%, p = .005) and Caspase 3 was lower (84 ± 4%, p = .018). In striatum, Bax and pAkt did not differ, but Bcl-2 increased (146 ± 11%, p = .001) and Caspase-3 decreased (81 ± 11%, p = .042). CONCLUSIONS: In this deep hypothermic circulatory arrest-LF model, when flow was 20 mL/kg/min, there was little difference between α-stat and pH-stat management. However, for LF-50, pH-stat management resulted in better cortical oxygenation during recovery and Bax, Bcl-2, pAk, and Caspase-3 changes were consistent with lesser activation of proapoptotic signaling with pH-stat than with α-stat.

The effect of hypothermia on neuronal viability following cardiopulmonary bypass and circulatory arrest in newborn piglets.

OBJECTIVE: To determine the effect of recovery with mild hypothermia after cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA) on the activity of selected key proteins involved in initiation (Bax, Caspase-3) or inhibition of apoptotic injury (Bcl-2, increased ratio Bcl-2/Bax) in the brain of newborn piglets. METHODS: The piglets were placed on CPB, cooled with pH-stat management to 18 degrees C, subjected to 30 min of DHCA followed by 1h of low flow at 20 ml/kg/min, rewarmed to 37 degrees C (normothermia) or to 33 degrees C (hypothermia), separated from CPB, and monitored for 6h. Expression of above proteins was measured in striatum, hippocampus and frontal cortex by Western blots. The results are mean for six experiments+/-SEM. RESULTS: There were no significant differences in Bcl-2 level between normothermic and hypothermic groups. The Bax levels in normothermic group in cortex, hippocampus and striatum were 94+/-9, 136+/-22 and 125+/-34 and decreased in the hypothermic group to 59+/-17 (p=0.028), 70+/-6 (p=0.002) and 48+/-8 (p=0.01). In cortex, hippocampus and striatum Bcl-2/Bax ratio increased from 1.23, 0.79 and 0.88 in normothermia to 1.96, 1.28 and 2.92 in hypothermia. Expression of Caspase-3 was 245+/-39, 202+/-74 and 244+/-31 in cortex, hippocampus and striatum in the normothermic group and this decreased to 146+/-24 (p=0.018), 44+/-16 (p=7 x 10(-7)) and 81+/-16 (p=0.01) in the hypothermic group. CONCLUSION: In neonatal piglet model of cardiopulmonary bypass with circulatory arrest, mild hypothermia during post bypass recovery provides significant protection from cellular apoptosis, as indicated by lower expression of Bax and Caspase-3 and an increased Bcl-2/Bax ratio. The biggest protection was observed in striatum probably by decreasing of neurotoxicity of striatal dopamine.