Antegrade cerebral perfusion reduces apoptotic neuronal injury in a neonatal piglet model of cardiopulmonary bypass

Avoiding use of total circulatory arrest in the practice of congenital heart surgery

Deep hypothermic circulatory arrest (DHCA) technique has been an important armamentarium in the correction of congenital heart diseases. There have been many controversies and concerns associated with DHCA, particularly neurological damage. Selective ante grade cerebral perfusion (SACP) was introduced as an adjunct to DHCA with the objective of limiting the neurologic injury during aortic arch repairs. Over the past two decades, various aspects of cardiopulmonary bypass and DHCA have been studied and modified such as optimisation of flows, anti-inflammatory interventions, haematocrit, and temperature to improve neurologic outcomes. With the changes in practice of DHCA, outcomes have significantly improved but SACP intuitively appears attractive to offer better neuroprotection. The strategy of conduct of SACP is evolving and needs to be standardised for comparing outcomes. In this review we have discussed the various physiological and technical factors involved in conduct of SACP in paediatric cardiac surgery and outcomes with SACP.

Reduced brain mammillary body volumes and memory deficits in adolescents who have undergone the Fontan procedure

BACKGROUND

Adolescents with single ventricle heart disease (SVHD) who have undergone the Fontan procedure show cognitive/memory deficits. Mammillary bodies are key brain sites that regulate memory; however, their integrity in SVHD is unclear. We evaluated mammillary body (MB) volumes and their associations with cognitive/memory scores in SVHD and controls.

METHODS

Brain MRI data were collected from 63 adolescents (25 SVHD; 38 controls) using a 3.0-Tesla MRI scanner. Cognition and memory were assessed using Montreal Cognitive Assessment (MoCA) and Wide Range Assessment of Memory and Learning 2. MB volumes were calculated and compared between groups (ANCOVA, covariates: age, sex, and total brain volume [TBV]). Partial correlations and linear regression were performed to examine associations between volumes and cognitive scores (covariates: age, sex, and TBV).

RESULTS

SVHD group showed significantly lower MoCA and WRAML2 scores over controls. MB volumes were significantly reduced in SVHD over controls. After controlling for age, sex, and TBV, MB volumes correlated with MoCA and delayed memory recall scores in SVHD and controls.

CONCLUSION

Adolescents with SVHD show reduced MB volumes associated with cognitive/memory deficits. Potential mechanisms of volume losses may include developmental and/or hypoxic/ischemic-induced processes. Providers should screen for cognitive deficits and explore possible interventions to improve memory.

Neurodevelopmental outcomes of children with congenital heart disease: A review

Congenital heart defects are the most common birth anomaly affecting approximately 1% of births. With improved survival in this population, there is enhanced ability to assess long-term morbidities including neurodevelopment. There is a wide range of congenital heart defects, from those with minimal physiologic consequence that do not require medical or surgical intervention, to complex structural anomalies requiring highly specialized medical management and intricate surgical repair or palliation. The impact of congenital heart disease on neurodevelopment is multifactorial. Susceptibility for adverse neurodevelopment increases with advancing severity of the defect with initial risk factors originating during gestation. Complex structural heart anomalies may pre-dispose the fetus to abnormal circulatory patterns in utero that ultimately impact delivery of oxygen rich blood to the fetal brain. Thus, the brain of a neonate born with complex congenital heart disease may be particularly vulnerable from the outset. That vulnerability is compounded during the newborn period and through childhood, as this population endures a myriad of medical and surgical interventions. For each individual patient, these factors are likely cumulative and synergistic with progression from fetal life through childhood. This review discusses the spectrum of risk factors that may impact neurodevelopment in children with congenital heart disease, describes current recommendations and practices for neurodevelopmental follow-up of children with congenital heart disease and reviews important neurodevelopmental trends in this high risk population.

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.

Effects of phentolamine infusion during selective cerebral perfusion in neonatal piglets

BACKGROUND

An optimal selective cerebral perfusion protocol in pediatric cardiac surgery is unknown. Phentolamine is frequently used in pediatric cardiopulmonary bypass. We sought to determine the effects of continuous phentolamine infusion during selective cerebral perfusion.

METHODS

Twenty-seven neonatal piglets (3.38 ± 0.32 kg) were randomly assigned to 3 groups; sham (n = 7, anesthesia alone, no surgery or bypass), control (n = 10, saline infusion), or experimental (n = 10, phentolamine infusion 0.1 mg/kg per hour). Animals underwent 90 minutes of selective cerebral perfusion. Cerebral vascular resistance index (CVRI) and metabolic rate of oxygen (CMRO2) were determined every 15 minutes. Standardized sections of hippocampus, basal ganglia, and neo-cortex were obtained. Tissue samples were stained for caspase-3 and analyzed for positive apoptotic cell count. Data were analyzed with repeated measures and one-way analysis of variance.

RESULTS

The CVRI tended to increase over time in the control group and decrease over time in the experimental group, but difference was not statically significant (0.46 ± 0.24 vs 0.39 ± 0.10 mm Hg × min × kg(2/3)/mL, p = 0.15). Mean CMRO2 was higher in the control group compared with the experimental group (0.90 ± 0.27 vs 0.59 ± 0.12 mLO2/min × kg(2/3), p = 0.005) and decreased over time in both groups. The percentage of caspase-3 positive cells was significantly different among regions (hippocampus = 16.9 ± 8.8; basal ganglia = 14.6 ± 7.5; neocortex = 10.8 ± 6.3; p < 0.0001) but not significantly different among sham (11.8% ± 2.68%), control (14.4% ± 2.24%), and experimental (15.5% ± 2.24%) groups.

CONCLUSIONS

A continuous infusion of phentolamine during selective cerebral perfusion significantly decreases CMRO2 and tends to decrease CVRI when compared with control. At the dose studied and at the time of tissue sampling, phentolamine does not appear to decrease apoptosis during or early after selective cerebral perfusion.

Usefulness of Deep Hypothermic Circulatory Arrest and Regional Cerebral Perfusion in Children

To compare the safety and usefulness of deep hypothermic circulatory arrest (DHCA) and regional cerebral perfusion (RCP) during pediatric open heart surgery. Between January 1, 2004 and September 30, 2012, 1250 children with congenital cardiac defect underwent corrective operation with the DHCA or RCP technique in the Shanghai Children's Medical Center. Of them, 947 cases underwent the operation with the aid of DHCA (DHCA group), and 303 cases with RCP (RCP group). The mean DHCA time was 30.64±15.81 (7-63) minutes and mean RCP time was 36.18±12.86 (10-82) minutes. The mortality rate was 7.18% (68/947) and 6.60% (20/30) in two groups, respectively. The postoperative incidences of temporary and permanent neurological dysfunction were 6.23% (59/947) in the DHCA group and 2.64% (8/303) in the RCP group (p<0.01). The incidence of other complications such as low cardiac output, renal dysfunction, and lung issues are similar in both groups. RCP is a reliable technique for cerebral protection and it facilitates time-consuming corrected procedures for complex congenital cardiac defect repair procedures.

Early changes in cerebral oxidative stress and apoptotic neuronal injury after various flows for selective cerebral perfusion in piglets

BACKGROUND

The impact of various flows for selective cerebral perfusion (SCP) on cerebral oxidative stress in the immature brain is unknown. We examined early changes in cerebral markers of oxidative damage, apoptotic protein activation and histological outcome after different flows for SCP in a piglet model of deep hypothermic circulatory arrest (DHCA).

METHODS

Twenty piglets, randomly divided into four groups (each n = 5), were placed on cardiopulmonary bypass (CPB) at 20°C, then underwent DHCA for 60 minutes. SCP was conducted at flow rates of 0, 25, 50 and 80 ml·kg(-1)·min(-1) through the innominate artery in the DHCA, SCP 25, SCP 50, and SCP 80 groups, respectively. The animals were killed at 2 hours off CPB. Brain tissues were examined for the activity of SOD, MDA and caspase-3, and histological damage was quantitatively assayed by light microscopic examinations.

RESULTS

There were no significant differences in the activities of SOD, MDA and the SOD/MDA index between the groups. Caspase-3 activity significantly decreased in the SCP 25, SCP 50 and SCP 80 groups compared with the DHCA group. However, the caspase-3 level was higher in the SCP 80 group than in the SCP 25 and SCP 50 group. There were no significant correlations between MDA, SOD, SOD/MDA index and caspase-3.

CONCLUSIONS

In this acute model, under different flows for SCP, cerebral MDA and SOD activities show no change, whereas activated caspase-3 has a marked change. There was no relationship between oxidative stress, indicated by MDA and SOD, and apoptotic protein activation in the early phase after DHCA.

New approaches to neuroprotection in infant heart surgery

Advances in surgical techniques and perioperative management have led to dramatic improvements in outcomes for children with complex congenital heart disease (CHD). As the number of survivors continues to grow, clinicians are becoming increasingly aware that adverse neurodevelopmental outcomes after surgical repair of CHD represent a significant cause of morbidity, with widespread neuropsychologic deficits in as many as 50% of these children by the time they reach school age. Modifications of intraoperative management have yet to measurably impact long-term neurologic outcomes. However, exciting advances in our understanding of the underlying mechanisms of cellular injury and of the events that mediate endogenous cellular protection have provided a variety of new potential targets for the assessment, prevention, and treatment of neurologic injury in patients with CHD. In this review, we will discuss the unique challenges to developing neuroprotective strategies in children with CHD and consider how multisystem approaches to neuroprotection, such as ischemic preconditioning, will be the focus of ongoing efforts to develop new diagnostic tools and therapies. Although significant challenges remain, tremendous opportunity exists for the development of diagnostic and therapeutic interventions that can serve to limit neurologic injury and ultimately improve outcomes for infants and children with CHD.

Lower perfusion pressure during hypothermic cardiopulmonary bypass is associated with decreased cerebral blood flow and impaired memory performance 6 months postoperatively

OBJECTIVES

We undertook to determine the influence of perfusion pressure during hypothermic cardiopulmonary bypass (CPB) on cerebral blood flow (CBF) and cognitive memory outcome at 6 months postoperatively.

METHODS

Nineteen patients who underwent hypothermic nonpulsatile CPB for elective coronary artery bypass (CAB) surgery were evaluated by (133)Xe measurement of the CBF and by the Incidental Memory Assessment for evaluating cognitive memory (IMTscore), both at baseline before the operation (T(1)) and again at 5 to 6 months postoperatively (T(2)).

RESULTS

Overall, the mean CBF fell significantly from 39 +/- 5 mL.(100 g)(-1).min(-1) at T(1) to 33 +/- 3 mL.(100 g)(-1).min(-1) at T(2) (P < .001). The decrease in CBF from T(1) to T(2) (DeltaCBF(2-1)) correlated with a significant reduction in the IMTscore from T1 to T2 (DeltaIMTscore(2-1)) (P < .001) and with a mean arterial pressure during CPB (MAPCPB) of <60 mm Hg (P = .05). Cluster analysis of DeltaCBF(2-1) and DeltaIMTscore(2-1) demonstrated that the patients with the greatest decrease in CBF showed the greatest decrease in IMTscore, whereas cluster analysis of DeltaCBF(2-1) and MAPCPB indicated that patients with a perfusion pressure maintained at a mean of <60 mm Hg during CPB were prone to a greater decrease in later postoperative CBF.

CONCLUSION

This study demonstrated that a MAPCPB of <60 mm Hg during CPB was associated with a significant decrease in CBF 6 months after CAB surgery and with an associated decrease in memory performance.

Factors associated with adverse neurodevelopmental outcomes in infants with congenital heart disease

OBJECTIVE

To review reported neurodevelopmental outcome data for patients with congenital heart disease, identify risk factors for adverse neurodevelopmental sequelae and summarize potential neuromonitoring strategies that have been described.

METHODS

A Medline search was performed utilizing combinations of the keywords congenital heart, cardiac, neurologic, neurodevelopment, neuromonitoring, quality of life, and outcome. All prospective and longitudinal follow-up studies of patients with congenital heart disease were included. Additionally, studies that examined neuroimaging, neuromonitoring, and clinical factors in relation to outcome were examined. Case reports and editorials were excluded. Additional references were retrieved from selected articles if the abstract described an evaluation of neurodevelopmental outcomes and/or predictors of outcome in patients with congenital heart disease.

RESULTS

Overall, patients with CHD have increased rates of neurodevelopmental impairments, although intelligence appears to be in the normal range. Preoperative risk stratification, intraoperative techniques, postoperative care, and neuromonitoring strategies may all contribute to ultimate long-term neurodevelopmental outcomes in patients with CHD postsurgical repair.

CONCLUSIONS

As advances in the medical and surgical management improves survival in patients with CHD, increasing knowledge about neurodevelopmental outcomes and the factors that affect them will provide for strategies to optimize long-term outcome in this high-risk population.

Principles of antegrade cerebral perfusion during arch reconstruction in newborns/infants

Antegrade cerebral perfusion (ACP) is a cardiopulmonary bypass technique that uses special cannulation procedures to perfuse only the brain during neonatal and infant aortic arch reconstruction. It is used in lieu of deep hypothermic circulatory arrest (DHCA), and thus has the theoretical advantage of protecting the brain from hypoxic ischemic injury. Despite this, recent comparative studies have shown no difference in neurodevelopmental outcomes with ACP versus DHCA for neonatal arch repair. This article presents animal and human data demonstrating that ACP flows less than 30 mL/kg/min are inadequate for many patients, and may be the explanation for lack of outcome difference versus DHCA. A technique for ACP, its physiologic basis, and a neuromonitoring strategy are presented, and then the results of an outcome study are reviewed, showing that with ACP technique at higher flows of 50 to 80 mL/kg/min guided by neuromonitoring, periventricular leukomalacia is eliminated on postoperative brain magnetic resonance imaging after neonatal cardiac surgery.

Prolonged deep hypothermic circulatory arrest in rats can be achieved without cognitive deficits

Cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA) enable surgical repair of cardiovascular defects. However, neurological complications can result after both CPB and DHCA. We sought to investigate if 75 min of CPB or DHCA caused motor, cognitive or histological deficits in rats. Three groups were studied: DHCA, CPB, and sham. Rats in the DHCA group were subjected to 75 min DHCA at 15 degrees C, with a total CPB duration of 75 min. Rats in the CPB group were subjected to 75 min of normothermic CPB. Shams received the same anesthesia, cannulations and infusions. Motor function was assessed using beam testing on days 3-13. Cognitive performance was evaluated using Morris water maze tasks on days 7-13. Overall Performance Category (OPC) and Neurologic Deficit Score (NDS) were assessed daily. Histological Damage Score (HDS) was assessed in survivors on day 14. Sustained deficits on beam testing were seen only in the CPB group. Rats in the CPB and DHCA groups exhibited similar cognitive performance vs. sham. There were no differences in OPC or NDS between groups. Neuronal degeneration was present only in small foci in rats after DHCA (n=4/7). However, HDS was not different in individual brain regions or viscera between DHCA or CPB vs. sham. Surprisingly, CPB, but not DHCA was associated with motor deficits vs. sham, and no cognitive deficits were seen in either group vs. sham. Future studies with longer DHCA duration will be necessary to provide targets to assess novel preservation strategies.