Preoperative high dose methylprednisolone attenuates the cerebral response to deep hypothermic circulatory arrest

FGF2 Functions in H2S's Attenuating Effect on Brain Injury Induced by Deep Hypothermic Circulatory Arrest in Rats

Deep hypothermic circulatory arrest (DHCA) can protect the brain during cardiac and aortic surgery by cooling the body, but meanwhile, temporary or permanent brain injury may arise. H2S protects neurons and the central nervous system, especially from secondary neuronal injury. We aim to unveil part of the mechanism of H2S's attenuating effect on brain injury induced by DHCA by exploring crucial target genes, and further promote the clinical application of H2S in DHCA. Nine SD rats were utilized to provide histological and microarray samples, and further the differential expression analysis. Then we conducted GO and KEGG pathway enrichment analyses on candidate genes. The protein-protein interaction (PPI) networks were performed by STRING and GeneMANIA. Crucial target genes' expression was validated by qRT-PCR and western blot. Histological study proved DHCA's damaging effect and H2S's repairing effect on brain. Next, we got 477 candidate genes by analyzing differentially expressed genes. The candidate genes were enriched in 303 GO terms and 28 KEGG pathways. Then nine genes were selected as crucial target genes. The function prediction by GeneMANIA suggested their close relation to immunity. FGF2 was identified as the crucial gene. FGF2 plays a vital role in the pathway when H2S attenuates brain injury after DHCA. Our research provides more information for understanding the mechanism of H2S attenuating brain injury after DHCA. We infer the process might probably be closely associated with immunity.

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

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

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.

Neuroprotection against stroke and encephalopathy after cardiac surgery

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

Steroids in paediatric heart surgery: eminence or evidence-based practice?

Steroids in paediatric heart surgery are given prophylactically to blunt the systemic inflammatory response induced by the extracorporeal circuit and to improve clinical outcomes. However, there is an ongoing controversy about the impact of steroids on clinical outcomes after paediatric heart surgery. The hypothalamic-pituitary-adrenal axis is the primary neuroendocrine system activated during the stress of surgery. Relative adrenal insufficiency can accompany paediatric heart surgery; therefore, perioperative steroid supplementation is still administered by some centres. The studies that investigate the hypothalamic-pituitary-adrenal axis physiology during surgery have many limitations, and it is unclear how to define what is adrenal insufficiency. In this review, we focus on discussing the available evidence for steroid use in paediatric cardiac surgery.

Neuroprotective Strategies in Repair and Replacement of the Aortic Arch

Aortic arch surgery is a technical challenge, and cerebral protection during distal anastomosis is a continued topic of controversy and discussion. The physiologic effects of hypothermic arrest and adjunctive cerebral perfusion have yet to be fully defined, and the optimal strategies are still undetermined. This review highlights the historical context, physiological rationale, and clinical efficacy of various neuroprotective strategies during arch operations.

Corticosteroids in Pediatric Heart Surgery: Myth or Reality

Background: Corticosteroids have been administered prophylactically for more than 60 years in pediatric heart surgery, however, their use remains a matter of debate. There are three main indications for corticosteroid use in pediatric heart surgery with the use of cardiopulmonary bypass (CPB): (1) to blunt the systemic inflammatory response (SIRS) induced by the extracorporeal circuit; (2) to provide perioperative supplementation for presumed relative adrenal insufficiency; (3) for the presumed neuroprotective effect during deep hypothermic circulatory arrest operations. This review discusses the current evidence behind the use of corticosteroids in these three overlapping areas. Materials and Methods: We conducted a structured research of the literature using PubMed and MEDLINE databases to November 2017 and additional articles were identified by cross-referencing. Results: The evidence suggests that there is no correlation between the effect of corticosteroids on inflammation and their effect on clinical outcome. Due to the limitations of the available evidence, it remains unclear if corticosteroids have an impact on early post-operative outcomes or if there are any long-term effects. There is a limited understanding of the hypothalamic-pituitary-adrenal axis function during cardiac surgery in children. The neuroprotective effect of corticosteroids during deep hypothermic circulatory arrest surgery is controversial. Conclusions: The utility of steroid administration for pediatric heart surgery with the use of CPB remains a matter of debate. The effect on early and late outcomes requires clarification with a large multicenter randomized trial. More research into the understanding of the adrenal response to surgery in children and the effect of corticosteroids on brain injury is warranted.

Comparison of hollow-fiber membrane oxygenators in terms of pressure drop of the membranes during normothermic and hypothermic cardiopulmonary bypass in neonates

The objective of this study was to investigate the effects of two hollow-fiber membrane oxygenators, the Capiox SX10 and the Lilliput 901, on pressure drop of the membranes during normothermic and hypothermic cardiopulmonary bypass (CPB) in neonates.

Methods: Twenty-six congenital heart surgery patients (n=13 in each group) with a mean weight of 3 kg were included in this study. Pressure drops of the membranes, pre- and post-oxygenator extracorporeal circuit pressures (ECC) were recorded during normothermic CPB, hypothermic CPB (208C) and after rewarming. There were no differences between the groups in mean arterial pressure, pump flow rate, temperature, duration of CPB, cross- clamp time or the severity of the surgical repairs.

Results: Pressure drop of the Capiox SX10 oxygenator was significantly lower during normothermic (329/10 versus 559/16 mmHg, p B/0.001), hypothermic (389/15 versus 729/18 mmHg, p B/0.001) and post-rewarming (429/13 versus 729/21 mmHg, p B/0.001) periods compared to the Lilliput oxygenator. In the Capiox group, the pre-oxygenator ECC pressure was also significantly lower during normothermic CPB (1429/27 versus 1849/43 mmHg, p B/0.01), hypothermic CPB (1629/30 versus 1999/38 mmHg, p B/0.01) and after rewarming periods (1729/32 versus 2129/42 mmHg, p B/0.01). Post-oxygenator pressures in the Capiox group were also lower than in the Lilliput group, but results were not statistically significant.

Conclusions: These results suggest that the Capiox SX10 hollow-fiber membrane oxygenator produced significantly lower membrane pressure drops and pre- and post-oxygenator ECC during normothermic and hypothermic CPB. Thus, blood trauma with the Capiox during extracorporeal circulation may be significantly lower compared to the Lilliput. Further studies, including the level of complements, platelets, neutrophils and cytokines, with these oxygenators are warranted.

Acute Pain and Analgesic Requirements After Pulmonary Endarterectomy With Deep Hypothermic Circulatory Arrest

OBJECTIVES

To assess postoperative pain intensity and the analgesic requirements in the postoperative period in patients undergoing sternotomy for pulmonary endarterectomy involving deep hypothermic circulatory arrest.

DESIGN

Retrospective cohort study.

SETTING

Single-center hospital study.

PARTICIPANTS

Patients 18 years and older undergoing sternotomy for cardiac surgery between August 2012 and August 2014.

INTERVENTIONS

No modification to usual clinical practice.

MEASUREMENTS AND MAIN RESULTS

Intraoperative opioid and steroid administration, referral to the chronic pain unit, intensive care unit pain scores, and analgesic administration in the first 48 hours after the admission to the intensive care unit were recorded. Postoperative pain was evaluated by means of a categoric verbal scale from no pain (0) to severe pain (3); this is the routine analgesic scale used in the authors' intensive care unit. A total of 200 consecutive patients undergoing pulmonary endarterectomy (PEA group) were included in the study. No patient in the PEA group received morphine during surgery. The mean (standard deviation) postoperative pain intensity score at 24 hours was 0.30 (0.54) in the PEA group. Postoperative morphine was administered in 39% of patients. No PEA patient was referred to the chronic pain unit after hospital discharge.

CONCLUSION

The total analgesic requirements and pain score of patients undergoing sternotomy for pulmonary endarterectomy with deep hypothermic circulatory arrest seemed to be low.

Pulmonary Endarterectomy

Chronic thromboembolic pulmonary hypertension (CTEPH) results from recurrent or incomplete resolution of pulmonary embolism. CTEPH is much more common than generally appreciated. Although pulmonary embolism (PE) affects a large number of Americans, chronic pulmonary thromboembolic hypertension remains underdiagnosed. It is imperative that all patients with pulmonary hypertension (PH) be screened for the presence of CTEPH since this form of PH is potentially curable with pulmonary endarterectomy (PEA) surgery. The success of this procedure depends greatly on the collaboration of a multidisciplinary team approach that includes pulmonary medicine, cardiothoracic surgery, and cardiac anesthesiology. This review, based on the experience of more than 3000 pulmonary endarterectomy surgeries, is divided into 2 parts. Part I focuses on the clinical history and pathophysiology, diagnostic workup, and intraoperative echocardiography. Part II focuses on the surgical approach, anesthetic management, postoperative care, and complications.

Neurocognitive monitoring and care during pediatric cardiopulmonary bypass-current and future directions

Neurologic injury in patients with congenital heart disease remains an important source of morbidity and mortality. Advances in surgical repair and perioperative management have resulted in longer life expectancies for these patients. Current practice and research must focus on identifying treatable risk factors for neurocognitive dysfunction, advancing methods for perioperative neuromonitoring, and refining treatment and care of the congenital heart patient with potential neurologic injury. Techniques for neuromonitoring and future directions will be discussed.

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.

Glucocorticoids improve calcium cycling in cardiac myocytes after cardiopulmonary bypass

BACKGROUND

Glucocorticoids can reduce myocardial dysfunction associated with ischemia and reperfusion injury following cardiopulmonary bypass (CPB) and circulatory arrest. The hypothesis was that maintenance of cardiac function after CPB with methylprednisolone therapy results, in part, from preservation of myocyte calcium cycling.

METHODS

Piglets (5-7 kg) underwent CPB and 120 min of hypothermic circulatory arrest with (CPB-GC) or without (CPB) methylprednisolone (30 mgkg(-1)) administered 6h before and at CPB. Controls (No-CPB) did not undergo CPB or receive glucocorticoids (n=6 per treatment). Myocardial function was monitored in vivo for 120 min after CPB. Calcium cycling was analyzed using rapid line-scan confocal microscopy in isolated, fluo-3-AM-loaded cardiac myocytes. Phospholamban phosphorylation and sarco(endo)plasmic reticulum calcium-ATPase (SERCA2a) protein levels were determined by immunoblotting of myocardium collected 120 min after CPB. Calpain activation in myocardium was measured by fluorometric assay.

RESULTS

Preload recruitable stroke work in vivo 120 min after reperfusion decreased from baseline in CPB (47.4±12 versus 26.4±8.3 slope of the regression line, P<0.05), but was not different in CPB-GC (41±8.1 versus 37.6±2.2, P=0.7). In myocytes isolated from piglets, total calcium transient time remained unaltered in CPB-GC (368±52.5 ms) compared with controls (434.5±35.3 ms; P=0.07), but was prolonged in CPB myocytes (632±83.4 ms; P<0.01). Calcium transient amplitude was blunted in myocytes from CPB (757±168 nM) compared with controls (1127±126 nM, P<0.05) but was maintained in CPB-GC (1021±155 nM, P>0.05). Activation of calpain after CPB was reduced with glucocorticoids. Phospholamban phosphorylation and SERCA2a protein levels in myocardium were decreased in CPB compared with No-CPB and CPB-GC (P<0.05).

CONCLUSIONS

The glucocorticoid-mediated improvement in myocardial function after CPB might be due, in part, to prevention of calpain activation and maintenance of cardiac myocyte calcium cycling.

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.

Perioperative neuroprotective strategies

Long-term neurodevelopmental impairment is common in newborns and infants undergoing corrective or palliative congenital heart surgery. The etiologies of neurodevelopmental morbidity in these children are multifactorial and include prenatal, preoperative, intraoperative, and postoperative factors. Perioperative neurologic monitoring is thought to be integral to prevention or rescue from adverse neurologic events. Recent advances in perfusion techniques for congenital heart surgery now ensure adequate cerebral O(2) delivery during all phases of cardiopulmonary bypass. Periventricular leukomalacia and other serious neurologic injury can be minimized by an optimized perfusion strategy of continuous high-flow, high hematocrit cardiopulmonary bypass, minimal use of deep hypothermic circulatory arrest, antegrade cerebral perfusion during aortic arch reconstruction, pH-stat blood gas strategy, and cerebral monitoring with NIRS and trans-cranial Doppler. Because there is evidence that brain injury can also occur in the prenatal, preoperative, and postoperative periods, improved strategies to prevent injury in these arenas are much needed. Extensive further clinical investigation is warranted to identify neuroprotective management strategies for the operating room and intensive care unit to preserve neurologic function and optimize long-term neurodevelopmental outcomes in children with congenital heart disease.

Factors influencing neurologic outcome after neonatal cardiopulmonary bypass: what we can and cannot control

Advances in cardiopulmonary bypass and surgical techniques have led to progress in the early repair of congenital heart defects in children. However, as increasing numbers survive their initial cardiac operation, an awareness is emerging that significant early and late neurologic morbidities continue to complicate otherwise successful operative repairs. Adverse neurologic outcomes after neonatal cardiac surgery are multifactorial and relate to both fixed and modifiable mechanisms. The purpose of this review is to (1) review mechanisms of brain injury after neonatal cardiopulmonary bypass, (2) examine risk factors, and (3) speculate on how investigations may improve our understanding of neurologic injury.

Anesthetic management for the pediatric patient undergoing deep hypothermic circulatory arrest

Early definitive repair of complex congenital heart defects is now advocated. For the completion of many of these repairs, the use of deep hypothermic circulatory arrest (DHCA) is an absolute necessity. Unfortunately, there is undeniable neurologic morbidity, as well as other complications associated with DHCA. Anesthesiologists can aid in minimizing these unfortunate complications with the appropriate anesthetic management. Areas of current controversy in managing pediatric patients undergoing DHCA, which will be covered in this article, include cardiopulmonary bypass strategies (low-flow cardiopulmonary bypass versus DHCA), arterial blood gas management, hemodilution effects, glucose management, and the use of steroids, barbiturates, and antifibrinolytics. Every institution varies in their techniques, and there is always some new insight to be gained from discussion of these differences. At this time, anesthesiologists and surgeons alike are striving to gain further understanding of what truly occurs with the use of DHCA and in turn apply this clinically to provide better care for all pediatric patients undergoing this unique management.

The Use of a Miniaturized Circuit and Bloodless Prime To Avoid Cerebral No-Reflow After Neonatal Cardiopulmonary Bypass

BACKGROUND

Our miniaturized bloodless prime circuit for neonatal cardiopulmonary bypass (CPB) has previously been shown to elicit significantly reduced systemic inflammation. We studied the effects of this circuit on cerebral reperfusion because the pathophysiology of "no-reflow" is believed to have an inflammatory component.

METHODS

Twenty neonatal piglets were randomized to CPB with miniaturized circuitry using either blood (group 1) or bloodless (group 2) prime. At 18 degrees C, piglets underwent 60 minutes of either (A) deep hypothermic circulatory arrest (DHCA) or (B) continuous low-flow bypass (DHCLF). Analysis of cerebral blood flow (CBF) was undertaken before and after CPB in addition to quantification of circulating tumor necrosis factor-alpha (TNFalpha) and intracerebral TNFalpha messenger RNA (mRNA).

RESULTS

The final hematocrit in group 2 was 22% versus 28% (p < 0.05). The CBF fell in every animal in group 1A, but increased in every animal in group 2A (p < 0.001), despite no overall change in total cardiac output. The use of DHCLF was not associated with pronounced trends in either prime group. Final serum TNFalpha concentrations were significantly higher in group 1B (3166 +/- 843 pg/mL) than group 2B (439 +/- 192 pg/mL; p < 0.05). Irrespective of the CPB strategy used, the use of a blood prime generated significantly higher levels of intracerebral TNFalpha mRNA.

CONCLUSIONS

We attribute the hyperemic cerebrovascular response to reduced inflammation through avoiding allogeneic whole blood. The analysis of circulating and intracerebral TNFalpha in this study suggests that DHCLF in conjunction with a bloodless prime might offer advantages through avoiding ischemia, no-reflow, and in addition, resulting in a significantly reduced cerebral inflammatory response.

Use of hemoglobin vesicles during cardiopulmonary bypass priming prevents neurocognitive decline in rats

BACKGROUND

Homologous blood use is considered to be the gold standard for cardiopulmonary bypass (CPB) priming in infants despite exposure of the patient to potential cellular and humoral antigens. However, the use of hemoglobin vesicles (HbVs), artificial oxygen carriers that encapsulate a concentrated hemoglobin solution within phospholipid bilayer membranes, for CPB priming may prevent neurocognitive decline in infants. The goal of this study was to determine whether HbV use offsets hemodilution caused by patient/priming volume-mismatched CPB and thereby prevents the development of postoperative neurocognitive deficits.

METHODS AND RESULTS

CPB was established in 28 male Sprague-Dawley rats (age, 14 to 16 weeks; weight, 450 grams) after cannulation of the tail artery and right atrium. The animals were randomly assigned to 1 of 3 groups: sham surgery (n=9), HbV (-) prime (n=10), or HbV (+) prime (n=9). CPB was conducted for 90 minutes at 200 mL/kg per minute. The hematocrit during CPB was 10.0+/-1.2% in the HbV (+) prime group and 9.9+/-1.3% in the HbV (-) prime group (P=not significant). Learning and memory function were evaluated using 2 different maze tests (Maze-1 and Maze-2, in which the arrival times to the target were measured on the first, third, fifth, and seventh postoperative days). Learning and memory function were significantly better in the HbV (+) prime group than in the HbV (-) prime group (Maze-1, P=0.012; Maze-2, P=0.042); there was no difference between the HbV (+) prime and the sham surgery group.

CONCLUSIONS

The use of HbV for CPB priming may serve as a substitute for homologous blood to prevent the unacceptable hemodilution and contribute to maintenance of intact neurocognitive function.

Large-Dose Pretreatment with Methylprednisolone Fails to Attenuate Neuronal Injury After Deep Hypothermic Circulatory Arrest in a Neonatal Piglet Model

Conflicting results have been reported with regard to the neuroprotective effects of steroid treatment with cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA). We evaluated the mode and severity of neuronal cell injury in neonatal piglets after prolonged DHCA and the possible neuroprotective effect of systemic pretreatment (>6 h before surgery) with large-dose methylprednisolone (MP). Nineteen neonatal piglets (age, <10 days; weight, 2.1 +/- 0.5 kg) were randomly assigned to 2 groups: 7 animals were pretreated with large-dose systemic MP (30 mg/kg) 24 h before surgery, and 12 animals without pharmacological pretreatment (saline) served as control groups. All animals were connected to full-flow CPB with cooling to 15 degrees C and 120 min of DHCA. After rewarming to 38.5 degrees C with CPB, animals were weaned from CPB and survived 6 h before they were killed, and the brain was prepared for light and electron microscopy, immunohistochemistry, and TUNEL-staining. Quantitative histological studies were performed in hippocampus, cortex, cerebellum, and caudate nucleus. Systemic pretreatment with large-dose MP lead to persistent hyperglycemia but no significant changes of cerebral perfusion. Necrotic and apoptotic neuronal cell death were detected in all analyzed brain regions after 120 min of DHCA. In comparison to the control group, large-dose pretreatment with systemic MP lead to an increase of necrotic neuronal cell death and induced significant neuronal apoptosis in the dentate gyrus of the hippocampus (P = 0.001). In conclusion, systemic pretreatment with large-dose MP fails to attenuate neuronal cell injury after prolonged DHCA and induces regional neuronal apoptosis in the dentate gyrus.

Neonatal Brain Protection and Deep Hypothermic Circulatory Arrest: Pathophysiology of Ischemic Neuronal Injury and Protective Strategies

Deep hypothermic circulatory arrest (DHCA) has been used for the past 50 years in the surgical repair of complex congenital cardiac malformations and operations involving the aortic arch; it enables the surgeon to achieve precise anatomical reconstructions by creating a bloodless operative field. Nevertheless, DHCA has been associated with immediate and late neurodevelopmental morbidities. This review provides an overview of the pathophysiology of neonatal hypoxic brain injury after DHCA, focusing on cellular mechanisms of necrosis, apoptosis, and glutamate excitotoxicity. Techniques and strategies in neonatal brain protection include hypothermia, acid base blood gas management during cooling, and pharmacologic interventions such as the use of volatile anesthetics. Surgical techniques consist of intermittent cerebral perfusion during periods of circulatory arrest and continuous regional brain perfusion.

Congenital Heart Surgery 2005: The brain: It’s the heart of the matter

Operative mortality after repair of even the most complex congenital heart lesions has become rare. As such, the gaze of the surgical team has been diverted beyond that of early survival to focus on decreasing early and late morbidity. Important and concerning information is accumulating delineating the vulnerability of the neonatal brain to injury as the result of congenital heart disease and/or the techniques employed to correct the lesions. For many years the prevention of neurologic injury associated with congenital heart surgery has concentrated on "unraveling" the mysteries of the deleterious effects of intentional brain ischemia (in the form of deep hypothermic circulatory arrest) and developing methods to interrupt the pathway of irreversible injury. In the late 1990s, alternative perfusion techniques were developed to minimize or theoretically avoid the use of deep hypothermic circulatory arrest where it was once thought to be mandatory. Simultaneously, the rather routine use of noninvasive, real-time, neurologic monitoring has provided surgical teams the opportunity to intervene and prevent brain injury , thus eliminating the historic reliance on postoperative surrogate markers to define the presence of brain injury. It is yet undetermined whether these strategies will translate into improved short- and long-term neurologic outcome. Common to all surgical disciplines is a trend that as mortality decreases for a particular disease process, focus is adjusted, and refinements in treatment protocols are designed to minimize morbidity of the disease and its treatment. This natural refining process of a discipline's maturation is increasingly present in the field of congenital heart surgery.

Reducing risk in infant cardiopulmonary bypass: the use of a miniaturized circuit and a crystalloid prime improves cardiopulmonary function and increases cerebral blood flow

Advances in perfusion strategies have played an important role in improving outcomes following repair of complex congenital heart defects. The influence of cooling strategy, temperature, duration of circulatory arrest, and specific method of cerebral perfusion on neurologic morbidity have been extensively characterized. Similarly, the ability of pharmacologic agents to modulate the post-cardiopulmonary bypass (CPB) inflammatory response has been previously elucidated in both the laboratory and clinical arena. However, modification of the circuit and priming components have received comparably less attention. We recently showed that employment of a miniaturized circuit and a bloodless prime reduce inflammation and have salutary effects on cardiopulmonary function following hypothermic low-flow perfusion (HLF), and that this circuit may also improve cerebral protection following both deep hypothermic circulatory arrest and HLF. The current report, therefore, reviews current strategies utilized to minimize post-CPB inflammation and highlights the empirical evidence from our laboratory demonstrating the beneficial role of a miniaturized extracorporeal circuit in this context.

Blockade of the extracellular signal-regulated kinase pathway by U0126 attenuates neuronal damage following circulatory arrest

OBJECTIVES

The extracellular signal-regulated kinase pathway of the mitogen-activated protein kinase signal transduction cascade has been implicated in the neuronal and endothelial dysfunction witnessed following cerebral ischemia-reperfusion injury. Extracellular signal-regulated kinase is activated by mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2. We evaluated the ability of a mitogen-activated protein kinase/extracellular signal-regulated kinase 1/2-specific inhibitor (U0126) to block extracellular signal-regulated kinase activation and mitigate ischemic neuronal damage in a model of deep hypothermic circulatory arrest.

METHODS

Piglets underwent normal flow cardiopulmonary bypass (control, n = 4), deep hypothermic circulatory arrest (n = 6), and deep hypothermic circulatory arrest with U0126 (n = 5) at 20 degrees C for 60 minutes. The deep hypothermic circulatory arrest with U0126 group was given 200 microg/kg of U0126 45 minutes prior to initiation of bypass followed by 100 microg/kg at reperfusion. Following 24 hours of post-cardiopulmonary bypass recovery, brains were harvested. Eleven distinct cortical regions were evaluated for neuronal damage using hematoxylin and eosin staining. A section of ischemic cortex was further evaluated by immunohistochemistry with rabbit polyclonal antibody against phosphorylated extracellular signal-regulated kinase 1/2.

RESULTS

The deep hypothermic circulatory arrest and deep hypothermic circulatory arrest with U0126 groups displayed diffuse ischemic changes. However, the deep hypothermic circulatory arrest with U0126 group possessed significantly lower neuronal damage scores in the right frontal watershed zone of cerebral cortex, basal ganglia, and thalamus (P < or =.05) and an overall trend toward neuroprotection versus the deep hypothermic circulatory arrest group. This neuroprotection was accompanied by nearly complete blockade of phosphorylated extracellular signal-regulated kinase in the cerebral vascular endothelium.

CONCLUSIONS

In this experimental model of deep hypothermic circulatory arrest, U0126 blocked extracellular signal-regulated kinase activation and provided a significant neuroprotective effect. These results support targeting of the extracellular signal-regulated kinase pathway for inhibition as a novel therapeutic approach to mitigate neuronal damage following deep hypothermic circulatory arrest.

Changes in cerebral and somatic oxygenation during stage 1 palliation of hypoplastic left heart syndrome using continuous regional cerebral perfusion

OBJECTIVES

Stage 1 palliation of hypoplastic left heart syndrome requires the interruption of whole-body perfusion. Delayed reflow in the cerebral circulation secondary to prolonged elevation in vascular resistance occurs in neonates after deep hypothermic circulatory arrest. We examined relative changes in cerebral and somatic oxygenation with near-infrared spectroscopy while using a modified perfusion strategy that allowed continuous cerebral perfusion.

METHODS

Nine neonates undergoing stage 1 palliation for hypoplastic left heart syndrome had regional tissue oxygenation continuously measured by frontal cerebral and thoraco-lumbar (T10-L2) somatic (renal) reflectance oximetry probes (rSO(2), INVOS; Somanetics, Troy, Mich). Surgery was accomplished using cardiopulmonary bypass with whole-body cooling (18 degrees C-20 degrees C) and regional cerebral perfusion through the innominate artery at flow rates guided by estimated minimum flow requirements and measured rSO(2) during reconstruction of the aortic arch. Data were logged at 1-minute intervals and analyzed using repeated measures analysis of variance.

RESULTS

A total of 3176 minutes of data were analyzed. Prebypass cerebral rSO(2) was 65.4 +/- 8.9, and somatic rSO(2) was 58.9 +/- 12.4 (P <.001, cerebral vs somatic). During regional cerebral perfusion, cerebral rSO(2) was 80.7 +/- 8.6, and somatic rSO(2) was 41.4 +/- 7.1 (P <.001). Postbypass cerebral rSO(2) was 53.2 +/- 14.9, and somatic rSO(2) was 76.4 +/- 7.7 (P <.001). The risk of cerebral desaturation was significantly increased after cardiopulmonary bypass.

CONCLUSIONS

Cerebral oxygenation was maintained during regional cerebral perfusion at prebypass levels with deep hypothermia. However, after rewarming and separation from cardiopulmonary bypass, cerebral oxygenation was lower compared with prebypass or somatic values. These results indicate that cerebrovascular resistance is increased after deep hypothermic cardiopulmonary bypass, even with continuous perfusion techniques, placing the cerebral circulation at risk postoperatively.

Practice patterns in neonatal cardiopulmonary bypass

This article reviews practice patterns of numerous congenital heart surgeons, as collected from surveys (the Congenital Heart Surgeon's Society) and from audience response at the American Association of Thoracic Surgery (May 2003) and the Society of Thoracic Surgeons (January 2004). The information shows that there are numerous practice patterns, with unanimity only in the use of cardioplegia, although the delivery, type, and timing of doses varies. Hypothermic circulatory arrest continues to be used by the majority of congenital heart surgeons, although strategies for delivery have evolved in a way that reflects research contributions over the past decade.

Inferior Vena Cava Thrombus Removal Using Hypothermic Circulatory Arrest in Two Patients with Osteosarcoma

In this case report, the technique of deep hypothermia and circulatory arrest (DHCA) is used to successfully extract extensive symptomatic tumor thrombus from the inferior vena cava (IVC) in two patients with osteosarcoma. This is the first description of the use of this modality for treatment of osteosarcoma involving the IVC. Osteosarcoma and the use of DHCA are discussed.

Brain injury in children with congenital heart disease

The incidence of neurodevelopmental impairment in children with congenital heart disease is high. Its aetiology is multiple and complex. Prevention and treatment must start during the preoperative period and continue through the intra- and postoperative periods. Research has resulted in a clearer understanding of the relationship between congenital heart disease and the brain, and of the effects of cardiopulmonary bypass, hypothermia and circulatory arrest. This has led to modifications in management which may improve neurological outcome in the future.

Current strategies for optimizing the use of cardiopulmonary bypass in neonates and infants

The use of cardiopulmonary bypass is still necessary for the repair of many congenital cardiac defects. However, exposure to cardiopulmonary bypass can still lead to major morbidity and sometimes mortality, especially in neonates and infants, despite a perfect surgical repair. Various research-based strategies have been used to minimize some of the complications related to cardiopulmonary bypass, including the systemic inflammatory response, hemodilution, and transfusion requirement. This overview provides some of the strategies that we use in our practice in applying cardiopulmonary bypass in the repair of congenital cardiac defects in neonates and infants.

Systemic steroid pretreatment improves cerebral protection after circulatory arrest

BACKGROUND

This study evaluates whether systemic steroid pretreatment enhances neuroprotection during deep hypothermic circulatory arrest (DHCA) compared with steroid in cardiopulmonary bypass (CPB) prime.

METHODS

Four-week-old piglets randomly placed into two groups (n = 5 per group) were given methylprednisolone (30 mg/kg) into the pump prime (group PP), or pretreated intravenously 4 hours before CPB (group PT). All animals underwent 100 minutes of DHCA (15 degrees C), were weaned off CPB, and were sacrificed 6 hours later. Postoperative changes in body weight, bioimpedance, and colloid oncotic pressure (COP) were measured. Cerebral trypan blue content, immunohistochemical evaluation of transforming growth factor-beta1 (TGF-beta1) expression, and caspase-3 activity were performed.

RESULTS

Percentage weight gain (group PP 25.0% +/- 10.4% versus group PT 12.5% +/- 4.0%; p = 0.036), and percentage decrease in bioimpedance (PP 37.2% +/- 14.5% versus PT 15.6% +/- 7.9%; p = 0.019) were significantly lower, whereas postoperative COP was significantly higher in group PT versus group PP (PT 15.3 +/- 1.8 mm Hg versus PP 11.6 +/- 0.8 mm Hg; p = 0.003). Cerebral trypan blue (ng/g dry tissue) was significantly lower in group PT (PT 5.6 x 10(-3) +/- 1.1 x 10(-3) versus PP 9.1 x 10(-3) +/- 5.7 x 10(-4); p = 0.001). Increased TGF-beta1 expression and decreased caspase-3 activity were shown in group PT.

CONCLUSIONS

Systemic steroid pretreatment significantly reduced total body edema and cerebral vascular leak and was associated with better immunohistochemical indices of neuroprotection after DHCA.