Injury Pattern of the Neonatal Brain After Hypothermic Low-Flow Cardiopulmonary Bypass in a Piglet Model

Effect of hyperextension of the neck (rose position) on cerebral blood oxygenation in patients who underwent cleft palate reconstructive surgery: prospective cohort study using near-infrared spectroscopy

OBJECTIVES

To facilitate the best approach during cleft palate surgery, children are positioned with hyperextension of the neck. Extensive head extension may induce intraoperative cerebral ischemia if collateral flow is insufficient. To evaluate and monitor the effect of cerebral blood flow on cerebral tissue oxygenation, near-infrared spectroscopy has proved to be a valuable method. The aim of this study was to evaluate and quantify whether hyperextension affects the cerebral tissue oxygenation in children during cleft palate surgery.

MATERIALS AND METHODS

This prospective study included children (ASA 1 and 2) under the age of 3 years old who underwent cleft palate repair at the Wilhelmina Children's Hospital, in The Netherlands. Data were collected for date of birth, cleft type, date of cleft repair, and physiological parameters (MAP, saturation, heart rate, expiratory CO₂ and O₂, temperature, and cerebral blood oxygenation) during surgery. The cerebral blood oxygenation was measured with NIRS.

RESULTS

Thirty-four children were included in this study. The majority of the population was male (61.8%, n = 21). The mixed model analyses showed a significant drop at time of Rose position of - 4.25 (69-74 95% CI; p < 0.001) and - 4.39 (69-74 95% CI; p < 0.001). Postoperatively, none of the children displayed any neurological disturbance.

CONCLUSION

This study suggests that hyperextension of the head during cleft palate surgery leads to a significant decrease in cerebral oxygenation. Severe cerebral desaturation events during surgery were uncommon and do not seem to be of clinical relevance in ASA 1 and 2 children.

CLINICAL RELEVANCE

There was a significant drop in cerebral oxygenation after positioning however it is not clear whether this drop is truly significant physiologically in ASA 1 and 2 patients.

Modeling Pediatric Brain Trauma: Piglet Model of Controlled Cortical Impact

The brain has different responses to traumatic injury as a function of its developmental stage. As a model of injury to the immature brain, the piglet shares numerous similarities in regards to morphology and neurodevelopmental sequence compared to humans. This chapter describes a piglet scaled focal contusion model of traumatic brain injury that accounts for the changes in mass and morphology of the brain as it matures, facilitating the study of age-dependent differences in response to a comparable mechanical trauma.

Neonatal brain protection in cardiac surgery and the role of intraoperative neuromonitoring

Improving mortality rates in children undergoing surgery for congenital heart disease has enabled a shift in focus to improving morbidity, particularly with respect to neurological complications. Various factors have been implicated in influencing neurological outcomes. We share our experience in formulating a customized cardiopulmonary bypass (CPB) protocol based on currently available evidence. Theoretical advantages of intraoperative neuromonitoring during CPB, specifically use of near-infrared spectroscopy, will be discussed in the context of methodologies to monitor cerebral perfusion during surgery.

Cognitive P300-evoked potentials in school-age children after surgical or transcatheter intervention for ventricular septal defect

BACKGROUND

Some studies have suggested that neurological development may be adversely affected in children with severe coronary heart disease who have undergone long periods of deep hypothermic cardiopulmonary bypass (CPB). Reports of cognitive function in VSD patients in whom surgical repair required only a relatively brief period of CPB are rare. Also, CPB is unnecessary for VSD patients undergoing transcatheter closure. The aim of this study was to assess the cognitive function in patients with ventricular septal defect.

METHODS

A total of 29 patients treated with surgery, and 35 treated with transcatheter closure and their age- and sex-matched best friends completed the cognitive P300 auditory-evoked potentials test and the intelligence test.

RESULTS

The patients and their best friends had normal intelligence quotient; however, the patients had longer P300 peak latencies in cranial frontal lobe and cranial vertex leads (329.2 ± 24.8 and 335.1 ± 20.0 ms) than the healthy controls did (319.1 ± 20.6 and 313 ± 18.2 ms) (P < 0.05). Patients who underwent surgery had longer P300 peak latency in the cranial frontal lobe and cranial vertex leads than did those with transcatheter closure and controls. When cardiopulmonary bypass and aortic clamping were used, the duration was associated with P300 peak latency for patients (P < 0.05).

CONCLUSION

VSD patients, especially those undergoing surgery, showed poor cognitive function, which may be associated with duration of cardiopulmonary bypass or aortic-clamping.

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.

Differential neuronal vulnerability varies according to specific cardiopulmonary bypass insult in a porcine survival model

OBJECTIVE

We investigated whether the degree of vulnerability of different areas in the developing brain varies according to the specific mechanism of the insults caused by cardiopulmonary bypass.

METHODS

A meta-analysis of 2 experimental studies (n = 80) was conducted. The end points of the otherwise identical studies were tissue oxygen index in the first experiment, whereas cerebral microvessel vasoconstriction and inflammatory response of endothelial cells were directly visualized in the second study. We assigned ultra-low flow bypass at 25 °C for 60 minutes as control; circulatory arrest at 25 °C for 60 minutes as ischemic stress under circulatory arrest (ischemia-CA); and ultra-low flow bypass at 34 °C for 60 minutes as the stress under ultra-low flow bypass (ischemia-ULF). Histologic neuronal damage was the primary outcome. Secondary measures included neurologic recovery.

RESULTS

Vasoconstriction after ischemia and inflammation after bypass were independent predictors of severe histologic damage. The caudate nucleus was significantly vulnerable to ischemia-CA and was significantly influenced by vasoconstriction. In contrast, the hippocampus was significantly vulnerable to ischemia-ULF. The different forms of ischemic insults did not influence Purkinje cells, whereas Purkinje damage significantly correlated with inflammation. Tissue oxygen index had the ability to differentiate accurately regional damage. Neurologic recovery under ischemia-CA was significantly worse compared with ischemia-ULF. Neurologic recovery correlated with neuronal damage in the caudate nucleus, but it did not correlate with damage in the hippocampus.

CONCLUSIONS

Neuronal vulnerability in different areas of the developing brain varies according to mechanisms of bypass-induced ischemic stress. Certain regional damage may not be apparent in assessing acute neurologic recovery.

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.

Neurologic monitoring on cardiopulmonary bypass: what are we obligated to do?

Improving survival from congenital cardiac repairs using cardiopulmonary bypass has appropriately shifted focus to neurologic outcomes. Hypoxic-ischemic mechanisms are the major cause of neurologic injury in neonatal cardiac surgery, and modifications of techniques of cardiopulmonary bypass can affect organ oxygen delivery and the propensity to injury both during and after surgery. Through successive refinements in the techniques of cardiopulmonary bypass, the risk factors for hypoxic-ischemic injury have been reduced, but not eliminated. The application of specific monitoring to enhance detection of hypoxic conditions associated with neurologic injury would both allow intervention on individual patients and drive refinements in strategies to further reduce risk. Specific neurologic monitoring techniques that can be used during cardiopulmonary bypass include near-infrared spectroscopy, transcranial Doppler ultrasonography, and electroencephalographic techniques. Of these, only near-infrared spectroscopy provides a continuous quantitative signal of the physiologic variable most related to injury and most amenable to intervention. This review will advocate wide adoption of near-infrared spectroscopy monitoring throughout the perioperative period, to enhance detection of hypoxic conditions and to drive patient-specific interventions.

Attentional Dysfunction in Children After Corrective Cardiac Surgery in Infancy

BACKGROUND

Attentional dysfunction in children after corrective cardiac surgery in infancy has rarely been evaluated and is the topic of the present work.

METHODS

Forty unselected children, 20 with tetralogy of Fallot and hypoxemia and 20 with ventricular septal defect and cardiac insufficiency, operated on at a mean age 0.7 (SD 0.3) years with deep hypothermic circulatory arrest and low flow cardiopulmonary bypass, were evaluated at mean age 7.4 (SD 1.6) years by the computerized form of the Attention Network Test providing performance measures of three networks of attention: alerting, orienting, and executive control. Parental ratings of attentional dysfunction were derived from the Child Behavior Checklist. Results were compared with healthy controls, between patient groups, and correlated with perioperative risk factors and current neurodevelopmental status.

RESULTS

Executive control was reduced in the tetralogy of Fallot group, alerting and orienting were found normal and not different between patient groups. Durations of aortic cross clamping inversely correlated with orienting; durations of cardiopulmonary bypass correlated with mean reaction time and inversely correlated with executive control. Motor function and acquired abilities correlated with executive control and orienting. Parent-reported problems on the Child Behavior Checklist inversely correlated with executive control and mean accuracy.

CONCLUSIONS

Children with preoperative hypoxemia in infancy due to cyanotic cardiac defects are at increased risk for attentional dysfunction in the field of executive control, compared with normal children and with those who have acyanotic heart defects. Besides unfavorable perioperative influences, preoperative hypoxemia is considered responsible for additional damage to the highly oxygen sensitive regions of the prefrontal cortex and striate body assumed to be associated with the executive control network of attention.

Large animal models of traumatic injury to the immature brain

Large animal models have been used much less frequently than rodent models to study traumatic brain injury. However, large animal models offer distinct advantages in replicating specific mechanisms, morphology and maturational stages relevant to age-dependent injury responses. This paper reviews how each of these features is relevant in matching a model to a particular scientific question and discusses various scaling strategies, advantages and disadvantages of large animal models for studying traumatic brain injury in infants and children. Progress to date and future directions are outlined.