Time for a cool head-neuroprotection becomes a reality

A biochemical feedback signal for hypothermia treatment for neonatal hypoxic-ischemic encephalopathy: focusing on central nervous system proteins in biofluids

Hypothermia has been widely used to treat moderate to severe neonatal hypoxic-ischemic encephalopathy (HIE), yet evaluating the effects of hypothermia relies on clinical neurology, neuroimaging, amplitude-integrated electroencephalography, and follow-up data on patient outcomes. Biomarkers of brain injury have been considered for estimating the effects of hypothermia. Proteins specific to the central nervous system (CNS) are components of nervous tissue, and once the CNS is damaged, these proteins are released into biofluids (cerebrospinal fluid, blood, urine, tears, saliva), and they can be used as markers of brain damage. Clinical reports have shown that CNS-specific marker proteins (CNSPs) were early expressed in biofluids after brain damage and formed unique biochemical profiles. As a result, these markers may serve as an indicator for screening brain injury in infants, monitoring disease progression, identifying damage region of brain, and assessing the efficacy of neuroprotective measures. In clinical work, we have found that there are few reports on using CNSPs as biological signals in hypothermia for neonatal HIE. The aim of this article is to review the classification, origin, biochemical composition, and physiological function of CNSPs with changes in their expression levels after hypothermia for neonatal HIE. Hopefully, this review will improve the awareness of CNSPs among pediatricians, and encourage future studies exploring the mechanisms behind the effects of hypothermia on these CNSPs, in order to reduce the adverse outcome of neonatal HIE.

Neuroprotective body hypothermia among newborns with hypoxic ischemic encephalopathy: three-year experience in a tertiary university hospital. A retrospective observational study

CONTEXT AND OBJECTIVE

Neonatal hypoxic-ischemic encephalopathy is associated with high morbidity and mortality. Studies have shown that therapeutic hypothermia decreases neurological sequelae and death. Our aim was therefore to report on a three-year experience of therapeutic hypothermia among asphyxiated newborns.

DESIGN AND SETTING

Retrospective study, conducted in a university hospital.

METHODS

Thirty-five patients with perinatal asphyxia undergoing body cooling between May 2009 and November 2012 were evaluated.

RESULTS

Thirty-nine infants fulfilled the hypothermia protocol criteria. Four newborns were removed from study due to refractory septic shock, non-maintenance of temperature and severe coagulopathy. The median Apgar scores at 1 and 5 minutes were 2 and 5. The main complication was infection, diagnosed in seven mothers (20%) and 14 newborns (40%). Convulsions occurred in 15 infants (43%). Thirty-one patients (88.6%) required mechanical ventilation and 14 of them (45%) were extubated within 24 hours. The duration of mechanical ventilation among the others was 7.7 days. The cooling protocol was started 1.8 hours after birth. All patients showed elevated levels of creatine phosphokinase, creatine phosphokinase- MB and lactate dehydrogenase. There was no severe arrhythmia; one newborn (2.9%) presented controlled coagulopathy. Four patients (11.4%) presented controlled hypotension. Twenty-nine patients (82.9%) underwent cerebral ultrasonography and 10 of them (34.5%) presented white matter hyper-echogenicity. Brain magnetic resonance imaging was performed on 33 infants (94.3%) and 11 of them (33.3%) presented hypoxic-ischemic changes. The hospital stay was 23 days. All newborns were discharged. Two patients (5.8%) needed gastrostomy.

CONCLUSION

Hypothermia as therapy for asphyxiated newborns was shown to be safe.

Structural remodeling of gray matter astrocytes in the neonatal pig brain after hypoxia/ischemia

Astrocytes play a vital role in the brain; their structural integrity and sustained function are essential for neuronal viability, especially after injury or insult. In this study, we have examined the response of astrocytes to hypoxia/ischemia (H/I), employing multiple methods (immunohistochemistry, iontophoretic cell injection, Golgi-Kopsch staining, and D-aspartate uptake) in a neonatal pig model of H/I. We have identified morphological changes in cortical gray matter astrocytes in response to H/I. Initial astrocytic changes were evident as early as 8 h post-insult, before histological evidence for neuronal damage. By 72 h post-insult, astrocytes exhibited significantly fewer processes that were shorter, thicker, and had abnormal terminal swellings, compared with astrocytes from control brains that exhibited a complex structure with multiple fine branching processes. Quantification and image analysis of astrocytes at 72 h post-insult revealed significant decreases in the average astrocyte size, from 686 microm(2) in controls to 401 microm(2) in H/I brains. Sholl analysis revealed a significant decrease (>60%) in the complexity of astrocyte branching between 5 and 20 microm from the cell body. D-Aspartate uptake studies revealed that the H/I insult resulted in impaired astrocyte function, with significantly reduced clearance of the glutamate analog, D-aspartate. These results suggest that astrocytes may be involved in the pathophysiological events of H/I brain damage at a far earlier time point than first thought. Developing therapies that prevent or reverse these astrocytic changes may potentially improve neuronal survival and thus might be a useful strategy to minimize brain damage after an H/I insult.

Delayed neurological signs following isolated parasagittal injury in asphyxia at term

BACKGROUND

Parasagittal cerebral injury is a type of cerebral injury in term infants, which is characterized by the predominant injury of the arterial border zones of the anterior, middle and posterior cerebral arteries, however its early clinical manifestation is mostly unclear.

AIM

To understand early clinical features of parasagittal cerebral injury.

METHODS

The clinical details of 18 newborn infants who were diagnosed as having parasagittal cerebral injury on magnetic resonance imaging (MRI). Eleven infants had localized injury within parasagittal regions ("Limited" group), 7 infants had diffuse extensive injury involving the deep gray matter and/or periventricular white matter ("Extensive" group). These infants were compared with 9 infants with perinatal asphyxia without MRI abnormalities ("Normal" group).

RESULTS

There was no significant difference in the rate of cardiotocographic abnormalities, low Apgar scores, low blood pH and base excess, and the requirement for mechanical ventilation among three groups. Compared with the Normal group, fewer infants in the Limited group developed neonatal encephalopathy within an hour after birth. Neonatal seizures were more frequent in the Limited and the Extensive groups. Hepatic and/or renal dysfunction was more often observed in the Limited group. Cerebral palsy and/or mental retardation were common in the Extensive group. Electro-cortical depression was more in the Extensive group. Progressive suppression of electro-cortical activity was common within infants in the Limited group (33%) and the Extensive group (60%).

CONCLUSION

Infants with parasagittal cerebral injury developed serious neurological abnormalities despite less serious physiological and neurological manifestation shortly after birth, suggesting the importance of careful longitudinal observation of asphyxiated infants.

Hypothermia

Experimental studies show that, following hypoxic ischaemic injury, mild induced hypothermia-a reduction of body temperature by about 3 degrees C -- preserves cerebral energy metabolism, reduces cerebral tissue injury and improves neurological function. Randomized trials in full-term and near-full-term newborns suggest that treatment with mild hypothermia is safe and improves survival without disabilities up to 18 months of age. Although the optimal time of initiation, the depth and duration, and the method of cooling are uncertain, in the absence of specific treatments many clinicians will wish to consider treating asphyxiated infants with hypothermia. Guidance now needs to be provided to promote uniform practice, to avoid inappropriate treatment and to foster continuing collaboration in future studies of neuroprotection following asphyxia. If the promising results of the current trials are confirmed by the findings from other on-going studies, with longer follow-up, the impact of such a treatment on the babies, their families and health resources in the shorter and longer terms will be considerable.

Theoretical limits on brain cooling by external head cooling devices

Numerous experimental studies have demonstrated that mild hypothermia is a rather promising therapy for acute brain injury in neonates. Because measurement of the resultant cooling of human brain in vivo is beyond current technology, an understanding of physical factors limiting the possible brain cooling would be a substantial achievement. Herein brain cooling by external head cooling devices is studied within the framework of an analytical model of temperature distribution in the brain. Theoretical limits on brain hypothermia induced by such devices are established. Analytical expressions are obtained that allow evaluation of changes in brain temperature under the influence of measurable input parameters. We show that a mild hypothermia can be successfully induced in neonates only if two necessary conditions are fulfilled: sufficiently low cerebral blood flow and sufficiently high value of the heat transfer coefficient describing the heat exchange between the head surface and a cooling device.

Delayed whole-body cooling to 33 or 35 degrees C and the development of impaired energy generation consequential to transient cerebral hypoxia-ischemia in the newborn piglet

OBJECTIVES

Fundamental questions remain about the precise temperature providing optimal neuroprotection after perinatal hypoxia-ischemia (HI). Furthermore, if hypothermia delays the onset of the neurotoxic cascade and the secondary impairment in cerebral energy generation, the "latent phase" may be prolonged, thus extending the period when additional treatments may be effective. The aims of this study were to investigate the effects of delayed systemic cooling at either 33 degrees C or 35 degrees C on the following: (1) latent-phase duration, and (2) cerebral metabolism during secondary energy failure itself, in the 48-hour period after transient HI.

METHODS

Piglets were randomly assigned to the following: (1) HI-normothermic (HI-n) rectal temperature (Trectal; n = 12), (2) HI-Trectal 35 degrees C (HI-35; n = 7), and (3) HI-Trectal 33 degrees C (HI-33; n = 10). Groups were cooled to the target Trectal between 2 and 26 hours after HI. Serial magnetic resonance spectroscopy was performed over 48 hours. The effect of cooling on secondary energy failure severity (indexed by the nucleotide triphosphate/exchangeable phosphate pool [NTP/EPP] and phosphocreatine/inorganic phosphate [PCr/Pi] ratios) was assessed.

RESULTS

Compared with HI-n, HI-35 and HI-33 had a longer NTP/EPP latent phase and during the entire study duration had higher mean NTP/EPP and PCr/Pi. The latent phase (both PCr/Pi and NTP/EPP) and the whole-brain cerebral energetics were similar for HI-35 and HI-33. During the hypothermic period, compared with HI-n, PCr/Pi was preserved in the cooled groups, but this advantage was not maintained after rewarming. Compared with HI-n, HI-35 and HI-33 had higher NTP/EPP after rewarming.

CONCLUSIONS

Whole-body hypothermia for 24 hours at either 35 or 33 degrees C, commenced 2 hours after resuscitation, prolonged the NTP/EPP latent phase and reduced the overall secondary falls in mean PCr/Pi and NTP/EPP during 48 hours after HI. Reducing the temperature from 35 to 33 degrees C neither increased mean PCr/Pi and NTP/EPP nor further lengthened the latent phase.

The origins of cerebral palsy

PURPOSE OF REVIEW

Cerebral palsy is the most common and visible motor disability of childhood. Its aetiology remains a topic of hot debate between those who see it as a reflection of medical mismanagement of an avoidable complication and those who see its origins in the development of the fetal brain affected at many points along a causal pathway to damage. This review outlines the themes of research publications over the year 2004/2005.

RECENT FINDINGS

The review looks at recent findings relating to epidemiology, infection and inflammation, prematurity, multiple pregnancy, thrombophilias, genetics, placenta, neuroimaging and rescue therapies in cerebral palsy.

SUMMARY

Papers this year have helped clarify risk groups and identify some areas (e.g. the management of thrombophilias and the potential of induced hypothermia) with the potential to be rapidly introduced into clinical practice. In this enigmatic and multifactorial condition, however, progress remains slow. New tools such as magnetic resonance imaging are providing valuable insights into the lesions that result in cerebral palsy but the pathways to injury remain unclear. The future of cerebral palsy research lies in understanding the complex interactions of multiple factors on the road to cerebral palsy or in looking for final common pathways such as inflammation which may be amenable to manipulation.

Fetal hypoxic and ischemic injuries

PURPOSE OF REVIEW

The principles of neonatal neurological protection following intrapartum hypoxia are briefly reviewed. The physiological principles behind the use of cardiotocograph patterns in defining the timing and mechanism of fetal hypoxia and injury are then demonstrated.

RECENT FINDINGS

Fetal neurological injury may result from progressive hypoxemia, acidosis, diminished cardiac output and cerebral ischemia, manifested at birth as low Apgar scores, multisystem compromise, severe acidosis and encephalopathy. More commonly, however, intrapartum injury results from often intermittent, regional ischemia secondary to umbilical cord or head compression resulting in hemorrhage or infarction. Under these circumstances, the amount of umbilical acidosis and neonatal encephalopathy varies and the potential candidate for neuroprotection may escape recognition and timely treatment. Selecting infants likely to benefit from neuroprotection requires information on the timing, duration and mechanism of hypoxia. Neonatal parameters, including low Apgar scores, acidosis, even seizures, lack sensitivity and specificity. Cardiotocograph patterns are capable of determining the duration, mechanism and severity of hypoxia and occasionally, the timing of neurological injury.

SUMMARY

Protecting the newborn from the neurological consequences of intrapartum hypoxia requires critical definition of the mechanism and timing of this exposure. cardiotocograph tracings offer the opportunity to refine the selection of candidates for neonatal rescue.