Cerebral resuscitation after traumatic brain injury and cardiopulmonary arrest in infants and children in the new millennium

Cerebral Edema in Traumatic Brain Injury: a Historical Framework for Current Therapy

PURPOSE OF REVIEW

The purposes of this narrative review are to (1) summarize a contemporary view of cerebral edema pathophysiology, (2) present a synopsis of current management strategies in the context of their historical roots (many of which date back multiple centuries), and (3) discuss contributions of key molecular pathways to overlapping edema endophenotypes. This may facilitate identification of important therapeutic targets.

RECENT FINDINGS

Cerebral edema and resultant intracranial hypertension are major contributors to morbidity and mortality following traumatic brain injury. Although Starling forces are physical drivers of edema based on differences in intravascular vs extracellular hydrostatic and oncotic pressures, the molecular pathophysiology underlying cerebral edema is complex and remains incompletely understood. Current management protocols are guided by intracranial pressure measurements, an imperfect proxy for cerebral edema. These include decompressive craniectomy, external ventricular drainage, hyperosmolar therapy, hypothermia, and sedation. Results of contemporary clinical trials assessing these treatments are summarized, with an emphasis on the gap between intermediate measures of edema and meaningful clinical outcomes. This is followed by a brief statement summarizing the most recent guidelines from the Brain Trauma Foundation (4th edition). While many molecular mechanisms and networks contributing to cerebral edema after TBI are still being elucidated, we highlight some promising molecular mechanism-based targets based on recent research including SUR1-TRPM4, NKCC1, AQP4, and AVP1.

SUMMARY

This review outlines the origins of our understanding of cerebral edema, chronicles the history behind many current treatment approaches, and discusses promising molecular mechanism-based targeted treatments.

A Precision Medicine Approach to Cerebral Edema and Intracranial Hypertension after Severe Traumatic Brain Injury: Quo Vadis?

PURPOSE OF REVIEW

Standard clinical protocols for treating cerebral edema and intracranial hypertension after severe TBI have remained remarkably similar over decades. Cerebral edema and intracranial hypertension are treated interchangeably when in fact intracranial pressure (ICP) is a proxy for cerebral edema but also other processes such as extent of mass lesions, hydrocephalus, or cerebral blood volume. A complex interplay of multiple molecular mechanisms results in cerebral edema after severe TBI, and these are not measured or targeted by current clinically available tools. Addressing these underpinnings may be key to preventing or treating cerebral edema and improving outcome after severe TBI.

RECENT FINDINGS

This review begins by outlining basic principles underlying the relationship between edema and ICP including the Monro-Kellie doctrine and concepts of intracranial compliance/elastance. There is a subsequent brief discussion of current guidelines for ICP monitoring/management. We then focus most of the review on an evolving precision medicine approach towards cerebral edema and intracranial hypertension after TBI. Personalization of invasive neuromonitoring parameters including ICP waveform analysis, pulse amplitude, pressure reactivity, and longitudinal trajectories are presented. This is followed by a discussion of cerebral edema subtypes (continuum of ionic/cytotoxic/vasogenic edema and progressive secondary hemorrhage). Mechanisms of potential molecular contributors to cerebral edema after TBI are reviewed. For each target, we present findings from preclinical models, and evaluate their clinical utility as biomarkers and therapeutic targets for cerebral edema reduction. This selection represents promising candidates with evidence from different research groups, overlap/inter-relatedness with other pathways, and clinical/translational potential. We outline an evolving precision medicine and translational approach towards cerebral edema and intracranial hypertension after severe TBI.

The frequency of cerebral ischemia/hypoxia in pediatric severe traumatic brain injury

INTRODUCTION

The frequency of adverse events, such as cerebral ischemia, following traumatic brain injury (TBI) is often debated. Point-in-time monitoring modalities provide important information, but have limited temporal resolution.

PURPOSE

This study examines the frequency of an adverse event as a point prevalence at 24 and 72 h post-injury, compared with the cumulative burden measured as a frequency of the event over the full duration of monitoring.

METHODS

Reduced brain tissue oxygenation (PbtO(2) < 10 mmHg) was the adverse event chosen for examination. Data from 100 consecutive children with severe TBI who received PbtO(2) monitoring were retrospectively examined, with data from 87 children found suitable for analysis. Hourly recordings were used to identify episodes of PbtO(2) less than 10 mmHg, at 24 and 72 h post-injury, and for the full duration of monitoring.

RESULTS

Reduced PbtO(2) was more common early than late after injury. The point prevalence of reduced PbtO(2) at the selected time points was relatively low (10 % of patients at 24 h and no patients at the 72-h mark post-injury). The cumulative burden of these events over the full duration of monitoring was relatively high: 50 % of patients had episodes of PbtO(2) less than 10 mmHg and 88 % had PbtO(2) less than 20 mmHg.

CONCLUSION

Point-in-time monitoring in a dynamic condition like TBI may underestimate the overall frequency of adverse events, like reduced PbtO(2), particularly when compared with continuous monitoring, which also has limitations, but provides a dynamic assessment over a longer time period.

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.

Current and future therapies of pediatric cardiopulmonary arrest

OBJECTIVE

To review contemporary guidelines and therapies for pediatric cardiac arrest and discuss potential novel therapies.

METHODS

Key articles and guidelines in the field were reviewed along with recent publications in the fields of neurointensive care and neuroscience germane to cerebral resuscitation.

RESULTS

A total of 45 articles were reviewed. The majority of arrests in the pediatric population are asphyxial in origin--which differs importantly from the adult population. The International Consensus on CPR guidelines are discussed, including good quality CPR, chest compressions without interruptions, resuscitation with 100% oxygen and subsequent titration of oxygen to normal oxygen saturations, correct dose of epinephrine, and use of hypothermia in the first 12-24 hours. Novel therapies that showed success in animal studies, such as hypertensive reperfusion, thrombolytics, hemodilution and extracorporeal CPR are also discussed.

CONCLUSION

With only 30% return of spontaneous circulation, 12% survival to hospital discharge and 4% intact neurologic survival, pediatric cardiac arrest remains an area of intense research for therapies to improve its outcomes. In addition to the rapid implementation of basic and advanced life support interventions, new therapies that may have value include mild hypothermia, extracorporeal support, promotion of cerebral blood flow and other more novel therapies targeting oxidative stress, excitotoxicity, neuronal death, and rehabilitation.

An 18-yr prospective study of pediatric diabetic ketoacidosis: an approach to minimizing the risk of brain herniation during treatment

BACKGROUND

During the late 1900s, raised intracranial pressure (ICP) during treatment of pediatric diabetic ketoacidosis (DKA) surfaced as the most important cause of morbidity and mortality in pediatric DKA. The contribution of fluid and electrolyte therapy to neurologic deterioration during treatment remains controversial.

METHODS

We proposed a physiologic approach to treatment of DKA, incorporating the principles of rehydration of hypertonic states. Consecutive episodes of pediatric DKA were managed using continuous intravenous insulin, an individualized assessment of the degree of dehydration, and rehydration solutions of tonicity approximating that of the patient. Gradual replacement of the volume of deficit after correction of shock, if present, was planned over 48 h with special attention to changes in effective osmolality along with intensive cardiorespiratory, neurologic, and biochemical monitoring. Mannitol was given for signs or symptoms of raised ICP.

RESULTS

Six hundred and thirty-five consecutive episodes of pediatric DKA were treated from January 1988 to September 2005. Means +/- standard deviation (SD) for initial measured concentrations of total carbon dioxide, glucose, and urea nitrogen were 7.8 +/- 3.3 mmol/L, 602 +/- 271 mg/dL (33.4 +/- 15 mmol/L), and 21 +/- 1 mg/dL (7.4 +/- 3.6 mmol/L), respectively. Pretreatment blood gases were available for 477 episodes. The mean initial partial pressures of arterial and venous carbon dioxide +/- SD were 16.8 +/- 7 mmHg (kP(a)CO(2)= 2.24 +/- 0.93) for n = 308 and 26.6 +/- 7 mmHg (kP(v)CO(2)= 3.54 +/- 0.93) for n = 169, respectively. Although repair was planned to occur over 48 h, the mean time to achieve clinical rehydration and correction of DKA was 11.6 +/- 6.2 h. Mannitol was given in 35 (5.5%) episodes. There was no neurologic morbidity or mortality.

CONCLUSION

Management of pediatric DKA using this multifaceted physiologic approach and the principles of rehydration described is safe and appears to minimize the risk of brain herniation during treatment.

Alpha-II-spectrin after controlled cortical impact in the immature rat brain

Proteolytic processing plays an important role in regulating a wide range of important cellular functions, including processing of cytoskeletal proteins. Loss of cytoskeletal proteins such as spectrin is an important characteristic in a variety of acute central nervous system injuries including ischemia, spinal cord injury and traumatic brain injury (TBI). The literature contains extensive information on the proteolytic degradation of alpha-II-spectrin after TBI in the adult brain. By contrast, there is limited knowledge on the characteristics and relevance of these important processes in the immature brain. The present experiments examine TBI-induced proteolytic processing of alpha-II-spectrin after TBI in the immature rat brain. Distinct proteolytic products resulting from the degradation of the cytoskeletal protein alpha-II-spectrin by calpain and caspase 3 were readily detectable in cortical brain parenchyma and cerebrospinal fluid after TBI in immature rats.

Brain Injury from Cardiac Arrest in Children

This article reviews the important differences between children and adults suffering brain injury following cardiac arrest. The differences in etiology, pathophysiology, neuronal vulnerability, and repair in the context of the developing brain are reviewed. The available clinical data are reviewed, and selected treatment priori-ties are declared. The article includes a discussion of knowledge gaps and future directions.

Pathophysiology of traumatic injury in the developing brain: an introduction and short update

Current understanding about the main peculiarities in pathophysiology of immature brain traumatic injury involves marked developmental discrepancy of biomechanical properties, aspects of altered features in water and electrolyte homeostasis as well as maturation dependent differences in structural and functional responses of major transmitter systems. Based on the fact that traumatic brain injury (TBI) is one of the major causes of morbidity and mortality in infants and children, the currently available epidemiological data are reviewed in order to gain insights about scope and dimension of health care engagement and derive the requirements for reinforced pathogenetic research. To this end, the main aspects of peculiarities in primary and secondary TBI mechanisms in the immature/developing brain are discussed, including structural and functional conditions resulting in a markedly diminished shear resistance of the immature brain tissue. As such, the immature brain tissue appears to be more susceptible to mechanical alterations, because similar mechanical load induces a more intense brain tissue displacement. Furthermore, available indications for increased incidence of brain swelling in the immature brain after TBI are reviewed, focusing on the interrelationship between the age-dependent differences in extracellular space and aquaporin-4 expression during brain maturation. The developmental differences of TBI induced cerebrovascular response as well as some relevant aspects of altered neurotransmission following TBI of the immature brain in regard to the glutamatergic and dopaminergic transmitter system are assessed. Thus, this mini-review highlights some progress but also an increased necessity for expanded pathogenetic research on a clinical scale in order to develop a solid foundation for adequate therapeutic strategies for the different life-threatening consequences of TBI in infancy and childhood, which mainly have failed up to now.

Anesthetic management of the complications of previously undiagnosed ingested foreign body in a pediatric patient

A case of a previously undiagnosed ingested foreign body, subsequent acquired tracheoesophageal fistula and airway obstruction in a pediatric patient is described. We suggest that the capability to provide cardiopulmonary bypass was a key factor in this patient's survival.

Biomarkers of proteolytic damage following traumatic brain injury

The history of numerous failed clinical trials designed to identify therapeutic agents to assist in improving outcomes after traumatic brain injury points to the critical importance of understanding biochemical markers of injury. Such biomarkers should be readily accessible, provide information specific to the pathologic disruptions occurring in the central nervous system, and allow improved monitoring of the progression of secondary damage. Additionally, these biomarkers should may provide investigators a window on the individual patient's response to treatment, and should contribute to prediction of outcome. Most research on this topic to date has focused on neuronspecific enolase (NSE) and S-100 proteins but these have not proven to be satisfactory for a variety of reasons. A different approach is provided by the study of 2 important proteases, caspase-3 and calpain. This paper reports the current state of knowledge concerning caspase and calpain as specific markers of TBI, and discusses all-spectrin, a principal substrate for both caspase and calpain, as well as initial findings regarding neurofilament 68 protein (NF-68).

Experimental model of pediatric asphyxial cardiopulmonary arrest in rats

OBJECTIVE

Develop a clinically relevant model of pediatric asphyxial cardiopulmonary arrest in rats.

DESIGN

Prospective interventional study.

SETTING

University research laboratory.

SUBJECTS

Postnatal day 16-18 rats (n = 9/group).

INTERVENTIONS

Anesthetized rats were endotracheally intubated and mechanically ventilated, and vascular catheters were inserted. Vecuronium was administered, and the ventilator was disconnected from the rats for 8 mins, whereupon rats were resuscitated with epinephrine, sodium bicarbonate, and chest compressions until spontaneous circulation returned. Shams underwent all procedures except asphyxia.

MEASUREMENTS AND MAIN RESULTS

Asphyxial arrest typically occurred by 1 min after the ventilator was disconnected. Return of spontaneous circulation typically occurred <30 secs after resuscitation. An isoelectric electroencephalograph was observed for 30 mins after asphyxia, and rats remained comatose for 12-24 hrs. Overall survival rate was 85%. Motor function measured using beam balance and inclined plane tests was impaired on days 1 and 2, but recovered by day 3, in rats after asphyxia vs. sham injury (p <.05). Spatial memory acquisition measured using the Morris-water maze on days 7-14 and 28-35 was also impaired in rats after asphyxia vs. sham injury (total latency 379 +/- 28 vs. 501 +/- 40 secs, respectively, p <.05). DNA fragmentation was detected in CA1 hippocampal neurons bilaterally 3-7 days after asphyxia. Neurodegeneration detected using Fluorojade B was seen in bilateral CA1 hippocampi and layer V cortical neurons 3-7 days after asphyxia, with persistent neurodegeneration in CA1 hippocampus detected up to 5 wks after asphyxia. CA1 hippocampal neuron survival after asphyxia was 39-43% (p <.001 vs. sham). Evidence of DNA or cellular injury was not detected in sham rats.

CONCLUSIONS

This model of asphyxial cardiopulmonary arrest in postnatal day 17 rats produces many of the clinical manifestations of pediatric hypoxic-ischemic encephalopathy. This model may be useful for the preclinical testing of novel and currently available interventions aimed at improving neurologic outcome in infants and children after cardiopulmonary arrest.

Traumatic brain injury in infants and children: mechanisms of secondary damage and treatment in the intensive care unit

Unfortunately no specific pharmacologic therapies are available for the treatment of TBI in patients. Current investigation of contemporary therapies for the treatment of TBI consists of recycling of previously tested therapies in the era of contemporary neurointensive care. These therapies include hypothermia, decompressive craniectomy, osmotherapy, and controlled hyperventilation. It is hoped that more detailed knowledge regarding the dominant pathophysiologic mechanisms associated with TBI-excitotoxicity, CBF dysregulation, oxidative stress, and programmed cell death-will catapult an efficacious intervention from the laboratory bench to the bedside. This intervention may be a potent agent targeting a single dominant pathway, a broad-spectrum intervention such as hypothermia, or, more likely, a combination of therapies. Meanwhile, practitioners must offer meticulous supportive neurointensive care using clinically proven therapies aimed at minimizing cerebral swelling for the management of pediatric patients who are victims of TBI.

Jugular venous oxygen saturation or arteriovenous difference of lactate content and outcome in children with severe traumatic brain injury

OBJECTIVE

To assess the association between neurologic out-come and the alterations of jugular venous oxygen saturation (SjvO2) or the increase in arteriovenous difference of lactate content (AVDL) in children with severe traumatic brain injury.

DESIGN

Observational prospective cohort study.

SETTING

Multidisciplinary pediatric intensive care unit of a university hospital.

PATIENTS

A total of 27 pediatric patients with severe traumatic brain injury, with a Glasgow Coma Scale after resuscitation of <9, who were admitted to the pediatric intensive care unit within 36 hrs after injury.

INTERVENTIONS

Intermittent measurement of SjvO2 and AVDL.

MEASUREMENTS AND MAIN RESULTS

SjvO2 and AVDL were assessed simultaneously every 6 hrs. The primary dependent variable measured was assessed independently 3 months after trauma according to the Pediatric Cerebral Performance Category. Patients were classified into two groups: group 1 (favorable outcome, Pediatric Cerebral Performance Category 1-3) and group 2 (unfavorable outcome, Pediatric Cerebral Performance Category 4-6); 81% were included in group 1 and 19% in group 2. A total of 354 measurements of SjvO2 and AVDL were made, with a mean of 13.1 +/- 7.9 per patient. The number of abnormal measurements of SjvO2 and increased AVDL used to predict the neurologic outcome was selected according to the area under the receiver operating characteristic curve. Mortality was 15% (four patients). The strongest association was found between a poor neurologic outcome and two or more pathologic AVDL measurements (higher than -0.37 mmol/L; relative risk, 17.6; 95% confidence interval, 2.5-112.5; p = .001). The presence of two or more measurements of SjvO2 of < or = 55% was significantly associated with a poor neurologic outcome (relative risk, 6.6; 95% confidence interval, 1.5-29.7; p = .003). The frequency of measurements of SjvO2 of > or = 75% was not different between groups 1 and 2.

CONCLUSION

In children with severe traumatic brain injury, two or more measurements of SjvO2 of < or = 55% or two or more pathologic AVDL measurements were associated with a poor neurologic outcome. Further studies are needed to recommend the use of these variables as a guideline to optimize treatment.

Increased S-nitrosothiols and S-nitrosoalbumin in cerebrospinal fluid after severe traumatic brain injury in infants and children: indirect association with intracranial pressure

Nitric oxide (NO) is implicated in both secondary damage and recovery after traumatic brain injury (TBI). Transfer of NO groups to cysteine sulfhydryls on proteins produces S-nitrosothiols (RSNO). S-nitrosothiols may be neuroprotective after TBI by nitrosylation of N-methyl-D-aspartate receptor and caspases. S-nitrosothiols release NO on decomposition for which endogenous reductants (i.e., ascorbate) are essential, and ascorbate is depleted in cerebrospinal fluid (CSF) after pediatric TBI. This study examined the presence and decomposition of RSNO in CSF and the association between CSF RSNO level and physiologic parameters after severe TBI. Cerebrospinal fluid samples (n = 72) were obtained from 18 infants and children on days 1 to 3 after severe TBI (Glasgow Coma Scale score < 8) and 18 controls. Cerebrospinal fluid RSNO levels assessed by fluorometric assay peaked on day 3 versus control (1.42 +/- 0.11 micromol/L vs. 0.86 +/- 0.04, P< 0.05). S-nitrosoalbumin levels were also higher after TBI (n = 8, 0.99 +/- 0.09 micromol/L on day 3 vs. n = 6, 0.42 +/- 0.02 in controls, P< 0.05). S-nitrosoalbumin decomposition was decreased after TBI. Multivariate analysis showed an inverse relation between CSF RSNO and intracranial pressure and a direct relation with barbiturate treatment. Using a novel assay, the presence of RSNO and S-nitrosoalbumin in human CSF, an approximately 1.7-fold increase after TBI, and an association with low intracranial pressure are reported, supporting a possible neuroprotective role for RSNO. The increase in RSNO may result from increased NO production and/or decreased RSNO decomposition.

Submersion and asphyxial injury

Drowning and other asphyxial injuries are important causes of childhood morbidity and mortality. In this review, the epidemiology, pathophysiology, and treatments applied to near-drowning victims are discussed, with an emphasis on the difficulties encountered attempting to predict outcome using current methods.