Background

1
Hypoxic-Ischemic Encephalopathy
in the Term Infant
Jeffrey M Perlman MB Professor of
Pediatrics Weill Medical College
Cornell Medical Center
New York
2
Background

• Hypoxic-ischemic brain injury that occurs during
  the perinatal period remains the most prominent
  cause of neonatal mortality and long term
  neurologic morbidity often referred to as
  cerebral palsy.
• It is noted in approximately 1 to 2 per 1000
  deliveries.
• An understanding of the pathogenesis of injury is
  critical prior to the implementation of targeted
  interventions.

3
Outline

• Pathogenesis
• Adaptative fetal mechanisms
• Identification of High risk Infants
• Treatment strategies
• Delivery room
• - room air
  versus 100 O2
• Beyond the delivery room
• -
  supportive care
• -
  neuroprotective strategies

4
Pathogenesis

• Impaired cerebral blood flow (CBF) is the
  principal pathogenetic mechanism underlying most
  of the neuropathology attributed to perinatal
  brain injury. It is most likely to occur as a
  consequence of interruption of placental blood
  flow and gas exchange a state that is referred
  to as asphyxia.

5
Definitions

• Hypoxia - refers to an abnormal reduction in
  oxygen delivery to the tissue
• Ischemia - refers to a reduction in blood flow to
  the tissue
• Asphyxia - refers to progressive hypoxia,
  hypercarbia and acidosis. However the biochemical
  definition of what constitutes asphyxia is
  imprecise - a cord pH lt 7.00 is defined as
  pathologic or severe fetal acidemia.

6
Characteristics of Hypoxic-Ischemic Brain Damage

• Hypoxic-ischemic brain injury is an evolving
  process that begins during the insult and extends
  into a recovery period - reperfusion period
• Tissue injury takes the form of
• Necrosis - characterized by tissue
  swelling, membrane
• disruption and an inflammatory cellular
  response or
• Apoptosis programmed cell death
  characterized by
• cellular and nuclear shrinkage, chromatin
  condensation
• and DNA fragmentation.
• A severe insult results in necrosis and a less
  severe and prolonged insult in apoptosis

7
Electron microscopic images of dying neurons in
neocortex from an infant rat 48 hours after
hypoxia-ischemia
Apoptotic neuron with one large apoptotic body
including condensed chromatin
Necrotic neuron with chromatin dispersed into
numerous small irregular shaped structures
and disrupted nuclear and cytoplasmic membranes
8


Pathogenesis of Hypoxic-Ischemic Cerebral Injury
Interruption of Placental Blood Flow
Acute Intermittent
Hypoxia-Ischemia
Resuscitation
In-utero Postnatal
Reperfusion Injury
9
Effects of Hypoxia-Ischemia on Carbohydrate and
Energy Metabolism-Anaerobic Glycolysis

• ? Brain Glycogen
• ? Lactate production
• ? Phosphocreatine
• ? Brain Glucose
• ? ATP
• Tissue acidosis

10
Adenosine Triphosphate (ATP)

• Critical regulator of cell function because of
  its role in energy transformation.
• One major function is to preserve ionic gradients
  across plasma and intracellular membranes, i.e.,
  Na ?, K ?, Ca ? ?
• Ionic pumping utilizes 50-60 of total cellular
  expenditure

11
Ischemia
Anaerobic Glycolysis
? PCr ? ATP ? Lactate
Na out
K out
Ca in
12
Deleterious Effects of Calcium in Hypoxia-Ischemia

• Activates phospholipases membrane injury
• Activates proteases cytoskeleton degraded
• Activates nucleases DNA breakdown
• Uncouples oxidative phosphorylation ? ATP
• ?? neurotransmitter release i.e. glutamate
• Activates NOS generates nitric oxide

13
Additional Mediators of Cell Death During and
Following Hypoxia-Ischemia (HI)

• Free radicals
• - highly reactive compounds
• - can react with
  certain cellular constituents
• e.g. membrane lipids
  generating more
• radicals and thus a
  chain reaction with
• irreversible
  biochemical injury.
• Glutamate
• - Excitatory amino acid
  acts on NMDA
• receptors to
  facilitate intracellular Ca
• entry and delayed
  cell death
• - Glutamate accumulates
  during HI in part
• because of ? reuptake
  that requires ATP

14
Potential Mechanisms of Injury Following
Hypoxia-Ischemia
HYPOXIA-ISCHEMIA
ANAEROBIC GLYCOGLYSIS
ATP
ADENOSINE
GLUTAMATE
LACTATE
NMDA RECEPTOR
HYPOXANTHINE
INTRACELLULAR Ca
XANTHINE OXIDASE
ACTIVATES NOS
ACTIVATES LIPASES
XANTHINE
FREE FATTY ACIDS
O2
NITRIC OXIDE
O2
FREE RADICALS FREE RADICALS
FREE RADICALS
15
Calcium
NOS
Nitric Oxide
Peroxynitrite
Mitochondria
Cytochrome C
Caspace
Energy Failure
DNA Fragmentation
Nuclear /Cytoplasmic Breakdown
Apoptosis
Necrosis
16
Delayed Injury - Reperfusion Injury

• Following resuscitation cerebral oxygenation and
• perfusion is restored. During this initial
  recovery
• phase, the concentration of the phosphorus
• metabolites (ATP) and intracellular pH
  returns
• to baseline.
• However the process of cerebral energy failure
• recurs from 6 to 48 hours later in a
  secondary
• phase of injury. This phase is characterized
  by
• a decrease in phosphocreatinine although the
  
• intracellular pH remains normal. Moreover
  this
• phase occurs despite stable
  cardio-respiratory
• status

From Lorek et al Pediatr Res 1994
17


Pathogenesis of Hypoxic-Ischemic Cerebral Injury
Interruption of Placental Blood Flow
Acute Intermittent
Hypoxia-Ischemia
Resuscitation
In-utero Postnatal
Reperfusion Injury
18
Mechanisms of Reperfusion Injury

• The mechanisms of secondary energy failure likely
  secondary to extended reactions from the primary
  insults e.g. calcium influx, excitatory
  neurotoxicity, free radicals and nitric oxide
  formation adversely alters mitochondrial
  function.
• Recent evidence suggests that circulatory and
  endogenous inflammatory cells/mediators also
  contribute to the ongoing injury.
• These processes result in apoptotic cell death.

19
Infection and/or the fetal inflammatory
response as a potential contributing factor to
brain injury during hypoxia-ischemia
20
IL-6, IL-8, RANTES IN CORD BLOOD CONTROL VS
CHORIO
Control
Chorio
p lt0.05
21
CHANGES IN IL-6 OVER THE FIRST 36 HRS IN
CHORIOAMNIONITIS INFANTS
22
IL-6 AND MODIFIED DUBOWITZ SCORES AT 6 HOURS
OF AGE IN CHORIO INFANTS
23
IL-6, IL-8, RANTESNo HIE vs HIE
24
CONCLUSIONS

• In infants exposed to chorioamnionitis, there was
  a spectrum of abnormalities in the neurological
  exam from normal, to transient hypotonia, to HIE
• IL-6, IL-8 and RANTES were significantly elevated
  in all infants with Chorio as compared to
  controls
• - IL6 at 6 hours were correlated with
  hypotonia
• by Modified Dubowitz Scores
• - IL6, IL8 and RANTES at 6 hrs were highest
  in
• infants that developed HIE and/or seizures

25
SPECULATION

• Chorioamnionitis Hypotonia HIE /
  Seizures
• 
  
• 
  

CYTOKINES
26
Potential Mechanisms of Injury Following
Hypoxia-Ischemia
HYPOXIA-ISCHEMIA
ANAEROBIC GLYCOGLYSIS
ATP
ADENOSINE
GLUTAMATE
LACTATE
NMDA RECEPTOR
HYPOXANTHINE
INTRACELLULAR Ca
XANTHINE OXIDASE
ACTIVATES NOS
ACTIVATES LIPASES
XANTHINE
FREE FATTY ACIDS
O2
NITRIC OXIDE
O2
FREE RADICALS FREE RADICALS
FREE RADICALS
27
HYPOXIA-ISCHEMIA
ANAEROBIC GLYCOGLYSIS
ATP
ADENOSINE
GLUTAMATE
LACTATE
IL-? TNF-?
NMDA RECEPTOR
HYPOXANTHINE
IL-? TNF-? Interferon ?
INTRACELLULAR Ca
XANTHINE OXIDASE
ACTIVATES NOS
ACTIVATES LIPASES
XANTHINE
FREE FATTY ACIDS
O2
NITRIC OXIDE
O2
FREE RADICALS FREE RADICALS
FREE RADICALS
28
Foundation Fact

• Although interference in placental blood flow and
  consequently gas exchange is fairly common,
  residual neurologic sequelae are infrequent and
  are more likely to occur when the asphyxial event
  is severe.

29
WHY?

• The fetus immediately adapts to an asphyxial
  event to preserve cerebral blood flow and oxygen
  delivery. This adaptation includes both
  circulatory and non circulatory responses.

30
CARDIOVASCULAR RESPONSES TO ASPHYXIA

• ASPHYXIA (?PaO2, ?PaCO2, ?pH)
• Redistribution of Cardiac Output
• ?Cerebral, Coronary, Adrenal ?Renal, Intestinal
• Blood Flow Blood Flow
• Ongoing Asphyxia
• ?Cardiac Output
• ?Cerebral Blood Flow

31
ADAPTIVE MECHANISMS ASSOCIATED WITH ASPHYXIA TO
MAINTAIN CEREBRAL PERFUSION

• Circulatory Responses
• Non-circulatory Responses

32
NON-CIRCULATORY RESPONSES FACTOR CONTRIBUTING TO
NEURONAL PRESERVATION

• Slower depletion of high energy compounds.
• Use of alternate energy substrate - the neonatal
  brain has the capacity to use lactate and ketone
  bodies for energy production.
• The relative resistance of the fetal and neonatal
  myocardium to hypoxia ischemia.
• Potential protective role of fetal hemoglobin.

33
Foundation Fact

• The ability to identify infants at highest risk
  for progressing to hypoxic-ischemic
  encephalopathy is critical for two reasons
• a) The therapeutic window i.e. that time whereby
  intervention strategies may be effective in
  preventing the processes of ongoing injury in the
  newborn brain is short and considered to be less
  than six hours
• b) Novel therapeutic strategies to prevent
  ongoing injury have the potential for significant
  side effects

34
Early Identification of High Risk Infants
1) Evidence of an Acute Perinatal Insult
Indicated by a combination of markers
1) Sentinel event
2) Delivery room resuscitation
3) 5 Minute Apgar score ? 5
4) Cord arterial pH ? 7.00
2) Postnatal evidence of encephalopathy
1) Clinical
2) EEG
Sensitivity (80), Specificity 98, Positive
Predictive value (50) Perlman Risser
Pediatrics 97,1996
35
Clinical Assessment of Encephalopathy
Neurologic Evaluation Level of Consciousness Neuro
muscular control Reflexes Autonomic
function Evidence of Seizures
Staging of Encephalopathy
Stage 1 - Mild Stage 2 - Moderate
Stage3 - Severe
Sarnat Arch of Neurol. 33696,1976
36
Long term outcome of term infants with Perinatal
Hypoxic-Ischemic Encephalopathy

• Death Disability
• Mild 0 0
• Moderate 6 30
• Severe 60 100

37
a-EEG Assessment of Cerebral Function

• A Cerebral Function Monitor via a single channel
  EEG (a-EEG), records activity from two biparietal
  electrodes. The signal is smoothed and the
  amplitude integrated.
• Three distinct patterns of electrical activity
  are noted i.e. normal, moderate and severe
  suppression.
• Early evidence of moderate and/or severe
  suppression identifies abnormal neurologic
  outcome with a sensitivity of 100, positive
  predictive value of 85 and negative predictive
  value of 100.

Naqeeb, et al. Pediatrics 19991031263
38
Representative aEEG tracings
Normal
Moderate Suppression
Severe Suppression
39
Abnormalities in both the Clinical and a-EEG
evaluation enhances the early detection of
infants who progress to irreversible brain injury.
Study Criteria 1) 50 infants with an acute
perinatal insult 2) Clinical examination within
6 hours- Abnormal Sarnat stage 2 or 3
encephalopathy 3) Simultaneous a-EEG assessment
Abnormal Moderate or severe suppression
4) Persistent encephalopathy gt 5 days was the
outcome of interest- this developed in 14/50
infants
Shalak et al Pediatrics in press
40
Prediction of Persistent Encephalopathy (n14)
based on either an abnormal clinical or a-EEG
evaluation, or a combination of abnormalities in
both

• Test N S SP
  PPV NPV
• Abnormal Exam 19 78 78 58
  90
• Abnormal EEG 15 89 73 91
  91
• Both Abnormal 13 78 94 85
  92
• 
  

Nnumber potentially enrolled in a study, S
sensitivity SPspecificity PPVpositive
predictive value, NPVnegative predictive value
41
Management of the Infant at Risk for Hypoxic -
Ischemic Cerebral Injury

• Delivery Room
• Beyond the Delivery Room

42
HYPOXIA-ISCHEMIA
ANAEROBIC GLYCOGLYSIS
ATP
ADENOSINE
GLUTAMATE
LACTATE
NMDA RECEPTOR
HYPOXANTHINE
INTRACELLULAR Ca
XANTHINE OXIDASE
ACTIVATES NOS
ACTIVATES LIPASES
XANTHINE
FREE FATTY ACIDS
O2
NITRIC OXIDE
O2
FREE RADICALS FREE RADICALS
FREE RADICALS
43
Room Air (RA)versus 100 O2

• There is considerable debate whether to use RA
  versus 100 during DR resuscitation. This is
  highly relevant given the importance of free
  radicals in the genesis of ongoing injury.
• Studies indicate that RA versus 100 O2 during DR
  resuscitation in term infants appears to be
  comparable with regard to short term outcome
  measures i.e. encephalopathy and /or death within
  7 days

Ramji et al Pediatr Res 199334809, Saugstad
etal Pedaitrics 1998102e1
44
Room Air (RA) versus 100 O2- new data

• )
• Infants n40 and gt36 weeks with Asphyxia -
  umbilical PaO2 lt
• 70 mmHg PaCO2 gt 60 mmHg pH lt 7.15 and
  clinical - hypotonia, apnea,
• bradycardia (lt80BPM) were randomly
  resuscitated with RA or 100 O2.
• RA vs O2 group needed
• a) ? time to first cry (1.2 ? 0.6 vs 1.7 ?
  .05 min)
• b) ? time to regular respiratory pattern (4.6
  ? 0.7 vs 7.5 ? 1.8 m)
• c) ? reduced-to-oxidized- glutathione ratio

Vento et al Resuscitation with room air instead
of 100 oxygen prevents oxidative stress in
moderately asphyxiated term neonates. Pediatrics
107642-6472001
45
Management Beyond the Delivery Room

• General Measures
• Neuroprotective Strategies

46
Management Beyond the Delivery Room-General
Measures

• Ventilation
• Fluid Status
• Oliguria
• Hypotension
• Glucose status
• Seizures
• Cerebral edema

47
Role of Glucose

• Both hyper and hypoglycemia may be seen in the
  post resuscitative phase.
• Both may exacerbate neuronal injury
• Hyperglycemia may contribute to ? levels of
  lactate and thus to continuing acidosis
• Hypoglycemia may contribute to injury
  particularly in parieto-occipito cortex
• The goal should be to maintain glucose levels in
  the normal range

48
Characteristics of Infants with a Blood Sugar lt
40mg/dl versus Infants with a Blood Sugar gt
40mg/dl
Salhab et al Pediatrics 114 361.2004
49
Salhab et al Pediatrics 114 361.2004
50
Salhab et al Pediatrics 114 361.2004
51
Salhab et al Pediatrics 114 361.2004
52
Management Beyond the Delivery Room-General
Measures

• Ventilation
• Fluid Status
• Oliguria
• Hypotension
• Glucose status
• Seizures
• Cerebral edema

53
Prophylactic Phenobarbital

• Thiopental (30mg/kg) initiated within two hours
  and infused for 24 hours did not alter the
  frequency of seizures or short term
  neurodevelopmental outcome. Systemic hypotension
  was a complication.
• Phenobarbital (40mg/kg) administered between
  1-6hours to asphyxiated infants, did not reduce
  neonatal seizures , but reduced
  neurodevelopmental sequelae i.e. 18 vs73 for
  controls at 3 years

Goldberg et al J Pediatr.1986, Hall et al J
Pediatr 1998132345
54
Management Beyond the Delivery Room

• General Measures
• Neuroprotective Strategies

55
Neuroprotective strategies - Clinical issues

1) WHO TO TREAT - INFANT AT HIGHEST RISK. 2)
WHEN TO TREAT - EARLY - THERAPEUTIC
WINDOW IS SHORT 3) HOW LONG TO TREAT -
UNCLEAR. 4) WHAT TO TREAT WITH.
56
POTENTIAL STRATEGIES FOR PREVENTING REPERFUSION
INJURY
HYPOXIA-ISCHEMIA
ANAEROBIC GLYCOGLYSIS
MILD HYPOTHERMIA
ATP
GLUTAMATE
ADENOSINE
NMDA RECEPTOR BLOCKER
MAGNESIUM SULFATE DEXTROMETHORPHAN KETAMINE
NMDA RECEPTOR
HYPOXANTHINE
Ca
XANTHINE OXIDASE INHIBITORS
NOS INHIBITORS
ALLOPURINOL
LIPASES
XANTHINE
NITRIC OXIDE SYNTHASE inhibitors
ARACHIDONIC ACID
FREE RADICAL SCAVENGERS
SUPEROXIDE DISMUTASE LAZEROIDS
FREE RADICALS
EICOSANOIDS
57
Evidence of Oxygen Free Radical Injury
1) Immature 7 day rats subjected to Hypoxic
Ischemic injury 2) The administration of
Allopurinol or Saline 30 minutes prior to
the insult resulted in treated animals
exhibiting less severe cerebral edema at
42 hours when compared to controls 3) Chronic
neuropathologic alterations were less severe
in the treated compared to control animals
Palmar et al Pediatr Res 1990
58
Van Bel et al Pediatrocs 1998101185
59
Magnesium Neuroprotection
Adult Human Studies 1) Prevention of seizures
with pre-eclampsia 2) Treatment of headache 3)
Prevention of traumatic hearing loss Animal
studies Conflicting data is noted- some studies
indicate neuroprotection, whereas others do not.
Factors such as timing of administration as well
as dosing appear to be important.
60
POTENTIAL STRATEGIES FOR PREVENTING REPERFUSION
INJURY
HYPOXIA-ISCHEMIA
ANAEROBIC GLYCOGLYSIS
MILD HYPOTHERMIA
ATP
GLUTAMATE
ADENOSINE
NMDA RECEPTOR BLOCKER
MAGNESIUM SULFATE DEXTROMETHORPHAN KETAMINE
NMDA RECEPTOR
HYPOXANTHINE
Ca
XANTHINE OXIDASE INHIBITORS
NOS INHIBITORS
ALLOPURINOL
LIPASES
XANTHINE
NITRIC OXIDE SYNTHASE inhibitors
ARACHIDONIC ACID
FREE RADICAL SCAVENGERS
SUPEROXIDE DISMUTASE LAZEROIDS
FREE RADICALS
EICOSANOIDS
61
MODEST HYPOTHERMIA AS AN INTERVENTION STRATEGY

• RECENT EVIDENCE INDICATES THAT THE MECHANISMS
• MEDIATING NEURONAL DEATH FOLLOWING ISCHEMIA
• ARE TEMPERTURE DEPENDENT.
• MILD TO MODEST DECREASES IN BRAIN TEMPERATURE
• MAY GREATLY INFLUENCE THE RESISTANCE OF THE
• BRAIN TO BRIEF PERIODS OF ISCHEMIA.

62
Potential Mechanisms of Action of Hypothermia
Reduces cerebral metabolism Preserves ATP
levels Decreases energy utilization Suppresses
Excitotoxic AA accumulation Reduces NO synthase
activity Suppresses free radical activity
Inhibits apoptosis Prolongs therapeutic window?
63
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64
Treatment of Comatose Survivors of
out-of-Hospital Cardiac Arrest with Induced
Hypothermia
Outcome Hypothermia
Normothermia
(n43) (n34) Normal
15
7 Moderate Disability 6
2 Severe Disability
0
2 Death 22
23
P.04 Unadjusted odds ratio for good outcome
2.65( CI,1.02 to 6.88)
Bernard et al NEJM 2002346557-563
65
Mild Therapeutic Hypothermia to Improve
Neurologic Outcome after Cardiac Arrest
Outcome Hypothermia
Normothermia RR (95 CI) P value
Good Outcome
75/136(55) 54/137(39) 1.40 (1.08-1.81)
0.009 Death 56/137(41)
76/138(55) 0.74 (0.58-0.95) 0.02
The risk ratio(RR) was calculated as the rate of
a favorable neurologic outcome or the rate of
death in the hypothermia group divided by the
rate in the normothermia group. One patient in
each group was lost to followup
NEJM 2002346549
66
Potential Adverse Effects of Hypothermia in
Neonates
Hypertension Cardiac arrhythmia Persistent
acidosis Increased oxygen consumption Increased
blood viscosity Reduction in platelet count
Pulmonary hemorrhage Sepsis Necrotizing
enterocolitis
67
How to Cool Babies? - Selective -
Total Body
68
Selective Cooling
Systemic Cooling
Laptook et al Pediatrics 10813012001
69
Selective Head Cooling in Term Infants with
Intrapartum Asphyxia Early Outcome Pilot study

Degree of
Cooling Outcome Measure
Control Minimal Mild
(n10)
(n6) (n6)
CT Scan Abnormal
5 3
2 normal
2 2 4
EEG Abnormal
2 3 0
normal
4 2 6
Dead
2 2 0
Neurological Deficits 3
2 0 Normal (6-12
months) 5 2
0
Mild temperature 35.5-35.9 Gunn et al
Pediatrics 1998
70
Total Body Hypothermia for Neonatal
Encephalopathy- Pilot study
Study
Population Term
infants (n16) with Birth Asphyxia
Cord arterial pH 6.74 (median)
Abnormal a-EEG (n10)
Normal a-EEG (n6) Total body cooling to
Managed as per routine
33.2C rectally for 48 hrs
Neonatal Seizures
Normal Neonatal Course Severe
encephalopathy Follow
up(12-18m) 6 3
1 Normal Outcome
Minor Died CP Abn.
Azzopardi Peds 2000106684
71
Modest Hypothermia as a Neuroprotective Strategy

• Two multicenter randomized studies evaluating
  hypothermia as a neuroprotective strategy have
  been conducted
• The first utilizing selective hypothermia has
  been completed .
• No difference between hypothermia and controls
  for all patients were observed.
• For infant with moderate encephalopathy (aEEG
  determined) more cooled versus control infants
  i.e. 52 versus 34 (p0.02) had a favorable
  outcome. In addition the cooled versus control
  infants were less likely to be severely affected
  i.e. 11 versus 28 (p0.03) respectively

Gluckman et al Pediatr Res 2004
72
Neuroprotective Strategies

• Hypothermia
• Oxygen Free Radical Inhibitors/Scavengers
• Prevention of Nitric Oxide Formation
• Excitatory Amino Acid Antagonists
• Growth Factors
• Strategies currently being evaluated in clinical
  trials.

73
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74
Future Strategies
Hypothermia expand the window of

opportunity Adjunct therapies Growth
factors
Free radical scavengers
NOS inhibitors Supportive therapy
Phenobarbital
75
Conclusions
1 Recent advances in the understanding of
ongoing injury following hypoxia-ischemia has
facilitated the implementation of
neuroprotective strategies which may reduce
long-term neurologic morbidity 2. Future
strategies should include optomizing both
supportive as well considering combination
therapy for infants at highest risk for severe
brain injury following intrapartum
hypoxia-ischemia.