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Sudden Infant Death Syndrome (PowerPoint)

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					SUDDEN INFANT
DEATH SYNDROME
Michael Klufas, MS III
INTRODUCTION
   Sudden Infant Death Syndrome (SIDS) continues
    to be the most common cause of postneonatal
    infant death
       25% of all deaths between 1 month and 1 year of age
 SIDS is a complex, multifactorial disorder of
  which the cause is not fully understood
 Some environmental risk factors are modifiable
       Reducing exposure to modifiable risk factors has
        lowered the incidence of SIDS
   New research indicates genetic risk factors
       Actual risk of SIDS may depend on interaction of
        environmental and genetic risk factors
DEFINTION
   Sudden death of an infant under 1 year old
    that is unexpected by history and unexplained
    after a thorough postmortem examination

   Investigation includes:
     Complete autopsy
     Investigation of the scene of death
     Review of medical history
EPIDEMIOLOGY

   SIDS rate in United States
     1990 – 1.3 per 1000 live births
     2002 – 0.6 per 1000 live births
     ~ 3000 SIDS deaths/yr




   Changes in classification of sudden unexpected
    deaths in infants from SIDS to categories of
    asphyxia and “unknown” has occurred in recent
    years
       May be falsely reducing SIDS rates while overall
        death rate from unexpected infant deaths remains
        the same
DEMOGRAPHICS
   less frequently in 1st month of life
   Peaks 2-4 month of age
   90% in first 6 months of life
   Boys 30-50% more likely to be affected than girls
   Racial and ethnic disparities
      2-3x risk for African American, Native American or
       Alaska Native (irrespective of socioeconomic status)‫‏‬
      African Americans twice as likely to place infants
       prone to for sleep & twice as likely to bedshare
      High rates of smoke exposure and bedsharing among
       Native Americans and Alaskan Natives
      Asian, South Pacific, Hispanic infants lowest
       incidence
   Winter seasonal predominance has declined or
    disappeared
PATHOPHYSIOLOGY
   Multifactorial in origin

   Triple Risk Hypothesis
      Vulnerable infant
      Critical developmental period in
       homeostatic control
      Exogenous stressors


   Final pathway believed to involve
    immature cardiorespiratory and
    autonomic control along with
    failure of arousal responsiveness
    from sleep
AUTONOMIC CONTROL
AND AROUSAL
   SIDS infants higher baseline heart rates, lower heart rate
    variability, prolonged QT indexes, lower parasympathetic tone
    and/or high sympathovagal balance
   Abnormalities of arousal
      Kato and colleagues report infants who died of SIDS had fewer
       spontaneous arousals from sleep and immature sleep patterns
   Prone sleeping
      Increases total time infants spend asleep particularly time
       spent in quiet sleep, a state of reduced arousability
      Also decreased spontaneous arousability, induced arousability
       and fewer full cortical arousals
      Associated with altered autonomic control manifest by raised
       heart rates, decreased heart rate variability and increased
       sympathetic tone
   Infants exposed to smoking in utero have decreased spontaneous
    and stimulus-induced arousal from sleep
AUTOPSY FINDINGS
   No pathognomonic findings
   Common findings:
      Petechial hemorrhages of thymus gland, visceral pleura in 68-
       95%
      Pulmonary congestion (89%) and edema (63%) indicative of
       terminal left ventricular failure
      Oronasal secretions that are typically frothy, mucoid and pink
       or bloody
      2/3 structural evidence of pre-existing, chronic low-grade
       asphyxia
         Study identified increased VEGF in CSF of SIDS infants, 308

          versus 85 pg/dL in controls
         Hypoxia frequently precedes death in SIDS

      One study of 20 SIDS infants found 50% had levels of IL-6 in CSF
       equivalent to those found in infants who died of infectious
       diseases
         Staphylococcus aureus may have role in infection as 56% of
          healthy infants and 86% of SIDS infants had these bacteria in
          the respiratory tract
    NEUROANATOMICAL FINDINGS

   Structural and neurotransmitter alterations in
    brainstem consistent with autonomic dysregulation
      Increase in dendritic spines (marker of delayed
       neuronal maturation) and delayed maturation of
       synapes in medullary respiratory centers
      Decreased tyrosine hydroxylase immunoreactivity in
       catecholaminergic neurons
      Increased number and density of 5-HT neurons with
       decreased serotonin 1A and 2A receptor
         Serotonin affects various autonomic functions

         including cardiorespiratory and circadian rhythms
NEUROANATOMICAL FINDINGS
   60% SIDS cases hypoplasia of arcuate nucleus
     Vital area of autonomic control and integration
     Receptor abnormalities relevant to autonomic control
           Decreases in binding to kainate, muscarinic cholinergic and
            5-HT receptors
   Lavezzi showed alterations of the cerebellum
       62% of SIDS compared to 10% controls showed
        neuronal immaturity, altered apoptotic programs,
        negative expression somatostatin and EN2 gene,
        intense c-fos expression and astrogliosis in cortex and
        dentate nucleus
   Water reported increased neuronal apoptosis in
    hippocampus and brainstem
       Neuronal loss in regions sensitive to hypoxia and
        regions associated with sensation in the face
RISK FACTORS
                              PREGNANCY
    SOCIAL                    RELATED
    FACTORS                   FACTORS
   Increased risk with:         Mothers of SIDS infants:
     Lower socioeconomic            Less prenatal care
      status                         Care initiated later in
     Younger maternal age            pregnancy
     Lower maternal                 Low birth weight
      education                      Preterm birth
     Single marital status          IUGR
                                     Shorter intervals between
                                      pregnancies (< 18 mo)
                                     More often 2nd or higher
                                      order birth child
SUBSTANCE USE

   Major association between intrauterine exposure to
    cigarette smoking and risk of SIDS
      Risk of death is progressively greater with increased
       smoking
      May be small independent effect of paternal smoking
      An independent effect of postnatal exposure to
       tobacco smoke has been found in a small number of
       studies as well as dose-response effect with number
       of household smokers
   Evidence linking prenatal illegal drug is conflicting
      Opiates increase risk of SIDS 2-15 fold
      Alcohol not clearly linked, but siblings of infants with
       FAS 20 fold increased risk of SIDS compared to
       controls
INFANT SLEEP PRACTICES &
ENVIRONMENT
   Prone sleeping consistently shown to increase risk of SIDS
      Highest risk when usually placed in another sleeping
        position but were placed on stomach for last sleep,
        “unaccustomed prone”, more likely to occur outside the
        home such as day care centers
      Also risk of choking highest in prone position
   Placing infant on side still places risk twice as likely to die
    of SIDS compared to sleeping supine
      Exceptions may be made with certain medical conditions
   Soft sleeping surfaces 2 to 3 fold increase risk of SIDS
      Prone sleeping + soft bedding  20 fold increase
   Overheating with increased room temperature, high body
    temperature, sweating or excessive clothing increase incidence
      No increase with high external environment temperature
   No protective effect from bed sharing
      Advocates of this practice typically promoters of breast
        feeding
      1/3 reduction with sleeping in parent’s bedroom in separate
        crib
    INFANT FEEDING PRACTICES &
    EXPOSURES
   Association between breast-feeding and SIDS inconclusive
       Recent study showed breast-feeding associated with decreased risk
        of postneonatal deaths overall but not decreased risk of SIDS

   Decreased risk with pacifier use
      Not known whether direct effect or
       associated infant or parental behaviors
      Pacifier use and dislodgement may
       enhance arousability
      No association between pacifier use and
       breast-feeding duration
      Small increased in otitis media,
       respiratory tract and GI tract illnesses
      Must use consistently, one study showed
       increased risk of SIDS if pacifier was not
       used before last sleep
      AAP recommends pacifier use once
       breast-feeding has been established
OTHER CONCERNS
   Upper respiratory tract infection has not been
    found to be independent risk factor for SIDS
       However, these and other minor infections may play
        a role in the pathogenesis if SIDS
           For instance, if in prone position, heavily wrapped or head
            covered during sleep there was increased risk of SIDS with
            infection


   Parents should be reassured that
    immunization does not present a risk for
    SIDS
       No temporal relation between vaccine administration
        and death


   Not caused by vomiting or choking
GENE ENVIRONMENT
INTERACTIONS
GENETIC RISK FACTORS
   Sodium (SCN5A) and Potassium channel polymorphisms
    associated with long QT syndrome
      5-10% of SIDS cases associated with defective cardiac ion
       channel with increased potential for lethal arrhythmia
   Polymorphisms in serotonin transporter (5-HTT) gene
       Increased in transporter activity, reducing 5-HT concentrations at
        nerve endings
   Autonomic nervous system development genes (PHOX2A,
    RET, ECE1, TLX3, EN1)‫‏‬
   Polymorphisms in promoter of anti-inflammatory cytokine
    IL-10  decreased antibody production and increased
    inflammatory cytokines
   SIDS infants w/mild respiratory infections before death were
    more likely than SIDS infants without infection and controls
    to have deficient complement C4 gene (C4A, C4B)‫‏‬
DIAGNOSIS
   By definition, SIDS is a diagnosis of exclusion
   Protocols for standardized autopsies and death scene investigations
    have been published
   However, wide variability in protocols in both content and
    frequency with which they are implemented across jurisdictions,
    within countries and across different countries
   Cause of death can be difficult to diagnose from autopsy alone
      Examination of circumstances present immediately before death
       including detailed description of sleep environment have been
       increasingly emphasized in recent years
   Surveys of medical examiners and coroners have reflected how much
    more complicated, confusing and time consuming SIDS case
    have become
      Most also noted they used to label many more infant death cases
       as SIDS than they do now
      This may be an effect of confusing risk factors for SIDS
   Reaching consensus internationally on a classification scheme is
    essential to accurately monitor trends and direct future research
AAP SIDS RISK REDUCTION
RECOMMENDATIONS 2005
RISK REDUCTION
   Campaign to reduce risk of SIDS began
    in 1994 in the United States
     Largely focused on reducing prone
      sleeping and promoting supine
      positioning
     Some campaigns also included messages to
      reduce smoking during pregnancy
           No significant changes in these behaviors and
            reduced SIDS rates mostly attributed to
            avoidance of prone sleeping
   Breast-feeding advocates have opposed
    discouraging bed sharing as they worry
    these measures will reduce breast-
    feeding frequency and duration and
    prevent families from enjoying the
    experience and benefits of bed sharing
MANAGEMENT AND SUPPORT
   Loss of infant is devastating for everyone concerned
   In addition to loss of infant, families face could face
    police investigation, long wait for autopsy results and
    continued uncertainty leading to prolonged
    emotional distress consequently affecting the
    grieving process
   Physician can play active role by advocating for
    an autopsy, discussing autopsy results with the
    family and providing emotional support
   Surviving siblings and other family members need
    age appropriate emotional support
   If appropriate refer family for genetic counseling
    and/or metabolic testing
   Direct family to local counseling and support groups
    which are available in most communities
FUTURE DIRECTIONS
   Despite decrease in prevalence of SIDS, more work is needed
   Elucidation of risk and protective factors with appropriately
    targeted and implemented interventions leading to increased
    adoption by families
   Unlikely disorder is completely eliminated or reduced to
    lowest possible rates until specific causative mechanisms are
    more fully understood
      Need studies with larger sample sizes and infants from
       highest risk groups
      Investigations of still births and sudden unexplained
       deaths in children over 1 year of age might provide
       additional insights
   Surveillance of trends in rates of SIDS comparisons across
    jurisdictions and internationally according to a universal,
    standardized classification protocol
   Will require multidisciplinary and collaborative effort to
    understand more
REFERENCES
Hunt CE, Hauck FR. Sudden infant death syndrome. Cmaj. Jun
20 2006;174(13):1861-1869.
Moon RY, Horne RS, Hauck FR. Sudden infant death syndrome.
Lancet. Nov 3 2007;370(9598):1578-1587.
Weese-Mayer DE, Ackerman MJ, Marazita ML, Berry-Kravis
EM. Sudden Infant Death Syndrome: review of implicated genetic
factors. Am J Med Genet A. Apr 15 2007;143A(8):771-788.
Gurbutt D, Gurbutt R. Risk reduction and sudden infant death
syndrome. Community Pract. Jan 2007;80(1):24-27.
Fleming P, Blair PS. Sudden Infant Death Syndrome and
parental smoking. Early Hum Dev. Nov 2007;83(11):721-725.
Damato EG. Safe sleep: can pacifiers reduce SIDS risk? Nurs
Womens Health. Feb 2007;11(1):72-76.
Haycock G. Recent research in sudden infant death syndrome. J
Fam Health Care. 2007;17(5):149-151.

				
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