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A. Definitions

  1. Sudden Infant Death Syndrome (SIDS)
    1. Sudden death of an infant between 1 and 12 months' old
    2. Event unexplained by medical history
    3. Post mortem exam fails to demonstrate cause
    4. Also called "Sudden Unexplaind Death in Infancy" (SUDI)
  2. Acute Life Threatening Event (ALTE)
    1. Once known as "near-miss SIDS" or "aborted SIDS"
    2. Apparent life threatening event in young child without identifiable cause
    3. Caregiver notes apnea, skin color changes (pallor, cyanosis, redness), or decreased muscle tone
    4. Resuscitative efforts often made
    5. Child survives without lasting sequelae from acute event
    6. Compared to the general population, these infants have an increased risk of SIDS
    7. Only a small portion of kids who die of SIDS had a prior ALTE

B. Epidemiology

  1. Leading cause of death between 1 month and 1 year in the US
  2. Peak incidence at 2-4 months
  3. Premature infants are at increased risk until 10 months of age
  4. Yearly US incidence is ~0.6 per 1000 infants; lowest in Japan and Netherlands (0.1/1000)
  5. In USA, African Americans, Native Americans, or Alaska Natives have ~3X higher rates [1]
  6. More common in winter months
  7. Majority of cases occurs between midnight (12:00 AM) and 9 AM

C. Risk Factors [4]

  1. Sleeping Position [4]
    1. Multiple international studies have shown a statistically higher incidence of SIDS among those infants positioned prone (on stomach) versus supine (on back)
    2. Odds ratio for SIDS in prone versus supine sleeping is 13.1
    3. Odds ratio for SIDS on turning from side to prone position is 45.4
    4. Sleeping on side is also less desirable than sleeping supine
    5. Large public education campaigns have increased public awareness
    6. Changes in sleep position have lowered SIDS incidence worldwide by ~35-90%
    7. Children should sleep on back or side rather than on stomach to reduce SIDS risk
    8. Soft bedding and soft sleeping surfaces including pillows associated with increased risk
  2. Cigarette Smoke
    1. Increased risk from both in utero and second hand smoke exposure
    2. Risk is dose dependent: the greater the exposure the higher the risk
    3. Infant <2 weeks old sharing bed with mother who smokes has 27X risk for SIDS [4]
  3. Lower Socioeconomic Status
  4. Premature Infants ~4X risk
  5. Low birth weight ~4X risk
  6. Late or no prenatal care
  7. Prolonged QTc (> 440 ms) [6]
    1. Several studies have demonstrated connection between prolonged QTc and SIDS
    2. Electrocardiograms (ECG) were done on 34,000 babies on day 3 or 4 of life
    3. Infants were followed prospectively for one year
    4. 24 children died of SIDS
    5. 3% of normal children and 50% of SIDS victims had prolonged QTc
    6. Odds ratio for SIDS in infants with prolonged QTc was 41
    7. Prolonged QTc may increase risk of life threatening ventricular arrhythmias
  8. Genetic Mutations and SIDS
    1. Several mutations associated with prolongation of QTc
    2. Long QTc syndrome is most commonly caused by mutation in the slow delayed rectifier potassium (K+) channel gene KVLQT1 on chromosome 11p15
    3. De novo mutation of KVLQT1 associated with case of SIDS [7]
    4. One infant resuscitated from SIDS shown to have long QTc and sodium channel (SCN5a) mutations [8]
    5. Two of 93 infants with SIDS had mutations in SCN5a which likely resulted in arrhythmia and death [9]
  9. Child Abuse [5]
    1. Recent retrospective study showed correlation between reported ALTE and child abuse
    2. 39 infants admitted following an ALTE with age matched controls were continuously videotaped while in the hospital
    3. Video surveillance revealed abuse in 33 of 39 cases (documented suffocation in majority of cases)
    4. Parents who intentionally suffocate their children or otherwise fabricate illness exhibit Munchausen by proxy
    5. Study used high risk families for video serveillance (selection bias)
  10. Infections with E. coli or Staphylococcus aureus have also been implicated in some SIDS [12]
  11. Screening electrocardiogram at age 2-3 weeks has been recommended [7]
    1. Most infants have normal QTc <440 miliseconds (msec)
    2. About 2% of infants will have borderline high QTc 440-469 msec
    3. Infants with borderline high QTc should be rescreened within several weeks
    4. Infants with QTc >469 msec have prolonged QTc and molecular diagnosis sought
    5. Arrhythmic complications of prolonged QTc can usually be prevented with ß-blockers
  12. Maternal Alpha-Fetoprotein (AFP) Levels [10]
    1. Direct association between 2nd trimester maternal AFP levels and SIDS
    2. Risk from lowest to highest quintiles was 2.8X
    3. May be associated with preterm birth and reduced birth-weight
  13. Reduced risk, and added protective effect, with use of pacifier at sleep time [1]
  14. Women whose infants die from SIDS have increased ~2X risk of subsequent pregnancy complications including preterm birth, small for gestational age [11]

D. Pathophysiology

  1. Despite extensive medical studies, the cause of SIDS remains unclear
  2. Autonomic dysfunction with failure of arousal responses from sleep implicated
  3. No consistent pattern of obstructive or central apnea found in SIDS victims
  4. Careful home monitoring with event recorders shed little light on etiology [2]
  5. Serotonergic Abnormalities [3]
    1. SIDS had significantly higher levels of serotonergic (5-HT) neuron count and density compared with infants dying of non-SIDS
    2. Lower density of 5-HT1A (serotonin receptor 1A) in medulla in SIDS than non-SIDS
    3. Abnormalities in 5-HT1A more pronounced in male SIDS than female SIDS
    4. Medullary 50HT pathology in SIDS is extensive and may play a role in, and increased male sucseptibility to, SIDS
  6. SIDS cases are likely a heterogeneous collection rather than a single entity

E. Pathology

  1. No pathognomonic finding on post-mortem examination
  2. Petechiae of lungs and intrathoracic thymus are commonly seen
  3. Findings suggest negative intrathoracic pressure from upper airway obstruction
  4. Cerebellar abnormalities recently implicated

F. Evaluation of ALTE

  1. Must exclude other medical conditions:
    1. Gastroesophageal reflux disease
    2. Sepsis
    3. Respiratory Syncytial Virus (RSV)
    4. Pertussis
    5. Metabolic disturbances
    6. Seizures
    7. Arrhythmias
    8. Prematurity
  2. Laboratory studies to consider
    1. CBC with differential
    2. Blood culture
    3. Electrolytes with calcium, magnesium and phosphate
    4. Arterial blood gas
    5. Chest Ray
    6. Electrocardiogram (ECG, see below)
    7. Electroencephalogram
    8. Gastric pH probe
    9. Pneumogram (not predictive of later SIDS in large prospective studies)
  3. ECG
    1. Measure QTc
    2. <1% of infants with prolonged QTc will have SIDS (but prolonged QTc is a risk factor)
    3. Appropriate management and monitoring for infants with prolonged QTc is controversial
    4. Further clinical studies needed
  4. Consider evaluation for child abuse in selected cases
  5. Home Monitoring [1,4]
    1. Demonstrate increased rates of ALTEs in infants at high risk for SIDS
    2. High risk includes sibling with SIDS death, prematurity, and infants with one ALTE
    3. However, only premature infants have substantially increased ALTE rates
    4. Significant ALTEs found in normal, healthy infants as well
    5. Most ALTEs were related to obstructive breathing

G. Prevention

  1. Treat any underlying conditions
  2. Sleeping Position
    1. American Association of Pediatrics (AAP) recommends infants should sleep on back
    2. Side sleeping is an alternative position (infant sometimes able to roll to prone position)
    3. Prone positioning for infants with symptomatic GERD (consider monitoring if high risk)
    4. Avoid soft pillows or quilts in bed that might smother infant
  3. Limit exposure to cigarette smoke
  4. Encourage breast feeding
  5. CPR instruction for caregivers of infants
  6. Home Monitoring [1,4]
    1. Alarmed cardiac and apnea monitors for use while infant sleeps
    2. Indications for high risk patients (as above) and with chronic cardiopulmonary diseases
    3. Monitoring often increases parents feelings of security
    4. Vast majority of monitor events will be false alarms
    5. Sufficient professional support services and education must be available to families
    6. Unlikely that home monitoring affects mortality
    7. Monitoring should be stopped after 1-3 months of event free time

References

  1. Moon RY, Horne RS, Hatuck FR, et al. 2007. Lancet. 370(9598):1578 abstract
  2. Ramanathan R, Corwin MJ, Hunt CE, et al. 2001. JAMA. 285(17):2199 abstract
  3. Paterson DS, Trachtenberg FL, Thompson EG, et al. 2006. JAMA. 296(17):2124 abstract
  4. Carpenter RG, Irgens LM, Blair PS, et al. 2004. Lancet. 363(9404):185 abstract
  5. Southall DP. Pediatrics. 100(5):735
  6. Schwartz PJ, Stramba-Badiale M, Segantini A, et al. 1998. NEJM. 338(24):1709 abstract
  7. Schwartz PJ, Priori SG, Bloise R, et al. 2001. Lancet. 358(9290):1342 abstract
  8. Schwart PJ, Priori SG, Dumaine R, et al. 2000. NEJM. 343(4):262 abstract
  9. Ackerman MJ, Siu BL, Sturner WQ, et al. 2001. JAMA. 286(18):2264 abstract
  10. Smith GCS, Wood AM, Pell JP, et al. 2004. NEJM. 351(10):978 abstract
  11. Smith GC, Wood AM, Pell JP, Dobbie R. 2005. Lancet. 366(9503):2107 abstract
  12. Weber MA, Klein NJ, Hartley JC, et al. 2008. Lancet. 371(9627):1848 abstract