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The Limits of Viability: How Small Is Too Small?

The Limits of Viability: How Small Is Too Small?. Istvan Seri M.D., Ph.D. USC Division of Neonatal Medicine Women’s and Children’s Hospital LAC/USC Medical Center and Children Hospital Los Angeles Keck School of Medicine University of Southern California Los Angeles, CA.

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The Limits of Viability: How Small Is Too Small?

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  1. The Limits of Viability:How Small Is Too Small? Istvan Seri M.D., Ph.D. USC Division of Neonatal Medicine Women’s and Children’s Hospital LAC/USC Medical Center and Children Hospital Los Angeles Keck School of Medicine University of Southern California Los Angeles, CA

  2. The Limits of Viability:How Small Is Too Small? 1960’s - 30-31 weeks 1980’s - 26-27 weeks 2000 - 24 weeks Gestational age at which a newborn had a 50% chance of survival

  3. The Limits of Viability:How Small Is Too Small? Mandatory Unreasonable Gray Zone Too small Too immature Too big Too mature Active Intervention Comfort Care Only ??? Intervention ???

  4. The Limits of Viability:How Small Is Too Small? Percent Survival by Gestational Age Percent Survival by Gestational Age 23-62% 0-55% 0-12%

  5. The Limits of Viability:How Small Is Too Small? Percent Survival by Birth Weight Percent Survival by Birth Weight 16-37% 1-38%

  6. The Limits of Viability:How Small Is Too Small? Number of Patients Outcome of Neonates with Birth Weights of 401-500 g Gestational age = 23.3 ±2.1 weeks Percent Lucey et al, Pediatrics 113:1559, 2004

  7. The Limits of Viability:How Small Is Too Small? Outcome of Neonates with Birth Weights of 401-500 g Gestational age = 23.3 ±2.1 weeks Total Neonates Registered N = 4172 (100%) Died in Delivery Room N = 2186 (52%) Survived DR to NICU N = 1986 (48%) Died in NICU N = 1253 (30%) Survived to NICU D/C N = 690 (17%) Survival Status Unknown N = 43 (1%) Gestational Age = 25.3 ±2 weeks Lucey et al, Pediatrics 113:1559, 2004

  8. The Limits of Viability:How Small Is Too Small? Outcome of Neonates with Birth Weights of 401-500 g Gestational age = 23.3 ±2.1 weeks • Compared to patients who died in the DR, neonates who survived to be admitted to the NICU were more likely to • Be female (58% vs 49%) • Be small for gestational age (56% vs 11%) • Have received prenatal steroids (61% vs 12%) • Have been delivered via cesarean section (55% vs 5%) Lucey et al, Pediatrics 113:1559, 2004

  9. The Limits of Viability:How Small Is Too Small? Synnes et al, 1994 Percent Survival by Gestational Age and Birth Weight

  10. The Limits of Viability:How Small Is Too Small? Burdens of Prolonging Support in Infants at the Limits of Viability %

  11. The Limits of Viability:How Small Is Too Small? Infants born <23 weeks too immature to survive Comfort care only

  12. The Limits of Viability:How Small Is Too Small? Effect of Fetal Compromise on Survival Batton et al, 1998

  13. The Limits of Viability:How Small Is Too Small? Gestational Age-Dependent Mortality (1991-1999) Pediatrics 110:143, 2002 Vermont-Oxford Network (362 Institutions)

  14. The Limits of Viability:How Small Is Too Small? Birth Weight-Specific Survival of VLBW Neonates (1977-2000) Parkland Memorial Hospital, Dallas, TX Kaiser et al, J Perinatol 24:343, 2004

  15. Decision-Making at the Threshold of Infant ViabilityEstimating Survival & Intact Survival GA BW Survival Intact Survival* (weeks) (g) ( % ) ( % ) 23 600 50 % 25 % 24 700 70 % 70 % 25 800 80 % 80 % 26 900 90 % 70 % 27 1000 95 % 80 % * Among Survivors

  16. The Limits of Viability:How Small Is Too Small? Infants born >25 weeks are mature enough Full support warranted

  17. The Limits of Viability:How Small Is Too Small? • Target range for “Gray Zone” based onsurvival: 23-24 6/7th weeks and 500-600 g • What are the complications and outcome data of premature neonates in the “Gray Zone”?

  18. The Limits of Viability:How Small Is Too Small? Percent Severe Head Ultrasound Abnormalities by Gestational Age %

  19. The Limits of Viability:How Small Is Too Small? Percent Chronic Lung Disease at 36 weeks by Gestational Age at Birth %

  20. The Limits of Viability:How Small Is Too Small? Percent Survival and Intact Survival by Gestational Age % Doyle et al Pediatrics, 2001

  21. The Limits of Viability:How Small Is Too Small? Bottoms et al, NICHD Network, 1997 Percent Survival and Intact Survival by Birth Weight %

  22. The Limits of ViabilityImpact of BPD, Brain Injury and ROP on 18-Month Outcome of ELBW Infants These 3 common neonatal morbidities strongly predict the risk of later death or disability Schmidt et al: JAMA 289:1121, 2003

  23. The Limits of ViabilityImpact of BPD, Brain Injury and ROP on 18-Month Outcome of ELBW Infants Overall probability of poor outcome at 18 m (35%) These 3 common neonatal morbidities strongly predict the risk of later death or disability Schmidt et al: JAMA 289:1121, 2003

  24. The Limits of ViabilityPulmonary Outcome VON 2000

  25. The Limits of ViabilityIVH and PVL: Incidence by Birth Weight VON 2000

  26. The Limits of ViabilitySequelae of Prematurity (1)Place of Birth and Mortality in Canadian NICUs 17 NICUs Admits = 19,265 Period = 1996-97 Number of NICU Admits Birth Weight (kg) Sankaran K et al; CMAJ 166:173-8, 2002

  27. The Limits of ViabilitySequelae of Prematurity (2)Place of Birth and Mortality in Canadian NICUs Sankaran K et al; CMAJ 166:173-8, 2002

  28. The Limits of ViabilitySequelae of Prematurity (3)Place of Birth and Mortality in Canadian NICUs Sankaran K et al; CMAJ 166:173-8, 2002

  29. The Limits of ViabilityPlace of Birth and Mortality in Infants with Birth Weight of 500-1499 g * SPC=Subspecialty Perinatal Center Warner et al; Pediatrics 2004; 113:35-41

  30. The Limits of ViabilitySurvival and 2-year Outcome in Infants <27 wks (1996-1997) Rijken et al; Pediatrics 2003; 112:351-58

  31. The Limits of ViabilitySurvival and Outcome of ELBW infants born at 23-26 weeks (1986-2000) Hoekstra et al; Pediatrics 2004; 113:e1-e6

  32. The Limits of Viability Factors Affecting Outcome of ELBW infants at 47.5 Months of Age (1986-2000) Hoekstra et al; Pediatrics 2004; 113:e1-e6

  33. The Limits of Viability:How Small Is Too Small? Problems with predicting long-term outcome • Adverse medium-term neurodevelopmental outcomes in ELBW infants correlate with severe brain injury, CLD, NEC, steroid use for CLD, male gender (Vohr et al, 1999) • However, long-term neurodevelopmental outcomes do not correlate well with these predictors andmaternal education and home environmentare more important than all other factors except severe brain injury

  34. The Limits of Viability:How Small Is Too Small? Outcome of ELBW Infants - NICHD American Experience • Patient population of 1126 infants (BW = 501 - 800 g) • Females have a survival advantage of 90 g • SGA neonates had a survival advantage of 57 g • Antenatal steroids confer a survival advantage of 67 g Tyson et al JAMA 1996; 276:1645

  35. The Limits of Viability:How Small Is Too Small? Odds of Survival between 23 and 246/7 weeks • Chance of survival improves by 2% a day during 23 to 26 weeks gestational age • Overall, 50% survive and 50% of the survivors are handicapped (the “50 - 50” rule)

  36. The Limits of Viability:How Small Is Too Small? The Gray Zone:23 - 24 6/7 weeks gestation and 500 - 600 grams • Recent survival data (especially on non-compromised ELBW neonates) • Lower incidence of severe ROP, CLD and/or severe head ultrasound abnormalities • Overall “intact” survival has increased from <10% to > 40% • Outcome still very uncertain for individual patient especially at 23 weeks gestational age

  37. The Limits of ViabilityDecision Making at The Threshold of Infant Viability Three approaches to care • Wait Until Certainty Approach Treatment begins on every infant thought to have any chance of survival, wait until all information is in before deciding whether continuing care is the right decision (eg: USA) • Statistical Approach Determine categories of patients in which treatment may be limited or withheld (eg: Sweden) • Individualized Approach (eg: UK) Clin Perinatol, 1996

  38. The Limits of Viability:Decision-Tree Unreasonable Mandatory Gray Zone 23-24 6/7 wks and 500-600 g <23 wks 25 wks Comfort Care Only Full Critical Care Parents indicate definite wishes for non-active intervention (importance of counseling regarding impact of initial condition/perinatal stress on outcome) Parents desire active intervention or defer to medical judgement Follow parents wishes, unless evidence parents not working in best interest of the baby Extent of active intervention based on condition and response

  39. Decision-Making at the Threshold of Infant Viability  500g* or < 23wk Gray Zone 23 - 246/7 wk and 500 - 599g  600g or  25wks No resuscitation Initiate comfort care measures Initiate resuscitation Clinical course will dictate management Heart rate Present >40-50 Bag/Intubate Low or Absent HR > 100/min HR = 60 - 100/min Give surfactant; insert lines; check ABG; start fluids Can’t intubate or poor response (HR < 60/min for 5mins) Consider brief CPR, drugs and bolus fluids x1 good response Poor response Transfer to NICU Discontinue interventions & initiate comfort care measures Parents desire active management carry on, set limits NICU Care Ongoing evaluation Poor clinical status * The occasional infant <500g BW (usually IUGR), who is vigorous at birth may warrant active intervention

  40. Decision-Making at the Threshold of Infant Viability • The algorithm assumes appropriate antenatal counseling • Gestational age should be determined antenatally • Birth weight must be obtained at the time of delivery • At each stage of resuscitation, the prognosis for reasonable outcome should be reevaluated • Parental wishes regarding extent of intervention in the gray zone should be honored until parents except their baby’s fate

  41. Decision-Making at the Threshold of Infant ViabilityRelative weighting of parental, clinician and societal views of active interventionwith increasing gestational age Relative Weighting 22 23 24 25 26 27 28 Gestational Age at Birth Parents Clinicians Society

  42. Limits of Viability Questions?

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