Oxygen therapy for the premature infantRetinopathy of prematurity (ROP)

Teaching Evidence-based Practise15th September 2015

Kenneth TanMonash Newborn

the RITCHIE CENTRE for baby health researchthe RITCHIE CENTRE for baby health research

Objectives

•Preterm infants definitions

•Complications of preterm birth, including ROP

•Early trials oxygen

•NeoPROM collaboration trials

Preterm infant

Med J Aust. 1951;2(2):48-50

Campbell 1951

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MaculaMacula

Optic discOptic disc

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Right eyeRight eye Left eyeLeft eye

Ora Ora serrataserrata

ROP - ClassificationROP - Classification

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Classification of ROP

• Staging:5 stages - describe abnormal vascular response. Most severe stage is used to determine the stage of the eye as whole.

Stage 1: Demarcation line Stage 2: Ridge

Classification of ROP

• Stage 3: Extaretinal Fibrovascular Proliferation

• Stage 4: Partial Retinal Detachment

4a - Extrafoveal

4b – Foveal• Stage 5: Total Retinal

Detachment

Major cause of childhood blindness in developed world

Retinopathy of Prematurity

Clinical trials in the 1950s confirmed that restricting oxygen reduced the risk of eye damage, then called Retrolental Fibroplasia (RLF), and blindness

History of oxygen use in preterm neonates

Children's Hospital, Buffalo, NYAccessed via http://www.nei.nih.gov/rop/photos.asp

Side-effects of oxygen Therapy

• Preterm infants lack a fully functioning antioxidant defence system (Frosali 2004)

•Oxygen rich environment

•Antioxidant defences

•Glutathione peroxidase, superoxide dismutase

•Other diseases of the preterm neonate where oxidative stress plays a role:

Lungs - BPD (Davis, 2002) Brain - PVL (Kakita et al, 2009)

Reduced oxygen Therapy

•Less inspired oxygen (to target SpO2 <90%) may increase

•patent ductus arteriosus•pulmonary vascular resistance•apnoea•impair survival and neurodevelopment

Newburger N Engl J Med 1984, 310:1495-1499.Skinner JR, Arch Dis Child Fetal Neonatal Ed 1999, 80: F81-F87.Subhedar Arch Dis Child Fetal Neonatal Ed 2000, 82:F243-F247.

Cost of preventing ROP

• For each case of RFLP by oxygen restriction prevented about 16 infants died or had cerebral palsy

• Competing goals of treatment

Kenneth CrossLancet 1973;2(7835):954–956

Monitoring of oxygenation

•Monitoring paO2

•Levels of pO2 that is damaging to the retina 80 mmHgFlynn JT et al N Engl J Med 1992, 326:1050-1054.

•tcpO2

•Arterialised capillary bed

•Disadvantage that it heats the skin up (40 C)

•SpO2

•Introduced in 1980s

History of oxygen therapy in preterm infants

•After trials in 1950s, very little study on oxygen therapy (Silverman 1980)

•Northern Neonatal Network (North of England)

•Newcastle, Middlesbrough et al

•Centres with 4 different SpO2 targets policy

•Problem with this was a studyShows association cannot determine cause-effect relationship

Outcomes – Northern Neonatal Network

Arch Dis Child Fetal Neonatal Ed. 2001 Mar;84(2):F106-10

What type of study is this?

NeOProM

Aim

• To determine whether, in infants < 28 weeks gestation, targeting SpO2 85 – 89% versus 91 – 95% when in supplementary oxygen leads to a lower rate of death or disability at two years

Target 88 – 92%

Alarm limits: upper - 94%lower – 86%

Primary Outcome

• Death or major disability at two years corrected for gestationon Bayley III scales

• Secondary outcomes:– Retinopathy, chronic lung disease, PDA,

NEC, Sepsis, Growth

Actual target 85-89% Actual target 91-95% (3% below displayed value) (3% above displayed value)

Study oximeter adjusted to display either 3% above or 3% below actual saturation for values between 85% - 95%. Outside that range the true

values are displayed.

Staff are asked to target display with masked study oximeter SpO2

88-92%

Lower group Higher group

Masking O2 saturation in BOOST II

SUPPORT Trial

SUPPORT Study Group of the Eunice Kennedy Shriver NICHD Neonatal Research NetworkN Engl J Med 2010; 362:1959-1969

What about the other RCTs?

• Continue or stop RCT

• Data and safety monitoring committee of BOOST- Aus ANZ

Stopping the RCT

Stenson B et al. N Engl J Med 2011;364:1680-1682.

BOOST-II• In December 2010, a joint safety analysis of survival at 36

weeks' postmenstrual age was undertaken– 2315 infants in the U.K., Australian, and New Zealand trials

with the 1316 infants in the SUPPORT trial

• Investigators be told the results if the difference in 36-week survival between groups for all infants, or for those recruited after introducing the new calibration algorithm, exceeded 3 SE (equivalent to 99.73% CI, with P=0.003) (UK BOOST protocol)

Stenson et al N Engl J Med 2011; 364:1680-1682

Implications for practise

• Main question: should we change current practise from 88-92% targetting to 91-95%

• Two NICUs (USA, UK) have already implementation this

• Most NICUs in Australia have changed practise to higher SpO2 target

Take home message

• Meta-analysis

• Odd ratios

• Cohort study

• Randomised control trial (double blind)

• Individual patient meta-analysis