Early MRI in term infants with perinatal hypoxic-ischaemic brain injury: interobserver agreement and MRI predictors of outcome at 2 years

AIM

To compare diffusion-weighted imaging (DWI) and non-DWI magnetic resonance imaging (MRI), proton MR spectroscopy (1H-MRS), and clinical biomarkers for prediction of 2 year developmental outcome in term infants with perinatal hypoxic-ischaemic encephalopathy (HIE).

MATERIALS AND METHODS

Nineteen infants ≥36 weeks gestation with HIE were recruited and MRI performed day 3-7 (mean = 5). MRI was scored independently by three radiologists using a standardized scoring system. Lactate-to-N-acetylaspartate ratio (Lac:NAA) in the lentiform nucleus was calculated. Developmental assessment was performed at 2 years using the Bayley Scales of Infant and Toddler Development (BSID-III). Interobserver agreement about abnormality in 10 brain regions was measured. Univariate analysis was performed to determine variables associated with adverse outcome (i.e., death or Bayley score for any domain <70).

RESULTS

Good interobserver agreement (kappa = 0.61-0.69) on scores for DWI was obtained for the cortex, putamen, and brainstem, but not for any region on non-DWI. A significant association was found between outcome and Lac:NAA (p < 0.003) and DWI scores for lentiform nucleus, thalamus, cortex, posterior limb of the internal capsule (PLIC), and paracentral white matter (p = 0.001-0.013), but for non-DWI score only in the vermis or brainstem. A combination of Lac:NAA ≥0.25 or DWI/apparent diffusion coefficient (ADC) signal abnormality in the PLIC had 100% specificity and sensitivity for poor outcome.

CONCLUSION

Interobserver agreement for non-DWI performed during the first week is poor. Agreement by three radiologists about the presence of abnormal signal within the PLIC on ADC/DWI images or elevation of Lac:NAA above 0.25 improved sensitivity without reducing the prognostic specificity of MRS in the 19 patients, but this requires validation in a larger group of infants with HIE who have been treated with hypothermia.

The cost of improving the outcome for infants of birthweight 500-999 g in Victoria. The Victorian Infant Collaborative Study Group

The aim of this study was to conduct an economic evaluation of neonatal intensive care for extremely low birthweight (ELBW) infants born in the state of Victoria. Two distinct eras (1979-80 and 1985-87) were compared. Follow-up data at 2 years of age were available for all 89 survivors from the 351 live births in 1979-80, and for 211 of 212 survivors from the 560 live births in 1985-87. The overall cost-effectiveness for ELBW infants during 1985-87 compared with 1979-80 was $104,990 ($A 1987) per additional survivor, or $5390 ($A 1987) per additional life year gained. Cost-effectiveness improved with increasing birthweight. If the quality of life of the survivors was considered, the economic outlook was more favourable. The cost per quality-adjusted life year gained was $5090 ($A 1987), approximately one-tenth of that obtained from the only previous full economic evaluation of neonatal intensive care. Although neonatal intensive care is expensive, it compares favourably with some other health care programmes, particularly as the outcome for ELBW infants continues to improve.

Improving health status in extremely low birthweight children between two and five years

The 5-year outcome of 101 extremely low birthweight (ELBW, < 1000 g) children discharged from the Neonatal Intensive Care Unit was reported. Over this period, there were four post-discharge deaths. The neurodevelopmental impairment rate was 18% overall: cerebral palsy 7%, blindness 3%, deafness 3% and developmental delay 10%. Seventy-one percent of children were readmitted to hospital. The mean number of admissions was 2.4 per child and the mean duration of total hospital stay was 11.3 days per child in the 5-year period. A trend was observed in a reduction in the readmission rate and hospital days in the 2-5-year period compared to the period between discharge and 2 years, though the differences were not statistically significant. The most common reason for readmission was for surgical procedures, primarily aural ventilation tube insertion and tonsillectomy and adenoidectomy. Significant health problems included recurrent wheezing episodes, stridor and croup in the period up to 2 years and otitis media and tonsillitis between 2 and 5 years. There was some catch-up growth, especially in height, between 2 and 5 years. Children with < 800 g birthweight had similar rates of neurodevelopmental impairment and hospital readmission to those of 800-999 g birthweight. However, they experienced more otitis media and pneumonia, had more ear, nose and throat operations, and at 5 years of age, more were below the 3rd centile for weight. This study showed that the health status of ELBW children had improved between 2 and 5 years, but they continued to experience recurrent health problems and hospital readmissions which would have resulted in added financial and emotional burdens to their families.

A comparison of episodic heart-rate patterns in the fetus and newborn

Fourier analysis was applied to episodes of high and low heart-rate variation in the near-term fetus. The spectral densities of the variations in pulse intervals from 1 to 7 cycles/min, were almost identical with those found by De Haan et al. (1977) in the newborn infant during both active and quiet sleep. A computer programme, designed to separate low and high heart-rate variation episodes in the fetus, identified seven of the eight quiet sleep episodes in four infants. None of the other neonatal behavioural states had low heart-rate variation. It was concluded that, with other published data, there is increasing, although indirect, evidence that low heart-rate variation episodes indicate quiet sleep in the human fetus near term.

Oxygen and carbon dioxide tensions, breathing and heart rate in normal infants during the first six months of life

Daytime measurements were made of the relationship between sleep state, cardio-respiratory changes and oxygen (transcutaneous PO2) and carbon dioxide (mass spectrometer alveolar PCO2) tensions in eleven normal infants from birth to 6 months of age. Sequential records were made at 1 week, 1, 3 and 6 months. The babies were not restrained, slept in a cot, and were constantly observed. Heart rate was higher in active sleep than in quiet sleep at all ages and rose between 1 week and 1 month (P less than 0.01) in both quiet sleep and active sleep and then decreased at 3 and 6 months. Respiratory rate only changes with age in active sleep at 6 months, showing a decrease (P less than 0.05) but was higher in active sleep that in quiet sleep at 1 month (P less than 0.002) and 3 months (P less than 0.02). A fall in heart rate (less than 100 beats/min) occurred chiefly in association with apnoea. The incidence of apnoea (of greater than 3 s duration) varied widely between babies at the same age and in the same baby at different ages but was most common in the first 3 months of life. No evidence of obstructive apnoea was found and no apnoea of greater than 12 s duration was observed. Period breathing occurred in all babies at 1 month normally following sighs but was uncommon at 1 week and 3 months and absent at 6 months. A fall in transcutaneous PO2 did not precede but often resulted from an episode of periodic breathing.