Escalating consumption of nursery resources by extremely immature infants

Relationship between Epigenetic Maturity and Respiratory Morbidity in Preterm Infants

OBJECTIVE

To assess associations between epigenetic maturity of extremely preterm babies (born at less than 28 weeks of gestation), neonatal interventions, and respiratory outcomes, including the administration of surfactant and postnatal corticosteroids, duration of assisted ventilation, and development of bronchopulmonary dysplasia (BPD).

STUDY DESIGN

DNA was extracted from neonatal blood spots collected after birth from 143 extremely preterm infants born 1991-1992 in Victoria, Australia and used to determined DNA methylation (DNAm). A DNAm based gestational age was determined using our previously published method. The residual of DNAm gestational age and clinically estimated gestational age (referred to as "gestational age acceleration") was used as a measure to assess developmental maturity. Associations between gestational age acceleration and respiratory interventions and morbidities were determined.

RESULTS

Infants with higher gestational age acceleration were less likely to receive surfactant (P = .009) or postnatal corticosteroids (P = .008), had fewer days of assisted ventilation (P = .01), and had less BPD (P = .02). Respiratory measures are known to correlate with gestational age; however, models comparing each with clinically estimated gestational age were improved by the addition of the gestational age acceleration measure in the model.

CONCLUSIONS

Gestational age acceleration correlates with respiratory interventions and outcomes of extremely preterm babies. Surfactant and postnatal corticosteroid use, assisted ventilation days, and BPD rates were all lower in babies who were epigenetically more mature than their obstetrically estimated gestational age. This suggests that gestational age acceleration is a clinically relevant metric of developmental maturity.

Neonatal assisted ventilation: predictors, frequency, and duration in a mature managed care organization

OBJECTIVES

Reference data are lacking on the frequency and duration of assisted ventilation in neonates. This information is essential for determining resource needs and planning clinical trials. As mortality becomes uncommon, ventilator utilization is increasingly used as a measure for assessing therapeutic effect and quality of care in intensive care medicine. Valid comparisons require adjustments for differences in a patient's baseline risk for assisted ventilation and prolonged ventilator support. The aims of this study were to determine the frequency and length of ventilation (LOV) in preterm and term infants and to develop models for predicting the need for assisted ventilation and length of ventilator support.

METHODS

We performed a retrospective, population-based cohort study of 77 576 inborn live births at 6 Northern California hospitals with level 3 intensive care nurseries in a group-model managed care organization. The gestational age-specific frequency and duration of assisted ventilation among surviving infants was determined. Multivariable regression was performed to determine predictors for assisted ventilation and LOV.

RESULTS

Of 77 576 inborn live births in the study, 11 199 required admission to the neonatal intensive care unit and of these, 1928 survivors required ventilator support. The proportion of infants requiring assisted ventilation and the median LOV decreased markedly with increasing gestational age. In addition to gestational age, admission illness severity, 5-minute Apgar scores, presence of anomalies, male sex, and white race were important predictors for the need for assisted ventilation. The ability of the models to predict need for ventilation was high, and significantly better than birth weight alone with an area under the receiver operating characteristic curve of.90 versus.70 for preterm infants, and.88 versus.50 for term infants. For preterm infants, gestational age, admission illness severity, oxygenation index, anomalies, and small-for-gestational age status were significant predictors for LOV, accounting for 60% of the variance in the length of assisted ventilation. For term infants, oxygenation index and anomalies were significant predictors but only accounted for 29% of the variance.

CONCLUSIONS

Considerable variation exists in the utilization of ventilator support among infants of closely related gestational age. In addition, a number of medical risk factors influence the need for, and length of, assisted ventilation. These models explain much of the variance in LOV among preterm infants but explain substantially less among term infants.neonatal intensive care, assisted ventilation, Score for Neonatal Acute Physiology, resource consumption, prematurity.

Cost efficiency of neonatal nurseries: the significance of unit size

The cost of neonatal intensive care is high, and human and financial resources are finite. It is therefore essential to provide such care efficiently in terms of costs while still maintaining standards of care. We looked at the relationship of unit size to cost and determined the optimum and minimum size of the unit in terms of cost efficiency. Our data suggest that units with fewer than 6 ventilator cots were less cost-efficient than those with more cots while those with 12 ventilator cots were the most efficient. The calculations were done only up to 16 ventilator cots. Similarly, level II units were most cost-efficient when attached to an intensive care unit and had over 16 cots.

Duration of hospitalization in extremely preterm infants

This study reports the age at hospital discharge of 233 survivors and age at death of 209 infants who were born at 23-28 weeks gestation over a 10 year period, 1977-86. The mean duration of hospitalization of survivors was 95 days and was inversely related to maturity at birth; those born at 23-25 weeks remained in hospital on average 1-2 weeks beyond term while those born at 26-28 weeks went home on average at term or 1 week before term. The mean age at death was 12 days: 53% within 1 day, 23% between 2 and 7 days, 15% between 8 and 28 days and 9% between 28 days and 1 year. The proportions of death in the post-neonatal period for infants born at 23-24 weeks, 25-26 weeks and 27-28 weeks were 2, 9 and 16% respectively. There was no significant trend in prolonged hospitalization of survivors or postponement of neonatal deaths to the post-neonatal period over the 1977-86 period. Nevertheless, both neonatal and post-neonatal mortality should continually be monitored in this extremely preterm group.

Increasing the survival of extremely-immature (24- to 28-weeks' gestation) infants--at what cost?

In one tertiary perinatal centre, the advent of positive-pressure assisted ventilation in the 1970s improved the survival of neonates of 24 to 28 completed weeks of gestation. However, the rate of increase in the resources for assisted ventilation and the improvements in survival rates were stepwise and not smooth. Consequently, it has been possible to calculate the cost-effectiveness of neonatal intensive care up to the time of hospital discharge over two separate eras of stable consumption of resources for assisted ventilation. During 1977-1983, to produce one survivor at 24-weeks' gestation compared with one at 28-weeks' gestation consumed 14.4-times the number of patient-days of assisted ventilation, and 4.9-times more of the total nursery resources; the cost-effectiveness of intensive care during this period decreased with decreasing maturity. The over-all cost-effectiveness up to the time of hospital discharge for infants of 24- to 28-weeks' gestation during 1977-1983, compared with 1971-1974, when assisted ventilation was rare, was $62,268 per additional survivor. After 1983, the consumption of resources for assisted ventilation more than doubled in infants of 24- to 28-weeks' gestation. However, there was a diminishing return with respect to the gains in survival during 1984-1986 and the costs per additional survivor averaged $99,574, which was 60% more than were those for 1977-1983. We speculate that to improve survival further in the most-immature infants by increasing resources for assisted ventilation only can be more difficult and more expensive, and even less cost-effective.

Retinopathy of prematurity in infants of 24-30 weeks' gestational age

Over the 10-year period from January 1, 1977 to December 31, 1986, 1114 infants with gestational ages of 24 to 30 completed weeks were cared for on a long-term basis in our nursery; 757 (68%) infants survived. As expected, both the mortality rate and the prevalence of stage-3 or stage-4 retinopathy of prematurity among survivors fell with increasing maturity at birth (P less than 0.0001). Adjusting for gestational age, and excluding infants with lethal malformations, the mortality rate decreased significantly (P = 0.018) over time by an estimated 11.5%; also the survival rate of infants with at least stage-3 retinopathy of prematurity increased significantly (P = 0.005) by an estimated 6.8%. In other words, for every 10 additional survivors over the decade, six survivors would have been expected to show at least stage-3 retinopathy of prematurity in either eye. Although the prevalence of advanced stages of retinopathy of prematurity increased in immature survivors, it was not in epidemic proportions; however, it was more likely to be related to the survival of the increasing numbers of at-risk immature infants who, in earlier times, would have died.