Joyce Peabody

A New Look at Intrauterine Growth and the Impact of Race, Altitude, and Gender

Background. Growth curves described in the 1960s are used to classify neonate intrauterine growth as normal or abnormal. Our objective was to determine whether continued use of these curves is appropriate. Methods. From 1996 to 1998, we collected birth weight, length, head circumference, estimated gestational age (EGA), gender, race, and place of birth (<4000 feet or ≥4000 feet) on 27 229 neonates to evaluate the effects of each on intrauterine growth and the diagnoses of small for gestational age (SGA) and large for gestational age (LGA). We compared the gestation-specific growth parameters derived from our sample with those reported in 1966 and 1969. Results. Gestational age had the largest influence on each growth parameter. Race and gender both had effects on birth weight. Female neonates were smaller than male neonates, and black neonates were smaller than Hispanic and white neonates at each EGA. For neonates with an EGA <30 weeks, our data had a smaller variance and lower average weights, lengths, and head circumferences than those reported in 1966 and in 1969. For neonates >36 weeks, the variance was similar, but our curves showed that neonates in our sample were larger and heavier. Use of the older growth curves to classify neonates as SGA, LGA, and appropriate for gestational age (AGA) led to significantly different rates of each by gender and race. Conclusions. Intrauterine growth patterns previously described and commonly used to classify neonates as AGA are inaccurate for use in current populations and lead to gender- and race-specific diagnoses of SGA and LGA that are misleading. neonates, growth, race, gender.

Abnormal cerebral blood flow patterns in preterm infants with a large patent ductus arteriosus

To determine whether there are significant alterations in cerebral blood flow patterns in infants with a patent ductus arteriosus and whether these alterations correlate with alterations in aortic blood flow, we performed range-gated pulsed-Doppler examinations of the aorta and cerebral arteries in 20 infants. Ten infants had a PDA and ten control infants did not. We analyzed these flow patterns quantitatively by calculating the pulsatility index (peak systolic frequency minus trough diastolic frequency)/peak systolic frequency. In the ten control infants and in three infants with a small PDA, there was no significant diastolic flow in the descending aorta; flow in the cerebral arteries was antegrade throughout systole and diastole (PI = 0.75 +/- 0.03 for control infants and 0.73 +/- 0.07 for small PDA infants). In seven infants with a large PDA, there was retrograde diastolic flow in the descending aorta. This pattern was not seen after PDA closure. In the cerebral arteries of the seven infants with a large PDA, diastolic flow was retrograde in three and decreased or absent in four, and PI was significantly higher (PI = 0.96 +/- 0.06. P less than 0.001 vs controls). After PDA closure, cerebral diastolic flow was antegrade in all seven infants (PI = 0.74 +/- 0.04). We conclude that a large PDA can cause abnormal flow patterns in the descending aorta and cerebral arteries. These flow patterns may predispose these infants to CNS ischemia or intraventricular hemorrhage.

Experience with Anencephalic Infants as Prospective Organ Donors

Recent advances have made organ transplantation in newborns feasible, but the paucity of organs small enough for this age group remains a major limitation. Because anencephalic infants can survive for no more than a few weeks, they have been considered as possible organ donors for other infants. Under current law, however, they cannot be used as donors until their brain-stem activity ceases and the criteria for total brain death are thereby met. If anencephalic infants receive customary care, their solid organs usually undergo irreversible hypoxic injury during the process of dying and become unsuitable for donation by the time of death. We modified the medical care of 12 live-born anencephalic infants for one week to determine whether organ viability could be maintained and whether the criteria of total brain death could be met. Six received intensive care from birth, and six only when signs of imminent death developed. Only two infants met the criteria for total brain death within one week, and no solid organs were procured. Most organs were suitable for transplantation at birth. When intensive care was provided from birth, organ function was maintained; however, brain-stem activity ceased in only one infant within the first week. When intensive care was delayed until death was imminent, most organs were damaged to an extent that made them no longer suitable for transplantation. Our findings suggest that it is usually not feasible, with the restrictions of current law, to procure solid organs for transplantation from anencephalic infants.

Effect of antenatal and postnatal corticosteroid therapy on weight gain and head circumference growth in the nursery.

OBJECTIVE To assess the effect of antenatal and postnatal corticosteroids on head circumference growth and weight gain from birth to discharge. METHODS We conducted a retrospective analysis of non‐anomalous newborns admitted to the neonatal intensive care unit from 23 to 34 6/7 weeks of gestation. Independent variables included maternal age, race, nulliparity, poor prenatal care, multiple gestation, obstetric complications, alcohol, tocolytic drugs, smoking, illicit drugs, gestational age at birth, presentation, method of delivery, 5‐minute Apgar score < 7, surfactant use, severe intracranial hemorrhage, and length of stay. RESULTS Antenatal and postnatal corticosteroids were given in 62% and 14% of the newborns, respectively, and 10% of newborns received both. The mean (±SD) weight gain and head circumference growth in the nursery was 440 ± 582 g (n = 14,217) and 2.54 ± 3.42 cm (n = 12,808), respectively. After multivariable analysis, use of antenatal corticosteroids did not affect weight gain (3.6 ± 4.6 g) and head circumference growth (0.05 ± 0.04 cm) compared with no exposure to perinatal corticosteroids, but postnatal corticosteroids were associated with significant reductions in weight gain and head circumference growth (−120 ± 12.2 g and −0.53 ± 0.11 cm, respectively). CONCLUSIONS Antenatal corticosteroid therapy did not affect weight gain or head circumference growth in the nursery, even when used in conjunction with postnatal corticosteroid therapy.

1598 MUSCLE RELAXANTS-A POTENTIAL DANGER TO INFANTS AT RISK FOR INTRAVENTRICULAR HEMORHAGE

Goldberg recently reported an increased incidence of intraventricular hemorrhage(IVH) in infants receiving muscle relaxants(MR). The mechanism is unknown. We studied 11 infants (BW 850-2800gm) before and during administration of curare or pancuronium. The effects of an increase of 4cm. peak inspiratory pressure (↑PIP) and of leg raising(LR) were tested. Intracranial pressure(ICP) was measured. Cerebral blood flow (CBF) was assessed by a doppler technique and expressed as pulsatility index (PI=systolic-diastolic/systolic) (Bada). Our results (Mean±SD):During MR, PI decreased, consistent with an increase in apparent CBF. There was no significant change in ICP due to MR alone. However, there was a significantly greater increase in ICP during ↑PIP and LR. Both observations suggest a loss of autoregulation during MR.We conclude, muscle relaxants affect cerebrovascular dqnamics and may be dangerous in infants at risk for IVH, particularly when high PIP is required.

190 NO BURNS, NO GRADIENT - PULSE OXIMETRY, AN ALTERNATIVE TO TRANSCUTANEOUS PO 2

Continuous monitoring of oxygenation in sick newborns is essential. However, transcutaneous PO2 (tcPO2) measurements have limitations. The extremely immature infant cannot tolerate a heated electrode. Older infants, and infants with BPD have large and unpredictable skin-arterial gradients. We report pulse oximetry as a technique for continuous, non-invasive measurement of arterial oxygen saturation (SaO2). We studied 20 infants, gestational ages 28–40 weeks, ages 1–49 days. Fetal hemoglobin (Hb) determinations were made on all infants and ranged from 5–100%. SaO2 readings from the Nellcor Pulse Oximeter were compared to the SaO2 measured with an IL282 CO-Oximeter on simultaneously obtained arterial blood samples. The method of Cornellisen (Clin. Chem., 1983) was used to correct for the fictitiously elevated carboxyhemoglobin levels caused by the presence of fetal Hb. The figure shows the close correlation for the 121 samples (Y=24.45+0.72X, r=.89.). The correlation was equally good for the 3 infants greater than 1 month of age with BPD. We conclude that the pulse oximeter provides an accurate, non-invasive alternative to tcPO2 monitoring, and overcomes some of the limitations previously encountered.

HUMAN CORD AND NEWBORN BLOOD IS DECREASED IN NATURAL KILLER CELL CYTOTOXICITY IN COMPARISON WITH NORMAL ADULT

Because natural killer cell cytotoxicity (NKC) is implicated in transplant rejection and we are involved in neonatal cardiac transplantation, it is important to understand normal NKC in neonates. We studied NKC in cord and newborn (2-4 days) blood from full term normal spontaneous vaginal delivery (FTNSVD) n=40, full term cesarean section (FTC/S) n=34, preterm normal spontaneous vaginal delivery(PTNSVD) n=18 and preterm cesarean section (PTC/S) n=14, and compared these with normal adult blood (NA), X=30,(22-42 yrs). NKC was measured by a standard 4 hr 51-Cr release assay using K562 as target cells. The Students t-test was used to determine differences in NKC. The results at the 50:1 ratio were significantly different, p<0.01, between NA and both cord and newborn blood in all four groups. The slopes of the response curves for all these groups were also significantly different from NA, p<0.01. Preterm categories for cord NSVD and newborn C/S were significantly lower than their respective full term category, p<0.01. In addition, there was no significant difference between NSVD and C/S for all groups. In conclusion, cord and newborn blood in all groups studied were found to have significantly lower NKC than that of NA blood. These data provide a better understanding of normal NKC maturation in the neonate relative to transplantation and immunosuppression.