William D. Engle

Neutropenia in high-risk neonates.

To determine the usefulness of neutrophil values in diagnosing neonatal sepsis among infants at risk of neutropenia, we evaluated the pattern of sequential absolute total and immature neutrophil counts and the immature to total neutrophil (I:T) proportion over the first 5 days of life in infants with sepsis (n = 13), asphyxia neonatorum (n = 12), or delivered of mothers with pregnancy-induced hypertension (PIH) (n = 20), comparing values to references ranges previously reported by us. Neutropenia was initially present in 67% and 50% of infants with asphyxia and those whose mothers had PIH, respectively, and persisted through the first 3 postnatal days. In contrast, infants with sepsis were less likely to be neutropenic initially (38%), and neutropenia did not persist after 36 hours of age. Elevated values for the total immature neutrophil count and I:T proportion were much more likely to occur in infants with sepsis (46% and 61%, respectively) than in infants of mothers with PIH (4% and 12%) or those with asphyxia (13% and 22%). The importance of considering the perinatal history as well as the differential neutrophil count in the evaluation of neonatal neutropenia is demonstrated.

Comparison of self-directed learning versus instructor-modeled learning during a simulated clinical experience.

Background: There are no reports in the literature that compare instructor-modeled learning to self-directed learning when simulation is used. Therefore, no evidence exists to know which approach is superior. This study aims to test the hypothesis that instructor-modeled learning is more effective compared with self-directed learning during a simulated clinical experience. Methods: This is a descriptive pilot study to compare instructor-modeled learning with self-directed learning during a clinical simulated experience. Four evaluation tools were used at three time points to evaluate knowledge, self-efficacy (self confidence), and behaviors. Results: Sixteen students participated. There were no statistically significant differences between the groups on the Knowledge Assessment Test. There were significant differences between the groups in the Self-Efficacy Tool (SET) at three times (time 1: P = 0.006, time 2: P = 0.008, time 3: P = 0.012). The only significance between the groups on the Technical Evaluation Tool was time to start Albuterol. The Behavioral Assessment Tool (BAT) showed significant differences between the groups in 8 out of 10 components of the tool. A strong correlation was observed between the overall score of the BAT and the SET Score. Conclusion: Although the small sample size prohibits definitive conclusions, the data suggest that instructor-modeled learning may be more effective than self-directed learning for some aspects of learning during a clinical simulated experience.

Blood pressure in the very low birth weight neonate

Few aspects of management of very low birth weight (VLBW; <1500 g) neonates have generated as much controversy as the assessment of blood pressure (BP) and need for treatment of perceived abnormalities of this physiologic variable. The approach to this problem may differ greatly among various institutions and even among clinicians within a given center. The purpose of this manuscript is to review available information regarding physiologic determinants and measurement of BP in VLBW neonates, normative data for BP, clinical factors that may affect BP in these at-risk neonates and studies in which presumed abnormalities of BP resulted in adverse clinical outcomes. Options for treatment of low BP in VLBW neonates also will be discussed.

Evaluation of a Transcutaneous Jaundice Meter Following Hospital Discharge in Term and Near-Term Neonates

OBJECTIVES:To evaluate performance of the Minolta JM-103 Jaundice Meter (JM) as a predictor of total serum bilirubin (TSB) in outpatient neonates during the first week postnatal, and to estimate the number of TSB determinations that might be avoided in clinical use.STUDY DESIGN:In neonates evaluated posthospital discharge, JM and TSB results were compared using linear regression and a Bland–Altman plot, and predictive indices were calculated for various JM cutoff values. Utilizing the 2004 American Academy of Pediatrics (AAP) guidelines, the ability of JM to predict risk zone status was determined.RESULTS:Overall correlation between JM and TSB was 0.77 (p<0.001; n=121). When TSB was >17 mg/dl, a cutoff value for JM of 13 mg/dl had a sensitivity of 1.0, and 50% of TSB determinations would be avoided.CONCLUSIONS:JM may facilitate outpatient management of hyperbilirubinemia by reducing the number of TSB determinations required; however, it does not provide a reliable substitute for laboratory measurement of TSB.

Diuresis and respiratory distress syndrome:Physiologic mechanisms and therapeutic implications

Previous studies have suggested that spontaneous diuresis may be important to the recovery from respiratory distress syndrome in preterm infants. Daily quantification of fluid intake (1) and urine output (O) were recorded, and O/I and alveolar-arterial oxygen gradients (AaDO2) were determined for sequential eight-hour periods in 10 inborn premature infants with RDS. Sequential timed-urine-plasma collections were obtained during the first four days of life to evaluate the role of hormonal and vasoactive factors in the acute phase of RDS. Diuresis (O/I greater than 0.80) occurred at 25 to 32 hours, preceded any significant improvement in AaDO2 (which occurred at 57 to 64 hours), and was associated with a 6.2 +/- 1.4% decrease in body weight. Although there was no significant change in glomerular filtration rate, plasma AVP concentrations, or urinary excretion of AVP in the infants, there were significant decreases in both plasma concentrations and urinary excretion of 6-keto-PGF1 alpha (stable metabolite of prostacyclin) in sequential studies. These results suggest that changes in renal function or AVP may not be of primary importance in the diuresis associated with RDS, and that decreasing levels of prostacyclin, a prostaglandin that increases vascular permeability and lowers blood pressure, may have an important physiologic role.

Pulse Oximetry Screening at 4 Hours of Age to Detect Critical Congenital Heart Defects

OBJECTIVE. The purpose of this prospective study was to assess the feasibility and reliability of pulse oximetry screening to detect critical congenital heart defects in a newborn nursery. METHODS. The study was performed in a large urban hospital with an exclusively inborn population. Stable neonates who had a gestational age of ≥35 weeks and birth weight of ≥2100 g and in whom a critical congenital heart defect was not suspected were admitted to the newborn nursery. When the 4-hour pulse oximetry reading was <96%, pulse oximetry was repeated at discharge, and when the pulse oximetry reading remained at persistently <96%, echocardiography was performed. RESULTS. Of 15299 admissions to newborn nursery during the 12-month study period, 15233 (99.6%) neonates were screened with 4-hour pulse oximetry. Pulse oximetry readings were ≥96% for 14374 (94.4%) neonates; 77 were subsequently evaluated before discharge for cardiac defects on the basis of clinical examination. Seventy-six were normal, and 1 had tetralogy of Fallot with discontinuous pulmonary arteries. Pulse oximetry readings at 4 hours were <96% in 859 (5.6%); 768 were rescreened at discharge, and 767 neonates had a pulse oximetry reading at ≥96%. One neonate had persistently low pulse oximetry at discharge; echocardiography was normal. Although 3 neonates with a critical congenital heart defect had a 4-hour pulse oximetry reading of <96%, all developed signs and/or symptoms of a cardiac defect and received a diagnosis on the basis of clinical findings, not screening results. CONCLUSIONS. All neonates with a critical congenital heart defect were detected clinically, and no cases of critical congenital heart defect were detected by pulse oximetry screening. These results indicate that pulse oximetry screening does not improve detection of critical congenital heart defects above and beyond clinical observation and assessment. Our findings do not support a recommendation for routine pulse oximetry screening in seemingly healthy neonates.

Urinary arginine vasopressin: pattern of excretion in the neonatal period

ABSTRACT. The pattern of arginine vasopressin (AVP) secretion in the immediate neonatal period is unclear. Plasma concentrations of AVP are reflected by its urinary excretion, thus providing a noninvasive method for studying the pattern of AVP release in the neonate. In these studies, we determined the pattern of urinary AVP excretion (μU/ mg creatinine) during the first 2-4 days after birth in 78 neonates, 53 of whom had various prenatal and/or neonatal complications. In well term (n = 12) and preterm (n =13) infants mean urinary AVP excretion decreased gradually during the first 24-36 h after birth. Although term and preterm infants with perinatal asphyxia had highest initial levels of urinary AVP (>200 μU/mg creatinine) and a significant negative correlation with the 1-min Apgar score was obtained, their pattern of excretion was similar to respective controls. After delivery, elevated values for urinary AVP excretion were found among infants with neonatal courses complicated by intracranial hemorrhage, hypoxic encephalopathy, and pneumothorax. Urine osmolality did not correlate linearly with urinary AVP levels, but rather attained a maximum value of ˜400 mosmol/kg at urinary AVP levels <200 μU/mg creatinine and then plateaued. It is concluded that the decrease in urinary AVP excretion observed soon after birth generally reflects diminution of the hypersecretion of AVP during parturition; neonates with evidence of intrapartum asphyxia initially have increased urinary AVP excretion; however, the pattern of excretion is similar to normal infants. During the neonatal period insults such as pneumothorax and intracranial hemorrhage may cause hypersecretion of this hormone.

Capillary refill time is an unreliable indicator of cardiovascular status in term neonates.

PURPOSEDecisions regarding the need for volume replacement in neonates often are made in the immediate newborn period. Capillary refill time (CRT) is used as an indicator of circulatory status; however, recent data show that CRT varies considerably with age, ambient and skin temperature, anatomical site of measurement, and duration of pressure. The purpose of this study was to (1) examine the relationship between CRT and heart rate (HR) and blood pressure (BP) in term neonates, and (2) evaluate the differences among CRT values measured at 3 body sites and with varying duration of cutaneous pressure. DESIGNThis was a prospective, cross-sectional, correlational study. SUBJECTSForty-two appropriate-weight-for-gestational-age (AGA) neonates with birthweights, (M = 3407; SD = ± 540 g), gestational ages (M = 39 weeks; SD = ± 1 week), and sex (21 males, 21 females). Infants had no history of perinatal distress or maternal chorioamnionitis. METHODSEach neonate was studied prospectively 1 to 4 hours after birth. The infants were clothed with only a diaper and evaluated on a radiant warmer bed set to achieve an axillary temperature of 36.5° to 37.0°C. Capillary refill time was measured with a digital stopwatch at 3 sites: volar surface of finger (F), plantar surface of heel (H), and lower sternum (St), using brief (1- to 2-second) and extended (3- to 4-second) pressure. Heart rate was auscultated and counted for 60 seconds, and BP was measured by oscillometry. Relationships among variables were assessed by Pearson correlation coefficient, analysis of variance, and multiple regression analysis. The Bonferroni correction for multiple comparisons was applied. MAIN OUTCOME MEASURESCapillary refill time, blood pressure, and heart rate. PRINCIPAL RESULTSThere was no significant site variation for CRT for either brief (2.4 ± 0.6 to 2.9 ± 1.0 seconds) or extended (3.8 ± 0.8 to 4.3 ± 0.8 seconds) pressure. However, regardless of site, CRT was greater when extended versus brief pressure was used (P < 0.001). There were no significant correlations between HR and CRT. There was a moderate, direct relationship between BP and CRT observed in the following anatomic sites: (1) sternum/extended pressure and systolic BP (SBP), diastolic BP, and mean BP (r = 0.35, P = 0.02; r = 0.49, P = 0.001; and r = 0.43, P = 0.005, respectively); (2) sternum/brief pressure and SBP (r = 0.31, P = 0.05); and (3) finger/extended pressure and SBP (r = 0.30, P = 0.05). CONCLUSIONSAn unanticipated moderate, direct correlation between BP and CRT was observed; prolongation of CRT occurred with elevated blood pressure. This finding may have been secondary to increased circulating vasoactive substances in the newborn period; measurement of these substances was beyond the scope of this study. In addition, CRT was highly dependent on the duration of cutaneous pressure, regardless of the site. These 2 findings indicate that CRT may be an unreliable indicator of cardiovascular status in the term neonate during the first 4 hours after birth.

Transcutaneous Bilirubin Nomograms: A Systematic Review of Population Differences and Analysis of Bilirubin Kinetics

OBJECTIVES To compare available nomograms in the literature defining trends in bilirubin levels across populations with different risk factor profiles and to study a mathematical bilirubin kinetics model describing the natural course of jaundice and the bilirubin rate of rise needed to cross percentile curves. DATA SOURCES We searched PubMed for publications between March 1999 and March 2009 that created transcutaneous nomograms. We performed the same search among abstracts presented in the past 2 years at meetings of the Pediatric Academic Societies or the European Society for Paediatric Research. STUDY SELECTION Inclusion criteria were gestational age of at least 35 weeks among study subjects, the use of an electronic transcutaneous bilirubinometer, and creation of a nomogram based on hour-specific bilirubin values. Four articles met the selection criteria. DATA EXTRACTION Jaundice risk factors were analyzed, and raw data were analyzed using nonlinear regression to describe trends in bilirubin levels and kinetics. The bilirubin exaggerated rate of rise needed to cross percentile curves was calculated. DATA SYNTHESIS Significant differences in bilirubin values exist across populations, and there is substantial variability in rates of rise. Hispanic neonates demonstrate higher rates of rise and later plateaus. Bilirubin rates of rise tend to plateau and become null (equilibrium between bilirubin production and elimination) at about 96 hours of life. Rates of rise needed to cross percentile curves decrease over time but are lower (approximately 0.11 mg/dL/h [to convert bilirubin level to micromoles per liter, multiply by 17.104]) in the first 48 hours of life than previously thought. CONCLUSIONS Transcutaneous bilirubin levels plateau and then decrease after about 96 hours of life in healthy neonates, with some differences across populations. A bilirubin rate of rise higher than in the previous period implies that bilirubin production exceeds elimination and indicates high risk for subsequent hyperbilirubinemia in neonates.

Determinants of blood pressure in very low birth weight neonates: lack of effect of antenatal steroids

OBJECTIVES To define the range of normal blood pressures (BP) for very low birth weight (VLBW;</=1500 g) neonates and to study perinatal variables affecting BP measurements after birth, including the effects of antenatal steroids. STUDY DESIGN Antenatal steroids were rarely administered at Parkland Memorial Hospital before May 1994, permitting us to establish a cohort of VLBW neonates exposed to antenatal steroids [n=70, 1166+/-253 (S.D.) g, and 28.7+/-2.1 weeks] who were matched with neonates delivered during the prior year (n=46, 1100+/-241 g, 28.9+/-1.8 weeks). Maternal and neonatal charts were abstracted for pertinent data, and neonatal BP measurements (determined directly when an arterial catheter was available or indirectly by the oscillometric method) were extracted every 3 h for the first 12 h and every 6 h until 72 h postnatal. RESULTS Antenatal steroids did not affect BP immediately after birth or for the subsequent 72 h postnatal. Therefore, data from all neonates </=1500 g were combined and the pattern of BP change over 72 h postnatal assessed. Systolic, diastolic and mean BP increased (P<0.001) 33%, 44% and 38%, respectively, during the first 72 h. Although neonates weighing </=1000 g and 1001-1500 g demonstrated gradual increases (P<0.001) in systolic, diastolic and mean BP by 72 h, values were consistently lower (P<0.01) in neonates </=1000 g. Of interest, only 11 neonates (9.5%) were treated for clinical hypotension. CONCLUSIONS In VLBW neonates antenatal steroids do not modify BP measurements either immediately after birth or the 30-40% rise occurring in the first 72 h postnatal. Further, BP is developmentally regulated and is gestationally and birth weight dependent. These data provide additional insight into assessing the need for treating hypotension.