Prediction of hyperbilirubinemia in near-term and term infants

OBJECTIVE

The purpose of this study was to determine whether end-tidal carbon monoxide (CO) corrected for ambient CO (ETCOc), as a single measurement or in combination with serum total bilirubin (STB) measurements, can predict the development of hyperbilirubinemia during the first 7 days of life.

METHODS

From nine multinational clinical sites, 1370 neonates completed this cohort study from February 20, 1998 through February 22, 1999. Measurements of both ETCOc and STB were performed at 30+/-6 hours of life; STB also was measured at 96+/-12 hours and subsequently following a flow diagram based on a table of hours of age-specific STB. An infant was defined as hyperbilirubinemic if the hours of age-specific STB was greater than or equal to the 95th percentile as defined by the table at any time during the study.

RESULTS

A total of 120 (8.8%) of the enrolled infants became hyperbilirubinemic. Mean STB in breast-fed infants was 8.92+/-4.37 mg/dl at 96 hours versus 7.63+/-3.58 mg/dl in those fed formula only. The mean ETCOc at 30+/-6 hours for the total population was 1.48+/-0.49 ppm, whereas those of nonhyperbilirubinemic and hyperbilirubinemic infants were 1.45+/-0.47 and 1.81+/-0.59 ppm, respectively. Seventy-six percent (92 of 120) of hyperbilirubinemic infants had ETCOc greater than the population mean. An ETCOc greater than the population mean at 30+/-6 hours yielded a 13.0% positive predictive value (PPV) and a 95.8% negative predictive value (NPV) for STB > or =95th percentile. When infants with STB > or =95th percentile at <36 hours of age were excluded, the STB at 30+/-6 hours yielded a 16.7% PPV and a 98.1% NPV for STB >75th percentile. The combination of these two measurements at 30+/-6 hours (either ETCOc more than the population mean or STB >75th percentile) had a 6.4% PPV with a 99.0% NPV.

CONCLUSIONS

This prospective cohort study supports previous observations that measuring STB before discharge may provide some assistance in predicting an infant's risk for developing hyperbilirubinemia. The addition of an ETCOc measurement provides insight into the processes that contribute to the condition but does not materially improve the predictive ability of an hours of age-specific STB in this study population. The combination of STB and ETCOc as early as 30+/-6 hours may identify infants with increased bilirubin production (eg, hemolysis) or decreased elimination (conjugation defects) as well as infants who require early follow-up after discharge for jaundice or other clinical problems such as late anemia. Depending on the incidence of hyperbilirubinemia within an institution, the criteria for decision making should vary according to its unique population.

Clinical use of pulmonary mechanics and waveform graphics

Decades of research have led to the understanding of neonatal pulmonary physiology and have influenced the clinical care that neonatologists provide to the sick newborn. Advances in microprocessor technology have allowed for clinical access of the research-based measurements of neonatal pulmonary functions. These evaluations are not only the integrated evaluation of the three primary vectors of respiration (driving pressure, air flow, and volume measured over time) but also values calculated by known physiologic equations. Clinical use of these data may not only be relevant and helpful in the bedside management, but also provides a uniquely objective and research-oriented data collection for individual newborns.

Prediction of hyperbilirubinemia in near-term and term infants

OBJECTIVE

The purpose of this study was to determine whether end-tidal carbon monoxide (CO) corrected for ambient CO (ETCOc), as a single measurement or in combination with serum total bilirubin (STB) measurements, can predict the development of hyperbilirubinemia during the first 7 days of life.

METHODS

From 9 multinational clinical sites, 1370 neonates completed this cohort study from February 20, 1998, through February 22, 1999. Measurements of both ETCOc and STB were performed at 30 +/- 6 hours of life; STB also was measured at 96 +/- 12 hours and subsequently following a flow diagram based on a table of hours of age-specific STB. An infant was defined as hyperbilirubinemic if the hours of age-specific STB was greater than or equal to the 95th percentile as defined by the table at any time during the study.

RESULTS

A total of 120 (8.8%) of the enrolled infants became hyperbilirubinemic. Mean STB in breastfed infants was 8.92 +/- 4.37 mg/dL at 96 hours versus 7.63 +/- 3.58 mg/dL in those fed formula only. The mean ETCOc at 30 +/- 6 hours for the total population was 1.48 +/- 0.49 ppm, whereas those of nonhyperbilirubinemic and hyperbilirubinemic infants were 1.45 +/- 0.47 ppm and 1.81 +/- 0.59 ppm, respectively. Seventy-six percent (92 of 120) of hyperbilirubinemic infants had ETCOc greater than the population mean. An ETCOc greater than the population mean at 30 +/- 6 hours yielded a 13.0% positive predictive value (PPV) and a 95.8% negative predictive value (NPV) for STB >/=95th percentile. When infants with STB >95th percentile at <36 hours of age were excluded, the STB at 30 +/- 6 hours yielded a 16.7% PPV and a 98.1% NPV for STB >75th percentile. The combination of these 2 measurements at 30 +/- 6 hours (either ETCOc more than the population mean or STB >75th percentile) had a 6.4% PPV with a 99.0% NPV. Conclusions. This prospective cohort study supports previous observations that measuring STB before discharge may provide some assistance in predicting an infant's risk for developing hyperbilirubinemia. The addition of an ETCOc measurement provides insight into the processes that contribute to the condition but does not materially improve the predictive ability of an hours of age-specific STB in this study population. The combination of STB and ETCOc as early as 30 +/- 6 hours may identify infants with increased bilirubin production (eg, hemolysis) or decreased elimination (conjugation defects) as well as infants who require early follow-up after discharge for jaundice or other clinical problems such as late anemia. Depending on the incidence of hyperbilirubinemia within an institution, the criteria for decision making should vary according to its unique population.

Managing the assessment of neonatal jaundice: importance of timing

In view of the limitations in the accurate visual assessment of jaundice and its potential role as a predictive vector for serious neurologic sequelae, we propose that a universal screening of bilirubin be considered concurrent to the routine pre-discharge metabolic screening. Universal bilirubin screening in the term and near-term newborns when plotted on "Hour-specific Bilirubin Nomogram" in lieu of the usual "day-specific" value will predict the high-risk and the low-risk groups and facilitate cost-effective and individualized follow-up of those babies at risk. A percentile based bilirubin nomogram for the first week of age was constructed from hour-specific pre- and post-discharge bilirubin values of 2840 healthy term and near-term babies. The accuracy of the pre-discharge bilirubin values was determined as a predictive vector. Pre-discharge (18-72 hours age), 6.1% of the study population had bilirubin values in the high-risk zone (> 95th percentile). Of these, 39.5% remained in that zone (likelihood ratio ¿LR¿ = 14.08). Pre-discharge, 32.1% of the study population had bilirubin values in the intermediate risk zone (40-75th percentiles). In a clinically significant minority of these babies (6.4%), the post-discharge values moved to the high-risk zone (L-R = 3.2 for the move from the upper-intermediate zone and 0.48 from the lower-intermediate zone). In the remainder 61.8% of the population who were identified to be at low risk, there was no measurable risk for significant hyperbilirubinemia (L-R = 0). The bilirubin nomogram can predict which infant is at high, intermediate, and low risk for subsequent excessive hyperbilirubinemia and allows for the individualized follow-up of these high-risk babies with particular attention to those who may need evaluation and intervention. Whereas, identification of the low risk group allows for a less intense bilirubin follow-up and in whom a visual check by an experienced care-provider may suffice.

Noninvasive measurement of total serum bilirubin in a multiracial predischarge newborn population to assess the risk of severe hyperbilirubinemia

BACKGROUND

Jaundice in near-term and term newborns is a frequent diagnosis that may prompt hospital readmission in the first postnatal week. Hyperbilirubinemia, when excessive, can lead to potentially irreversible bilirubin-induced neurotoxicity. Predischarge risk assessment (at 24-72 hours of age) for subsequent excessive hyperbilirubinemia is feasible by a laboratory-based assay of total serum bilirubin (TSB). Hypothesis. Noninvasive, transcutaneous, point-of-care measurement of transcutaneous bilirubin (TcB) predischarge by multiwavelength spectral analysis, using a portable BiliCheck device (SpectRx Inc, Norcross, GA), is clinically equivalent to measurement of TSB in a diverse, multiracial term and near-term newborn population and predictive of subsequent hyperbilirubinemia.

METHODOLOGY

We evaluated a hand-held device that uses multiwavelength spectral reflectance analysis to measure TcB (BiliCheck). The study population (490 term and near-term newborns) was racially diverse (59.1% white, 29.5% black, 3.46% Hispanic, 4.48% Asian, and 3.46% other) and was evaluated at 2 separate institutions using multiple (11) devices. The postnatal age ranged from 12 to 98 hours and the ranges of birth weights and gestational ages were 2000 to 5665 g and 35 to 42 weeks, respectively. All transcutaneous evaluations were performed contemporaneously and paired with a heelstick TSB measurement. All TSB assays were performed by high performance liquid chromatography, as well as by diazo dichlorophenyldiazonium tetrafluoroborate techniques.

RESULTS

TSB values ranged from .2 to 18.2 mg/dL (mean +/- standard deviation: 7.65 +/- 3.35 mg/dL). The overall correlation of TSB (by high performance liquid chromatography technique) to TcB (by BiliCheck devices) was linear and statistically significant (r =.91; r(2) =.83; TcB =.84; TSB = +.75; standard error of regression line = 1.38; P <.001; n = 490 infants; 1788 samples). Similar regression statistics were evident in subset populations categorized by race (white: r =.91 [n = 289 infants]; black: r =.91 [n = 145 infants]) as well as by gestation (term: r =. 91 [n = 1625 samples]; near-term: r =.89 [n = 163 samples]). Intradevice precision was determined to be.59 mg/dL (2-3 measurements per infant with 1 device; n = 210 infants; 510 samples in a separate subset). Interdevice evaluation of 11 devices determined the precision to be.68 mg/dL (2-4 devices used for measurements per patient). In 23 of 419 of the study population infants who were in the 24- to 72-hour age range, the predischarge TSB values designated them to be at high risk for subsequent excessive hyperbilirubinemia (above the 95th percentile track on the hour-specific bilirubin nomogram). For these infants, the paired BiliCheck TcB values were all above the 75th percentile track (negative predictive value = 100%; positive predictive value = 32. 86%; sensitivity = 100%; specificity = 88.1%; likelihood ratio = 8. 43).

CONCLUSIONS

Our data demonstrate the accuracy and reproducibility of the predischarge BiliCheck measurements in term and near-term newborn infants of diverse races and ethnicities. Infants with predischarge BiliCheck values above the 75th percentile of hour-specific TSB values on the bilirubin nomogram may be considered to be at high risk for subsequent excessive hyperbilirubinemia. Further studies are needed to assess the efficacy of this technique in preterm infants, those undergoing phototherapy, and those with TSB values of >/=15 mg/dL (>/=256 micromol/L).

Inhaled nitric oxide in premature neonates with severe hypoxaemic respiratory failure: a randomised controlled trial

BACKGROUND

Inhaled nitric oxide improves oxygenation and lessens the need for extracorporeal-membrane oxygenation in full-term neonates with hypoxaemic respiratory failure and persistent pulmonary hypertension, but potential adverse effects are intracranial haemorrhage and chronic lung disease. We investigated whether low-dose inhaled nitric oxide would improve survival in premature neonates with unresponsive severe hypoxaemic respiratory failure, and would not increase the frequency or severity of intracranial haemorrhage or chronic lung disease.

METHODS

We did a double-blind, randomised controlled trial in 12 perinatal centres that provide tertiary care. 80 premature neonates (gestational age < or = 34 weeks) with severe hypoxaemic respiratory failure were randomly assigned inhaled nitric oxide (n=48) or no nitric oxide (n=32, controls). Our primary outcome was survival to discharge. Analysis was by intention to treat. We studied also the rate and severity of intracranial haemorrhage, pulmonary haemorrhage, duration of ventilation, and chronic lung disease at 36 weeks' postconceptional age.

FINDINGS

The two groups did not differ for baseline characteristics or severity of disease. Inhaled nitric oxide improved oxygenation after 60 min (p=0.03). Survival at discharge was 52% in the inhaled-nitric-oxide group and 47% in controls (p=0.65). Causes of death were mainly related to extreme prematurity and were similar in the two groups. The two groups did not differ for adverse events or outcomes (intracranial haemorrhage grade 2-4, 28% inhaled nitric oxide and 33% control; pulmonary haemorrhage 13% and 9%; chronic lung disease 60% and 80%).

INTERPRETATION

Low-dose inhaled nitric oxide improved oxygenation but did not improve survival in severely hypoxaemic premature neonates. Low-dose nitric oxide in the most critically ill premature neonates does not increase the risk of intracranial haemorrhage, and may decrease risk of chronic lung injury.

Predictive ability of a predischarge hour-specific serum bilirubin for subsequent significant hyperbilirubinemia in healthy term and near-term newborns

OBJECTIVE

To assess the predictive ability of a universal predischarge serum bilirubin measurement to screen for risk of subsequent significant hyperbilirubinemia in the direct Coombs negative healthy term and near-term newborn during the first postnatal week.

METHODS

Total serum bilirubin (TSB) levels were obtained at the time of the routine metabolic screen in all term and near-term newborns cared for in the Pennsylvania Hospital Well Baby Nursery (n = 13 003). Postnatal age (in hours) at the time of TSB measurement was recorded. A percentile-based bilirubin nomogram for the first week was constructed from hour-specific predischarge and postdischarge TSB values of newborns (n = 2840; median BW = 3230 g and median gestational age = 39 weeks) who met classification criteria for healthy newborns (excluding those with a positive direct Coombs test or those requiring phototherapy before age 60 hours) and who were enrolled in a hospital supervised home or outpatient follow-up program. The accuracy of the predischarge TSB as a predictor of subsequent degree of hyperbilirubinemia was determined.

RESULTS

The study patients in the nomogram were racially diverse. Nearly 60% were breastfed. Predischarge, 6.1% of the study population (172/2840) had TSB values in the high-risk zone (>/=95th percentile) at 18 to 72 hours; of these, 39.5% (68/172) remained in that zone (likelihood ratio [LR] = 14.08, sensitivity = 54%; specificity = 96.2%, probability = 39.5%). Predischarge, 32.1% of the population (912/2840) had TSB values in the intermediate-risk zone. In a clinically significant minority of these newborns (58/912 or 6.4%), the postdischarge TSB moved into the high-risk zone (LR of this move: 3.2 from the upper-intermediate zone and.48 from the lower-intermediate risk zone). The predischarge TSB in 61.8% of the newborns (1756/2840) was in the low-risk zone (<40th percentile) and there was no measurable risk for significant hyperbilirubinemia (LR = 0, sensitivity = 100%; specificity = 64.7%; probability = 0%).

CONCLUSIONS

An hour-specific TSB before hospital discharge can predict which newborn is at high, intermediate or low risk for developing clinically significant hyperbilirubinemia (specifically defined as TSB levels >/=95th percentile for age in hours). Risk designation and subsequent increases or decreases of in TSB can be easily monitored on an hour-specific percentile based predictive bilirubin nomogram. A predischarge TSB measured as a universal policy would facilitate targeted intervention and follow-up in a safe, cost-effective manner. In conjunction with bilirubin practice parameter of the American Academy of Pediatrics, it could reduce the potential risk for bilirubin-induced neurologic dysfunction.

Perinatal bacterial infection: an update

This article reviews the current trends in the evaluation and management of bacterial infection involving the uterus, placenta, membranes, amniotic fluid, and fetus occurring near the time of birth. The discussion includes information regarding risk, incidence, pathophysiology, bedside diagnosis, interventional options including antibiotics, corticosteroids, fetal monitoring, and delivery, and possible preventive measures which affect the outcome. The adequate evaluation and management of perinatal infection requires a team approach with obstetricians and pediatricians. Clinical screening is useful in developing the diagnosis, but amniotic fluid evaluation remains the proposed gold standard. The role of cytokines is becoming increasingly important, as is seen in the association of IL-6 with positive amniotic fluid cultures and periventricular leukomalacia. Prompt recognition and management of the pregnancy affected by infection can improve perinatal outcomes. A management protocol is presented to help structure the approach to suspected infection. Premature delivery due to perinatal infection may be preventable.

Guidelines for management of the jaundiced term and near-term infant

Factors believed to have contributed to the reemergence of kernicterus in the United States during the 1990's are discussed: these include decreased concern about toxicity of bilirubin in term and near-term infants, increased prevalence of breastfeeding, and increasingly shortened postnatal hospital stays. The rationale for a universal predischarge bilirubin measurement at the time of the routine predischarge metabolic screen is presented: the hour-specific level of bilirubin at discharge, plotted on an Hour-Specific Bilirubin Nomogram, improves prediction of risk of excessive jaundice postdischarge and facilitates safe, cost-effective follow-up. This minimizes repeat bilirubin measurements and maximizes recognition of confounding variables and risk of hyperbilirubinemia so that timely, minimally invasive, preventive therapy can be instituted if needed.

Respiratory and systemic effects of inhaled dexamethasone on ventilator dependant preterm infants at risk for bronchopulmonary dysplasia

Short-term inhaled dexamethasone therapy was evaluated in a double blind placebo controlled trial in 36 ventilator dependent preterm neonates (BW < 1500 gm, postnatal age > 7 days) who were at risk for bronchopulmonary dysplasia. Pulmonary and systemic effects were compared at early (day 3), late (7-10 days) and post (14 days after initiation) phases of therapy. Airflow mechanics improved as demonstrated by a net 101% improvement in pulmonary resistance (a decrease from 139 to 101 cm H2O/L/s in the dexamethasone treated infants as compared to an increase from 153 to 267 cmH2O/L/s in the placebo treated infants during the early phase of therapy); this was associated with a 45% increase in inspiratory airflow (1.29 +/- 0.43 to 1.87 +/- 0.978 L/min; p < 0.01), and 37% increase in expiratory airflow. These changes resulted in a significant reduction in the work of breathing such that the mean tidal driving pressure significantly decreased from 13.6 cmH2O to 9.4 cm H2O with inhaled steroid administration. Though the brief duration of therapy did not result in cessation of ventilatory support, the level of support was significantly reduced (decreased values of oxygen supplementation, mean airway pressure and oxygenation index and increased ventilatory efficiency index). The inhaled dexamethasone therapy was also associated with systemic absorption of the drug as evidenced by transient but apparently reversible reduction in serum cortisol levels. No systemic side effects of hypertension, hyperglycemia or nosocomial sepsis were observed. These data demonstrate beneficial effects of short-term inhaled dexamethasone on the resistive airflow properties of preterm infants at risk for BPD and may provide adjunctive means to facilitate weaning in the ventilator dependent neonates.

Gastrointestinal and renal blood flow velocity profile in neonates with birth asphyxia

Pulsed Doppler ultrasound blood flow profiles were studied, before the initiation of enteral feedings, in 23 neonates with birth asphyxia. We observed a significant direct correlation between the reduction of peak velocity and increased resistance in the renal and superior mesenteric arteries to the severity of asphyxia (r = 0.8; p < 0.05); the changes often persisted up to 3 days of age. Longitudinal evaluation of flow in these vessels might help to time the initiation of enteral nutrition in neonates with asphyxia.

Role of positive end-expiratory pressure changes on functional residual capacity in surfactant treated preterm infants

Both surfactant replacement and positive end-expiratory pressure (PEEP) increase lung volume in infants with respiratory distress syndrome (RDS). We measured pulmonary mechanics and functional residual capacity (FRC) in 21 preterm infants with RDS, > 48 hr post-surfactant therapy (BW, 1,168 +/- 441 g; GA, 28.3 +/- 2.8 weeks; postnatal age, 3-7 days). A non-linear but significant increase in mean FRC was noted as PEEP increased from 2 to 5 cmH2O: 18.4 +/- 4.7 mL/kg at 2 cmH2O; 19.7 +/- 4.3 mL at 3 cmH2O; 22.6 +/- 5.5 ml/kg at 4 cmH2O; and 26.2 +/- 6.2 mL/kg at 5 cmH2O (P < 0.01). Because of the synergistic combined effect on lung volume, surfactant treated neonates should be weaned cautiously from PEEP during ventilatory management. Our study also suggests that the occurrence of inadvertent end-distending pressure during FRC measurement in the ventilated neonate lead to erroneous results.

Influence of head-neck posture on airflow and pulmonary mechanics in preterm neonates

The influence of head-neck posture (neutral, 15 degrees, 30 degrees, and 45 degrees extension and flexion) on airflow and pulmonary mechanics was evaluated in 10 spontaneously breathing healthy preterm neonates (mean +/- SD; birth weight, 1.32 +/- 0.23 kg; gestational age, 29.4 +/- 2.4 weeks; study age, 36.6 +/- 1.6 weeks) who had had respiratory distress syndrome. Head-neck postures were quantified using specially constructed wooden wedges. Airflow was measured by a pneumotachometer via face mask. Lung compliance (CL) and resistance (RL) were measured using an esophageal balloon. Airflow interruption was designated as mild (10-40%), moderate (40-80%), and severe (> 80-100%) decrease of airflow. At neutral head-neck posture, 42.8 +/- 7.5% SEM of breaths had airflow interruption (71.4% mild, 19.9% moderate, 8.7% severe). There was no significant change with 15 degrees and 30 degrees head-neck flexion and extension. However, at 45 degrees flexion the overall incidence of airflow interruption (77.3 +/- 4.8%, P < 0.05) and RL (86.6 +/- 6.7 vs. 64.2 +/- 3.9 cmH2O/L/s, mean +/- SEM; P < 0.05) significantly increased. Extension to 45 degrees caused severe airflow interruption and increased RL in some infants, but no statistically significant change for the whole group. The incidence of severe airflow interruption significantly increased (P < 0.05) from 8.7% at neutral head-neck posture to 26.3% at hyperflexion (45 degrees). No changes in CL were observed. We conclude that minor (15-30 degrees) deviations from neutral neck posture are insignificant, whereas hyperflexion, and in some infants, hyperextension, can significantly affect airflow and pulmonary mechanics.

Effect of enteral gavage feeding rate on pulmonary functions of very low birth weight infants

To compare the effects of intermittent and continuous feedings on pulmonary function, we studied 24 very low birth weight neonates (mean +/- SD: birth weight, 1.2 +/- 0.3 kg; gestational age, 30.5 +/- 1.1 weeks) at 2 to 4 weeks of age. All infants had a previous diagnosis of respiratory distress syndrome but no subsequent diagnosis of bronchopulmonary dysplasia. Pulmonary mechanics were measured before the beginning of intermittent or continuous feedings and 10 minutes after each meal was completed. Twelve infants were randomly assigned to intermittent and 12 to continuous feedings. These infants had similar birth weight, gestational age, study age, and baseline lung function. After intermittent feedings, there was a significant decrease in tidal volume (38%), minute ventilation (44%), and dynamic compliance (28%), whereas pulmonary resistance increased significantly (100%). In comparison, the pulmonary function data remained unchanged after continuous feedings. These data demonstrate that intermittent feeding of very low birth weight infants can lead to airflow and respiratory instability. These adverse effects appear to be dependent on the rate that feedings are administered. A slower pace of feeding may be more advantageous for infants prone to respiratory instability.

Long-term pulmonary consequences of respiratory distress syndrome in preterm infants treated with exogenous surfactant

The pulmonary outcome for preterm infants 1 year after synthetic surfactant replacement for respiratory distress syndrome was assessed by examining their pulmonary status and the results of pulmonary function tests. A total of 47 infants were followed: 13 infants mean +/- SD: birth weight, 1960 +/- 616 gm; gestation, 32 +/- 1.1 weeks) had been assigned to the placebo group and 34 (birth weight = 1890 +/- 530 gm; gestation = 32 +/- 2.5 weeks) to surfactant treatment. The infants were examined at 3 to 6 months of age (n = 45) and at 9 to 12 months of age (n = 36). There were no significant differences between the two groups in predisposing clinical conditions that would lead to chronic lung disease. The infants had similar patterns of growth, respiratory-related illness, and need for theophylline therapy, diuretic therapy, or both. None had hypoxemia by pulse oximetry. Mean (+/- SEM) values for pulmonary mechanics and energetics in surfactant-treated infants were significantly (p < 0.01) lower for total pulmonary resistance in late infancy (57.7 +/- 11.7 vs 35.3 +/- 4.6 cm H2O/L per second). Lower values (mean +/- SEM) of resistive work of breathing were also measured in the surfactant-treated group (60.7 +/- 12.0 vs 38.2 +/- 3.6 gm-cm/kg per breath). The dynamic pulmonary compliance values were in the low-normal range for both groups, and the mean (+/- SEM) peak-to-peak esophageal pressure values were elevated (11.47 +/- 2.26 cm H2O in the placebo group; 9.24 +/- 0.69 cm H2O in the surfactant group). Forced expiratory flow measurements in late infancy demonstrated significant (p < 0.01) improvement in expiratory reserves and reduced evidence of airflow obstruction in the surfactant-treated infants (peak flow (mean +/- SEM): 287.1 +/- 69 vs 396.9 +/- 27 ml/sec; forced expiratory flow (mean +/- SEM) at functional residual capacity: 56.3 +/- 7.5 vs 83.4 +/- 19.5 ml/sec). No significant differences in pulmonary functions were noted in early infancy. These data suggest that surfactant replacement for respiratory distress syndrome may be associated with beneficial long-term effects on the resistive airflow properties of larger preterm infants.

Evaluation of pulmonary functions during pressure-limited manual ventilation in preterm neonates

Manual ventilation (MAV) or handbagging is a frequent and often life-saving procedure for neonates; however, few studies allow for an objective evaluation of techniques or possible risks. We compared parameters of ventilation and pulmonary mechanics obtained during routine pressure-limited MAV to those obtained during spontaneous breathing (SPB) in the same infant at approximately the same time. We selected 20 preterm neonates in the recovery phase of respiratory distress syndrome who received periodic MAV and were capable of optimum spontaneous minute ventilation (> 300 mL/kg/min). During MAV compared to SPB we measured higher tidal volume (8.1 +/- 0.5 SE vs. 5.4 +/- 0.4 SE mL/kg, P < 0.001), lower total pulmonary compliance (0.65 +/- 0.05 vs. 1.16 +/- 0.11 SE mL/cmH2O, P < 0.001), end-inspiratory compliance, higher pulmonary resistance (121 +/- 11 vs. 61 +/- 7 SE cmH2O/L/s, P < 0.001) and higher peak inspiratory airflow (2.8 +/- 0.2 vs. 1.6 +/- 0.1 L/s, P < 0.001). Inspiratory time (Ti) was consistently longer during MAV (0.49 +/- 0.02 vs. 0.36 +/- 0.02 SE, P < 0.001) such that during MAV the difference between actual Ti and minimal effective Ti (fivefold inspiratory time constant) was larger (0.29 +/- 0.03 vs. 0.13 +/- 0.03 s, P < 0.05). Our study suggests that operator-dependent ventilatory variables such as tidal volume, inspiratory time, frequency, and airflow need to be further evaluated in order to develop standardized guidelines for the safe administration of MAV. Until then the ventilator used for brief or augmented ventilatory support is a reasonable alternative to administering MAV by inconsistent standards.

Adaptive control of inspired oxygen delivery to the neonate

Adaptive adjustment of inspired oxygen (FIO2), based on a desired percent arterial hemoglobin saturation (SO2) was achieved by on-line bedside control of the oxygen concentration delivered to the neonate. Fourteen infants with bronchopulmonary dysplasia (BW, 860 +/- 80 g; GA, 26 +/- 1 weeks; study age, 41 +/- 8 days) receiving oxygen-air mixtures by hood were studied. The desired range of SO2 from 92 to 96% with a target value of 95% was determined by pulse oximetry and maintained with adjustment of FIO2 using three modes: 1) standard neonatal intensive care protocol with oxygen delivery evaluated at 20 minutes intervals; 2) bedside manual control with FIO2 manipulation every 2 to 5 minutes; and 3) adaptive control with on-line adjustment of FIO2 according to a specifically designed adaptive program. Each study period was of 40 minute duration. SO2 values within a steady 94 to 96% range was achieved for 54% of the time with standard protocol, compared to 69% (P less than 0.01) with bedside manual control and 81% (P less than 0.01) with adaptive control. In addition, fluctuations in SO2 values and overshoots were less apparent with adaptive control of oxygen delivery. These data describe adaptive FIO2 control as an efficient alternative technique for achieving a stable desired range of oxygenation in neonates.

Alpha-adrenergic bronchoprovocation in neonates with bronchopulmonary dysplasia

Ophthalmic administration of phenylephrine caused decreased pulmonary compliance, tidal volume, and peak airflow values in infants with bronchopulmonary dysplasia but not in control infants. The alpha-adrenergic effects of phenylephrine may aggravate the bronchospastic component of bronchopulmonary dysplasia.

Long-term pulmonary consequences in survivors with bronchopulmonary dysplasia

The clinical and pulmonary function test evidence of abnormal airway function in infants with BPD is now well established. Studies have shown persistence of airway obstruction into childhood and evidence of residual dysfunction into adulthood. Furthermore, preterm neonates who have been mechanically ventilated but do not meet any of the BPD definitions also have residual pulmonary dysfunction during infancy. As an increasing number of very low birth weight infants survive in the surfactant era, care must be taken to note that their airways are likely to be extremely compliant and thereby exceedingly susceptible to airway barotrauma in the neonatal period. The long-term consequences of airway injury could lead to residual abnormal airway function during infancy. It is hoped that barotrauma can be minimized substantially with a reduction in both the magnitude and duration of ventilatory support following surfactant therapy. With the advent of user-friendly commercial pulmonary function testing equipment, most neonatal follow-up services should include a comprehensive pulmonary follow-up ancillary to the existing neurodevelopmental follow-up services and may thereby reduce the severity of respiratory morbidities and the need for hospital readmissions.

Relative likelihood of bronchopulmonary dysplasia based on pulmonary mechanics measured in preterm neonates during the first week of life

We studied 143 low birth weight infants (less than or equal to 1500 gm) with respiratory distress syndrome who required mechanical ventilation, and determined the efficacy of using the alterations in pulmonary mechanics (measured at 1 to 3 days, 4 to 7 days, 2 weeks, and 4 weeks) as possible predictors for the subsequent diagnosis of bronchopulmonary dysplasia (BPD). The sensitivity and specificity of pulmonary compliance and resistance as predictors of BPD were ascertained by logistic regression correlation (p less than 0.01) and receiver operating characteristic curves. With these pulmonary mechanics data and logistic discriminant analysis techniques, we developed BPD prediction models based on pulmonary mechanics, measured between 4 and 7 days of age, to define the likelihood ratio for the subsequent diagnosis of BPD. Eight different BPD prediction models were developed by using combinations of four vectors (pulmonary compliance, total pulmonary resistance, birth weight, gestational age), and each model was validated in a subsequent low birth weight study population (n = 53). All models were deemed accurate for negative prediction of BPD. The models dependent on gestational age and dynamic pulmonary compliance had the highest positive predictive accuracy. The predictive impact of total pulmonary resistance appeared to be minimal. These prediction models may be used to calculate the likelihood ratio for a subsequent BPD diagnosis and thereby objectively categorize both the risk and the magnitude of acute lung injury by the first week of life.

Pulmonary mechanics and energetics in preterm infants who had respiratory distress syndrome treated with synthetic surfactant

Pulmonary mechanics and energetics were determined in 32 neonates with respiratory distress syndrome, who were randomly assigned to receive treatment with an exogenous synthetic surfactant, Exosurf Neonatal, or air placebo. Pulmonary mechanics were measured before and 2 hours after surfactant (n = 13) or air placebo (n = 19) treatment, then longitudinally at 24, 48, and 72 hours after treatment, and again at 7, 14, and 28 days of age. There were no significant differences in the values for pulmonary mechanics or energetics 2 hours after the first dose of surfactant. Improvement in pulmonary mechanics was apparent 24 hours after surfactant treatment, when dynamic compliance was 36% greater than in the placebo group (p less than 0.03). Lung compliance values were also higher in surfactant-treated infants 48 and 72 hours after treatment, with a maximal increase of 64% at 7 days of age (p less than 0.03). Surfactant treatment also caused a significant decrease in total pulmonary resistance at 48 and 72 hours after initial treatment and at 14 days of age (p less than 0.04). Similarly, a decrease in flow-resistive work of breathing was demonstrated 24, 48, and 72 hours after surfactant treatment. At 28 days of age, pulmonary mechanics were not different in the two groups. We conclude that beneficial effects of surfactant on pulmonary mechanics were not apparent 2 hours after dosing but were evident 24 hours after dosing and persisted for the first 7 to 14 days of life.