Increased blood pressure following pupillary dilation with 2.5% phenylephrine hydrochloride in preterm infants.

Heart rate and blood pressure changes following 0.5% tropicamide and 2.5% phenylephrine hydrochloride were evaluated in seven ill preterm infants (birth weight, 910 to 2,060 gm; gestational age, 26 to 36 weeks) during the first day of life. Each infant was monitored continuously for 30 minutes before and for 75 minutes after, instillation of the pupillary dilators. There were no significant changes in the heart rate, whereas a significant increase in systolic, diastolic, and mean arterial blood pressure was found. The increase in arterial blood pressure was detected at two minutes, peaked at eight minutes, and remained at significantly higher levels for 30 minutes after instillation. Because of the potential relationship between increased blood pressure and intraventricular hemorrhage, arterial blood pressure must be monitored during instillation of mydriatic drugs in the preterm infant.

Incidence and clinical features of patent ductus arteriosus in low-birthweight infants: a prospective analysis of 150 consecutively born infants.

The incidence of persistent patency of the ductus arteriosus beyond the third day of life was prospectively determined in 100 preterm infants with birthweights of 2,000 gm or less and 50 infants with birthweights of 2,001 to 2,500 gm. The overall incidence was 21% and was inversely related to increasing gestational age and birthweight. The data suggest that immaturity is the major determinant of the persistent patency of the ductus arteriosus. Spontaneous delayed closure of the ductus occurred in 79% of patients that survived the immediate neonatal period. There was a high degree of association between the presence of a patent ductus arteriosus (PDA) and respiratory distress syndrome (RDS). Eight infants with severe RDS and PDA developed heart failure and four required surgical ligation of the ductus. None of the infants with birthweights greater than 2,000 gm who had PDA developed heart failure or required surgical ligation of the ductus arteriosus.

Cardiovascular and catecholamine changes after administration of pancuronium in distressed neonates.

Heart rate, blood pressure, transcutaneous gases, and catecholamine changes following intravenous injection of pancuronium were evaluated in seven ill newborn infants (birth weight: 1,280 to 4,500 g; gestational age, 29 to 42 weeks). Each infant was monitored continuously for 30 minutes before and 50 minutes after infusion of the paralyzing agent. There were no significant changes in transcutaneous gases, whereas significant increases in heart rate; systolic, diastolic, and mean blood pressures; and blood norepinephrine and epinephrine levels were found. The increase in heart rate lasted for 30 minutes, and the increase in blood pressure persisted for 50 minutes after administration of the drug. Because of the potential relationship between increased blood pressure and intraventricular hemorrhage and myocardial dysfunction, heart rate and blood pressure must be monitored during infusion of pancuronium in distressed newborns. These data suggest that pancuronium stimulates sympathetic activity in distressed newborns.

Factors affecting heart rate variability in preterm infants.

Neonatal heart rate variability (NHRV) was studied in 92 preterm infants (birth weight, 750 to 2,500 gm; gestational age, 28 to 36 weeks). Each infant was monitored continuously during the first 6 hours and for one hour at 24, 48, and 168 hours of life. During each hour NHRV was quantified and related to the following parameters: sex, gestational age, postnatal age, heart rate, and the presence and severity of respiratory distress syndrome (RDS). NHRV in healthy preterm infants was inversely related to heart rate level and directly related to the infant's postnatal age. In healthy babies with gestations of 30 to 36 weeks there was no significant correlation between NHRV and gestation. Decrease in NHRV was significantly related to the severity of RDS, and the reappearance of NHRV in infants with RDS was associated with a good prognosis. Decreased NHRV significantly differentiated the infants with RDS who survived after the fifth hour of life. The data reveal that NHRV (1) should be corrected for heart rate level and postnatal age; (2) is decreased in RDS; and (3) can be used as an indicator of morbidity and mortality in preterm infants with RDS.

Hyperammonemia associated with perinatal asphyxia.

Twelve infants with severe perinatal asphyxia were found to have elevated blood ammonia levels (302 to 960 microgram/100 ml). In the seven survivors, hyperammonemia was associated with CNS irritability, hyperthermia, hypertension, and wide neonatal heart rate oscillations. Follow-up examinations revealed severe neurologic dysfunction in five of seven infants. CNS depression, hyperthermia, hypertension, and a nonreactive, fixed heart rate characterized the infants that died. These findings suggest a clinical entity secondary to perinatal asphyxia whose signs and symptoms may be related to hyperammonemia.

Evaluation of the FELMA microviscosimeter in predicting fetal lung maturity.

A new, rapid technique for determining fetal lung maturity, the FELMA, was tested against the standard lecithin/sphingomyelin (L/S) ratio in predicting hyaline membrane disease (HMD). The FELMA was tested on 236 samples, 154 of which were compared with the L/S ratio; 102 neonates were delivered within 48 hours. There was a significant correlation between methods ( r = 0.47). No neonate with a mature FELMA score developed HMD. Of 5 neonates with HMD, 2 had mature L/S ratio in predicting lung immaturity, providing a rapid result without the necessity of thin-layer chromatography.

Hemodynamic variables in infants weighing less than 1000 grams.

VVLBW infants pose a challenge in the management of their hemodynamic changes. Data are just accumulating regarding the hemodynamic variables in this very special group. We have described several newly developed methods of monitoring hemodynamic variables in infants less than 1000 gm. In the coming decade, some of these methods may become more refined and routine.

Episodes of bradycardia during early infancy in the term-born and preterm infant.

OBJECTIVE: To document the incidence of transient episodes of bradycardia in a group of healthy term and preterm infants during the first 1 to 6 months of life. DESIGN: Longitudinal polysomnographic study. SETTING: Sleep laboratory in a university-affiliated urban medical center. PARTICIPANTS: Fourteen healthy term-born infants, nine preterm infants with apnea in the nursery, and 10 preterm infants without apnea. Infants with neonatal morbidity except apnea were excluded. MEASUREMENTS: Transient episodes of bradycardia (< or = 100 beats per minute) were identified in 2- to 4-hour early evening polysomnographic tracings. The relationship with apnea, transcutaneous oxygen levels, and sleep state was determined. RESULTS: Transient episodes of bradycardia to 60 to 70 beats per minute were common, but there were no drops below 50 beats per minute. The incidence of transient episodes of bradycardia was inversely related to heart rate. Results for apneic and nonapneic premature infants were similar. CONCLUSIONS: Transient episodes of bradycardia are considered normal reflex responses and are not related to risk for sudden infant death syndrome. These results have implications for the setting of monitor alarms.

Effect of antenatal glucocorticoids on clinical closure of the ductus arteriosus.

The incidence of clinically detectable patient ductus arteriosus (PDA) in a group of preterm infants whose birth weights were less than 2,000 g was compared with that of a similar group of infants whose mothers received antenatal glucocorticoids. A PDA was diagnosed on the basis of a typical heart murmur, increased precordial activity, and bounding peripheral pulses beyond the third day of life. Whereas 14 (44%) of 32 infants who were not exposed to antenatal glucocorticoids showed evidence of a PDA, only one (6.5% of 15 infants whose mothers received antenatal glucocorticoids had similar findings. The incidence of ruptured membranes (greater than 72 hours), the number of infants who were small for gestational age, and clinical management of the infants in the two groups were similar.

Cardiovascular changes in infants with beta-hemolytic streptococcus sepsis.

Sequential hemodynamic and biochemical changes were studied in 24 infants with sepsis due to beta-hemolytic streptococcus to define the temporal patterns of physiologic events and to compare them in surviving (n = 11) and nonsurviving (n = 13) infants. Septicemia was documented by positive blood culture in all. Biophysical and biochemical measurements were obtained before and hourly, for 11 h after antibiotic therapy was initiated. Surviving infants had significantly higher Hct and systolic and mean arterial pressures than nonsurvivors. In nonsurvivors, low BP was associated with a concomitant rise in CVP and severe metabolic acidosis refractory to therapy. Although there were no differences in PaO2 or PaCO2 between survivors and nonsurvivors, arterial-alveolar oxygen gradients were significantly greater in nonsurviving infants. These data show cardiorespiratory and metabolic alterations that differentiate surviving and nonsurviving infants with beta-hemolytic streptococcal septicemia.

Apnea, transient episodes of bradycardia, and periodic breathing in preterm infants.

The occurrence of central apnea of 15 seconds or longer, transient episodes of bradycardia (TEB), and periodic breathing were studied in 66 healthy premature infants when at least 1 week old and between 32 and 36 weeks postconceptual age. Eight-hour cardiorespiratory recordings were visually scanned for the presence of these patterns. Central apnea of 15 seconds or longer was seen in almost half of the infants. The TEB were numerous, and the majority were not associated with central apnea; however, all but five of the apneic episodes that lasted 15 seconds or longer were accompanied by a TEB. Infants spent as much as 40% of their time in periodic breathing. The frequency with which these patterns are seen in healthy premature infants strongly suggests that they are normal findings. Our results do not support the opinion that brief periods of apnea are abnormal when accompanied by a TEB.

Cardiopulmonary and intracranial pressure changes related to endotracheal suctioning in preterm infants.

Although endotracheal (ET) suctioning is performed frequently in sick newborn infants, its effects on cardiorespiratory variables and intracranial pressure (ICP) have not been thoroughly documented in neonates greater than 24 h who were not paralyzed while receiving mechanical ventilation. This study evaluates these changes in preterm infants who required ventilatory assistance. We measured transcutaneous PO2 and PCO2 (PtcO2 and PtcCO2, respectively), intra-arterial BP, heart rate, ICP, and cerebral perfusion pressure (CPP) before, during, and for at least 5 min after ET suctioning in 15 low birth weight infants less than 1500 g and less than or equal to 30 days of age. One infant was studied twice. A suction adaptor was used to avoid disconnecting the patient from the ventilator and to attempt to minimize hypoxemia and hypercapnia during suctioning. The patients were studied in the supine position and muscle relaxants were not used. PtcO2 decreased 12.1% while PtcCO2 increased 4.7% 1 min after suctioning; however, greater increases in mean BP (33%) and ICP (117%) were observed during suctioning. CPP also increased during the procedure. ICP returned to baseline almost immediately, whereas BP remained slightly elevated 1 min after suctioning. Our findings demonstrate that ET suctioning significantly increases BP, ICP, and CPP in preterm infants on assisted ventilation in the first month of life. These changes appear to be independent of changes observed in oxygenation and ventilation.

Polygraphy after discharge in preterm infants with and without apnea in the nursery.

Nine of nineteen infants in this study exhibited two or more central apnea greater than or equal to 20 seconds when they were older than one week and between 32-36 weeks postconceptional age (PCA). We focused on the sequelae of these apneas. Apnea was separated from other morbidity associated with immaturity by the selection of consistently healthy infants. Following discharge, polygraphic tracings were obtained at 40, 44 and 52 weeks PCA in these non-apneic and previously apneic infants. Sleep states, minute by minute values for heart and respiratory rate, skin temperature and transcutaneous O2 (PtcO2) and CO2 (PtcCO2), apnea and transient decreases in PtcO2 were determined. Polygraphic measurements did not differentiate preterm infants with late apnea in the nursery from non-apneic ones. However, the apneic group exhibited a transient decrease in awakenings at 44 weeks PCA.

Transcutaneous oxygen and carbon dioxide during the first half year of life in premature and normal term infants.

Repetitive polysomnograms were recorded from a total of 33 infants, 19 healthy preterm infants, and 14 term controls between 40 wk postconceptional age and 6 mo of age. These nighttime recordings lasted 2-4 h, except at 52 wk in preterm infants and at 3 mo of age in term infants when an overnight 12-h recording was performed. Minute by minute values of transcutaneous PO2 (PtCO2) and transcutaneous PCO2 (PtcCO2) levels and variability during the awake state, active sleep, and quiet sleep were obtained through computer analyses of the polygraphic data. The results from preterm infants at corrected postconceptional age could not be differentiated from those of control infants. PtCO2 levels rose between 40 wk and 3 mo, and PtcCO2 levels declined. Sleep states modulated only the variability of PtcO2, not the level; in contrast, state modulation was seen in both variability and level of PtcCO2 throughout the age span studied. During sleep the number of transient declines in PtCO2 greater than 2.03 kPa (15 mm Hg) decreased with advancing age. Hypercapnic PtcCO2 values decreased with age as well, but their prevalence in healthy, young infants suggests the need for reevaluation of criteria for hypercapnia based on transcutaneous measurements. The data demonstrate that ventilatory regulation continues to undergo changes between 1 and 3 mo, the age of highest risk for sudden infant death syndrome.

Hyperreactivity to cow's milk in an infant with LE and tart cell phenomenon.

LE and tart cells were demonstrated in a black male infant whose serum contained milk-percipitating antibodies and who had pulmonary infiltrates. Immunoblasts, plasmocytoid lymphocytes, and an LE cell were found in a milk-stimulated skin window. The presence of LE cells corresponded to the presence of ENA antibody. Tart cells varied with oral milk challenge. A large Arthus type of skin reaction to injected milk was demonstrated. An oral feeding of milk resulted in a decrease in plasma C3. Lymphocyte transformation resulted from in vitro milk stimulation. ENA (extractable nuclear antigen) antibody and resulting LE cell formation possibly represented the combination of nuclear protein with milk antigen. The pulmonary infiltrates may represent a hypersensitivity pneumonitis characterized by both Arthus and cell-mediated reaction to milk.

Cardiogenic shock associated with perinatal asphyxia in preterm infants.

Fetal and neonatal biophysical and biochemical changes were studied in four preterm infants who developed cardiogenic shock as a result of severe perinatal asphyxia. Fetal distress was documented by the presence of severe late and variable decelerations associated with decreased fetal heart rate variability. Severity of fetal acidosis was decumented by scalp and umbilical cord blood pH. Apgar scores at 1, 5, and 10 minutes were all equal to or less than 5. Although the clinical findings shortly after birth resembled respiratory distress syndrome, it was possible to make a primary diagnosis of cardiac failure with the recognition of cardiomegaly, hepatomegaly, electrocardiographic changes of myocardial hypoxia, decreased myocardial contractility, elevated central venous pressure, and severe lactic acidosis. The treatment of heart failure, including use of inotropic agents, resulted in rapid improvement in the clinical condition, with reversal of the abnormal findings within 24 to 36 hours. Concomitant with this improvement, the increase in arterial blood pressure was paralleled by increase in peripheral (toe) temperature.

Effects of metaproterenol on pulmonary mechanics, oxygenation, and ventilation in infants with chronic lung disease.

Changes in pulmonary resistance, dynamic compliance, tidal volume, and transcutaneous PO2 and PCO2 after nebulized administration of metaproterenol were evaluated in eight newborn infants (birth weight 650 to 1060 g, gestational age 25 to 28 weeks) with chronic lung disease receiving mechanical ventilation. The infants were monitored continuously before and for 15 minutes after nebulization of metaproterenol during 3 consecutive days at mean age 34 days. There were significant increases in compliance, tidal volume, and tcPO2, and significant decreases in pulmonary resistance and tcPCO2. These data show that bronchospasm contributes significantly to the high pulmonary resistance in preterm infants with chronic lung disease and that metaproterenol is beneficial in the therapy of infants with chronic lung disease requiring mechanical ventilation.

Ventilatory control and carbon dioxide response in preterm infants with idiopathic apnea.

Idiopathic apnea in preterm infants, more than 30 weeks of gestation, after the first week of life is uncommon and poorly understood. To study ventilatory control in these infants we measured minute ventilation, respiratory frequency, tidal volume, end-tidal oxygen pressure and carbon dioxide pressure, and transcutaneous oxygen pressure before and during the fifth minute of breathing 4% carbon dioxide in air. Nine healthy preterm infants and eight infants with three or more episodes of apnea (greater than or equal to 20 s) in 24 hours were studied during active sleep. We found that infants with apnea had a significantly increased alveolar carbon dioxide pressure while respiratory frequency, minute ventilation, and slope were significantly decreased. Alveolar-transcutaneous oxygen gradients were essentially unchanged. These preterm infants with apnea have a decreased carbon dioxide sensitivity. They have a decreased minute ventilation primarily as a result of decreased respiratory frequency and their alveolar-transcutaneous oxygen gradient is normal. Our findings suggest that the major deficit in these infants is a central disturbance in the regulation of breathing.