Neutrophil and monocyte adhesion molecules in bronchopulmonary dysplasia, and effects of corticosteroids

AIMS

To study a longitudinal change in the expression of adhesion molecules CD11b, CD18, and CD62L on neutrophils and monocytes in very low birth weight babies who develop respiratory distress syndrome, to compare these levels between bronchopulmonary dysplasia (BPD) and non-BPD infants, and to assess the effect of corticosteroid treatment on these adhesion molecules.

METHODS

Of 40 eligible neonates, 11 neonates were oxygen dependent at 36 weeks (BPD 36 weeks), 16 infants were oxygen dependent at 28 days, but not at 36 weeks (BPD d28), and 13 infants did not develop BPD. Seventeen neonates received a six day course of steroid treatment. Expression of CD11b, CD18, and CD62L was measured on neutrophils and monocytes in arterial blood on days 1, 3, 7, 14, 21, and 28, and before and 2-3 days after initiation of dexamethasone treatment by flow cytometry.

RESULTS

CD18 expression on neutrophils and monocytes and CD62L on neutrophils, measured as mean fluorescent intensity, was significantly decreased in BPD neonates compared to non-BPD neonates on days 1-28. Dexamethasone treatment significantly decreased CD11b, CD18, and CD62L expression on neutrophils, and CD11b and CD18L expression on monocytes.

CONCLUSIONS

Decreased CD18 expression on neutrophils and monocytes, and decreased CD62L expression on neutrophils, measured as mean fluorescent intensity during the first four weeks of life in micropremies may be risk factors and early predictors of BPD. Dexamethasone use was associated with decreased expression of CD11b, CD18, and CD62L.

Octreotide-induced hypoxemia and pulmonary hypertension in premature neonates

The authors report 2 cases of premature neonates who had enterocutaneous fistula complicating necrotizing enterocolitis. Pulmonary hypertension developed after administration of a somatostatin analogue, octreotide, to enhance resolution of the fistula. The authors discuss the mechanism of the occurrence of this complication and recommend caution of its use in high-risk premature neonates.

Pharmacokinetics of betamethasone in twin and singleton pregnancy

OBJECTIVE

The aims of the study were to compare the pharmacokinetics of betamethasone in singleton pregnancy with the pharmacokinetics in twin pregnancy and to assess the adrenal suppression produced by betamethasone.

STUDY DESIGN

We measured serial betamethasone and cortisol levels in 30 singleton and 21 twin pregnancies after the first dose of betamethasone and calculated the pharmacokinetic parameters for betamethasone including volume of distribution, half-life, and clearance. We also measured cord and maternal blood levels of betamethasone at the birth of infants of 13 singleton and 9 twin pregnancies.

RESULTS

The half-life of betamethasone in mothers with twin pregnancies was significantly shorter than that in mothers with singleton pregnancies (7.2 +/-2.4 versus 9.0 +/- 2.7 hours; P <.017). Clearance of betamethasone in the twin pregnancies appeared greater than in singleton pregnancies (8.4 +/- 6.4 versus 5.7+/- 3.1 L/h; P =.06) but did not reach statistical significance. Volume of distribution was similar in the two groups. Because the time between the last dose of betamethasone and birth varied widely (range, 2-158 hours), mothers with a longer interval after treatment tended to have a higher cord-to-maternal betamethasone ratio than did mothers with a shorter interval in both twin and singleton pregnancies. This finding indicated delayed fetal clearance, but the correlation was weak (R (2) = 0.29 for twins and 0.08 for singletons).

CONCLUSION

The shorter half-life of betamethasone in twin pregnancy than in singleton pregnancy may cause the level of betamethasone to be subtherapeutic for lung maturation in twin pregnancy.

Ethical implications of aggressive obstetric management at less than 28 weeks of gestation

BACKGROUND

The purpose of this study is to evaluate the outcome of infants born between 23 and 28 completed weeks of gestational age for whom aggressive obstetric management was performed.

METHODS

Prenatal data were collected retrospectively from medical records. Neonatal mortality, early morbidity, and the outcome at one year corrected for postconceptional age (corrected age) were determined.

RESULTS

Ninety-seven infants were included in the study. Serious early morbidity decreased with increasing gestational age. All the infants born prior to 24 weeks showed serious early morbidity: only 26% of the infants born at 24 weeks or later did. There was a significant decline in mortality with increasing gestational age, as there was also in birth weight (p<0.001, p<0.001). Sixty-seven percent of the infants prior to 24 weeks showed disability at one year corrected age whereas only 13% at 24 weeks or older did. The likelihood of having a surviving child without disability was 12.5% at 23 weeks, 39% at 24 weeks, 50% at 25 weeks, 52% at 26 weeks, and 70% at 27 weeks.

CONCLUSION

Viability of fetuses at 23 and 24 weeks of gestation remains ethically and clinically controversial. It cannot be reliably established at that time that there is a fair balance of clinical goods over harms for the survivor at 23 weeks. On the other hand we should continue to treat fetuses at 24 weeks as viable, because 50% of them survived and 78% of those survived without disability. Neonatal mortality and survival with disability further decreases with increasing gestational age.

Nosocomial ringworm in a neonatal intensive care unit: a nurse and her cat

An outbreak of nosocomial ringworm involved five infants in a neonatal intensive care unit. The index case was a nurse infected with Microsporum canis by her cat. After standard infection control measures were initiated, the outbreak was resolved successfully by an interdisciplinary professional collaboration of physician and veterinary dermatologists and infection control personnel.

Functional residual capacity and pulmonary mechanics in premature infants receiving a 12-day dexamethasone course

The objective of this paper is to determine the effects of a 12-day dexamethasone course of the pulmonary function of preterm infants. The design consisted of a consecutive sample of eligible patients, before-after trial. The Regional referral center neonatal ICU was the setting. The patients were 13 preterm infants, 545-1315 g, requiring mechanical ventilation. The following was used: Intravenous dexamethasone for a 12-day tapering course beginning at 0.5 mg/kg every 12 hr. Main outcome measures were as follows: Measurements of functional residual capacity (FRC), compliance, resistance, arterial blood gases and alveolar-arterial differences, level of ventilatory assistance, weight, length. All measures of pulmonary function demonstrated significant improvement by Day 12 of treatment. Most improvement occurred in the first 6 days of treatment, in association with increased lung volume.

A program to reduce discharge delays in a neonatal intensive care unit

Our hypothesis was that a program designed to identify the causes of discharge delays would reduce the length of stay in our neonatal intensive care unit. We reviewed every admission from January, 1994, to December, 1995. A discharge delay was defined as any delay not related to illness after the infant was cleared for release. Discharge delays were divided into the following categories: primary healthcare team, organizational, discharge planning, family, monitor related, and other. Potential discharge delays were identified daily according to established criteria. Actual discharge delays were reviewed monthly at a staff meeting attended by representatives of a multidisciplinary team. We identified 116 discharge delays, which accounted for 480 patient days. Eighty-three discharge delays accounted for 302 patient days in 1994, and 33 discharge delays for 178 patient days in 1995. Discharge delays ranged from 1 to 34 days, with an average of 4.1 days added per patient. Infants with discharge delays had a case mix index of 9.32. The average case mix index for the neonatal intensive care unit was 6.25 during 1994 and 5.18 during 1995, an average of 5.71 for the review period. Forty-four percent of infants who had discharge delays had private insurance, 55% had Medicaid, and 1% had self-payment arrangements. Eighty-eight of 116 discharge delays were caused by circumstances beyond the control of the primary care team. An additional 25 of 116 discharge delays were the result of our policy requiring 48 hours free of apnea-bradycardia alarms before discharge. Discharge delays for 1994 cost $226,298 ($749/day). For 1995, discharge delays cost $41,553 ($233/day) for a total cost of $262,431. Total savings in 1995 versus 1994 was $184,745 ($516/day). Despite the low birth weight and relatively severe illnesses of the infants, we believe that a focused team approach and monitoring for potential discharge delays can result in considerable reduction in hospital stay and cost.

Responsibility for clinical innovation. A case study in neonatal medicine

Proper evaluation of clinical innovations and of the process of their diffusion is essential for the development of sound health care policy. This case study examines transcutaneous oxygen monitoring in neonatal intensive care, a procedure that was rapidly adopted in the late 1970s as a scientific breakthrough of great promise, then all but abandoned within a decade in favor of pulse oximetry, a still more recent technology. The study incorporates the results of interviews with representatives of industry as well as biomedical researchers and clinicians involved with these devices. Factors in technology diffusion are analyzed, with special attention to those susceptible to change by policy makers. Participants in the diffusion process also include nurses, hospital administrators, the legal profession, the news media, and the public, but the pivotal role--and hence ultimate responsibility--is seen to be that of the physician. The discussion is presented in the context of a proposed "ethics of evidence" pertinent to medical decision making.

Doctors and the health industry: a case study of transcutaneous oxygen monitoring in neonatal intensive care

This case study presents an industry perspective on medical innovation. Introduced as a scientific breakthrough in the late 1970s, transcutaneous oxygen monitoring was rapidly adopted for routine use in neonatal intensive care. But plagued by technical problems, it was within a decade being replaced by pulse oximetry, a still more recent technology. Its use in efforts to prevent retinopathy of prematurity, an eye disease of preterm newborns often leading to blindness, proved disappointing. The project included interviews with executives and design engineers of companies marketing the device, with investigators who had pioneered the technology, and with senior practicing neonatologists. The findings, reflecting complexity and uncertainty, are relevant to issues concerning health care in the United States and other developed nations. They centre on the key role and ultimate responsibility of the medical profession, with a need for greater attention to the scientific training of health care workers, as perceived by members of the medical device industry. The views of senior investigators are integrated into the picture, with discussion of major challenges faced by the medical community.

Voiding after neonatal circumcision

OBJECTIVE

To determine whether it is necessary to delay discharge of newly circumcised male neonates to observe voiding.

SUBJECTS AND METHODS

A prospective study was conducted in 1992 and 1993 of 51 healthy male, newly circumcised neonates between 0 and 10 days of age. The neonates were observed for the time of first voiding after circumcision was performed.

RESULTS

All neonates voided after circumcision at a mean age of 5.3 +/- 2.5 hours, and there were no complications noted in the study population.

CONCLUSION

Healthy male infants who are circumcised without obvious complications can be expected to void, and it is unnecessary to delay hospital discharge to make this observation.

Ventilation-perfusion relationships in preterm infants after surfactant treatment

Arterial-alveolar partial pressure differences for oxygen, carbon dioxide, and nitrogen were measured before and after surfactant replacement therapy on 15 occasions in 14 ventilator-dependent preterm infants with hyaline membrane disease (HMD). Eight treatments resulted in a significant improvement in arterial partial pressure of oxygen (PaO2) 2 hr after treatment; 7 did not. Neither group showed any significant change in arterial-alveolar partial pressure differences for oxygen, nitrogen, and carbon dioxide. This observation suggests that if surfactant replacement therapy produces an improvement in PaO2 it does so by recruitment of atelectatic alveoli with a balanced ventilation/perfusion ratio rather than by redistribution of ventilation within already ventilated alveoli.

Neonatal extracorporeal membrane oxygenation (ECMO): clinical trials and the ethics of evidence

Neonatal extracorporeal membrane oxygenation (ECMO), a technology for the treatment of respiratory failure in newborns, is used as a case study to examine statistical and ethical aspects of clinical trials and to illustrate a proposed 'ethics of evidence', an approach to medical uncertainty within the context of contemporary biomedical ethics. Discussion includes the twofold aim of the ethics of evidence: to clarify the role of uncertainty and scientific evidence in medical decision-making, and to call attention to the need to confront the irreducible nature of uncertainty.

Control of inspiratory timing in newborn infants

In order to determine if inspiratory time in preterm infants was influenced by lung volume, two studies were carried out. In the first investigation, carbon dioxide was used to stimulate tidal volume to a level three to six times normal. The anticipated decrease in inspiratory time at increased tidal volumes was not found. These preterm infants behaved in a similar fashion to vagotomized animals studied in the same way by Clark and von Euler. In the second investigation, Hering-Breuer activity was measured in relation to lung volume changes occurring with growth, measured in a body plethysmograph. Although thoracic gas volume correlated well with age and weight, inspiratory slowing with airway occlusion was found to be independent of both age and lung volume. These investigations suggest that neurologic factors have a significant influence on the inspiratory time in newborn human infants.

Characteristics associated with successful weaning in ventilator-dependent preterm infants

Eighteen ventilator-dependent preterm infants with hyaline membrane disease were studied for 24 hours before and after an attempt at extubation. All were treated with theophylline prior to weaning and achieved average levels of 8.9 +/- 1.7 micrograms/ml (49 +/- 9 mumol/liter) in 13 successfully weaned infants and 8.4 +/- 1.1 micrograms/ml (47 +/- 6 mumol/liter) in 5 infants not extubated, p > 0.05. Infants successfully weaned were significantly (p < 0.01) older, more mature (29 +/- 1 versus 26 +/- 2 weeks' gestational age) and heavier (1107 +/- 236 versus 1016 +/- 256 gm) than infants not successfully extubated. Infants successfully weaned differed only in developing a greater maximal inspiratory force (33.8 +/- 12.3 versus 23.3 +/- 15.0 cm H2O) and higher compliance (1.1 +/- 0.3 versus 0.7 +/- 0.3) during the preweaning treatment period. These results indicate that maturity and size play a significant role in the ability to wean a preterm infant from the ventilator successfully, that maximal inspiratory force and compliance are higher in preterm infants who can be successfully extubated, and that methylxanthines do not uniformly improve pulmonary function in all potentially extubatable preterm infants.

Ascorbic acid prevents oxidative stress in glutathione-deficient mice: effects on lung type 2 cell lamellar bodies, lung surfactant, and skeletal muscle

Glutathione deficiency in adult mice leads to lung type 2 cell lamellar body and mitochondrial damage; as reported here, these effects are associated with marked decrease of the levels of phosphatidylcholine (the main component of lung surfactant) in the lung and the bronchoalveolar lining fluid. Severe mitochondrial damage was also found in skeletal muscle. Treatment with ascorbate (1-2 mmol per kg of body weight per day), which led to greatly increased (approximately 2-fold) levels of lung and muscle mitochondrial glutathione, prevented damage to lamellar bodies and mitochondria as well as the decline of phosphatidylcholine levels in lung and alveolar lining fluid. The findings indicate that glutathione deficiency leads to depletion of lung surfactant and that this can be prevented with ascorbate. Administration of ascorbate spares glutathione and prevents cellular damage. Lamellar body degeneration in glutathione deficiency appears to be associated with oxidative damage to the perilamellar membrane, which contains the enzymes required for phosphatidylcholine synthesis. It is notable that although severe glutathione deficiency is lethal to newborn rats, which apparently do not synthesize ascorbate, adult mice are better able to survive such a deficiency because they can synthesize ascorbate. The present studies, which suggest that high doses of ascorbate may be of therapeutic value, emphasize that ascorbate and glutathione have actions in common and that they function together in a physiologically significant antioxidant system.

Aortic root blood flow increases after pancuronium in neonates with hyaline membrane disease

OBJECTIVE

To determine the effects of muscle paralysis on aortic root blood flow in preterm infants with hyaline membrane disease.

DESIGN

Each patient served as his/her own control in a prospectively controlled trial.

SETTING

Neonatal ICU in a university hospital.

PATIENTS

Ten ventilator-dependent preterm infants weighing 800 to 2820 g, 0 to 8 days of age, with hyaline membrane disease and seven control patients.

INTERVENTIONS

Noninvasive measurement of aortic root blood flow by Doppler echocardiography 30 min before and 60 min after respiratory paralysis with 0.1 to 0.5 mg/kg of iv pancuronium, or following ventilator changes in control subjects.

RESULTS

Mean aortic root blood flow increased significantly (p less than .001), from 212 to 276 mL/min.kg, accompanied by significant increases in stroke volume and heart rate.

CONCLUSIONS

Pancuronium bromide may have a direct beneficial effect on the circulation of preterm infants with hyaline membrane disease.

Ventilation-perfusion abnormalities in the preterm infant with hyaline membrane disease: a two-compartment model of the neonatal lung

Arterial-alveolar differences for oxygen, carbon dioxide, and nitrogen were measured in 7 non-distressed preterm infants and 21 ventilator-dependent preterm infants with hyaline membrane disease. The preterm infants with hyaline membrane disease had a significantly lower average arterial pH (7.34 vs. 7.44; P less than 0.001), and significantly higher arterial-alveolar differences for oxygen (286 mm Hg vs. 34 mm Hg; P less than 0.005) and nitrogen (118 mm Hg vs. 7 mm Hg; P less than 0.005). Both groups had elevated arterial-alveolar differences for PCO2 (9 mm Hg in infants with hyaline membrane disease, 5 mm Hg in nondistressed infants; P less than 0.2). When acute changes in mean airway pressure were produced in 14 distressed infants, arterial-alveolar CO2 and N2 differences moved in opposite directions in 11 infants. This observation suggests that changes in mean airway pressure do not acutely recruit atelectatic alveoli, but cause redistribution of ventilation within alveoli already ventilated.

Discrepancies between transcutaneous and end-tidal carbon dioxide monitoring in the critically ill neonate with respiratory distress syndrome

PaCO2, transcutaneous PCO2 (PtcCO2), and end-tidal PCO2 (PetCO2) measurements were studied in 12 critically ill neonates. PtcCO2 was measured using a combination CO2/O2 sensor during the routine care of these patients. End-tidal sidestream sampling was performed during blood gas measurement as dictated by the patient's clinical condition. There was a linear correlation between PtcCO2 and PaCO2 (n = 51, r = .71, slope = 0.90). PetCO2 and PaCO2 did not correlate as well (n = 51, r = .52, slope = 0.42). Acidosis negatively affected the correlation between PtcCO2 and PaCO2. When pH was greater than 7.30, r = .75 and slope = 1.28 (n = 38), whereas when pH was less than 7.30, r = .62 and slope = 0.73 (n = 13). The presence or absence of a metabolic acidosis did not have a significant effect on the slopes obtained. PtcCO2 monitoring using combined sensors is a useful and practical means of monitoring in the neonatal ICU, although acidosis affects the ability to correlate transcutaneous and arterial values. End-tidal sidestream measurements are not as clinically useful because they vary due to different ventilation/perfusion relationships in the sick neonate.

Pulmonary function in preterm infants following treatment with intravenous indomethacin

Pulmonary function tests, including measurements of arterial blood gas levels, total pulmonary compliance, and arterial-alveolar oxygen ratios, were performed in 38 ventilator-dependent preterm infants with respiratory distress syndrome who weighed less than 1500 g at birth. Twenty-seven had a physiologically significant patent ductus arteriosus (PDA). Twelve were assigned at random to receive three doses of intravenous indomethacin, 0.2 mg/kg per dose, on the fourth day of life. This treatment resulted in ductal closure in seven infants by the seventh day of life. Another concurrently observed group of 15 infants with PDA received no indomethacin. A third group of 11 infants lacked evidence of a PDA. Pulmonary function in the infants who received indomethacin did not differ significantly from that in the other two groups.

Effect of endotracheal continuous positive airway pressure on sensitivity to carbon dioxide and on respiratory timing in preterm infants

To determine the effects of continuous positive airway pressure (CPAP) on ventilatory response to CO2 and inspiratory and expiratory duration in preterm infants, 24 preterm infants with an average birth weight of 1220 g were studied at a mean age of 10.6 days. CPAP was applied via an uncuffed endotracheal tube. Testings were performed between ambient pressure and a positive airway pressure of 10 cm H2O. Approximately 2/3 of the applied pressure was transmitted to the esophagus. All infants demonstrated a ventilatory response to carbon dioxide of less than 50 ml/min per mm Hg Pco2 at ambient pressure, and no infant showed significant improvement at increasing levels of CPAP. Drive to breathe, as reflected in the inspiratory flow rate (Vt/Ti) also failed to change significantly. It may be concluded that in the apparent absence of significant changes in lung volume, CPAP fails to increase sensitivity to CO2 in preterm infants recovering from hyaline membrane disease.

Prevalence of "compressed" and asymmetric lateral ventricles in healthy full-term neonates: sonographic study

The premature infant brain has been thoroughly studied by sonography, and normal standards for ventricular size have been established. Whether these apply to normal full-term infants is uncertain. Fifty-three healthy full-term infants were electively examined by real-time sonography through the anterior fontanelle on the first to sixth days of life. Nine had asymmetric lateral ventricles; two of these had unexpected evidence of intracranial hemorrhage, while a third had a ventricular cyst. Forty-four infants had symmetric ventricles, but in 36 the ventricles had little or no cerebrospinal fluid. Vaginal delivery had a statistically significant association with these "compressed' lateral ventricles. This study indicates that seemingly healthy infants may have unsuspected intracranial hemorrhage, that asymmetric ventricular size may be normal, and that shortly after birth most healthy infants have "compressed" lateral ventricles that should not be interpreted as cerebral edema.

Incomplete baroreceptor responses in newborn infants

Previous studies of the baroreceptor response to a 45 degree head-up tilt in preterm and mature infants during the first 3 days of life failed to demonstrate a significant tachycardia while eliciting a 25% reduction in limb blood flow. In order to determine if maturity or respiratory distress affected the presence of tachycardia after tilting, 34 infants between 28 and 40 weeks gestation, including 15 infants with RDS, were studied serially during their hospitalization in a neonatal intensive care unit. In the first 5 seconds after a rapid (1-second) tilt to 45 degrees, individual infants responded with changes in heart rate (HR) ranging from a fall of 8 beats/min to an increase of 13 beats/min. Individual responses were not predictable on the basis of maturity at birth, age after birth, or presence of clinical respiratory distress. The group as a whole demonstrated a statistically significant increase of 2 +/- 4 beats/min in the first 5 seconds immediately after tilting. This may be compared to a coefficient of variation of +/- 4-5% in the resting HR of the same group of infants. Because of the unpredictability of individual responses and the small magnitude of the response for the group as a whole, it can be concluded that the HR component of the baroreceptor response is poorly developed during the neonatal period.

Growth achievement in low-birth-weight premature infants: relationship to neurobehavioral outcome at one year

Previously published studies present conflicting conclusions about the growth of small, premature infants. To provide further data on these infants, a well-defined group of 86 premature infants appropriate for gestational age, weighing less than 1501 gm at birth, was observed until 12 months after their expected dates of delivery. Length, weight, and head circumference were measured at one, three, six, nine, and 12 months postterm. At 12 months postterm, infants were evaluated by neurologic examination and the Bayley Scales of Infant Development. Premature infants with mean Bayley scores greater than or equal to 85 were found to be significantly larger than infants with mean Bayley scores less than 85 by three months postterm. Birthweight, gestational age, duration of hospitalization in the neonatal intensive care unit, pneumonia, hypoglycemia, perinatal neurologic impairment, acidosis, and hypoxemia were found to be associated with reduced growth at one year. Conflicting results in previous studies may be a result of failure to separate infants with good neurobehavioral outcome from those with poor outcome.

Premature rupture of the membranes (PROM): a neonatal approach

The risks to the infant following prolonged premature rupture of the amniotic membranes are those of prematurity and infection. After the 36th week of pregnancy, healthy infants of healthy mothers may be treated as uninfected neonates, as their risk of infection does not appear to be significant. Before this gestational age, infants should receive a complete laboratory evaluation for infection, including blood culture and spinal fluid examination, and antibiotic therapy should not be withheld until these laboratory tests are reported to the clinician. While the indiscriminate use of antibiotic treatment should be avoided, sepsis in the newborn can be a rapidly progressive disease, with minimal physical and laboratory findings at its onset. Therefore, until some method of laboratory evaluation that will detect all cases of neonatal sepsis rapidly, and leave no infected infant unidentified, the clinician must be alerted to the presence of an infant delivered after PROM and institute the appropriate evaluation and treatment as soon as possible.

Recent advances in hyaline membrane disease

Survival of infants with HMD has improved remarkably in the last decade. This has resulted from improved methods of diagnosis, which enables clinicians to recognize infection, the patent ductus, and the presence of pulmonary hypertension complicating HMD; from improved methods of ventilation, which result in a lower incidence of acute and chronic complications; and from a reduced incidence of pulmonary and extrapulmonary complications, such as bronchopulmonary dysplasia and retrolental fibroplasia. These advances arise from a deep understanding of pulmonary and metabolic physiology of the newborn infant with respiratory distress. Only an approach firmly rooted in an understanding of physiology, pharmacology, and biochemistry can be completely successful in the therapy of these infants.

Tissue surface pH monitoring during reduced blood flow: Metabolic implications and sources of error

To evaluate tissue surface pH as an indicator of the acid base status of arterial blood during periods of reduced blood flow, we examined the relationship between tissue surface pH, arterial pH, arterial lactic acid levels, and base deficit in fifteen spontaneously breathing anesthetized cats. Blood flow was reduced by hemorrhage to 50% of control blood pressure values (Fig. 3) or by infusing norepinephrine (10 mcg/kg/min intravenously) for one hour (Fig. 2). During these procedures, tissue surface pH was inversely related to arterial base deficit (r = - 0.665, p less than 0.02) and lactic acid (r = 0.822, p less than 0.001) but not related to blood pH (Fig. 4). The errors resulting from measuring tissue surface pH continuously for 2 1/2 to 8 hours were examined by comparing the in vivo recalibration drift of the electrodes. The pH and reference electrodes drifted less than 0.1 pH units during this time. However, when examined in separate experiments for recalibration drift in vitro, we observed up to 0.67 pH units drift after 24 hours of reference electrode contamination with blood, but only 0.02 pH units drift in the pH electrode after this period. Since tissue surface pH is linearly correlated with the blood concentration of lactic acid or the base deficit during periods of acute blood flow reduction, tissue surface pH monitoring may be helpful for following the severity of the resulting anaerobic metabolism in neonates at risk for reduced peripheral perfusion or hypoxia. However, improvements in the reference electrode will be necessary to make long term tissue surface pH monitoring reliable if there is a reasonable risk of contamination of the reference electrode with blood.

Oxygen consumption in apneic premature infants after low-dose theophylline

The effects of 2 mg/kg/day theophylline (serum concentrations, 2.9 to 4.7 micrograms/ml) on metabolic rate were observed in 11 premature infants with severe idiopathic apnea of prematurity. Oxygen consumption (VO2/kg) increased 25% from 6.5 +/- 0.4 (SEM) to 8.1 +/- 0.6 cc/min/kg after 24 to 48 hr of therapy. Respiratory quotient did not change. Apnea and bradycardia decreased from 8.6 +/- 1.4 to 1.6 +/- 0.5 episodes/hr and 4.4 +/- 1.1 to 1.2 +/- 0.4 episodes/hr, respectively. This dose of theophylline is effective in idiopathic apnea of prematurity and acts as a metabolic stimulant. In the premature infant, theophylline-induced increases in VO2 may be a result of changes in the sleep state.

Assisted ventilation: a critical review

Assisted ventilation is a complex technique that has been responsible for much of the improvement in neonatal morbidity and mortality during the last 10 to 15 years. In unskilled hands, however, it can be dangerous. Complications run as high as 30% in some series. Assisted ventilation requires a constantly available medical and nursing team that can supervise the care of a critically ill infant around the clock. It cannot be done from a remote office, but must be carried out by intensivists on the spot. A large investment in time, labor, and skill is needed to reap the benefits without paying an excessive price in terms of morbidity among surviving infants. While the community-based pediatrician must become expert at recognizing the signs of neonatal respiratory distress and initiating the first steps to diagnose and stabilize sick infants, it is not to be expected that the definitive care of such infants can take place in every locality. Therefore local hospitals must recognize their limitations of staff and financial commitment to the care of these infants and form close clinical and educational links with tertiary hospitals capable of long-term care of infants with respiratory distress who require assisted ventilation.

Flow-volume loops in newborn infants

Flow-volume loops were obtained during the performance of crying vital capacity (CVC) maneuvers in 31 infants, 18 of whom had hyaline membrane disease (HMD). Both healthy and distressed infants had flow-volume loops resembling those found in adults with variable intrathoracic obstruction of the central airways. Flow rates during inspiration and expiration increased as the CVC increased. Infants with HMD had narrower inspiratory loops and attained peak expiratory flow later than nondistressed infants, but these differences were not statistically significant. Vocalizations, loss of lung recoil associated with loss of lung volume, and partial collapse of intrathoracic airways may all contribute to the shape of the flow-volume loop in infants.

Low-dose theophylline therapy in idiopathic apnea of prematurity

The effects of theophylline at a dose of 2 mg/kg/day (with resultant serum concentrations of 2.8 to 3.9 micrograms/ml) were observed in seven premature infants with severe idiopathic apnea. The frequency of apneic episodes decreased 62 +/- 9% (SEM) and the frequency of episodes of bradycardia decreased 73 +/- 9% following 24-48 hours of this therapy. No changes in ventilatory response to CO2 resting respiratory minute volume, arterial blood gas values, resting heart rate, or serum electrolyte concentrations were observed. Theophylline at this dose appears to be a safe and effective treatment for idiopathic apnea in premature infants. It works by a mechanism other than increasing CO2 sensitivity.

Baroreceptors in preterm infants: their relationship to maturity and disease

Using passive tipping to a 45 degrees head-up position, an attempt was made to elicit reflex vasoconstriction in 13 non-distressed preterm infants and 27 infants with hyaline membrane disease, all between 26 and 38 weeks gestation. An increase in vascular tone associated with a significant reduction in peripheral blood-flow was found in 11 of the 13 non-distressed infants, while the same response was lacking in 23 of the 27 distressed infants. No infant demonstrated significant tachycardia with tilting, and the non-distressed infants failed to maintain their mean aortic blood-pressure during tilting. The results suggest that reflex control of vascular tone is present in non-distressed infants as early as 26 weeks gestation, but not in infats with hyaline membrane disease, possibly because of a maximal increase in vascular tone as a response to illness. This is indicated by the findings of significantly higher resting peripheral vascular resistance and lower peripheral blood-flow in infants with this diesease.

Osteomyelitis in a neonatal intensive care unit

Neonatal osteomyelitis presents with few clinical signs despite multiple sites of involvement. Four cases of osteomyelitis due to Staphylococcus aureus or Candida albicans were encountered in a neonatal intensive care unit. Three were unsuspected clinically and were detected as incidental radiologic findings. The fourth presented with soft-tissue abscesses. Long bone metaphyses were most frequently affected. Other sites included iliac bones, clavicles, and spine. On follow-up the bones healed, but one patient was left with hip deformity secondary to destruction of the cartilaginous femoral heads and another patient developed obstructive hydrocephalus due to Candida ventriculitis. Complete skeletal survey is indicated in any infant with osteomyelitis at one site to seek additional silent areas of involvement.

Evaluation of methods of assisted ventilation in hyaline membrane disease

Two methods of providing assisted ventilation were compared in infants severely ill with hyaline membrane disease (HMD). 10 infants were assigned to each group. One group received ventilation with a volume-cycled respirator, and the other was ventilated using a pressure-limited ventilator and reversed I:E ratio. Both groups were well matched for severity of illness in terms of pH and blood gases. pH and PO2 were quickly corrected by both ventilators. However, the pressure-cycled ventilator group had higher survival and lower complication rates. PAO2 after one hour was substantially improved at the same FIO2 in the pressure-limited group and after 8 hours the FIO2 required to maintain a PaO2 of 50--70 mmHg (6.6--9.3 kPa) was significantly decreased compared with the volume-cycled group. No effects on blood pressure were detected in either group. The study shows that the pressure-limited method is significantly better.

Alterations in state in apneic pre-term infants receiving theophylline

The present study is a report on 9 premature infants treated with aminophylline for relief of apnea. With serum theophylline levels of 2 to 10 microgram/ml, all infants experienced significant decrease of apneic episodes in association with increased wakefulness and increased amounts of active (REM) sleep. These effects may occur independently, but it is possible that the alteration of sleep states may be partially responsible for the decrease in apneic episodes in these infants.

Noninvasive estimation of arterial oxygenation in newborn infants

Two noninvasive methods of estimating arterial oxygenation were compared in a group of 48 infants ranging in birth weight from 870 to 4,000 gm, with diagnoses including apnea of prematurity, hyaline membrane disease, meconium aspiration, and congenital heart disease. Both transcutaneous oxygen measurements and ear oximetry gave reasonably accurate estimations of arterial oxygen levels within commonly used clinical ranges (PO2 50 to 70 mm Hg, arterial saturation 90 to 98%). Infants with shock demonstrated a wide range of values for transcutaneous oxygen levels, suggesting that this method has limited usefulness in this situation. Ear oximetry had limited ability to distinguish high, but safe, levels of arterial oxygen from excessively elevated levels. While neither method can be recommended for replacement of arterial oxygen sampling, both methods may be useful in a clinical setting if care is exercised in interpretation of the results and if the values obtained are checked against those from arterial blood.

Pulmonary function following feeding in low-birth-weight infants

Determination of functional residual capacity, arterial gas tensions and pH, and arterial-alveolar differences was carried out in a group of nondistressed premature infants to determine if significant alterations in lung volumes or ventilation perfusion relationships sufficiently large to cause cyanosis could be detected after feeding. The only statistically significant changes observed in these parameters were immediately following feeding, a fall of .01 pH units and a fall of 6 mm Hg in arterial oxygen tension; and 15 minutes after feeding, a fall of .01 pH units and a rise in arterial PCO2 of 3 mm Hg. In addition, significant falls in peripheral blood flow were observed five minutes after feeding in association with marked elevations in peripheral vascular resistance. The mild impairment in pulmonary function in association with the more profound changes in limb blood flow are consistent with other studies in premature and full-term infants. These data suggest that cyanotic attacks following feeding may have a complex etiology and require an aggressive multisystem approach for adequate diagnosis and therapy.

Serial determinations of oxygen profiles in infants with respiratory distress

Serial oxygen profiles were determined for 20 newborn infants by measuring arterial tensions at low (20--40%), intermediate (60--80%), and high (95--100%) levels of inspired oxygen. These points were plotted on a graph which estimated the percentage of venous admixture at any particular level of inspired oxygen. The infants' oxygen profiles were then determined. As much as 25% of venous admixture could be attributed to the presence of diffusion and distribution abnormalities in infants with hyaline membrane disease. A substantial number of infants showed increased shunting at high levels of oxygen, even in the presence of continuous distending airway pressure. It is hypothesised that a rising shunt is due to complete absorption of gas in poorly ventilated alveoli at high concentrations of inspired oxygen, resulting in the presence of atelectasis and redistribution of blood to poorly ventilated areas.

Sleep state, apnea and bradycardia in pre-term infants

Respiratory pattern and heart rate were studied in 28 pre-term infants and four full-term infants during the first weeks of life. Sleep state was identified by standard neurological and EEG criteria. Apneic spells lasting 10 seconds or more were most frequent in the least mature infants, and their frequency tended to diminish with increasing maturity. When these apneic attacks were related to sleep state they were found to occur more frequently during non-REM sleep in infants of 30 to 33 weeks gestation. This was the only statistically significant difference found. No over-all pattern relating sleep state to frequency of apnea could be detected for individual infants. It was also difficult to relate the occurrence of bradycardia to apnea in terms of sleep state or gestational age. It is concluded that no simple relationship between sleep state, apnea and bradycardia exists and that a complex interrelation between central and peripheral factors is involved in these events.

Quantitative estimation of ventilation in newborn infants using the impedance pneumogram

Impedance pneumography is potentially a non-invasive method of measuring infant tidal volumes. In order to evaluate the accuracy of impedance pneumography, eight healthy infants (weighing from 709 to 3506 grams) were randomly chosen and studied. Simultaneous measurements of tidal volumes were made by calibrated spirometry and by transthoracic impedance pneumography. The results were statistically compared. Transthoracic impedance pneumography provided a reliable estimate of tidal and minute volumes in these newborn infants.

Carbon monoxide diffusing capacity in newborn infants

In order to test the role of diffusing capacity in determining the arterial oxygen tension of newborn infants, pulmonary diffusing capacity for carbonmonoxide (DLCO) was measured in 21 healthy infants ranging in weight from 765 to 4,720 g. DLCO infants without respiratory distress correlated well with lung volume (r=0.76, P less than 0.001). A smaller correlation (r = 0.39, P less than 0.01) was obtained between DLCO and arterial oxygen tension. DLCO per unit volume of lung is similar when healthy premature infants, full term infants, and normal adults are compared. The wide range of normal values obtained in resting infants and the lack of correlation with arterial oxygen tensions are similar to observations made in adults.

Skin reflectance in the newborn infant

Skin reflectance in red, green, and blue light was measured at the sternum of 99 Caucasian infants ranging in gestational age from 26 to 44 weeks. Skin reflectance was consistently higher in female infants, but this difference was not statistically significant. Highly significant (P less than 0.001) increases in reflectance at all wave lengths were found when sternal reflectance during the first 48 hr of life was related to gestational age. The dispersion of data points about the regression line does not permit this method to be relied upon as the sole means of determining gestational age of infants. Serial studies indicate that reflectance increases in premature infants not given phototherapy, whereas premature infants receiving phototherapy show a fall in reflectance for the duration of therapy. This suggests that phototherapy may cause tanning of the skin.