Changes in mean esophageal pressure during early recovery in mechanically-ventilated neonates--evidence for airway-closure and gas-trapping?

We studied transmission of a constant mean airway pressure through the lungs to the pleural space in nine mechanically-ventilated neonates with low-compliance lung disease. Infants were studied for 3.1 +/- 1.6 hr during a period of clinical improvement, but at a time when lung compliance was still markedly reduced. Two of our infants were studied during recovery from fluid overload, while seven infants with hyaline membrane disease were studied at a stage of disease during which maximal diuresis has been found to occur. During the study period, mean esophageal pressure decreased in all infants from 5.6 +/- 1.3 to 4.2 +/- 1.8 cm H2O (P less than 0.001) while total compliance increased slightly.

Metabolic effects of methylxanthines

As predicted, methylxanthines influence several metabolic processes and increase the serum concentrations of glucose, FFAs, and catecholamines in adults. Although these increases are significant statistically, they may not be clinically important. Based upon a small number of studies, methylxanthines seem to affect infants in a more complex fashion. In infants, methylxanthines increase metabolic rate, do not increase catecholamine release, and produce variable effects on carbohydrate balance. The serum glucose concentration after methylxanthines likely represents a complex interplay of glycogen stores, types of nutrient administered, rate of nutrient administration, and degree of increased metabolic rate. Carefully controlled prospective studies are needed to determine the possible effects of methylxanthines on growth, carbohydrate balance, FFA release, and salt and water excretion at high and low serum concentrations. In addition, it is necessary to assess the effect on these variables of chronic pre- and postnatal exposure to methylxanthines.

Ventricular dimensions of the brain in premature and full-term infants

A total of 120 computed tomographic scans of the brain in premature and full-term infants were reviewed. Of these, 28 were judged to exhibit normal ventricular dimensions, and the bifrontal, bicaudate, and bioccipital indices of the lateral ventricles were determined. The bifrontal and bicaudate indices followed a Gaussian distribution, with mean values of 0.28 +/- 0.07 (SD) and 0.15 +/- 0.03 (SD), respectively, whereas the bioccipital index was uniform in its distribution (range, 0.13 to 0.26). For comparison, corresponding indices were determined in scans of ten infants with clinical evidence of hydrocephalus. Based on these data, guidelines are suggested to distinguish normal and abnormal ventricular dimensions in newborn infants.

Oxygen consumption and temperature control of premature infants in a double-wall incubator

The effects of a double wall in a forced convection-heated incubator were studied on ten naked, nondistressed, premature infants by measuring their mean skin temperature, esophageal temperature, and oxygen consumption when they were in thermal steady state, with, and without, the double wall in place. The incubator air temperature was maintained within the recommended thermoneutral zone during the consecutive paired experiments. Ambient room temperature and relative humidity were constant and the infant's activity (quiet sleep) and postprandial state were the same in both conditions. Together with a significant rise in operative temperature (P less than .05) induced by the double wall (accounted for by a 0.9 C mean increased in incubator wall temperature nearest the baby), their mean skin temperature and esophageal temperatures increased (P less than .025), while a decrease in oxygen consumption occurred in nine of the ten infants (P less than .05). These findings suggest that the double wall reduced radiant and total heat loss from the baby by diminishing the temperature gradient between the skin and incubator surfaces and that metabolic heat production (oxygen consumption) was reduced when the double wall was in place.

Understanding the Pleurevac

The infant nonmetered Pleurevac was studied under laboratory conditions. Evacuation of a spirometer was measured at various negative pressures through the infant thoracostomy tubes routinely used in the clinical setting. In addition, a tension pneumothorax model was designed, and factors affecting its evacuation rate were studied. In accordance with Poiseuille's law, the evacuation rate was proportional to the negative pressure applied to the thoracostomy tube, and the radius of the tube. The airflow rate (bubble rate) through the Pleurevac was found to be of minor importance in affecting evacuation.

Frequency of transient hypothyroxinaemia in low birthweight infants. Potential pitfall for neonatal screening programmes

Thyroid function was studied in 54 low birthweight infants during a 3-week period. Each infant was placed in one of three groups. Group 1 (n = 21), infants who were well and appropriately grown fro gestational age; group 2 (n = 23), infants who were appropriately grown but who had hyaline membrane disease; group 3 (n = 10), infants who were small-for-gestational-age. In group 1, 5 (24%) infants had at least one serum thyroxine value less than 3.0 micrograms/100 ml (39 nmol/l). There were 8 (35%) infants in group 2 who had similarly low serum thyroxine values as did 5 (50%) of the 10 infants in group 3. Serum thyrotropin levels and serum binding of the thyroid hormones, as measured by a T3-charcoal uptake test, were normal in all infants. In all instances but 2, serum thyroxine values were at least 4.0 micrograms/100 ml (51 nmol/l) by the end of the 3-week period. There is thus a high incidence of transient 'hypothyroxinaemia' in low birthweight infants, particularly if such infants have hyaline membrane disease or are small-for-gestational-age. These findings must be considered when interpreting results of screening programmes for congenital hypothyroidism and they lend further support to the use of a combination of serum thyroxine and thyrotropin determinations for optimum screening of such infants.

Outcome for survivors of mechanical ventilation weighing less than 1,250 gm at birth

We investigated the outcome in 28 survivors of mechanical ventilation weighing less than 1,250 gm at birth. Fifteen infants (54%) had neurodevelopmental sequelae, of whom eight had major handicaps. These eight infants differed significantly from the rest of the infants studied in the following manner: lower mean birth weight and gestational age, delay in transportation to our Neonatal Intensive Care Unit, and high incidence of bacterial sepsis. The remaining seven infants with NDS were functionally normal or minimally impaired at the time of the study, although significant problems may yet emerge with continued follow-up. Retrolental fibroplasia was diagnosed in 11 infants (39%) and resolved in two. The development of RLF was associated with prolonged oxygen exposure and the presence of bacterial sepsis. However, since major handicap, RLF, and sepsis were all problems observed in the smallest infants, a cause-and-effect relationship between sepsis and these sequelae remains speculative.

Prolonged orotracheal intubation in the newborn

One hundred seventy-four consecutive cases of newborn infants who required orotracheal intubation for longer than three days were studied retrospectively. The duration of intubation varied from 3 to 211 days with an overall mortality rate of 22.9%. There was one complication directly related to orotracheal intubation. One tracheotomy was performed. Orotracheal intubation is felt to be superior to nasal tracheal intubation and tracheotomy in managing infants in this age group who require prolonged assisted ventilation.

Oxygen consumption and insensible water loss in premature infants under radiant heaters

Oxygen consumption ((Vo2), carbon dioxide production (Vco2), and insensible water loss (IWL) were measured simultaneously in nine nondistressed, appropriately grown, premature infants less than 2 weeks old, nursed in a conventional, blow-warmed incubator, and were compared with measurements made on the same infants under a radiant heater. The infants had a pronounced increase (148% on average) in IWL when under the radiant heater (P < .001) whereas Vo2 increased by only 4.6% (P = .073). Abdominal skin temperature (servocontrolled to maintain 36.5 C) and esophageal temperature were the same under both conditions, but ambient air temperature was 0.7 C higher in the incubator (P < 05). Although a positive correlation was found between the increase in IWL and the change in Vo2 (r = .75, P < .01), the large increase in IWL (and, therefore, evaporative heat loss) under the radiant heater is out of proportion to, and cannot be accounted for, by the change in metabolic heat production. The heat transfer processes involved in maintaining body temperature constant under these conditions require further study.

Cerebral oxidative metabolism in perinatal post-hemorrhagic hydrocephalus

Survivors of perinatal intraventricular hemorrhage often develop a distinct clinical syndrome characterized by hydrocephalus and biochemical abnormalities in cerebrospinal fluid. The authors investigated six neonates with post-hemorrhagic obstructive hydrocephalus in order to identify cerebral metabolic disturbances responsible for the hypoglycorrhachia observed in this disorder. Lactic acid concentraions and lactate/pyruvate ratios in ventricular fluid were significantly elevated in infants with post-hemorrhagic hydrocephalus compared with the values in five with congenital (non-hemorrhagic) obstructive hydrocephalus. Comparable degrees of ventricular dilatation and intracranial hypertension were present in the two groups. There is evidence that neither residual cellular elements in ventricular fluid nor a disrupted blood-CSF barrier can fully explain the observed alterations in ventricular-fluid glucose, lactate or lactate/pyruvate ratios. It is suggested that when periventricular hemorrhage occurs, the associated cerebral ischemia leads to focal anaerobic glycolysis and increased glucose requirement. With inadequate cerebral glucose glycolysis and increased glucose requirement. With inadequate cerebral glucose delivery from the blood, glucose diffuses into the brain from the ventricular fluid, resulting in hypoglycorrhachia. Cerebral lactic acid production is enhanced, which accumulates in ventricular fluid in the presence of ventricular obstruction.

Congenital diaphragmatic hernia. New concept in management

The newborn infant with a congenital diaphragmatic hernia (CDH) who develops severe respiratory distress requiring operative repair within the first 24 hours of life represents one of the most challenging problems in pediatric surgery. The mortality in these infants still exceeds 50% and has historically been attributed to ventilatory insufficiency secondary to pulmonary hypoplasia. However, the primary abnormality in these neonates seems to be an increase in pulmonary vascular resistance with an elevation of pulmonary artery pressure, right-left ductal shunting, preductal shunting and progressive hypoxemia. Eighteen neonates with a CDH were operated upon within the first 24 hours of life with a mortality of 38%. In no instance did ventilatory insufficiency seem to be a major factor in the death of the patient. Seven infants with progressive hypoxemia were treated with a vasodilator, tolazoline. Six of the seven infants showed an initial response to treatment, with a rise in preductal PaO2 and a decrease in ductal shunting. Four of these seven desperately ill neonates survived. Pathologic examination of the pulmonary vasculature in the non-survivors revealed an increase in muscle mass within the pulmonary arterioles. An exaggerated vasoconstrictive response of an abnormally hypertrophied pulmonary vascular bed leading to an elevation of pulmonary vascular resistance, rather than abnormalities of ventilation, appears to be the important mechanism leading to the often fatal hypoxemia observed in the neonate with a CDH. Improved survival will depend upon the successful management of the deranged pulmonary vascular hemodynamics seen in these infants.

Intravenous alimentation and insensible water loss in low-birth-weight infants

Insensible water loss (IWL) was measured in six premature infants, between 4 and 21 days of age, by continuous weight monitoring on an electronic balance inside an incubator. Multiple measurements of IWL were made during the sequential infusion of 10% dextrose in 0.225% NaCl, 10% dextrose-amino acid solution, or 10% dextrose-amino acid and a commercial intravenous fat emulsion. Each solution was administered for three hours by constant infusion through a scalp vein needle. The order of the infusion was random and a 30- to 60-minute infusion with 5% dextrose water was given between each solution. During the infusion of 10% dextrose in 0.225% NaCl and 10% dextrose + amino acid solution, IWL was 1.0 +/- 0.8 gm/kg/hr and 1.1 +/- 0.8 gm/kg/hr, respectively. In contrast, IWL increased significantly to 1.6 +/- 0.7 gm/kg/hr when additional calories were given using the 10% dextrose-amino acid with the intravenous fat emulsion (P less than .005). There was a positive correlation between calorie intake and IWL. These data suggest that parenteral nutrition solutions with intravenous fat emulsion are rapidly metabolized and the increase in IWL is probably secondary to an increase in thermogenesis.

Head growth in sick premature infants--a longitudinal study

Serial weekly measurements of somatic growth and head circumference were made for ten weeks on 41 appropriately grown sick preterm infants (gestational age 28 to 32 weeks) with severe neonatal problems. Twenty-seven (66%) required prolonged assisted ventilation. During the period of acute illness, the velocity of growth for the sick infants was below that of the normal fetus, with deviation away from and below the normal fetal growth curve. During recovery, head growth paralleled that of normal fetal growth, and subsequently rapid "catch-up" growth in head circumference occurred. By comparison, six similar infants, whose head circumference followed the intrauterine growth curve, proved to have hydrocephalus. These results suggest that: (1) the brain participates in the growth retardation associated with being sick and premature and that apparently normal head growth under comparable circumstances may be associated with hydrocephalus; (2) in spite of an energy intake ranging from 80 to 120 kcal/kg/day by the end of the second postpartum week, normal growth in the sick low-birth-weight infant does not occur until their acute illness has resolved.

Furosemide in hyaline membrane disease

In a randomized clinical trial designed to evaluate the effect of diuresis on infants with hyaline membrane disease, seven infants were treated with furosemide (2 mg/kg intravenously) and five received 5% dextrose water in 0.225% sodium chloride (control group). Arterial blood gas analyses performed before and during the six hours after treatment showed no significant difference between control and treated infants. Urine output and urine sodium and calcium loss were significantly increased (P less than .05) in the infants receiving furosemide. The diuresis seemed to have no effect on left atrial size determined echocardiographically, whereas measurements of dynamic skinfold thickness suggested mobilization of subcutaneous water. One infant became seriously dehydrated and hypotensive secondary to a massive diuresis. We concluded that furosemide had a potent diuretic effect in infants with hyaline membrane disease but does not improve cardiorespiratory function acutely. This may be because of failure to mobilize pulmonary interstitial fluid in the time period tested. It may also be possible that the presence of pulmonary interstitial fluid does not play an important role in the impairment of gas exchange in the acute stage of hyaline membrane disease.

Digoxin therapy in low-birth-weight infants with patent ductus arteriosus

Digoxin therapy was evaluated retrospectively in a group of 30, and prospectively in a group of 16 low-birth-weight, premature infants with cardiorespiratory symptoms due to persistent patency of the ductus arteriosus. The response to decongestive therapy was equivocal. Digoxin levels in serum varied between 1.5 and 13 ng/ml. Digoxin half-life in serum exceeded three days in four patients. Fourteen of the combined group of 46 infants had signs of toxicity of digoxin. High dosage, inadvertent overadministration, and variable clearance of digoxin, as well as special characteristics of the patients studied, are postulated as explanations for the high incidence of toxicity. This study suggests that digoxin therapy in low-birth-weight, premature infants with patent ductus arteriosus is not without risk.

Urinary excretion of prostaglandin E following the administration of furosemide and indomethacin to sick low-birth-weight infants

Urinary excretion of prostaglandin E was measured in seven sick low-birth-weight infants. Four had severe hyaline membrane disease and one had chronic bronchopulmonary dysplasia; all received furosemide. Two infants had patent ductus arteriosus and received indomethacin. Following administration of furosemide, urine volume and the excretion rates of sodium and calcium were significantly increased; such changes were not seen following the administration of indomethacin. Prostaglandin E excretion rate was increased from 0.4 +/- 0.04 to 1.3 +/- 0.2 ng/mg Cr (mean +/- SEM) following administration of furosemide, but decreased in two patients following administration of indomethacin. The present results demonstrate that furosemide enhances urinary excretion of prostaglandin E by mechanisms which may reflect an increase in prostaglandin synthesis, a decrease in prostaglandin renal metabolism, or both. Indomethacin, which is a prostaglandin synthetase inhibitor, decreases the urinary excretion of prostaglandin E. These observations suggest that furosemide therapy in patients receiving indomethacin may be ineffective.

Indomethacin disposition and indomethacin-induced platelet dysfunction in premature infants

Indomethacin failed to produce permanent ductal closure in any of four premature infants with patent ductus arteriosus to whom the drug was given. Indomethacin half-lives measured in two premature infants were 21 and 24 hours, respectively, much longer than in full-term newborns or adults. Platelet function, as measured by platelet aggregation, was grossly abnormal for two to four days after indomethacin administration, normal values returning only by the ninth and tenth days. Gastrointestinal bleeding and transient renal dysfunction occurred in one infant. Measurement of plasma indomethacin concentrations in sick, low-birthweight infants could help guide indomethacin dose and dosage interval, prevent drug accumulation, and reduce toxicity. Further studies of potential toxicity seem to be indicated before instituting widespread indomethacin administration for ductal closure in premature infants.

Phototoxicity to the newborn primate retina

Newborn stump-tail monkeys were continuously exposed to 400 f-c of cool, white, fluorescent light for periods varying from 12 hr to 7 days. The right eye of each monkey was occluded by a patch of black velour material to serve as a control. The protected eyes retained normal ultrastructure; the exposed eyes showed progressive damage to the retina from the 12 hr to the 7-day exposure periods. Early changes were evident in the outer nuclear layer with darkly staining pyknotic nuclei and electrondense cytoplasmic processes that could be traced to their synaptic terminals. Late changes included marked distortion, vacuolization, and fragmentation of the rod and cone outer segments. The potential for phototoxicity to be additive to the normal aging of the retina is proposed, and we conclude that there is a sound basis for the current practice of patching the eyes of infants undergoing phototherapy.

Elective delivery of the term fetus. An obstetrical hazard

Of 1,020 consecutive admissions to a regional neonatal center, 38 infants were admitted following elective delivery in which no medical condition of the mother or fetus had necessitated immediate delivery. Twenty infants had problems that were not primarily the result of elective delivery, developed in 18. Fifteen of these 18 infants were delivered by cesarean section; in none of the mothers had any assessment of fetal maturity or size (other than the menstrual history and physical examination) been made. The infants remained in the hospital for an average of 12.7 days at a median cost of $2,678 per patient. One infant died. In the absence of pressing medical indications and without an objective assessment of fetal maturity, elective delivery remains potentially hazardous.

Chromosomal mosaicism in Down's syndrome: a diagnostic challenge

In individuals with mosaicism for trisomy 21, phenotype-karyotype correlations are unpredictable. Two patients are described--one with typical features of Down's syndrome and the other with severe mental retardation only. Both had normal karyotypes in their peripheral lymphocytes but high percentages of trisomic cells in skin fibroblasts.