T Riesenfeld

Deficient Herpes Simplex Virus-Induced Interferon-α Production by Blood Leukocytes of Preterm and Term Newborn Infants

ABSTRACT: The ability of peripheral blood mononuclear cells (PBMC) from newborn infants, gestational age 24-42 wk, to produce interferon-α (IFN-α) on the first day after birth was studied in vitro. Human amnion cells (WISH) coated with herpes simplex virus type I and fixed by glutaraldehyde were used as IFN-α inducers. Individual IFN-α producing cells (IPC) among PBMC were determined by an immunoplaque assay. The frequency of IPC was low in all premature (≤36 wk) infants (median 0.3 IPC/104 PBMC, range 0.0-2.6), and significantly higher (median 2.0 IPC/104 PBMC, range 0.0-16.4) in term infants (>37 wk). The frequencies were lower in both groups of infants than in adults (7.3 IPC/104 PBMC, range 2.0- 23.7). When a conditioned medium from cultures of herpes simplex virus type I-stimulated PBMC from adults was added to the IFN induction cultures, the frequencies of IPC increased in PBMC from both preterm and term infants, and in the latter group did not differ significantly from adult levels. The median production of IFN-α per IPC was 1.1 U (range 0.0-2.8) in premature infants, 1.0 U (range 0.0-8.8) in term infants and 3.2 U (range 1.5-8.0) were decreased, a decline of IPC frequencies occurred. This decline was more marked and started at higher PBMC concentrations in infants than in adults, and was prevented by addition of conditioned medium from herpes simplex virus type I-stimulated cultures of PBMC from adults. The results suggest that PBMC of preterm infants on the first day after birth are deficient both with respect to the proportion of actual IPC and to accessory mechanisms necessary for a normal IFN-αresponse. In contrast, IPC frequencies in term infants approach levels of adults, but accessory functions may still be deficient.

Irregular breathing in young lambs and newborn infants during heat stress

Ten healthy unanaesthetized full‐term lambs, aged 4‐12 days, were studied during moderate radiant heat stress, and 21 full‐term newborn infants were studied during moderate convective heat stress. The rate of breathing and the breathing pattern were recorded, using strain gauges made of mercury‐filled rubber tubing placed around the thorax and abdomen. In both the lambs and the infants the respiratory rate increased during heat stress. When this increase began, both the lambs and infants had short periods of very rapid breathing followed by short apnoeas. The concentrations of carbon dioxide and water in a flow‐through system collecting expired air increased during the short periods of rapid breathing and then decreased again during the subsequent short apnoeic period.

Respiratory Water Loss in Relation to Activity in Fullterm Infants on Their First Day after Birth

ABSTRACT. Respiratory water loss (RWL), oxygen consumption and carbon dioxide production were measured in ten fullterm infants on their first day after birth, using an open flow‐through system with a mass spectrometer, specially equipped with a water channel, for analysis of gas concentrations. Measurements were made both with the infant asleep and during different levels of motor activity. The ambient temperature was maintained at approximately 32.5°C and the ambient relative humidity at 50%. RWL increased from 4.2±0.7 (SD) mg/kg min when the infant was asleep to 6.3±1.0 mg/kg min when he or she was awake but calm; with increasing activity there was a further increase in RWL. The oxygen consumption increased from 5.4±0.9 (SD) ml/kg min during sleep to 6.9±0.8 (SD) ml/kg min when awake, and also increased further with increasing activity.

Respiratory water loss in relation to gestational age in infants on their first day after birth.

Respiratory water loss, oxygen consumption and carbon dioxide production were measured in 32 infants on their first day after birth. Gestational age was between 27 and 41 weeks. All infants were studied in incubators with 50% ambient relative humidity and an ambient temperature that allowed the infant to maintain a normal and stable body temperature. During the measurements the infants were usually asleep. Respiratory water loss was found to be highest in the most preterm infants and lower in more mature infants. Respiratory water loss per breath (mg/kg) was almost the same at all gestational ages and the higher respiratory water loss found in the most preterm as compared with the more mature infants is thus due to a higher rate of breathing. Oxygen consumption was lowest in the most preterm infants and increased with increasing gestational age. Thus, in full‐term infants respiratory water loss and transepidermal water loss are of approximately equal magnitude at an ambient humidity of 50%, while respiratory water loss constitutes a smaller proportion than trans‐epidermal water loss in very preterm infants. Respiratory water loss increases with the rate of breathing. ? Insensible water loss, oxygen consumption, preterm infants, respiratory water loss

Respiratory water loss and oxygen consumption in newborn infants during phototherapy

Respiratory water loss was measured together with oxygen consumption (±O2) and carbon dioxide production (±CO2) in 11 full‐term and eight preterm infants (mean gestational age 34 weeks, range 31‐36 weeks) before and during 1 h of phototherapy. The method for determination of respiratory water loss, ±O2 and ±CO2 was based on an open flow‐through system with a mass spectrometer for measurement of gas concentrations. All infants were studied naked in an incubator with an ambient relative humidity of 50% and with a controlled environment with respect to temperature and air velocity. The infants were calm during the measurements. Before phototherapy, in term infants respiratory water loss was 4.4 (SD 0.7) mg/kg min and ±O2 5.9 (0.9) ml/kg min and in preterm infants respiratory water loss was 4.7 (0.8) mg/kg min and ±O2 6.1 (0.8) ml/kg min. No significant difference was found between values obtained during or after 1 h of phototherapy and those obtained before.

Respiratory water loss and oxygen consumption in full-term infants exposed to cold air on the first day after birth

Respiratory water loss, oxygen consumption, carbon dioxide production and skin blood flow were measured continuously in nine full‐term infants on the first day after birth. After at least 18 min of measurements with the infant asleep in an incubator, with an air temperature of 33°C and a relative humidity of 50%, the temperature of the incubator air was lowered to less than 27.5°C. This resulted in a significant decrease in skin temperature and peripheral skin blood flow, while the infants core temperature remained unchanged. At the same time, mean respiratory water loss increased from 3.7 to 6.1 mg/kg‐min, which can be explained partially by the decrease in ambient humidity that accompanied the decrease in air temperature. In addition, mean oxygen consumption increased from 5.3 to 7.9 ml/kg. min and mean carbon dioxide production increased from 3.8 to 5.9 ml/kg‐min. There was no concomitant increase in motor activity. Thus, when the newborn infants were exposed to cool air, they reacted with an increase in respiratory water loss, oxygen consumption and carbon dioxide production before their core temperature was affected and without increasing their motor activity.

RESPIRATORY WATER LOSS IN RELATION TO GESTATIONAL AGE IN NEWBORN INFANTS

We have earlier shown that the transepidermal water loss is much higher in the preterm infant than in the fullterm infant. Recently we found that the respiratory water loss (RWL) contributes more than 50 % to the total insensible water loss at rest in fullterm infants on their first day after birth. We have now studied RWL, oxygen consumption and carbon dioxide production in preterm infants.The method used is based on an open flow-though system with a mass-spectrometer for gas analysies. Measurements were made in infants of gestational ages between 29 and 36 completed weeks with the infant at rest and at the first day after birth. The infants were studied in incubators with ambient humidity of 50 % and ambient temperature so that the body temperature was stable between 36.5 and 37 °C.The results showed no clear difference in RWL in relation to gestational age. In addition there was no clear difference in oxygen consumption in relation to gestational age. This means that the RWL contributes to a much lesser extent to the total insensible water loss in the preterm infant than in the fullterm infant.

23 RESPIRATORY WATER LOSS IN RELATION TO ACTIVITY IN FULLTERM NEWBORN INFANTS

In the newborn infant water loss from the skin has earlier been said to contribute 75% to the total insensible water loss. With a method for direct measurement of respiratory water loss (RWL) we have found that this loss contributes more than 50 % to the total insensible water loss at rest in fullterm infants on their first day after birth. The influence of activity on the respiratory water loss has now been studied in ten healthy fullterm infants on their first day after birth.RWL is measured with an open flow-through system, where air drawn over the face of the infant picks up the expired gas. The flow of mixed gas is measured with a Fleisch flow-head connected to a differential pressure transducer, and the concentrations of water vapour, oxygen and carbon dioxide in the mixed gas and in the ambient air are measured with a Perkin Elmer mass-spectrometer. RWL, oxygen consumption and carbon dioxide production are calculated from the obtained flows and concentrations. During the measurements the infant is placed in an incubator with carefully controlled air temperature, humidity and air flow velocity. The infants are then studied at different activities, from deep sleep to furious crying.RWL was 4.2 mg/kg min with the infant at rest in an ambient humidity of 50 % and an ambient temperature of 32.5 °C. Oxygen consumption was 5.4 ml/kg min. Both RWL and oxygen consumption increased with increasing motor activity. When the infant was crying RWL increased to 10.8 mg/kg min while oxygen consumption increased to 8.2 ml/kg min.

RESPIRATORY WATER LOSS IN FULLTERM INFANTS ON THEIR FIRST DAY AFTER BIRTH

The water loss from the skin, has been considered to constitute around 75 % of the insensible water loss (IWL), the remaining 25 % being respiratory water loss (RWL). In previous studies we have found that the water loss from the skin varies with environmental factors such as ambient humidity and air flow velocity, and with factors related to the infant, such as gestational age and postnatal age. In very preterm infants nursed in a dry environment the water losses from the skin were found to be very high on the first days of life.We have developed a method for measurement of RWL to be used in newborn infants. RWL is measured in an open flow-through-system, where air drawn over the face of the infant, picks up the expired gas. The flow of mixed gas is measured with a Fleisch flow-head connected to a differential pressure transducer, and the concentrations of water vapour, oxygen and carbon dioxide in the mixed gas and in the ambient air are measured with a Perkin Elmer mass-spectrometer. RWL, oxygen consumption and carbon dioxide production are calculated from the obtained flows and concentrations. Measurements were made on the first day of life in normal, fullterm infants. During the measurements the infants were placed in incubators with carefully controlled air temperature, humidity and air flow velocity.RWL was around 5 mg/kg min or 25 g/day per infant with the infant at rest in an ambient humidity of 50 % and an ambient temperature of 32.5 °C. Oxygen consumption was around 7 ml/kg min and RQ was around 0.8. Both RWL and oxygen consumption increased with increasing motor activity. When the infant was crying RLW often increased by 100 % as compared to at rest. A linear relationship was found between RLW and ambient humidity with higher values at a low humidity than at a high one.

80 RESPIRATORY WATER LOSS AND OXYGEN CONSUMPTION IN FULLTERM NEWBORN INFANTS EXPOSED TO COOL AIR

The response to an ambient air temperature (Tamb, °C) below the thermoneutral zone was studied in nine fullterm newborn infants. Respiratory water loss (RWL, mg/kg min), oxygen consumption (VO2, ml/kg min), carbon dioxide production (VCO2, ml/kg min), core (Tc, °C) and peripheral temperature (Tp, °C), and truncal (Qt, %) and peripheral (Qp, %) skin blood flow were continuously monitored during initial care at a Tamb within the thermoneutral zone (interval A) and after lowering Tamb, to below 27.5°C (interval B). Mean values for intervals A and B are given in the table. Values for Qp and Qt depict relative change in blood flow, with the mean value for interval A=100%.Newborn infants exposed to cool air react with an increase in respiratory water loss, oxygen consumption, carbon dioxide production and an decrease in peripheral skin blood flow and skin temperature before their core temperature is affected and without increased motor activity. RQ remains unchanged.