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Maintaining fluid and heat balance is of vital importance to the newborn infant. At birth, the infant is exposed to a cold and dry environment, and preterm neonates in particular, are then at risk of dehydration and hypothermia. These conditions may have serious consequences and significantly influence mortality and morbidity. Preterm neonates have a high rate of water and heat loss mainly as a consequence of their immature skin. The care environment influences the magnitude of water and heat exchange and needs to be individually tailored on the basis of the infant's clinical status, maturity at birth and postnatal age. This paper reviews data obtained from series of studies on neonatal water and heat exchange using non-invasive measurements of insensible water loss and calculations of different modes of heat exchange. These studies have influenced the way in which newborn infants are being nursed today.

Improvements in obstetrical and neonatal care during the last decades have led to a marked increase in survival rate of preterm and term infants. In order to study the short- and long-term outcome in infants who survived neonatal intensive care (NIC) and were born in the county of Uppsala between January 1st 1986 and April 30th 1989, a prospective long-term follow-up study was conducted. Epidemiological data on all infants born in the county during the study period and the short-term outcome, measured as overall neuromotor function at term and at 2, 4, 6 and 10 months of corrected age in 245 infants surviving NIC and 72 healthy control infants are presented. The infants' neuromotor function was evaluated with different clinical neurological methods. In the study population of NIC infants 85.9% survived the neonatal period. The early infant mortality was high in this group 11.6% compared to that of all infants born in the county of Uppsala (0.30%). Only a minority of the infants showed abnormal neuromotor function. A comparison of the results of the overall evaluation of neuromotor function at 10 months of age with those of the examinations made at an earlier age showed poor correspondence in individual infants, especially in preterm and very preterm infants.

Fetal human lung fibroblasts and feline lung epithelial cells were exposed to either a surfactant or N-acetylcysteine in various concentrations for 24-48 hours, after which the hyaluronan concentration in the culture medium was determined. Most of the experiments showed no stimulatory effect of either artificial or natural surfactant on hyaluronan synthesis. N-acetylcysteine 5-100 mg/mL induced progressive stimulation of hyaluronan synthesis by human fetal lung fibroblasts, resulting in a maximum hyaluronan concentration six times that released by unexposed cells. A slight increase in hyaluronan synthesis was also observed after exposure of feline fetal lung epithelial cells to N-acetylcysteine 50-100 micrograms/mL.

In an experimental study we determined the response trigger delay time of three infant ventilators with a capacity to detect and support spontaneous breathing. We measured this in anaesthetized cats as the time between the start of phrenic nerve activity and the increase in airway pressure caused by the subsequent inflation. Two modes of ventilatory support were used, namely Assist/Control (A/C) and synchronised intermittent mandatory ventilation (SIMV). We found that ventilators equipped with flow sensors close to the free end of the endotracheal tube had a shorter trigger delay than a ventilator which detected breathing with an abdominal sensor. Further, the trigger delay was shorter in SIMV mode than in A/C mode of operation. A higher set sensitivity reduced the response time. We conclude that triggered ventilation may be used in infants, at least when the spontaneous breathing rate is below 60 breaths per minute. This mode of ventilation could be useful when infants are to be weaned off the ventilator.

A new protocol for structured observation of motor performance, for use both in term and preterm infants, has been tested regarding interobserver agreement and intraobserver consistency. Ten different motor items are assessed concerning the developmental level as described in the protocol. Any deviations from the description of the level are noted. The two main observers twice reassessed video recordings of 17 infants who had primarily been assessed by them both in an ongoing follow-up study. The two observers arrived at the same level of development in 75% of the observed items at the first reassessment and in 81% at the second, and agreed concerning deviation in 73 and 79% of the observations at the two reassessments, respectively. Each observer arrived at the same level of development at all three assessments in 62% of the observed items. Thus when used by these two observers the protocol has an acceptable degree of interobserver agreement and intraobserver consistency.

This study was made to determine how oscillations superimposed on intermittent positive pressure ventilation (IPPV) influence the arterial blood gases, pH and the airway pressures during adequate alveolar ventilation i.e. at inhibition of inspiratory activity, before and after experimentally induced lung injury in the anaesthetized cat. Two IPPV frequencies were studied. The lung was injured by instillation of xanthine oxidase into the upper airways during IPPV. The peak, mean and end-expiratory intrapleural and airway (intratracheal) pressures at two levels were measured and the arterial blood gases and pH were determined at inhibition of inspiratory activity with and without superimposition of oscillations on the ventilatory pattern. Before lung injury, superimposed oscillations lowered the airway pressures only at an IPPV rate of 15 breaths per minute (b.p.m.). After lung injury, such oscillations increased the airway pressures only at 15 b.p.m. The airway pressures were always lower at 60 than at 15 b.p.m.

A speech and language assessment procedure was developed to study different aspects of speech and language skills in children 6.5 years old who had needed intensive care in the neonatal period. It was required that the procedure could be carried out at one examination session and that it should characterize a broad spectrum of language skills and permit detection of deviations in language development. The assessment comprises three parts. Part A is an evaluation of the child's spontaneous speech during a 10- to 15-minute conversation between the child and the assessor. Eight different variables are assessed, and an overview of the child's conversational behaviour is obtained. Part B is an assessment of speech and language skills. A set procedure is used to assess auditory discrimination, interaction between auditory and speech motor capacity, different comprehension functions, vocabulary and word fluency. Some motor tasks are included to elucidate the relationship between speech and non-linguistic fine motor activity. Part C is an interview with the parents. A control group of 40 children was tested. The assessment protocol is now being applied for follow-up examination of children who have needed neonatal intensive care at Uppsala University Hospital, Sweden.

A study was performed to investigate whether measurements of the evaporation rate from the skin of newborn infants by the gradient method are affected by the presence of non-ionizing radiation from phototherapy equipment or a radiant heater. The evaporation rate was measured experimentally with the measuring sensors either exposed to or protected from non-ionizing radiation. Either blue light (phototherapy) or infrared light (radiant heater) was used; in the former case the evaporation rate was measured from a beaker of water covered with a semipermeable membrane, and in the latter case from the hand of an adult subject, aluminium foil or with the measuring probe in the air. No adverse effect on the determinations of the evaporation rate was found in the presence of blue light. Infrared radiation caused an error of 0.8 g/m2h when the radiant heater was set at its highest effect level or when the ambient humidity was high. At low and moderate levels the observed evaporation rate was not affected. It is concluded that when clinical measurements are made from the skin of newborn infants nursed under a radiant heater, the evaporation rate can appropriately be determined by the gradient method.

This study was undertaken to determine whether oscillations superimposed on a regular ventilatory pattern influence the arterial blood gases and pH and the airway pressures at adequate alveolar ventilation at the onset of inhibition of inspiratory activity. The peak, mean and end-expiratory airway pressures were therefore measured at inhibition of this activity with and without superimposition of oscillations on the ventilatory pattern. It was found that superimposed oscillations lowered the airway pressure only at a low ventilatory frequency, whereas inhibition occurred at almost equal arterial PCO2 and pH values with and without superimposed oscillations on the ventilatory pattern.

Eight patients born at term in the years 1974-76, with neonatal convulsions due to severe perinatal asphyxia, were treated for 6-11 days with continuous intravenous infusion of diazepam. Doses of 1.0-1.5 mg per hour (mg/h) were usually required to stop the convulsions. In one infant 2.75 mg/h was needed. During the treatment, all infants had measurable serum concentrations of diazepam, half of them above 35 mumol/1. The convulsions stopped in all eight infants, and did not return after discontinuation of the infusion. Side-effects were noted in all infants, but they were all able to breathe adequately. At follow-up the psychomotor development was normal in all cases and there were no signs of neurological disorders, except in one patient, in whom mild epilepsy was observed. Continuous infusion of diazepam should be given in doses of at least 1 mg/h (corresponding to around 0.3 mg/kg h) to stop convulsions in full-term infants efficiently and should be increased under close supervision and with monitoring of respiration and heart rate until treatment is effective.

Factors that may influence the water transport through the skin in infants on their first day of life were studied with a method based on determination of the vapour pressure gradient in the air layer close to the skin surface. The evaporation rate from the skin was found to vary with the site of measurement, ambient humidity, temperature, activity, gestational age and nutritional status at birth. Differences related to maturity were shown to decrease with postnatal age.

A method for measuring water exchange through human skin has been developed. It is based on estimation of the vapour pressure gradient immediately above the surface of the skin and permits the skin area investigated to be exposed to the ambient air during the entire period of measurement. Influence on the microclimate above the skin, with respect to humidity and temperature, is thereby minimized. An instrument for measuring small amounts of water evaporated from or absorbed by a surface per unit time and area is described and its accuracy discussed. The instrument has a high degree of accuracy and better sensitivity than previously described devices used for this purpose. It has been used primarily to investigate the rate of evaporation from the skin surface in newborn infants and from the skin in patients with burns.

The effects of intra-arterial and intravenous injections of adenosine and hypoxanthine were investigated with special reference to respiratory variables in anesthetized young cats. Studies were made of the effects on inspiratory activity (phrenic nerve activity), heart rate, blood pressure and central venous pressure. To assess the risk of accumulation of adenosine degeneration products after several injections measurements were also made of hypoxanthine, xanthine and urate in plasma at intervals after the injections. It was found that intra-arterial and intravenous injections of adenosine increased central inspiratory activity during the first few breaths after the injection. The blood pressure and heart rate decreased slightly and central venous pressure increased slightly after the injection. Degradation of adenosine and its metabolites takes place rapidly and it is therefore unlikely that metabolites influence the results. It is concluded that adenosine causes brief stimulation of inspiratory activity.

The changes in blood pressure, heart rate, cardiac output and blood flow in the femoral and common carotid arteries on carotid sinus nerve stimulation (CSNS) were studied in chloralose anaesthetized dogs, both with spontaneous heart rhythm and during atrial pacing. Stimulation of the sinus nerves with impulse trains and with impulses of constant frequency had almost equal effects on the blood pressure. The former had a greater effect on the heart rate; these findings verified earlier observations. The reductions in cardiac output followed those in heart rate. During atrial pacing the stroke volume was reduced on CSNS. The total peripheral resistance, regional peripheral resistances and input impedance of the vascular bed of the femoral artery were calculated. The initial effects of CSNS varied in relation to the prestimulation total peripheral resistance and to stimulation frequency. Differences between stimulation with a constant frequency and the intermittent types, with the same number of impulses per cardiac cycle, were negligible as regards effects on stroke volume, blood flow and regional vascular resistances. CSNS caused changes in input impedance of the vascular bed of the femoral artery which were very similar to those observed earlier on intraarterial injection of vasodilator drugs. The different effects of intermittent and constant frequency CSNS on the heart rate in dogs with intact vagal nerves and no clamping of the common carotid arteries might be caused by asymmetries in the autonomic effects on the S.A. node. The neurophysiological mechanisms are discussed. It is deduced that greater reductions in blood pressure with intermittent stimulation are only obtained in the pre-existence of a high sympathetic tone.