Skin derivative control of thermal environment in a closed incubator

Defining a thermoneutral environment remains difficult because thermoneutrality depends on both physical and physiological factors. A servocontrolled skin temperature derivative (SCS) heating device has been designed to control the thermal environment in closed incubators without the necessity of setting an air or skin reference temperature. The thermal environment obtained with the SCS program is controlled only by the neonate's skin temperature changes. For each neonate, the program allows the attainment of a specific individual thermal equilibrium (Teq). Although the mean value of the thermal equilibrium level measured on 29 neonates does not differ significantly from the neutral air temperature defined from the charts of other researchers, individual values of Teq differed greatly among neonates of similar birthweight and postnatal age. When compared with on/off heating programs, the SCS system permits greater quiet sleep occurrence and seems to provide an optimal thermal environment. The results suggest that the skin temperature derivative heating program takes into account both the ambient and physiological factors affecting body temperature regulation of each neonate.

Characterization of human sperm antigens reacting with antisperm antibodies from autologous sera and seminal plasma: comparison among infertile subpopulations

Immunoblotting techniques were used to characterize the reactivity of human sperm antigens with sperm antibodies from different groups of infertile subjects. Sperm antigens of each subject were tested with autologous sperm antibodies present in serum and seminal plasma in order to assess whether there were qualitative differences in the antigenic structure of spermatozoa among the various infertile groups. Sixty-one infertile males, divided into six groups according to changes in the two main semen parameters (sperm concentration and motility), entered the study. Immunoreactivity to several antigens, in both serum and seminal plasma, was usually demonstrated in infertile subjects. Using a complex statistical package no significant difference was found in the distribution of antigens between groups; this included previously termed "fertility-related antigens' (28, 35, 57 and 62kDa proteins). This suggests that the most relevant sperm antigens involved in reproduction have no particular relationship to sperm concentration and motility.

Brain capillary perfusion during sleep

Brain capillary perfusion was evaluated in the different states of the wake-sleep cycle-quiet wakefulness (QW), quiet sleep (QS), and active sleep (AS)-in rats. The extent of the perfused capillary network was determined by intravascular distribution of a fluorescent marker. Evans blue (EB); it remained unchanged across the three behavioral conditions, QW, QS, and AS. The anatomical network was assessed by alkaline phosphatase (AP) endothelial staining, which is known to underestimate the number of existing capillaries. The resulting number of AP profiles were, therefore, significantly lower than the number of EB profiles, but the percentage of AP-stained capillaries that were perfused (96%) was also unchanged across the behavioral conditions. The results indicate that no capillary recruitment accompanies the wake-sleep cycle. Capillary surface area is a relevant factor in determining exchanges across the blood-brain barrier. In the absence of capillary recruitment (relative constancy of the surface area), the CBF changes during sleep should preferentially affect flow-limited with respect to diffusion-limited transport.

Body temperature regulation in the newborn infant: interaction with sleep and clinical implications

Thermoregulation in newborn infant differs from that of adult. Comparisons between sleep stages show that, during rapid eye movements (REM) sleep, the impairment of thermoregulatory responses in adult is not observed in newborn. Both behavioral and autonomic temperature regulations are always operative in the range of air temperatures usually imposed. The interaction between sleep and thermoregulation seems to be less important in newborns than in adults, suggesting that sleep processes are well protected, reducing the probability of occurrence of central dysfunction. According to the model describing thermoregulation during sleep on the basis of changes in the hierarchical dominance of brain structures, either the influence of diencephalic structures is never depressed in REM sleep or the functional autonomy of the rhombencephalon is still relevant in the immature encephalon of the newborn. The thermoregulatory model also allows understanding of inter-individual differences in thermoregulation and levels of thermoneutrality. An attempt has also been made to learn the role of heat stroke in the production of sudden infant death syndrome when body heat loss is hampered.

EEG features and epilepsy in patients with autism

Epileptic seizures are frequently reported (4-32%) in autism. These values are higher than in the normal population of children and adolescents (0.5%). In the literature there is no uniform description of epilepsy in autism. We examined 106 patients with autistic disorder divided into three groups on the basis of presence or absence of EEG paroxysmal abnormalities (PA) and / or epilepsy including febrile convulsions (FG). Our patients presented an autistic syndrome unrelated to clear congenital or acquired encephalopathy. The prevalence of epilepsy and EEG PA was 23.6% and 18.9%, respectively. Significant differences between the three groups appeared for (i) familial antecedents for epilepsy / FC and neurologic and psychiatric diseases (P < 0.004), (ii) a different proportion between the three groups for mental retardation (P < 0.03), (iii) and EEG fast activity (P < 0.04). Our patients showed several types of epilepsy, including idiopathic forms with seizure onset after the age of 10 in 45% of cases. Seizures were mainly partial, not frequent and controllable by anti-epileptic drugs. PA were mostly focal and multifocal and in 45% of cases were typical of benign childhood partial epilepsy with centro-temporal spikes. The higher incidence of epilepsy and EEG PA is apparently not related to organic pre-, peri- and postnatal antecedents or cerebral lesions. On the contrary, genetic factors responsible for autism and epilepsy seem important in the genesis of these two disorders.

Pharmacokinetics and pharmacodynamics of eltanolone (pregnanolone), a new steroid intravenous anaesthetic, in humans

Eltanolone, a new intravenous steroid anaesthetic agent was administered intravenously in a dose of 0.6 mg.kg-1 over 45 s to eight healthy male volunteers to evaluate some of its pharmacokinetic and pharmacodynamic effects. Drug concentration-time data were analysed by PCNONLIN, a non-linear regression programme, showing data consistent with a three-compartment model with initial distribution half-life t1/2 lambda 1 between 0.3 and 2 min, intermediate distribution half-life t1/2 lambda 2 between 12 and 29 min and terminal half-life t1/2 lambda z between 72 and 212 min. The total body clearance of eltanolone was rapid and with individual values in the range 1.6-2.3 l.h-1.kg-1. Eltanolone was initially distributed into a relatively large central compartment V1 between 0.09 and 0.98 l.kg-1 and then extensively further distributed (Vss between 1.80 and 5.44 l.kg-1 and V between 4.87 and 11.87 l.kg-1). The excretion of unchanged of eltanolone in urine was very small, the renal clearance was less than 0.5% of the total clearance. Induction of anaesthesia was trouble free with onset and duration of anaesthesia between 1-2 min and 6-13 min, respectively. There was slight respiratory depression, a small transient increase in heart rate, and a maximum reduction in arterial blood pressure of 23%, as compared with the resting level. Pain on injection and venous sequelae were not seen. Involuntary movements were seen in one subject. We conclude that eltanolone has a favourable pharmacokinetic profile with relatively rapid half-lives, large distribution volumes and rapid total body clearance.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of sleep and body temperature in response to exposure to cool and warm environments in neonates

BACKGROUND AND OBJECTIVE

Thermoregulation is impaired during desynchronized sleep in animals and in adults. This can lead to a conflict between homeothermy and sleep in nonthermoneutral conditions. This study aimed to analyze thermoregulation during sleep, especially during desynchronized sleep (active sleep, AS) and to determine whether the conflict between thermoregulation and sleep might exist in the newborn sleeping in warm or cool conditions.

METHODS

Esophageal and skin (cheek and abdomen) temperatures, local sweating rate (ventilated sweat collection capsule stuck on the abdomen), metabolism (indirect respiratory calorimetry), and sleep variables were recorded in 10 newborns exposed, in an incubator, to thermoneutral, warm, and cool environments. Body movements and apneas were also considered. Exposures were performed after a first habituation condition.

RESULTS

Sleep structure was not modified by the first exposure nor by the warm environment. Exposure to cool temperatures increased AS duration (+13% of total sleep time) and the quantity of body movements during AS (+11.3% of AS duration), whereas these parameters were not modified during quiet sleep. The thermoregulatory response to warm and cool environments was not impaired during AS. During exposure to mild thermal load, analyses revealed large interindividual differences in the strategy for thermoregulation during AS. Depending on the newborn, the thermoregulatory response to cool temperatures could be described by an increase either in nonshivering thermogenesis or in frequency of body movement. In warm conditions, most newborns exhibited an increased sweating rate. The interindividual differences (lack of increase sweating in three newborns) seemed to be linked to changes in the sensitivity of the sweating response.

CONCLUSION

Because thermoregulation is not impaired during AS, this sleep stage seems to be a well-protected one from a thermoregulatory point of view. This difference from adults and animals may be due to the important role of AS in newborn's nervous maturation.

Brain blood flow and extracerebral carotid circulation during sleep in rat

Cerebral blood flow (CBF) and blood flow (BF) in extracerebral head structures were measured during the sleep-wake cycle in rats using radioactive microspheres. While no statistically significant changes occurred in the transition from Waking to quiet sleep (also referred to as synchronized or non-REM Sleep), CBF increased significantly in active sleep (AS, also referred to as desynchronized or REM Sleep) in all structures considered, with the sole exception of the cerebellum. In extracerebral head structures, no significant state-dependent BF changes were found. Factor Analysis however extracted a common factor accounting for BF variability in the external carotid circulation. This factor was uncorrelated with CBF changes in AS, suggesting independent regulation of the two vascular beds in this sleep state.

Effect of continuous heat exposure on sleep during partial sleep deprivation

This study examined the effects of continuous heat exposure on sleep structure during a partial sleep-deprivation regime. The experimental protocol was divided into three periods. After a baseline period (5 days and nights at 20 degrees C), the sleep of the subjects was restricted to the second half of the night (3 a.m.-7 a.m.) for four consecutive nights. The restricted-sleep period was followed by two recovery days and nights. During the deprivation and recovery periods, the ambient temperature was 20 degrees C for six of the 12 subjects and 35 degrees C for the others. Sleep, esophageal and mean skin temperatures were continuously recorded. At 20 degrees C, the expected effect of sleep debt was apparent. There were significant reductions in time spent awake and in latencies for sleep and stage 4 sleep. The duration of stage 4 sleep significantly increased during the four successive restricted-sleep nights, whereas esophageal temperature significantly decreased over the successive days. When heat was added, esophageal temperature decrease was weakened, and the significant increase in stage 4 duration seen at 20 degrees C was not found. The findings suggest that the heat load imposed in our experimental condition has a suppressive effect on sleep stage 4 increase, which is induced by sleep restriction. The hypothesis that an increase in this sleep stage serves as a mechanism for energy conservation should be also considered.

Aerobic capacity of competitive ice hockey players 10-15 years old

Oxygen uptakes (VO2) recorded at anaerobic threshold and at the end of a maximal exercise (VO2 max) and their relation to left ventricular function were analyzed in 11 young ice hockey players during an incremental exercise on a bicycle ergometer. The children, highly trained, participated annually during 6 years (from the age of 10-15 years) in laboratory tests. The maturative status of the subjects was evaluated from peak height velocity (PHV). Heart rate was recorded by electrocardiogram. Oxygen uptake, CO2 production, respiratory frequency, pulmonary ventilation (VE) were recorded at rest and every 30 s during exercise through a Rudolph valve connected to a calibrated oxycon gas analyser. The anaerobic threshold was determined by a non-invasive method from pulmonary ventilation curves. Left ventricular volumes at end-systole and end-diastole were obtained, at rest, by M mode echocardiography. Results showed that both VO2 at anaerobic threshold and VO2max were positively correlated with body mass or with age of PHV. The increments were constant from year to year. At anaerobic threshold, the ratio VO2/VO2max was independent of maturative age. Similar findings were observed when considering VE except after the years of PHV where there was a remarkable increase in pulmonary ventilation. The results indicate that the growth of each cardiorespiratory component is optimalized with body size increase in order to keep constant the aerobic response to exercise. As judged by the explained variance of the different linear regression analyses between resting left ventricular dimensions and VO2, cardiac volume was of minimal importance in determining VO2. In the postpubertal period, stroke volume accounted for 26.7% of VO2 at anaerobic threshold and 30.0% of VO2max. This suggests that local changes occurring at muscular level are of paramount importance in determining the aerobic capacity of highly trained boys.

Spinal cord blood flow changes during the sleep-wake cycle in rat

Regional spinal cord blood flow was measured in rats during the sleep-wake cycle with the use of radioactive microspheres. Spinal cord blood flow decreases from wakefulness to quiet (synchronized) sleep while increasing in active (desynchronized) sleep. Blood-flow changes depend on changes in vascular resistance whose mechanisms have yet to be elucidated. Blood-gas tension or mean arterial pressure, however, do not play a relevant causal role.

Maximal oxygen uptake and aerobic-anaerobic transition on treadmill and bicycle in triathletes

The maximal aerobic capacity and the aerobic-anaerobic transition were analyzed on 14 triathletes performing an incremental work load on a bicycle ergometer and on horizontal or inclined treadmills. To compared the cardiorespiratory responses between cycling and running, the subjects were divided into 2 groups of 7 with similar aerobic capacity determined from cycle runs. The first group ran on horizontal treadmill while the second group performed similar exercise on inclined treadmill at constant grade (1.5%). Heart rate was recorded by electrocardiogram. Oxygen uptake (VO2), CO2 production (VCO2), respiratory frequency, and pulmonary ventilation were monitored at 30 s intervals through a Rudolph valve connected to a calibrated Oxycon V. Tidal volume, respiratory exchange ratio, equivalent O2 and CO2 were calculated from on-line computer. Aerobic and anaerobic thresholds were determined by a non-invasive method from pulmonary ventilation curves. The results showed that maximum oxygen uptake (VO2max) did not differ between the 2 types of ergometers. Pulmonary ventilation, heart rate and VO2 recorded at aerobic and anaerobic thresholds depended on the mode of exercise and reached the highest values on inclined treadmill. The amount of muscle mass, the type and the distribution of active motor units involved in each exercise test might be at the origin of these differences. This indicates that, when assessing a training program from anaerobic threshold values, it is necessary to take into consideration the type of ergometer used and the protocol performed.

Electroencephalogram and cardiovascular responses to noise during daytime sleep in shiftworkers

Intermittent noise occurring during sleep has been found to induce heart rate, peripheral vasomotor and electroencephalogram (EEG) changes. This study analysed these responses during the daytime and night-time sleep of shiftworkers doing a three shift system, to determine the influence of the inversion of the sleep-wake cycle on the sensitivity to noise. A group of 14 shiftworkers [aged 37 (SD 5) years] underwent an habituation daytime sleep, two experimental daytime sleeps and a night-time sleep. Traffic noises were presented during sleep [truck, 71 dB(A); motorbike, 67 dB(A); and car, 64 dB(A)] at a rate of nine each hour. The EEG measurements of sleep, electrocardiogram and finger pulse amplitude were recorded continuously. The results were expressed by computing the percentage of observed cardiac response (%HRR) and vasoconstrictive response (%FPR), magnitude of heart rate variation (heart rate response; HRR), percentage of reduction of the digital blood flow (finger pulse response, FPR), cardiac cost (CC = % HRR x HRR) and vasomotor cost (VC = % FPR x FPR). The results showed that, compared to night-time sleep, there was change in the structure of daytime sleep, that is an increase in slow wave sleep (SWS), especially stage 4 sleep decrease of stage 2 and rapid eye movement (REM) sleep latencies, and an earlier SWS and REM sleep barycentric point. During daytime sleep the % FPR was significantly smaller in SWS than in stage 2 or REM sleep. Large differences were observed in % HRR, HRR and CC between daytime sleep stages (SWS less than stage 2 less than REM sleep).(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular responses and electroencephalogram disturbances to intermittent noises: effects of nocturnal heat and daytime exposure

During sleep, in thermoneutral conditions, the noise of a passing vehicle induces a biphasic cardiac response, a transient peripheral vasoconstriction and sleep disturbances. The present study was performed to determine whether or not the physiological responses were modified in a hot environment or after daytime exposure to both heat and noise. Eight young men were exposed to a nocturnal thermoneutral (20 degrees C) or hot (35 degrees C) environment disturbed by traffic noise. During the night, the peak intensities were of 71 dB(A) for trucks, 67 dB(A) for motorbikes and 64 dB(A) for cars. The background noise level (pink noise) was set at 30 dB(A). The noises were randomly distributed at a rate of 9.h-1. Nights were equally preceded by daytime exposure to combined heat and noise or to no disturbance. During the day, the noises as well as the background noise levels were increased by 15 dB(A) and the rate was 48.h-1. Electroencephalogram (EEG) measures of sleep, electrocardiograms and finger pulse amplitudes were continuously recorded. Regardless of the day condition, when compared with undisturbed nights, the nocturnal increase in the level of heart rate induced by heat exposure disappeared when noise was added. Percentages, delays, magnitudes and costs of cardiac and vascular responses as well as EEG events such as transient activation phases (TAP) due to noise were not affected by nocturnal thermal load or by the preceding daytime exposure to disturbances.(ABSTRACT TRUNCATED AT 250 WORDS)

Relative and combined effects of heat and noise exposure on sleep in humans

In a counter-balanced design, the effects of daytime and/or nighttime exposure to heat and/or traffic noise on night sleep were studied in eight healthy young men. During the day, the subjects were exposed to baseline condition (ambient temperature = 20 degrees C; no noise) or to both heat (35 degrees C) and noise. The duration of the daytime exposure was 8 h ending 5 h before sleep onset. The following nights, the subjects slept either in undisturbed (20 degrees C; no noise) or in noise, heat, or noise plus heat-disturbed environments. During the day, the various types of traffic noise were distributed at a rate of 48/h with peak intensities ranging between 79 and 86 dB(A). The background noise level was at 45 dB(A). At night, the peak intensities were reduced by 15 dB(A), the rate was diminished to 9/h, and the background noise was at 30 dB(A). Electrophysiological measures of sleep and esophageal and mean skin temperatures were continuously recorded. The results showed that both objective and subjective measures of sleep were more disturbed by heat than by noise. The thermal load had a larger impact on sleep quality than on sleep architecture. In the nocturnal hot condition, total sleep time decreased while duration of wakefulness, number of sleep stage changes, stage 1 episodes, number of awakenings, and transitions toward waking increased. An increase in the frequency of transient activation phases was also found in slow-wave sleep and in stage 2. In the nocturnal noise condition, only total number of sleep stage changes, changes to waking, and number of stage 1 episodes increased.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in serum electrolyte and atrial natriuretic peptide concentrations, acid-base and haemodynamic status after rapid infusion of isotonic saline and Ringer lactate solution in healthy volunteers

Opinions differ on the use of isotonic sodium chloride and Ringer lactate solution for extracellular volume depletion. We have compared changes in serum electrolyte concentrations and acid-base and haemodynamic status after rapid infusion of 2 litre of either isotonic sodium chloride or Ringer lactate solution in healthy volunteers. Changes within groups were small and statistically insignificant. Central venous pressure changes were associated with secretion of atrial natriuretic peptide, but this response was delayed.

A randomized comparison between midazolam and thiopental for elective cesarean section anesthesia: II. Neonates

In a randomized blind trial, the general condition of 40 neonates was assessed following midazolam- or thiopental-based general anesthesia for elective cesarean section. Among 19 neonatal neurobehavioral observations and tests, statistically significant differences between the midazolam and the thiopental groups were rare. However, a statistically significant interaction with regard to body temperature, general body tone, and arm recoil was observed where results were inferior for midazolam, although only within the first 2 hours. It was concluded that midazolam is as safe as thiopental for the induction and maintenance of elective cesarean section anesthesia in neonates.

A randomized comparison between midazolam and thiopental for elective cesarean section anesthesia. I. Mothers

In a randomized blind trial midazolam (0.3 mg kg-1) was compared with thiopental (4 mg kg-1), both combined with meperidine-nitrous oxide, for elective cesarean section anesthesia in 40 women. We found no statistically significant differences between thiopental and midazolam at induction, during operation or recovery with regard to maintenance doses, change in maternal neurologic status based on a modified Glasgow Coma Scale, systolic blood pressure, and heart rate. Induction time was 120 seconds with midazolam and 111 seconds with thiopental. There were significant differences with regard to diastolic blood pressure. Side effects occurred with approximately equal frequencies, but vomiting was significantly more frequent after thiopental. Perivenous tenderness and erythema occurred in four patients, all after thiopental. Midazolam appears to be a suitable alternative to thiopental for the induction and maintenance of anesthesia for elective cesarean section.

A randomized comparison between midazolam and thiopental for elective cesarean section anesthesia: III. Placental transfer and elimination in neonates

Forty neonates delivered by cesarean section were studied, half being delivered of mothers in whom anesthesia was induced with midazolam (0.3 mg/kg intravenously) and half of mothers given thiopental (4 mg/kg). At delivery, blood samples from mother and the umbilical vein were drawn for determination of plasma concentrations of thiopental, midazolam, and alpha-hydroxymidazolam. Over the next 60 hours, three blood samples were drawn using a randomized procedure of two blood samples at 30 different times. Placental transfer, expressed as the umbilical/maternal concentration ratio, was 0.96, 0.66, and 0.28, respectively, for thiopental, midazolam, and alpha-hydroxymidazolam. The transfer of thiopental was significantly more rapid than the transfer of midazolam and alpha-hydroxymidazolam. The population average of elimination half-life in neonates was 6.3 hours for midazolam and 14.7 hours for thiopental. Both values are substantially larger than those found in previous studies in adults.

A comparison between two emergency cricothyroidotomy instruments

As part of a training programme for younger doctors, two commercially available, emergency cricothyroidotomy sets were evaluated. Prior to the surgical procedure, half of the doctors in each group received an audiovisual lesson. In a simulated but realistic emergency situation, involving autopsy material, cricothyroidotomy was performed utilizing either the "Nutrake" or the "Gentofte" system. The audiovisual lesson increased the speed and the success rate of the doctors performing this procedure as well as strengthening their confidence. Both systems allowed positive pressure ventilation. The participating doctors achieved a higher success rate at a faster speed with the "Nutrake" set.