[Assessment of noise prevailing in incubators for newborn infants].
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Small preterm infants usually require a heated environment to survive. After weaning, some infants become hypothermic, and eventually require external thermal support for an additional period. We hypothesized that preterm infants respond to weaning from an incubator by increasing their resting metabolic rate. Thermally stable infants were studied when they had reached a weight of at least 1600 g. Resting energy expenditure was measured 2 hours before weaning and at 6, 23, 30, and 53 hours after weaning. Two-way analysis of variance for repeated measures was used for analysis. Sixteen infants with mean birthweight of 1270 +/- 375 g and gestational age 31 +/- 2.3 weeks were studied. After weaning, there was a significant increase in energy expenditure from 95.0 +/- 21.9 kcal/d in the incubator, to a 30-hours peak of 111.9 +/- 10.5 kcal/d after weaning. Weaning from a convective incubator results in an increase in metabolic rate in very low birth weight infants. We speculate that the infants' ability to increase metabolic rate might influence weaning success.
Apneic spells were recorded in 8 of 19 premature infants nursed in high and low humidity alternately in servocontrol incubators. A significantly greater proportion of severe apnea occurred in low than in high humidity. It is postulated that this frequency and severity was due to the increased (as well as widely fluctuating) ambient temperature during low humidity.
Thirty pairs of healthy, growing preterm infants were included in this randomized prospective study comparing thermal weaning at 1700 g with that at 1800 g. Based on an intention-to-treat analysis, infants weaned at 1700 g were discharged 1.1 days sooner than those weaned at 1800 g. However, this result was not statistically significant (p = 0.13). On the other hand, differences are apparent between treatments in some strata based on birth weight (p = 0.0056). Evidence also existed that time from entry (at 1500 g) to discharge depended on birth weight stratum (p = 0.010). No infant in either group lost weight after successful weaning, and mean 24-hour weight gains were similar for both groups. Two infants were weaned at 1800 g requiring return to the incubator due to hypothermia, and four infants weaned at 1700 g likewise requiring return to the incubator. The number weaned at 1700 g who had birth weight of 1000 g or less and who developed hypothermia appeared substantial (three of six such infants). Thus, it appears that thermal weaning at 1700 g may be safe and effective only for prematures with birth weight above 1000 g. Additional study appears needed.
Oxygen consumption was measured under carefully controlled conditions during non-REM sleep in 16 infants less than 1,500 g in a computer-controlled incubator and a skin servo-controlled incubator. Oxygen consumption was 7.16 +/- SE 0.35 ml/kg/min in the computer-controlled incubator and 6.84 +/- SE 0.37 ml/kg/min in the skin servo-controlled incubator. Oxygen consumption was similar in the two incubator systems.
To assess the effect of open radiant heaters on bacterial colonization of neonates, 24 infants were raised under radiant heaters and 34 in standard incubators. Cultures of the nose, groin, and umbilicus were taken daily for the first 3 days of life. For infants raised in incubators, colonization rates with Staph. aureus ranged up to 47%. Among infants raised under radiant heaters (8 of whom had topical antibiotics applied to the umbilicus), only one was colonized with this organism. Even if the 8 treated infants were excluded, the prevalence of Staph. aureus was significantly greater at the umbilicus and groin in infants raised in incubators.
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It is not uncommon for a newborn to be blood culture negative, but urine latex particle agglutination (LPA) positive for group-B streptococcus (GBS). We hypothesized that whole-cell GBS contamination of urine, which is possible in bag-collected specimens, could cause LPA positivity. Serial tenfold dilutions through 10(-8) of an 18-hr broth suspension of GBS serotype III were prepared in sterile urine. Directigen (Becton-Dickenson Microbiologic Systems, Cockeyville, MD) LPA testing was performed on each sample at inoculation and, if negative, every 2 hr until becoming LPA positive. All tubes were quantitiatively cultured when becoming LPA positive. The assay was performed four times to evaluate independently the effects of urine sample centrifugation, volume, glucose content, and incubation temperature. An 18-hr GBS suspension dilution of 1:10,000 in urine and as few as 5.7 x 10(3) organisms/ml caused LPA positivity at time 0. Urine supported sufficient replication to enable log 0 concentrations (10(-8) dilution) to become LPA positive within 8 hr at 35 degrees C, a routine infant incubator setting. Alteration by centrifugation, volume, or glucose content had no effect on LPA positivity or time needed to become positive. We conclude that Directigen LPA can detect a relatively small concentration of GBS organisms in urine. Due to potential contamination from skin bacteria, positive LPA results from bag urine should be interpreted with caution in the absence of positive cultures.
Deep body temperature is an important and accepted index of health status in newborn infants. There are no easily used accurate methods for continuous deep body temperature measurements. Oral and tympanic membrane temperatures correlate well with rectal temperature but are not easily adapted to continuous measurement. We devised a noninvasive transcutaneous temperature sensor for continuous deep body temperature measurement that relies on the principle that, under steady state conditions, the temperature at the thermally insulated surface of a warm body, i.e. a zero heat loss surface, will be in equilibrium with the warmest part of the body. We used a standard clinical temperature probe placed between the skin and the mattress and attached to the skin with a foam adhesive disk. We used standard skin temperature probe attachment disks, which are also designed to provide thermal insulation to the skin temperature probe. We tested the hypothesis that this transcutaneous temperature would track body temperature as indicated by rectal temperature. In six anesthetized (pentobarbital) newborn piglets (1600 +/- 200 g) placed on their abdomen in a convectively warmed infant incubator, we measured continuously the following temperatures for 5 h: transcutaneous over lower and upper abdomen, brown fat, rectal, and descending aorta. To examine the influence of environment, we varied the incubator air temperature between 32 degrees and 36 degrees C. Both transcutaneous temperatures tracked the rectal temperature, within 0.2 degree C for transcutaneous over lower abdomen and within 0.3 degree C for transcutaneous over upper abdomen.(ABSTRACT TRUNCATED AT 250 WORDS)
OBJECTIVE: To report epidemiologic, bacteriologic, and clinical features of a Chryseobacterium meningosepticum outbreak. DESIGN: Outbreak investigation. SETTING: A neonatal intensive care unit (NICU) of a referral teaching hospital. METHODS: During 2 weeks in September 2001, four neonates in the NICU developed sepsis and underwent laboratory investigation. Multiple samples were obtained for cultures from endotracheal tubes, mechanical ventilators and humidifier boxes, infant incubators, parenteral and antiseptic solutions, feeding bottles, sinks, faucets, doors, and healthcare workers. RESULTS: C. meningosepticum was isolated from the blood cultures of four patients. The first isolate was identified 5 days after the death of the index case. Although all isolates were ciprofloxacin susceptible in vitro, the remaining three patients did not respond to ciprofloxacin therapy given for 6 or 7 days. Therapy was switched to vancomycin and rifainpin and all three patients survived, with one having a complication (hydrocephalus). Environmental surveillance revealed C. meningosepticum in the stock lipid solution as the source of the epidemic. The outbreak was controlled after discontinuation of intravenous lipid solution, restriction of further neonatal admissions, and thorough disinfection of the unit and its equipment. CONCLUSION: Early identification of an epidemic and its source is important in avoiding morbidity and mortality. A contaminated lipid stock bottle was the source of this outbreak associated with multiple cases and one death.
Changes in body temperature were recorded in freely moving rats given phosphate-buffered saline or leukocytic pyrogen (interleukin-1) while the animals were in an infant incubator maintained at 25.5 +/- 0.5 degrees C. The leukocytic pyrogen increased body temperature by at least 1 degree C within 1 h. This rise in temperature was prevented by premedication with indomethacin (10 mg/kg) but not dexamethasone (0.5 mg/kg) given 15 min before the leukocytic pyrogen. Local rates of glucose utilization were measured in 47 regions of the central nervous system. In none of the regions previously reported to have an increased rate of glucose utilization associated with an ambient temperature of 32.5 degrees C (McCulloch et al., 1982b) was an increase found in the present experiments. It was concluded that the intensity of the changes in local cerebral glucose utilization in response to the fever caused by the leukocytic pyrogen was insufficient to be measured. Neither indomethacin nor dexamethasone caused remarkable changes in rates of local glucose utilization.
In the present study, a rat hindlimb tourniquet model was used to investigate the effect of moderate hypothermia on ischemic muscle necrosis. Complete circulatory arrest was maintained for 4.5 h. During the ischemic period the animals were kept in an infant incubator at different temperatures. After 72 h survival the percentage of necrosis in the anterior tibial muscle was measured morphometrically on histological slides. At an ambient temperature of 24 degrees C there was 80% necrosis in the anterior tibial muscle. At 22 degrees C the necrosis was reduced to 29%. This reduction corresponds to more than 30 min shortening of the ischemia time. Differences in tissue temperature may explain some of the discrepancies reported in tolerance limits for muscle ischemia. To achieve consistent results in experimental muscle ischemia, it is necessary to control the ambient temperature.
A technique and nutritional regimen for intravenous feeding of neonatal rabbits is described. Central venous nutrition of 40- to 60-g newborn rabbits was accomplished in a modified infant incubator using a specially constructed catheter and light-weight harness to provide nutrients by central vein for periods up to 7 days. Throughout the infusion period the newborn rabbits appeared healthy and evidenced increasing activity with age. The pups grew an average of 6.3 g/day, while receiving an intake of 150 to 200 kcal/kg/day. This model appears capable of being utilized to provide information on neonatal growth and metabolism in response to parenteral nutrition.
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Air transport of infants in incubators should be undertaken in a manner that is safe for both staff and infant and satisfies all directives by appropriate regulatory bodies. In Scotland during the last two years, certification of an infant incubator system for use in both rotary and fixed wing aircraft has been accomplished. This is a report of the issues addressed during this project, which will be common to all neonatal transport services intending to develop air transport capability.
OBJECTIVE: The objective of this study was to compare radiant warmer and incubator care for preterm infants from birth with respect to temperature control and weight gain. METHODS: Sixty preterm infants <33 weeks' gestation were randomized at birth to radiant warmer or incubator care. The initial goal was to maintain abdominal temperature at 36.8 degrees C in both groups and axillary temperature at 36.8 to 37.3 degrees C; air servocontrol was used for incubator infants. Infants in both groups received added humidity for 5 days if their weight was <1000 g and for 3 days if they weighed between 1000 and 1249 g. During a 3-hour period on days 1 to 7, recordings of abdominal, forehead, and foot temperatures were obtained. The percentage of the recording time during which the abdominal temperature was in the target range of between 36 degrees C and 37.5 degrees C was determined as an indicator of temperature control. Weight gain from birth to 1800 g was compared. Secondary outcomes included fluid balance and clinical events. RESULTS: There were 30 infants in each group; 48 were <1500 g (of whom 17 were <1000 g). There were no significant differences in birth weight, gestation, gender, or illness severity scores in the 2 groups. Significant differences in temperature control were noted on day 1. Although admission temperatures were similar, lower abdominal temperatures were noted in the first 2 hours of life in the incubator group (medians were 36.6 degrees C and 35.9 degrees C in the radiant warmer and incubator groups, respectively). Similarly, mean abdominal temperatures during the 3-hour recording on day 1 were lower in the incubator group, and infants in this group spent a significantly greater percentage of the recording time with temperatures outside the target range (17.3% compared with 0.88%). Other temperature recordings from the forehead and foot were not significantly different in the groups. Fluid intakes were higher for infants under radiant warmer on days 2, 3, and 4, and the difference amounted to a mean of 12.8 mL/kg/d. Maximum sodium levels in the first week were similar in the 2 groups. Mean weight gain was 17.4 g/kg/d for the radiant warmer group and 17.1 g/kg/d for the incubator group; days to regain birth weight and length of hospital stay were not significantly different. Greater numbers of infants in the radiant warmer group required phototherapy, and adverse events (which included death, necrotizing enterocolitis, chronic lung disease, grade 3 or 4 intraventricular hemorrhage, periventricular leukomalacia, or retinopathy requiring laser treatment) were less frequent in the radiant warmer group (1 infant compared with 8 in the incubator group; relative risk 0.1; 95% confidence intervals: 0.01-0.82). CONCLUSIONS: This study has shown differences in abdominal temperatures on day 1 and outcome, although the latter finding should be viewed with caution because of the sample size. The results indicate benefits for the initial use of the radiant warmer after birth. Although fluid requirements were higher in the radiant warmer group for days 2 through 4, the increased fluid volumes were given without apparent adverse effect.
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