Assessment of radiant temperature in a closed incubator

In closed incubators, radiative heat loss (R) which is assessed from the mean radiant temperature [Formula: see text] accounts for 40–60% of the neonate’s total heat loss. In the absence of a benchmark method to calculate [Formula: see text]—often considered to be the same as the air incubator temperature—errors could have a considerable impact on the thermal management of neonates. We compared [Formula: see text] using two conventional methods (measurement with a black-globe thermometer and a radiative “view factor” approach) and two methods based on nude thermal manikins (a simple, schematic design from Wheldon and a multisegment, anthropometric device developed in our laboratory). By taking the [Formula: see text] estimations for each method, we calculated metabolic heat production values by partitional calorimetry and then compared them with the values calculated from [Formula: see text] and [Formula: see text] measured in 13 preterm neonates. Comparisons between the calculated and measured metabolic heat production values showed that the two conventional methods and Wheldon’s manikin underestimated R, whereas when using the anthropomorphic thermal manikin, the simulated versus clinical difference was not statistically significant. In conclusion, there is a need for a safety standard for measuring [Formula: see text] in a closed incubator. This standard should also make available estimating equations for all avenues of the neonate’s heat exchange considering the metabolic heat production and the modifying influence of the thermal insulation provided by the diaper and by the mattress. Although thermal manikins appear to be particularly appropriate for measuring [Formula: see text], the current lack of standardized procedures limits their widespread use

Influence of neonate's body position with and without a plastic blanket on body heat loss assessed from a thermal mannequin

International audienceThe present study aimed at assessing the net gain of body heat storage induced by a transparent plastic blanket draped over small premature neonates in the prone and the supine positions. Thermal stress is particularly important in premature and small-for-gestational-age infants characterized by high values of the ratio between skin surface area and body mass, the greater this ratio, the greater the body heat exchanges. The large skin permeability enhances body water loss. The risk of hypothermia is particularly increased at birth and during operations on naked neonates implying opening of the canopy (surgical operation, blood sampling and gastric aspiration). In the first day of life, the rate of evaporation can reach 100 g.h-1.m-2 in very preterm infants. To prevent the large amount of water loss it is sometimes recommended to cover the neonate with a plastic blanket. In closed incubator Fanaroff et al.(3) pointed out that a transparent plastic heat shield reduces the insensible water loss of 44 % in low birth weight neonates lower than 1250 g and postnatal age less than 10 days. For postnatal age greater than 10 days, the magnitude of this reduction was only 19 %. Bell et al.(2) also reported that the addition of a heat shield in an incubator decreased the water loss by 10 % in infants with mean birth weight of 1570 g. However the efficiency of this solution which depends on the physical environment but also on the inter individual difference in the ability to exchange heat with the environment remains questionable and the use of a plastic blanket is still a controversial topic. The total heat loss of premature infants depends on various factors such as gestational age, nutritional state, mean skin temperature, body hydromineral balance, vigilance state, metabolic rate and of the postnatal age which modifies the skin keratinisation. Thus, it is difficult to obtain homogeneous data base that takes into account all these factors and there are conflicting data on the effectiveness of plastic blanket. To rule out these confounding factors we use a sweating mannequin the advantage of which is that it measures directly the total heat loss with the environment without interference with these factors

Polyethylene bag wrapping to prevent hypothermia during percutaneous central venous catheter insertion in the preterm newborn under 32 weeks of gestation

International audienceAim: In preterm neonates, during nursing procedures, body temperature decreases. This study evaluates the interest of polyethylene bag wrapping to prevent this decrease during percutaneous central venous catheter (PCVC) insertion procedure, in preterm neonates under 32 weeks of gestation nursed in closed incubators. Methods: This prospective observational study compared two periods: [May 2009-September 2009]: ``without polyethylene bag wrapping'' and [October 2009-March 2010]: ``with polyethylene bag wrapping''. The main criterion was newborn skin temperature at the end of the procedure. Results: There was no difference between the two groups for skin temperature before the procedure (36.9 +/- 0.3 degrees C versus 36.9 +/- 0.3 degrees C; p = NS). The skin temperature at the end of the procedure was lower in the ``without bag wrapping'' group (36.0 +/- 0.5 degrees C) compared to the ``bag wrapping'' group (36.4 degrees C +/- 0.5 degrees C; p = 0.01). Furthermore, no skin temperature at the end was higher than 37.4 degrees C in the bag wrapping group. Conclusion: The use of a polyethylene bag was effective in decreasing skin temperature fall during a PCVC insertion procedure in our population. No side effects were observed. The benefit of prolonged wrapping or for shorter procedure should be evaluated

Use of a Polyethylene Bag to Reduce Perioperative Regional and Whole-Body Heat Losses in Low-Birth-Weight Neonates

International audienceIn the delivery room, wrapping a low-birth-weight neonate (defined as <= 2.499 g) in a polyethylene bag reduces the risk of hypothermia. However, extended use of the bag (e.g., during neonatal surgery) might conceivably increase the risk of thermal stress and thus body overheating. Here, we assessed the efficacy of a polyethylene bag in infants assigned to wrap (W) or nonwrap (NW, control) groups during placement of a percutaneous vena cava catheter by applying a new mathematical model that calculates heat exchanges for covered and uncovered body segments. At the end of the placement procedure, the Wand NW groups did not differ significantly in terms of whole-body heat loss (15.80 versus 14.97 kJ center dot h(-1) center dot kg(-1), resp.), whereas the abdominal skin temperature was slightly but significantly higher (by 0.32 degrees C) in the Wgroup. Greater evaporation in the Wgroup (2.49 kJ center dot h(-1) center dot kg(-1))was primarily balanced by greater whole-body radiant heat loss (3.44 kJ center dot h(-1) center dot kg(-1)1). Wrapping the neonate in a polyethylene bag provides a small thermal benefit when catheter placement takes a long time. Given that polyethylene is transparent to radiant energy, it might be of value to incorporate polymers that are less transparent at infrared wavelengths

Warming the premature infant in the delivery room: Quantification of the risk of hyperthermia

International audienceAim: The efficacy and safety of three polyethylene bags commonly used to prevent hypothermia in premature infants was assessed. Methods: To simulate transfer from the delivery room to a secondary care unit, a thermally stable, bonneted mannequin (skin temperature: 34.4 degrees C) was placed in a climate chamber under different conditions: with a radiant warmer, with various polyethylene bags (open on one side, closed by a draw-string at the neck, or a ``life support pouch'' with several access points) or without a bag. Results: With the radiant warmer turned on, the mean reduction in heat loss from the nude mannequin was 50.8 +/- 1.7% (p <0.0001, vs. warmer off). The mean reduction in heat loss (vs. no bag) was 55.0 +/- 0.9% for the drawstring bag, 49.0 +/- 2.2% for the standard bag (p= 0.0001), and 48.1 +/- 0.7% for the life support pouch (p = 0.006). When a radiant warmer + polyethylene bag were used, heat stress (body temperature: 38 degrees C) and severe hyperthermia (40 degrees C) occurred after 11 and 34 min, respectively. Conclusion: Caution must be taken when using a radiant warmer and polyethylene bag with a prematute infant. Heat stress can occur in only 11 min. Continuous body temperature monitoring is therefore required. (C) 2018 Published by Elsevier Ltd on behalf of IPEM

Warming the premature infant in the delivery room: Quantification of the risk of hyperthermia

International audienceAim: The efficacy and safety of three polyethylene bags commonly used to prevent hypothermia in premature infants was assessed. Methods: To simulate transfer from the delivery room to a secondary care unit, a thermally stable, bonneted mannequin (skin temperature: 34.4 degrees C) was placed in a climate chamber under different conditions: with a radiant warmer, with various polyethylene bags (open on one side, closed by a draw-string at the neck, or a ``life support pouch'' with several access points) or without a bag. Results: With the radiant warmer turned on, the mean reduction in heat loss from the nude mannequin was 50.8 +/- 1.7% (p <0.0001, vs. warmer off). The mean reduction in heat loss (vs. no bag) was 55.0 +/- 0.9% for the drawstring bag, 49.0 +/- 2.2% for the standard bag (p= 0.0001), and 48.1 +/- 0.7% for the life support pouch (p = 0.006). When a radiant warmer + polyethylene bag were used, heat stress (body temperature: 38 degrees C) and severe hyperthermia (40 degrees C) occurred after 11 and 34 min, respectively. Conclusion: Caution must be taken when using a radiant warmer and polyethylene bag with a prematute infant. Heat stress can occur in only 11 min. Continuous body temperature monitoring is therefore required. (C) 2018 Published by Elsevier Ltd on behalf of IPEM