Article

TEMPERATURE REGULATION AND HEAT PRODUCTION IN THE NEWBORN.

Pediatric Clinics of North America (Impact Factor: 2.2). 09/1965; 12:765-79.
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    • "Shivering is rare in newborn humans and most investigators assume that muscle activity in neonates contributes little to heat production (Oliver, 1965). Therefore, neonatal thermogenesis largely results from a generalized enhancement of oxidative metabolism and enhancement of a specific metabolic activity in brown fat. "
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    ABSTRACT: In utero fetuses are evidently exposed to several factors that cause an interruption of the oxygen flow through the umbilical cord causing asphyxia leading to hypoxia and metabolic acidosis. These conditions are important causes of intra-partum and neonatal mortality. The main objective of this review is to provide current information regarding the pathophysiology of asphyxia in piglets around parturition; the physiological mechanisms invoked by affected piglets to compensate perinatal hypoxemia are discussed. This review also addresses some similarities and differences of asphyxia between piglets and other mammals, including human neonates. Metabolic acidosis and hypoxia are sequela to asphyxia and can cause profound health effects in postnatal performance because of an abnormal suckling, a reduced absorption of colostrum and inadequate passive transfer of neonatal immunity. Acidosis also cause hypothermia, increased mortality and reduced survival in neonates. One of the first deleterious effects of intrauterine hypoxia is the expulsion of meconium into the amniotic sac leading to meconium staining of the skin, and in severe cases, meconium aspiration into the lungs. Even though there have been technological changes and improvements in husbandry, piglet mortality due to asphyxia remains a major problem. One potential alternative to reduce neonatal mortality in pigs is the monitoring of fetal stress during birth and the implemention of strategies such as the Apgar score, that is often used in human pediatrics. It is also important to consider the physiological, behavioral and biochemical changes that take place during parturition which subsequently impact the vitality, maturity and development of neonatal pigs. Understanding the pathophysiology of fetal hypoxia should help practitioners and farmers implement more effective delivery techniques aimed at reducing neonatal mortality and improving postnatal performance.
    Animal Reproduction Science 12/2005; 90(1-2):1-30. DOI:10.1016/j.anireprosci.2005.01.007 · 1.58 Impact Factor
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    • "Additionally, in contrast to the obvious shivering reaction occurring in adults, their thermoregulatory metabolic increase is mostly due to non-shivering thermogenesis in the brown adipose tissue. Thus, the "invisibility" of the cold defense reaction may lead to an underestimation of the maximum thermal stress exerted on the neonates by ambient temperatures which would still be quite comfortable for adults [1] [2] [3] [4] [5]. "
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    ABSTRACT: Due to its small body size, which in the case of prematurity is associated with increased skin permeability and incomplete brown fat development, the human neonate is highly prone to heat loss. Hence, thermal protection is mandatory to prevent neonatal hypothermia with its adverse metabolic and hemodynamic effects. This is usually attempted by the selection of “thermoneutral” ambient temperatures to maintain core temperature constant without regulatory metabolic increase. Since, however, core temperature decreases only after metabolic increase has failed to counteract heat loss, and metabolic increase in its turn is preceded by peripheral vasoconstriction, recording of thermal gradients between core and peripheral temperatures has now proven superior in early detection of thermal stress and maintenance of thermal comfort in the neonate. The long-lasting thermal lability of preterm babies partly results from the fact that an elevated basal metabolic rate, which in term neonates compensates for the small body size, is only achieved with delay. As this is correlated to the growth retardation typical of prematurity, the postnatal metabolic increase is usually considered to be a precondition for growth. However, a comparative calorimetric investigation has revealed that in a marsupial species normally born in a very immature state, a rapid weight increase occurs at a low metabolic rate. Obviously, these animals retain a growth efficiency which in humans is confined to intrauterine life and interrupted by preterm birth. Moreover, their low O2 consumption rate is adaptive to restricted respiratory surface area and incomplete tissue vascularization and contributes to hypoxia tolerance. Therefore, although postnatal metabolic increase promotes thermal stability and weight increase in term and slightly preterm human neonates, metabolic reduction may be the more appropriate strategy in cases where O2 and substrate supply are limited by extreme immaturity. As long as the factors mediating natural metabolic suppression are unknown, careful thermal protection seems to be one of the most promising ways to prevent uneconomic metabolic activation in highly preterm human neonates.
    Thermochimica Acta 01/1998; DOI:10.1016/S0040-6031(97)00427-9 · 2.11 Impact Factor
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    • "When this is done the estimates for the lower limit of the neutral environment are found to agree quite closely with the conclusions about optimum incubator air temperature reached by a number of clinicians on empirical grounds (cf. Oliver, 1965). "
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    ABSTRACT: The optimum thermal environment in which to nurse a baby naked in an incubator has been defined from a knowledge of the magnitude of the factors affecting thermal balance.Such a neutral environment allows body temperature to remain normal while oxygen consumption and evaporative water loss are both at a minimum.
    Archives of Disease in Childhood 07/1970; 45(241):328-34. DOI:10.1136/adc.45.241.328 · 2.91 Impact Factor
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