Sweating Responses of Neonates to Local Thermal Stimulation

Abstract

Local sweating responses to conducting heat were tested in newborn infants during the first week after birth, under controlled thermal conditions. Two thirds of the mature, full-size neonates and a significantly lower proportion of premature low-brith\x=req-\ weight infants showed positive reactions.Minimal effective thermal stimulus exceeded thresholds defined for adults. Usually, f ul l \ x=req-\ size neonates with negative reactions to heating showed sweating responsiveness to local stimulation with epinephrine hydrochloride or acetylcholine chloride. The same dissociation of responses occurred in some low-birth-weight babies, while others were unresponsive to both kinds of stimuli.These sweating deficits are of central nervous system origin, resulting from incompetence of autonomic centers. Functional immaturity of sweat glands cannot be ruled out as additional cause in neonates who failed to respond to either kind of local stimulation.Our previously reported studies on the sweating capacity of neo¬ nates concerned "pharmacologie sweating" as explored by intradermal stimulation tests with sudorific drugs.We could demonstrate that full-size infants, aged 1 to 8 days, have posi¬ tive responses to the direct effect of epinephrine hydrochloride and acetyl¬ choline chloride,1 show axon reflex sweating when tested with nicotine,2 and sweat in response to the cholinesterase-inhibiting action of neostigmine methylsulfate.3 In contrast, reactivity to all these drugs is signifi¬ cantly lacking in low-birth-weight in¬ fants of gestational ages below 37 completed weeks.13 A few pertinent observations made by others have been quoted before.3It remains questionable whether the evidenced physiologic deficits re¬ flect functional immaturity of the end-organ, the peripheral trans¬ mission mechanism, or the autonomie centers. Many data could be ac¬ counted for by limitations in both glandular reactivity and neural regu¬ lation. To further elucidate this ques¬ tion, a trial with still another testing method, namely, local thermal stimu¬ lation, seemed indicated. According to studies made in adults,411 such lo¬ cal heating tests may permit dis¬ crimination between a direct-acting and a neurally mediated component of the sweating response. Material and MethodsThis report is based on heating tests performed, with parental consent, on 48 healthy full-size and 22 healthy low-birthweight infants, ranging in postnatal age from 20 hours to 8 days; their gestational age, taken as originating with the first day of the mother's last menstrual period, was from 28 to 42 completed weeks. Birth weight varied from 1,276 to 4,409 gm (3 to

Skin Barrier Properties in the Newborn

“…The relative deficiency in eccrine activity in neonates, par ticularly low birth weight infants, is well docu mented. Qualitative evidence of this effect is presented by Green and Behrendt (20) and quantitative evidence by Foster et al (21). After stimulation with an intradermal injection of acetylcholine, they detected a much larger number of active sweat glands per unit area in the newborn than in the adult, but a lower mean peak sweat rate.…”

Transepidermal Water Loss <i>in vivo</i>

“…Adults seem to actively sweat when the skin tempera ture reaches 34 °C and ambient temperature is 32.3 °C (15), but full-term infants who are able to sweat 24 h after birth have thermal thresh olds above that of adults throughout the newborn period (1). Green and Behrendt (7) noted that local heating of full-sized neonates with a disk 15 mm in diameter for 10 min at temperatures of 38.5-38.8 °C produced no sweating. They selected a standard disk tem perature of 41.5 ± 0.3 °C and tested infants ranging from 28 to 42 weeks for a sweating response; infants below 35 weeks generally failed to sweat; those above did.…”

Relationship between Maturation of the Skin and Electrical Skin Resistance

“…The influence of the sweat glands moistening the skin may be less distinct when using wet electrodes for long periods. The activity of sweat glands is poor in newborn infants (6,15). In mature neonates to initiate the sweating response requires three times the thermal stimulus of that of an adult (6).…”