We performed a controlled clinical trial in a General Hospital in Celaya, Mexico. Infants of 28-37 weeks of gestation, and weighing 1000-2499 g at birth were included [5]. Infants suffering from loss of cutaneous integrity, or suspected congenital heart disease (based on inspection and auscultation findings such as the presence of cyanosis and abnormal heart rate, rhythm, regularity, and heart sounds) were not included. The study was approved by the Institutional Ethics Committee and informed written consent was obtained from the parents.

Immediately after birth, all infants were kept under a radiant warmer at 36.5ºC (Blosson, Series 900). In group I, infants were routinely dried with a sterile preheated field (heated under the radiant warmer for 10 minutes at 36.5ºC), according to the International Guidelines for Neonatal Resuscitation [6], and wrapped with another preheated field until they were placed into the incubator where airway and vital signs were managed conventionally (traditional care). In group II, they were dried similarly and wrapped with a polyethylene bag. In group III without previous body drying (only the head was dried), they were wrapped with the polyethylene bag. Later, all infants were placed in a single walled incubator (Medix TR 306).

We estimated the time to achieve axillary temperature (AT) of 36.5ºC and compared AT at 120 minutes from baseline at birth between all the groups. The incubator temperature was registered at baseline and every 15 minutes until two hours after birth. Glucose levels were determined with a (Optium Xceed) monitor and blood pressure was measured by the flushing technique.

For comparison of continuous variables between groups, ANOVA test and Sheffé’s test were used. In case of skewed distribution, we used Krushkal-Wallis and chi-square tests. SPSS software (version 17) was used.

Birthweight was higher in the preheated field group than the other groups without difference in other variables (Table I). No difference was found on heart rate, respiratory rate or blood pressure levels between groups.

TABLE I Clinical Characteristics of Study Newborns 

Axillary temperature in the to groups at different time intervals is depicted in Table II. Both groups of polyethylene use achieved a mean AT of 36.5ºC at 30 minutes compared with 75 minutes for the group of traditional care (Table II). However, no difference was found in AT between those newborns that were small or adequate for gestational age. Hypothermia was reported in 5 (16.6%) newborns in group I, and their gestational age was not different from the rest of the group (34.1±2.7 vs 34.7± 2.4; P=0.59). One case of hyperthermia was found in the polyethylene bag without previous drying (37.7ºC). None of the neonates in whom polyethylene bag was used developed lesion of the skin or infection. Incubators in all cases started at 34ºC. However, temperature of the incubator at 120 minutes, was higher in group I (35.15±0.89ºC) than group II (34.20±1.14ºC) and III (34.20±0.75ºC) (P=0.0001).

TABLE II Comparison of Axillary Temperature Between Groups

Fig. 1 Flow diagram depicting the distribution of newborns in the three groups.

We have confirmed that polyethylene occlusive skin wrapping immediately after birth in preterm infants provides better thermal protection in the delivery room than conventional drying, independently of previous body drying or not. The polyethylene bag was placed immediately after birth until two hours after birth in our study, compared with previous studies where the bag was placed at different times after birth [3,6-10]. Furthermore, all these studies only compared traditional care and one group of intervention (with or without previous drying), and studied infants of different birthweight and gestational age. Vohra, et al. [7] found better corporal temperature in the intervention group in those <28 weeks of gestational age (difference = 1.9ºC, P<0.001) but Duman, et al. [6] found this difference in both <28 weeks and >28 weeks of gestational age. In our study, the thermal protection of the polyethylene bag was independent of the stratification of birthweight according to gestational age.

In addition to the more appropriate control of the temperature in those infants who used the polyethylene bag, none had hypothermia and only one had hyperthermia, contrary to the group with the traditional care where five infants had hypothermia. Previous reports also found higher proportion of hypothermia in infants with the traditional care, and a borderline increase in hyperthermia [3,9]. The risk of overheating is a potential concern when using the polyethylene wrap and it has to be monitored. Care should be taken to avoid hyperthermia, especially in those infants who are at risk of hypoxic ischemic encephalopathy [11]. The wrap procedure was well accepted by the neonatal staff and did not interfere with resuscitation in the delivery room.

Contributors: CLM and AN concieved and designed the study and revised the manuscript for important intellectual content. The AN will act as guarantor of the study. GML and JMG analyzed the data and helped in manuscript writing. The final manuscript was approved by all authors.

Funding: None; Competing interests: None stated.

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