Med. J. Cairo Univ., Vol. 81, No. 1, March: 169-173, 2013
www.medicaljournalofcairouniversity.com
Effect of Plastic Bag (Vinyl Bags) on Prevention of Hypothermia in
Preterm Infants
BOSHRA T. AHMED, Ph.D.; MAGDY HUSSEIN, M.D. and HODA MONIR, Ph.D.
The Department of Paediatrics, Al Galaa Teaching Hospib21, Cairo
Abstract
Introduction
Objective: To evaluate the safety and efficacy of vinyl
bags in prevention of hypothermia during resuscitation at
birth in very low birth weight infants (VLBW) <1500gm and
gestational age 32 weeks.
INCIDENCE of hypothermia among preterm neonates born at or below 1500gm varies from 31 to
78% [ii. VLBW i.e Very Low Birth Weight
(<1500g) preterm infants are likely to become
hypothermic despite the use of traditional techniques for decreasing heat loss [2].
Methods: Fifty neonates of gestational age 32 weeks
and birth weight 1_500gm were randomised to either study
group, or control group. Study group neonates (n=25) were
put in vinyl bags immediately following delivery without
drying. Control group neonates (n=25) were resuscitated by
conventional drying under radiant warmer. Axillary and rectal
temperature was recorded on admission to the neonatal unit.
Temperature control during resuscitation in the
delivery room is particularly important in reducing
mortality and morbidity in very low birth infants
[3,4]. In preterm newborn infant, there will be a
drop in body temperature after birth unless measures are taken to prevent this heat loss. Costello
et al., 2000 showed that with decreasing gestational
age, there was a very high incidence of cold stress
[5]. The introduction of different transparent membranes has made it possible to limit evaporative
and convective heat loss and to permit heat gain
through radiation.
Results: Mean axillary and rectal temperature recorded
immediately after admission to N1CU were significantly higher
in the study group (36.12±0.78 °C and 36.28±0.61°C) compared to control group (35.24±0.83°C and 35.08±0.81°C)
respectively.
Although the cord blood pH and cord base excess were
similar between the vinyl bag group (7.32+0.05 and 2.15±0.25)
and the control group (7.33±0.02 and 2.28±0.29) respectively,
the worst pH and base excess in the first 6 hours of life was
significantly lower in the control group (7.23±0.049 and
—7.90±1.56) than in vinyl bag group (7.33±0.019 and
—3.65±0.936) respectively.
Vohra et al., [6] and Vohra et al., [7] found that
wrapped infants <28 weeks gestational age had
higher mean rectal admission temperatures. Knobel
et al., recently showed similar results with polyurethane wrapping [8,9]. This appears to be a very
inexpensive and effective mode of preventing
hypothermia in extremely premature infants.
There was a significant increase in maximal oxygen
requirement during the first 24 h in the control group (82.9±7.3)
than in the vinyl bag group (45.3±3.5) with p<0.001.
Blood glucose after two hours of admission was significantly higher in the vinyl bag group (80.28±1.84 mg/di) than
the control group (60.16±2.12 mg/di) with p<0.001.
Conclusion: As temperature maintenance in these VLBW
neonates is of tremendous importance, it would make sense
to recommend the use of vinyl bags during their resuscitation.
Vinyl bags are a simple and effective intervention in preventing
hypothermia in the delivery room and early acidosis in premature infants.
Key Words: Hypothermia
—
Vinylbag
—
New guideline of neonatal resuscitation program
recommended wrapping of premature newborns
in polyethylene bags Rol and because of controversies in use of different transparent membranes
in studies, the aim of this study is determination
of effect of plastic bag on prevention of hypothermia of neonate of gestational age 32 weeks and
birth weight <1500gm.
VLBW Infants.
Correspondence to: Dr. Boshra T. Ahmed, The Department
of Paediatrics, Al Galaa Teaching Hospital, Cairo
169
170
Effect of Plastic Bag (Vinyl Bags) on Prevention
Material and Methods
Statistical analysis:
This study was conducted at the neonatal intensive care unit at the Al Galaa Teaching Hospital
between August and December 2012. The present
study enrolled 50 patients who met the inclusion
criteria of the study i.e inborn, gestational age 32
week, birth weight <1500 gms. Twenty five infants
were placed in vinyl bags immediately following
delivery without drying. Twenty five control infants
received standard care with drying and placement
under a radiant warmer.
Data were entered and analyzed using the Statistical Package for Social Science (SPSS); version
15. Nominal data were expressed as frequency and
percentage. Numerical data were expressed as
means and standard deviations and were compared
using student's t-test. Associations were tested
using Pearson's correlations. p-value less than 0 05
were considered significant.
Exclusion criteria: Infants with major congenital malformations, open neural tube defects, abdominal wall defects or blistering skin conditions
were excluded.
There were no statistical differences in the
baseline characteristics such as sex, gestational
age, birth weight. Apgar scores and antenatal steroids between the vinyl bag and standard care
(control) groups (Table 1).
All infants were resuscitated on a radiant warmer with a radiant heat source. Infants were either
placed in a plastic bag or received conventional
drying and placement under a radiant warmer. The
infants resuscitated in the vinyl bags were placed
in the bag up to the neck immediately following
delivery without drying. The bag was secured
loosely around the neck by the straps. Only the
head was dried and covered by a hat.
Auscultation was done over the bag and if
umbilical access was required, a hole was cut in
the bag to provide access. The infants were transported to the NICU in a pre warmed transport
incubator set at 35°C. Following admission to the
NICU the infant was immediately transferred into
a pre warmed isolette adjusted to the neutral thermal
environment for the gestational age of the infant.
Axillary and rectal temperature was then measured
using an electronic thermometer, (Suretemp Welch
Allyne). For recording axillary temperature, the
clinical thermometer was placed high in the axilla,
and the arm then held against the side of the baby
for at least five minutes and for recording rectal
temperature (best guide for core temperature in
cold hypothermic neonates), the thermometer was
placed in the rectum to a maximum depth of 2cm,
where it was held for at least three minutes.
Vital signs including axillary and rectal temperature were taken on admission and after one
hour to the neonatal unit. Gestational age (GA)
was assessed by New Ballard Score [iii. Patient
characteristics such as GA, birth weight, sex, mode
of delivery, Apgar score and antenatal steroids
were ascertained from the maternal records.
The worst pH and base deficit in the first 6
hours, highest oxygen requirement in the first 24
hours, blood glucose at birth, after 2 hours and
mortality at 30 days were evaluated.
Results
The cord pH and base deficit were similar
between the two groups (Table 1).
Mean axillary and rectal temperature recorded
immediately after admission to NICU were significantly higher in the study group (36.12±0.783 °C
and 36.28±0.61°C) compared to control group
(35.24±0.83°C and 35.08±0.81°C) respectively.
Temperatures recorded after 1 hour of admission
to NICU were however comparable between the
two groups (Table 2).
Although the cord blood pH and cord base
excess were similar between the vinyl bag group
(7.32+0.05 and 2.15± 0.25) and the control group
(7.33±0.02 and 2.28±0.29) respectively, the worst
pH and base excess in the first 6 hours of life was
significantly lower in the control group (7.23±0.049
and -7.90±.56) than in vinyl bag group (7.33±0.019
and -3.65±0.936) respectively (Table 2).
There was a significant increase in maximal
oxygen requirement on ventilator or continuous
positive airway pressure (CPAP) during the first
24 h in the control group (82.9±7.3) than in the
vinyl bag group (45.3±3.5) with p<0.001 (Table
2).
Blood glucose after two hours of admission
was significantly higher in the vinyl bag group
(80.28±1.84mg/d1) than the control group (60.16±
2.12mg/d1) with p<0.001 (Table 2).
There were 3 deaths in the neonatal period (28
days postnatal life) in the control group compared
to 1 in the treatment group. This did not reach
statistical significance.
171
Boshra T Ahmed, et al.
Table (1): Clinical characteristics of the studied newborns.
Study
group
(n=25)
Control
group
(-25)
value
Gender (female/male)
Birth weight (kg)
(Mean±SD)
17/8
1.19±0.20
14/11
1.25±0.04
0.38
0.12
Gestational age (weeks)
Mean±SD
29.56±1.00
30.04±1.75
0.08
Mode of delivery (number)
Vaginal
Cesarean
22
3
18
7
0.16
0.16
Apgar score at 1 minute
Mean±SD
7.92±0.81
7.60±0.70
0.14
Ante natal steroid (n/%)
10 (40%)
7 (28%)
0.37
stages based on core temperature, prognoses and
action required [12] Cold stress: 36.0 to 36.4°C
Moderate hypothermia, 32.0 to 35.9°C and Severe
hypothermia: <32.0°C.
Hypothermia has been posited to predispose
infants to infection due to lethargy, leading to
aspiration pneumonia [13,141. Central nervous system depression also results in bradycardia, apnea
and poor feeding [15,16]. The consequences of
increased metabolism during hypothermia include
hypoglycemia, hypoxia and metabolic acidosis
[15,17].
Cord PH (Mean±SD)
7.32±0.05
7.33±0.02
0.12
Cord Base excess (Mean±SD)
2.15±0.25
2.28±0.29
0.10
There was no Statistical Difference in the Baseline Characteristics
between the Groups.
Table (2): Outcome results of the studied group.
Study
group
(n=25)
Control
group
(n=25)
value
Temperature Immediately
after admission to NICU (°C)
(Mean±SD)
Axillary
Rectal
36.12±0.78
36.28±0.61
35.24+0.83
35.08±0.81
0. 00 1
0. 00 1
Temperature After 1 hour
of admission to NICU (°C)
(Mean±SD)
Axillary
Rectal
36.04±1.08
36.92±0.35
36.41±0.67
36.77±0.29
0.15
Hypothermia (<35°C)
Worst pH in the
first 6 hours (Mean±SD)
0
7.33+0.019
8 (32%)
7.23±0.049
Worst base deficit in
first 6 hours (mEq/L)
(Mean±SD)
—3.65±0.936 —7.90±1.56
0.001
Maximal Oxygen (%)
(Mean±SD)
45.3± 3.5
82.9±7.3
0. 00 1
Glucose at birth (mg/di)
(Mean±SD)
55.84± 1.46
56.08±6.58
0.85
Glucose at 120 min (mg/di)
(Mean±SD)
80.28± 1.84
60.16± 2.12 0.001
Death in 30 days (%)
1
3
o.ii
o.00i
0. 00 1
0.30
Discussion
Neonatal hypothermia is defined as an abnormal
thermal state in which the newborn's body temperature drops below 36.5°C. Progressive reduction
in body temperature leads to adverse clinical effects
ranging from mild metabolic stress to death. In
1997, WHO categorized hypothermia into three
Study group neonates had a significantly higher
temperature recorded immediately after admission
than control group neonates but after 1 hour of
admission, temperature recorded in both study
group and control group were comparable. Similar
observation was made by Mathew et al. [18].
Vohra et al. [6] compared the effects of wrapping
(with polythene) neonates of <31 weeks of gestation
by measuring rectal temperature at nursery admission. They reported that the use of occlusive wrapping resulted in significantly higher admission
rectal temperature in infants <28 weeks compared
to non wrapped group.
Vohra et al. [7] in another study had shown
higher mean rectal temperature of 36.5° C±0.8° C
in wrapped group compared to 3 5.6°C±1.8°C in
control infants, however one hour later, mean rectal
temperature was similar in both the groups. These
observations are similar to the present study.
Alison and Joniz [19] observed improved admission temperature in infants <31 weeks gestation
by increasing the ambient temperature in operation
theatre and wrapping premature infants in polyethylene wrap. Ibrahim et al. [20] and McCall et al.
[21] made similar observations.
The worst pH and base excess in the first 6
hours of life was significantly lower in the control
group (7.23±0.049 and —7.90±1.56) than in vinyl
bag group (7.33±0.019 and —3.65±0.936) respectively.
There was an increased incidence of acidosis
in the control group during the first 6 hours of life
probably secondary to hypothermia [15,17].
Blood glucose after two hours of admission
was significantly higher in the vinyl bag group
(80.28±1.84mg/d1) than the control group (60.16±
2.12mg/d1) with p<0.001.
172
Effect of Plastic Bag (Vinyl Bags) on Prevention
F. Nayeri, F. Nili found a significant relationship
between hypothermia and respiratory distress in
the first six hours of birth and death, as well as,
hypoglycemia and metabolic acidosis in the first
three days of birth [22].
The incidence of neonatal mortality was higher
in the control group although this did not achieve
statistical significance. Less number of infants in
control group received a complete course of antenatal steroids (also statistically insignificant) than
the infants in the vinyl bag group and this may
also contribute to the higher incidence of death in
this group.
It seems probable that when a wet infant covered
with amniotic fluid is placed in a vinyl bag, the
evaporative water loss from the skin surface that
is not in contact with the bag membrane will contribute to a high humidity and vapor pressure in
the air between the membrane and the skin and
this will cause a drop in evaporative heat loss [3].
All areas of the vinyl bag and the skin under this
transparent bag that face the radiant warmer will
be heated through radiation, causing a heat gain
to the infant. Absence of drying also retains vernix
caseosa (if any present in premature infants). It is
possible that retention of a highly hydrated biological material such as vernix would decrease evaporative heat loss [23].
Conclusion:
Vinyl bags are an effective yet inexpensive
intervention that is shown to significantly improve
admission temperature in VLBW infants. This
technique can be adapted in the delivery rooms
to improve admission temperatures in VLBW
premature infants. Improved admission temperature
may lead to better clinical outcomes in terms of
mortality and neurodevelopmental outcomes.
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