A Review on Non-Pharmacological Treatments for Pain Management in Newborn Infants

Abstract

Pain is a major problem in sick newborn infants, especially for those needing intensive care. Pharmacological pain relief is the most commonly used but may be ineffective, have side effects, including long-term neurodevelopmental sequelae. The effectiveness and safety of alternative analgesic methods are ambiguous. The objective is to review the effectiveness and safety of non-pharmacological methods of pain relief in newborn infants and to identify those that are the most effective. PubMed and Google Scholar were searched using the terms: ‘infant’, ‘premature’, ‘pain’, ‘acupuncture’, ‘skin to skin contact’, ‘sucrose’ ‘massage’, ‘musical therapy’ and ‘breastfeeding’. We included 24 studies assessing different methods of non-pharmacological analgesic techniques. Most resulted in some degree of analgesia but many were ineffective and some were even detrimental. Sucrose, for example, was often ineffective but more effective than music therapy, massage, breast milk (for extremely premature infants) or non-invasive electrical stimulation acupuncture. There were also conflicting results for acupuncture, skin to skin care and musical therapy. Most non-pharmacological methods of analgesia provide some modicum of relief for preterm infants but none are completely effective and there is no clearly superior method. Study is also required to assess potential long-term consequences of any of these methods.

Full text

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A Review on Non-Pharmacological Treatments for Pain Management in Newborn Infants
Avneet K Mangat1,2, Ju-Lee Oei MBBS, FRACP, MD3, Kerry Chen4, Im Quah-Smith MD, PhD5,
Georg M. Schmölzer MD, PhD2,6
1Faculty of Science, University of Alberta, Edmonton, Alberta, Canada
2Centre for the Studies of Asphyxia and Resuscitation, Neonatal Research Unit, Royal Alexandra
Hospital, Edmonton, Alberta, Canada
3School of Women’s and Children’s Health, University of New South Wales, Kensington, NSW,
Australia
4Faculty of Medicine, University of New South Wales, Kensington, NSW, Australia
5School of Women’s and Children’s Health University of New South Wales, Kensington, NSW,
Australia
6Department of Pediatrics, University of Alberta, Edmonton, Alberta, Canada
Corresponding author:
Georg M. Schmölzer, MD, PhD
Centre for the Studies of Asphyxia and Resuscitation,
Neonatal Research Unit, Royal Alexandra Hospital,
10240 Kingsway Avenue NW,
T5H 3V9, Edmonton, Alberta, Canada
Telephone +1 780 735 4660
Fax: +1 780 735 4072
Email: georg.schmoelzer@me.com
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© 2018 by the author(s). Distributed under a Creative Commons CC BY license.

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Abstract
Pain is a major problem in sick newborn infants, especially for those needing intensive
care. Pharmacological pain relief is the most commonly used but may be ineffective, have side
effects, including long-term neurodevelopmental sequelae. The effectiveness and safety of
alternative analgesic methods are ambiguous. The objective is to review the effectiveness and
safety of non-pharmacological methods of pain relief in newborn infants and to identify those that
are the most effective. PubMed and Google Scholar were searched using the terms: ‘infant’,
‘premature’, ‘pain’, ‘acupuncture’, ‘skin to skin contact’, ‘sucrose’ ‘massage’, ‘musical therapy’
and ‘breastfeeding’. We included 24 studies assessing different methods of non-pharmacological
analgesic techniques. Most resulted in some degree of analgesia but many were ineffective and
some were even detrimental. Sucrose, for example, was often ineffective but more effective than
music therapy, massage, breast milk (for extremely premature infants) or non-invasive electrical
stimulation acupuncture. There were also conflicting results for acupuncture, skin to skin care and
musical therapy. Most non-pharmacological methods of analgesia provide some modicum of relief
for preterm infants but none are completely effective and there is no clearly superior method. Study
is also required to assess potential long-term consequences of any of these methods.
Keywords
INFANT; PREMATURE; PAIN; ACUPUNCTURE; SKIN TO SKIN CONTACT; SUCROSE;
MASSAGE; MUSICAL THERAPY; BREASTFEEDING;
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Introduction
Newborn infants admitted to the Neonatal Intensive Care Unit (NICU) undergo an average
of 134 painful procedures within the first two weeks [1,2]. Even more concerning, some infants
might even experience more than 3000 painful procedures during the entire course of their NICU
admission [3]. These procedures are often necessary to ensure best care, such as heel pricks for
blood sampling or endotracheal suctioning. Some of these procedures are also performed
repeatedly on the same infant and have been shown to cause adverse physiological consequences,
such as hypoxemia, bradycardia and hypertension [1].
Apart from acute discomfort, there is now growing evidence, that painful (and particularly,
repetitive) procedures have adverse consequences on long-term neurological development. Animal
models demonstrate that painful events in early life increases the number of glucocorticoid
receptors in the hippocampus, which may affect future stress response [4]. Pain may not even need
to be chronic or repetitive to elicit adverse future outcomes. For example, infants have increased
stress behavior during routine immunizations at 4-6 months if circumcision was conducted at birth
without analgesia [5]. This highlights the lifelong implication of pain management during this
critical period in life [1, 6].
Pharmacological methods are the most frequently used means to ameliorate or prevent
pain. However, many analgesics have adverse effects. For example, morphine, an opioid, is
commonly used for severe pain but may impair neuronal survival, differentiation and growth [7].
Morphine may take several minutes to take effect, rendering it superfluous for urgent procedures.
It may also cause respiratory depression, making it unsuitable for use in spontaneously breathing,
opioid-naïve patients.
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Alternatives to pharmacological analgesia are therefore needed. Non-pharmacological
analgesic methods include acupuncture, non-nutritive sucking, breastfeeding, sucrose/glucose
solution, skin to skin care, swaddling, therapeutic massage, and musical therapy (Box 1). These
methods utilize environmental, behavioral, and pharmacological approaches by activating a “gate
control mechanism” that prevents the pain sensation from traveling to the central nervous system
[8] but evidence for each remain scarce. We therefore aimed to summarize the current evidence
about the efficacy, safety, and feasibility of non-pharmacological interventions for pain
management in newborn infants to determine if they could be considered an alternative to other
methods of analgesia, including medications.
Methods
PubMed and Google Scholar were systematically searched include the following search-
terms “infants”, “pain”, “acupuncture”, “skin to skin contact”, “sucrose”, “massage”, “musical
therapy” and “breastfeeding” between 1965 and 2018 (Appendix 1). List of references of identified
articles were manually searched. Articles were included if they described non-pharmacological
techniques in preterm or term infants and excluded if they compared pharmacological and non-
pharmacological intervention or there was no behavioural measurement of pain (e.g., PIPP
(Premature Infant Pain Profile), or NIPS (Neonatal Infant Pain Scale)). Only human studies were
included and no language restrictions were applied.
Results
A total of 24 studies describing acupuncture (n=3), skin to skin care (n=3), non-nutritive
sucking (n=3), swaddling (n=3), sucrose/glucose solution (n=2), massage (n=4), musical therapy
(n=3), and breastfeeding (n=3) were noted [9-32].
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Environmental control
Creating a more comforting environment with skin to skin care (SSC), swaddling,
therapeutic touch/massage, and music therapy for the infant can produce analgesic effects. SSC’s
analgesia may be due to a release of cholecystokinin (neuropeptide) [9]. Swaddling, the practice
of wrapping infants in blankets and can help simulate the environment of the womb which may
translate to analgesia [10, 11]. Massage can potentially saturate the senses and decrease the pain
signals that are sent to the central nervous system [12]. Music uses distraction to activate the
infant’s attention and thus distracts them from the pain and decreases their sensation of pain [13].
Skin to Skin Care (SSC)
Overall, most studies reported decreased pain responses during SSC compared to placebo
methods. Seo et al reported 35% less pain and an 88% decrease in crying duration with SSC
compared to controls during heel pricks [14]. Similarly, Freire et al compared SSC with oral
glucose solution or placebo for pain relief of 95 preterm infants during heel prick. The infants
randomized to SSC had significantly lower heart rates (mean ±SD, 5 ±4 vs. control 11 ±7 vs. oral
glucose 10 ±6 bpm; p=0.0001) and oxygen saturation variation (1.5 ±1.7 vs. control 2.6 ±1.5 vs.
oral glucose 1.9 ±1.5%; p=0.0012) than those given glucose or to controls [15]. However, Olsson
et al reported similar pain scores between SSC and placebo during venepuncture of 10 preterm
infants [16]. In summary, SSC might reduce pain in preterm and term infants. However, SSC is
limited to times when the infant’s position is not crucial and is not suitable for emergency
procedures or for procedures dependent on position (e.g., lumbar puncture).
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Swaddling
Efendi et al randomized 30 preterm infants to either swaddling and pacifier or control
during painful procedures and demonstrated a significantly lower heart rate and pain scores in
infants receiving swaddling and a pacifier [17]. As the study combined NNS and swaddling, it is
therefore impossible to differentiate which of these methods might have provided pain relief. Other
studies have reported that swaddling alone decreases pain during heel prick [18, 19]. Erkut et al
reported a 50% pain reduction, a 30% decrease in duration of crying time, and a significantly
increased oxygen saturation (mean ±SD, 97 ±2 vs. control: 95 ±2%, p=0.006) in the swaddled
group after a heel prick procedure in 74 term infants [18]. Ho et al randomized 54 premature
infants to swaddling or control and reported lower pain scores (7 ±3 vs. control: 145 ±3, p<0.001),
lower heart rate (162 ±10 vs. control: 182 ±17 bpm, p<0.001), and higher oxygen saturation (96
±4 vs. control 87 ±7%, p<0.001) after heel prick [19]. These studies suggest that swaddling alone
or combining with a pacifier has the potential to decrease pain in preterm and term infants.
Therapeutic touch/ massage
Two observational studies reported that massage therapy significantly reduced mean crying
time (4.4 ±1.8 vs. control: 5.3 ±1.7 hours/day, p <0.001) in infants with infant colic [20] and
decreased NIPS scores (3.9 vs. control: 4.8, p=0.002) in term infants [11]. Two randomized trials
reported that an upper limb massage significantly decreased pain responses during venipuncture
in preterm and term infants [21,22]. Chik et al randomized 80 infants and found significantly lower
pain scores between the massage and control group (-6.0) (p<0.001) [21]. Similarly, Jain et al
found a 60% decrease in pain and a significant decrease in heart rate (mean ±SD: 149±14 vs.
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control: 159 ±13 bpm, p=0.03) after venipuncture of 23 infants [22]. These studies suggest that a
gentle massage prior a heel prick is safe and can decreases pain.
Musical therapy (MT)
Using MT, a case study with five infants in a cardiac intensive care unit showed a decreased
average heart rate in 4/5 infants in 66% of the sessions [23]. In addition, respiratory rate and blood
pressure were also decreased, while oxygen saturation increased in some of the infants [23].
Furthermore, Olischar et al reported more mature sleep-wake cycles in newborn infants >32
weeks’ gestation exposed to music when compared to controls suggesting a calming effect on quiet
sleep [24]. These data suggest that MT has a stabilizing effect on physiological parameters and
sleep, which could be translate to a decreased pain response. However, the current available
evidence has conflicting results.
Shabani et al randomized 20 preterm infants to MT or control during venous blood
sampling and reported a significant decrease in heart rate (mean ±SD: 148 ±4 vs. control 163 ±4
bpm, p=0.005) and an 80% decrease in the infants’ mean facial pain expressions with MT [13].
Zhu et al randomized 250 term infants to either MT, MT + BF, BF, or control and observed that
the BF group had a 50% decrease in pain and a 70% decrease in duration of crying time [25]. In
addition, no difference between BF or BF + MT was observed, suggesting that MT was ineffective
for pain relief [40]. Shah et al randomized 35 infants to MT, sucrose, or MT + sucrose using a
cross-over design [41]. Overall, median (IQR) pain scores were significantly lower in the MT +
sucrose group (3, 0-4) compared to MT (6, 3-11) or sucrose (5, 3-10) alone [26]. In addition, pain
scores were similar between the MT and sucrose groups [26]. These data suggest that a
combination of MT + sucrose provides improved pain relief compared to sucrose or music alone.
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Feeding Methods
BF and NNS might release cholecystokinin (neuropeptide) and therefore support analgesia
in newborn infants [9, 27].
Breastfeeding (BF)
Zurita-Cruz et al randomized 144 infants to either BF, milk substitute, or no analgesia
(control group) during vaccination and reported that infants who received BF had reduced pain
and 50 % reduction in median crying time compared with milk substitute or controls [28]. There
were no significant differences in any of the parameters between the milk substitute and control
groups suggesting that milk substitute was ineffective at decreasing pain [28]. Similarly, Erkul et
al randomized 100 infants to either BF or control prior vaccination and observed lower pain scores
(mean ±SD: 1.9 ±2.2 vs. 6.8 ±0.7, p<0.05), lower duration of crying (mean ±SD: 20.5 ±16.2 vs.
45.1 ±14.5 sec, p=0.005), lower heart rate (mean ±SD: 164 ±17 vs. 172 ±15 bpm, p<0.05), and
higher mean oxygen saturation (mean ±SD: 98 ±3 vs. 94 ±7%, p<0.05) [29]. It is noteworthy to
mention that in premature infants even the smell of breast milk had a 50% reduction in pain scores
during venipuncture and a decrease in percent of duration of crying (0.17 ±0.6 vs. 9.7 ±17.3 sec,
p=0.04) after venipuncture [30]. These results are important in situations where breast feeding is
not feasible in the NICU (e.g., mother not present) since the smell of breast milk has the potential
to decrease pain.
Non-nutritive sucking (NNS)
A case-control study compared infants who sucked on an adult’s little finger (n=20) with
BF (n=20) and without any analgesia (n=23, control group) during venipuncture [31]. Overall BF
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and NNS had similar pain experience (35 vs. 24%, p>0.05) suggesting a similar efficacy in
analgesia [31]. While NNS has some effect on pain relief further studies are needed to examine
different approaches of NNS (e.g., use of finger or pacifier) or combination with glucose.
Other Interventions
Acupuncture
Acupuncture activates pressure points leading to analgesia by increasing endogenous
endorphins [32]. Body acupuncture and pain management is well known with the spinal pain
pathways being recruited for attenuation of pain signaling in needle acupuncture. However, more
recent research reveals the bigger impact of acupuncture on the individual. Now considered a
complex sensory stimulation, acupuncture effects also include autonomic re-regulation and
regulatory changes in functional connectivity centrally – mitigating the effects of physical and
emotional trauma in the individual [33, 34]. The non-invasive approach (no needling modalities
of acupuncture such as low level laser and magnet application), is more autonomically driven to
gain direct access to central pain control centers [33]. Neuroimaging studies have confirmed the
re-regulatory capacity of acupuncture centrally [35].
Several studies examined the effects of non-invasive acupuncture on neonatal pain [32, 36,
37]. Chen et al randomized 30 term infants to either auricular non-invasive magnetic acupuncture
or placebo to decrease infant pain during heel pricks [36]. The study reported a 30% reduction in
pain in infants receiving magnetic acupuncture [36]. Abbasoglu et al reported a 45% reduction in
mean duration of crying with acupressure compared to control infants during heel pricks in 32
preterm infants, but no significant differences in pain score between groups [37]. Mitchell et al
reported that non-invasive electrical stimulation at acupuncture points (NESAP) (n=37) during
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heel prick resulted in no significant effects on mean PIPP scores [32]. Conversely, pain scores
were significantly lower in groups receiving sucrose alone (n=37, mean ±SD: 4 ±1.8) or NESAP
+ sucrose (n=40, mean ±SD: 3.6 ±1.2) compared to control infants (n=39, mean ±SD: 4.9 ±4)
(p<0.01) [32]. Differences in these studies could have been due to the use of varying techniques
(e.g., acupuncture or acupressure) or different acupuncture points. Future studies should
distinguish between the optimal points and duration of treatment (e.g., duration of placement of
acupuncture) and to elucidate the long-term implications of different methods of acupuncture.
Sucrose/Glucose Solutions
Oral sucrose solution is most commonly used as non-pharmacological interventions for
pain management in newborn infants. Sucrose may exert its analgesic effects through endogenous
opioid pathways or via an increase in dopamine and acetylcholine [1, 38]. However, the evidence
for pain relief is conflicting. Lima et al reported a 40% reduction in pain scores and a 70%
reduction in crying time with oral glucose compared to NNS in 78 healthy newborns during
immunization [39]. Gouin et al randomized 1 to 3 months old children undergoing a venipuncture
to either sucrose or placebo and found similar pain scores (mean ± SD: sucrose 2.3 ±0.5 vs. placebo
1.6 ±0.5, p=0.6), heart rate variability (mean ±SD: sucrose 33 ±6 vs. placebo 24 ±5 bpm, p=0.44),
and crying time (mean± SD: sucrose 63 ±3 vs. placebo 49 ±5 sec, p=0.17) for both groups [40].
Similarly, a randomized trial with 66 preterm infants >28weeks gestation administered expressed
breast milk or oral sucrose for pain management during venipuncture [41]. Overall, similar pain
scores with 7 (range 4–9) with expressed breast milk and 6 (range 4–8) with sucrose were observed
[41]. These studies suggest that oral sucrose might not effective in all infants and that expressed
breast milk has similar analgesic effects. Furthermore, the analgesia effect of sucrose might be
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ineffective in infants’ experience opioid withdrawal [42]. However, a recent study reported similar
pain scores for opioid exposed and non-exposed infants suggesting that oral sucrose might be
effective in both exposed and non-exposed infants [43].
There may, however, be negative effects of oral sucrose. Asmerom et al randomized 131
premature infants undergoing a heel lance procedure to either control, placebo with NNS, or
sucrose [44]. Although, a 22% decrease in median pain scores was observed with sucrose
compared to control, increased markers of oxidative stress and increased use of adenosine
triphosphate could indicate cellular injury in infants receiving sucrose. Furthermore, infants
receiving sucrose had a significant increase in the heart rate from (mean± SD): 155±14 to 171
±155 bpm compared to infants the control (154 ±13 to 155±14 bpm) and placebo groups (156±14
to 165±15 bpm, p<0.001) [44].
However, there might be also some positive long-term effects of sucrose on spatial learning
and memory [45]. Rat models showed that chronic pain impaired short-term memory, but sucrose
prevented such impairment and increased endorphin levels [45]. Sucrose also prevented a decrease
levels of brain derived neurotropic factor, which occurs during chronic pain [45]. This conflicting
evidence suggests that further studies are needed to examine long-term effects (e.g., long-term
neurodevelopmental outcomes or obesity) of oral sucrose.
Discussion
Non-pharmacological techniques have the potential to provide pain relief for preterm and
term infants. Most studies included in this review demonstrated an improvement in behavioral pain
responses including facial expressions, duration of crying or latency to first cry, and physiological
parameters (e.g., heart rate, oxygen saturation). This indicates that non-pharmacological
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techniques are beneficial and were successful at reducing pain. However, other studies were unable
to find any difference between intervention and control [25,40,41]. These contradictory results
raise questions about the potential mechanism of these interventions. Further research is needed to
determine the best non-pharmacological intervention, duration of the intervention, and dose
response for optimal pain relief in newborn infants.
While sucrose is now considered the gold standard in non-pharmacological pain relief, the
current evidence remains contradicting. Although, several studies identified a clear benefit of
sucrose compared to other techniques (e.g., music, massage, NNS, or non-invasive electrical
stimulation acupuncture) [20,26,32,39], other studies reported lower pain score with alternative
technique including magnetic acupuncture or SCC [15,36]. The mechanism of sucrose has also
been controversial. Many believe that sucrose decreases pain through opioid mechanisms but
methadone-exposed newborn infants do not appear to be susceptible to the effects of sucrose,
probably because of opioid-receptor blockade by methadone [42]. However, Marceau et al
reported that opioid exposed neonates had decreased pain responses with the use of sucrose which
suggests additional other mechanisms for sucrose’s analgesic effects [43]. There is also conflicting
evidence regarding any long-term effects of sucrose. Rat models reported that sucrose increased
endorphins and brain-derived neurotrophic factor, which up-regulates neurogenesis and restores
memory functions [45-47]. Interestingly, an increase in oxidative stress markers, which might lead
to cellular damage was also reported after sucrose administration [44]. This raises questions as to
whether sucrose can be should be the gold standard for non-pharmacological pain relief and studies
examining long-term effects are needed.
The main limitation of the studies included in this review was the subjective nature of pain
assessments scales used. In preterm infants, heart rate or oxygen saturation variations may also
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have been due to physiological immaturity, entirely unrelated to the painful procedure or to the
intervention. There is no standardized approach to the measurement of pain and each study used
different scores e.g., Premature Infant Pain Profile score, Neonatal Infant Pain Scale score,
Douleur Aiguë du Nouveau-né scale (a French scale of neonatal pain) [30], Face, Legs, Activity,
Cry and Consolability Pain Scale [40], which makes it impossible to compare studies in a meta-
analysis.
It is noteworthy that preterm and term infants might respond differently to analgesia and
therefore findings between studies might not be comparable. Studies comparing sucrose with
breast milk reported similar pain scores in infants >28 weeks’ gestation [29], while infants <28
weeks’ gestation had significantly lower pain scores after oral sucrose but not after breast milk
[41]. These studies suggest that gestational age might influence the response to non-
pharmacological treatments. Also, the sample sizes of most studies were small ranging between
10-35 infants, which might have impacted the results of the study and no study reported long-term
follow-up.
The major benefit of non-pharmacological treatments includes i) ease of use, ii) apparent
safety, iii) feasibility, and iv) ease of learning, which would allow universal implementation of any
of these interventions. However, acupuncture using needle or laser would require training and
experience about the specific acupuncture points, and lasers might not be readily available. There
might also be parental reluctance to use needle acupuncture in their infants. The long-term effects
of any non-pharmacological intervention have not been studies and is a major knowledge gap, that
needs to be addressed.
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Conclusion
Newborn infants in an NICU undergo many painful but necessary procedures during
hospitalizations. The implications of the pain associated with these procedures and the types of
pain relief given to the infants have considerable implication for both short- and long-term
outcomes. The evidence for non-pharmacological analgesia is sparse and needs further study.
While most appear to be safe and relatively effective, their effects on the long-term outcomes of
the infants is unknown, especially when coupled with pharmacological analgesia.
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Box 1: Non-Pharmacological Treatments for Pain Relief
Non-Pharmacological Treatments for Pain Relief
Environmental control
 Skin to skin care
 Swaddling
 Therapeutic touch/ massage
 Musical therapy
Feeding methods
 Non-nutritive sucking
 Breastfeeding
Other Interventions
 Acupuncture
 Sucrose/glucose solutions
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Abbreviations:
NICU -Neonatal Intensive Care Unit
SSC -Skin to Skin care
NNS -Non-nutritive sucking
BF -Breast Feeding
PIPP -Premature Infant Pain Profile
NIPS -Neonatal Infant Pain Scale
NESAP -Non-invasive electrical stimulation at acupuncture points
MT -Musical therapy
MS -Milk substitute
MO -Milk Odor
HR -Heart Rate
HRV -Heart Rate variability
RR -Respiratory Rate
SpO2 -Oxygen Saturation
bpm -beats per minute
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Funding sources
We would like to thank the public for donating money to our funding agencies: GMS is a recipient
of the Heart and Stroke Foundation/University of Alberta Professorship of Neonatal Resuscitation,
a National New Investigator of the Heart and Stroke Foundation Canada and an Alberta New
Investigator of the Heart and Stroke Foundation Alberta. This research has been facilitated by the
Women and Children’s Health Research Institute through the generous support of the Stollery
Children's Hospital Foundation.
Author’s contribution:
Conception and design: GMS, JLO, IQS, AKM
Collection and assembly of data: GMS, JLO, IQS, AKM
Analysis and interpretation of the data: GMS, JLO, IQS, AKM
Drafting of the article: GMS, JLO, IQS, AKM
Critical revision of the article for important intellectual content: GMS, JLO, IQS, AKM
Final approval of the article: GMS, JLO, IQS, AKM
No reprints requested
Conflict of Interest: None
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Appendix 1
Search of PubMed –last performed June 4th, 2018
#1 infant (n=1,119,189)
#2 infants (n= 1,159,867)
#3 preterm (n=62,246)
#4 premature (n=170,785)
#5 pain (n=733,273)
#6 relief (n=84,761)
#6 acupuncture (n= 28,139)
#7 skin to skin care (n=47,999)
#8 non nutritive sucking (n=367)
#9 sucrose (n=74,579)
#10 massage (n=13,982)
#11 music (n=22,562)
#12 breastfeeding (n=49,518)
#13 non-pharmacological (n=6513)
Search of Google Scholar –last performed June 4th, 2018
#1 infant (n=3,220,000)
#2 infants (n= 2,080,000)
#3 preterm (n=1,010,000)
#4 premature (n=2,840,000)
#5 pain (n=3,770,000)
#6 relief (n=2,390,000)
#6 acupuncture (n= 592,000)
#7 skin to skin care (n=3,820,000)
#8 non nutritive sucking (n=21,900)
#9 sucrose (n=2,640,000)
#10 massage (n=773,000)
#11 music (n=3,770,000)
#12 breastfeeding (n=649,000)
#13 non-pharmacological (n=2,540,000)
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