Exposure to the smell and taste of milk to accelerate feeding in preterm infants

Scoping review of systematic reviews of nursing interventions in a neonatal intensive care unit or special care nursery

AIM(S)

To identify, synthesise and map systematic reviews of the effectiveness of nursing interventions undertaken in a neonatal intensive care unit or special care nursery.

DESIGN

This scoping review was conducted according to the JBI scoping review framework.

METHODS

Review included systematic reviews that evaluated any nurse-initiated interventions that were undertaken in an NICU or SCN setting. Studies that reported one or more positive outcomes related to the nursing interventions were only considered for this review. Each outcome for nursing interventions was rated a 'certainty (quality) of evidence' according to the Grading of Recommendations, Assessment, Development and Evaluations criteria.

DATA SOURCES

Systematic reviews were sourced from the Cochrane Database of Systematic Reviews and Joanna Briggs Institute Evidence Synthesis for reviews published until February 2023.

RESULTS

A total of 428 articles were identified; following screening, 81 reviews underwent full-text screening, and 34 articles met the inclusion criteria and were included in this review. Multiple nursing interventions reporting positive outcomes were identified and were grouped into seven categories. Respiratory 7/34 (20%) and Nutrition 8/34 (23%) outcomes were the most reported categories. Developmental care was the next most reported category 5/34 (15%) followed by Thermoregulation, 5/34 (15%) Jaundice 4/34 (12%), Pain 4/34 (12%) and Infection 1/34 (3%).

CONCLUSIONS

This review has identified nursing interventions that have a direct positive impact on neonatal outcomes. However, further applied research is needed to transfer this empirical knowledge into clinical practice.

IMPLICATIONS FOR THE PROFESSION AND/OR PATIENT CARE

Implementing up-to-date evidence on effective nursing interventions has the potential to significantly improving neonatal outcomes.

PATIENT OR PUBLIC CONTRIBUTION

No patient or public involvement in this scoping review.

Exposure to the smell and taste of milk to accelerate feeding in preterm infants

BACKGROUND

Preterm infants (born before 37 weeks' gestation) are often unable to co-ordinate sucking, swallowing, and breathing for oral feeding because of their immaturity. In such cases, initial nutrition is provided by orogastric or nasogastric tube feeding. Feeding intolerance is common and can delay attainment of full enteral and sucking feeds, prolonging the need for nutritional support and the hospital stay. Smell and taste play an important role in the activation of physiological pre-absorptive processes that contribute to food digestion and absorption. However, during tube feeding, milk bypasses the nasal and oral cavities, limiting exposure to the smell and taste of milk. Provision of the smell and taste of milk with tube feeds offers a non-invasive and low-cost intervention that, if effective in accelerating the transition to enteral feeds and subsequently to sucking feeds, would bring considerable advantages to infants, their families, and healthcare systems.

OBJECTIVES

To assess whether exposure to the smell or taste (or both) of breastmilk or formula administered with tube feeds can accelerate the transition to full sucking feeds without adverse effects in preterm infants.

SEARCH METHODS

We conducted searches in CENTRAL, MEDLINE, Embase, CINAHL, and Epistemonikos to 26 April 2023. We also searched clinical trial databases and conference proceedings.

SELECTION CRITERIA

We included randomised and quasi-randomised studies that evaluated exposure versus no exposure to the smell or taste of milk (or both) immediately before or at the time of tube feeds.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies, assessed risk of bias, and extracted data according to Cochrane Neonatal methodology. We performed meta-analyses using risk ratios (RRs) for dichotomous data and mean differences (MDs) for continuous data, with their respective 95% confidence intervals (CIs). We used GRADE to assess the certainty of evidence.

MAIN RESULTS

We included eight studies (1277 preterm infants). Seven studies (1244 infants) contributed data for meta-analysis. The evidence suggests that exposure to the smell and taste of milk with tube feeds has little to no effect on time taken to reach full sucking feeds (MD -1.07 days, 95% CI -2.63 to 0.50; 3 studies, 662 infants; very low-certainty evidence). Two studies reported no adverse effects related to the intervention. The intervention may have little to no effect on duration of parenteral nutrition (MD 0.23 days, 95% CI -0.24 to 0.71; 3 studies, 977 infants; low-certainty evidence), time to reach full enteral feeds (MD -0.16 days, 95% CI -0.45 to 0.12; 1 study, 736 infants; very low-certainty evidence) or risk of necrotising enterocolitis (RR 0.93, 95% CI 0.47 to 1.84; 2 studies, 435 infants; low-certainty evidence), although the evidence for time to reach full enteral feeds is very uncertain. Exposure to the smell and taste of milk with tube feeds probably has little to no effect on risk of late infection (RR 1.14, 95% CI 0.74 to 1.75; 2 studies, 436 infants; moderate-certainty evidence). There were no data available to assess feeding intolerance. The included studies had small sample sizes and methodological limitations, including unclear or lack of randomisation (four studies), lack of blinding of participants and personnel (five studies), unclear or lack of blinding of the outcome assessor (all eight studies), and different inclusion criteria and methods of administering the interventions.

AUTHORS' CONCLUSIONS

The results of our meta-analyses suggest that exposure to the smell and taste of milk with tube feeds may have little to no effect on time to reach full sucking feeds and time to reach full enteral feeds. We found no clear difference between exposure and no exposure to the smell or taste of milk on safety outcomes (adverse effects, necrotising enterocolitis, and late infection). Results from one ongoing study and two studies awaiting classification may alter the conclusions of this review. Future research should examine the effect of exposing preterm infants to the smell and taste of milk with tube feeds on health outcomes during hospitalisation, such as attainment of feeding skills, safety, feed tolerance, infection, and growth. Future studies should be powered to detect the effect of the intervention in infants of different gestational ages and on each sex separately. It is also important to determine the optimal method, frequency, and duration of exposure.

Vanilla odor promotes oral feeding in premature infants-A randomized controlled trial

PROPOSE

Introducing early oral feeding in premature infants is important because it supports intestinal maturation and helps prevent infections. In addition, early oral feeding is likely to contribute to improved neurocognitive outcomes in preterm infants. Several holistic therapeutic strategies have been developed to improve feeding skills, food tolerance, and the ability to drink independently, including practices such as early breastfeeding, oral stimulation, and subsequent olfactory stimulation. Based on several studies using olfactory stimulation with food odors (vanilla, breast milk) to promote oral feeding in preterm infants this study was conducted to test the following hypothesis: Does olfactory stimulation with vanilla or milk odor (breast milk or formula) lead to a reduction in the time required for nasogastric tube weaning in premature infants older than 26 + 6 weeks of gestational age? In addition, does it influence secondary outcomes such as length of hospital stay, weight development, and attainment of greater amounts of independently consumed food?

METHODS

Premature with complete or partial feeding by gastric tube and without ventilation were included. For this study, 207 infants over 26 + 6 gestational weeks were randomized into three different study groups. Before each feeding, an olfactory presentation was made with milk odor, a vanilla Sniffin' Stick, or a control stick. In the final analysis, 165 infants were included (87 males, 78 females). At the time of randomization, infants were on average 12 ± 9.5 days old.

RESULTS

While the influence of vanilla and milk odor did not provide a significant difference from the control for the primary outcome, a secondary analysis showed a significant group difference in the cumulative amount of independently drunk food consumed in the first ten days was the highest amount in the vanilla group. This time period was chosen due to the high dropout rate after the first ten days. In addition, there was a promising significance for earlier hospital discharge for prematurely below 32 weeks of gestation receiving vanilla odor stimulation in comparison to milk odor stimulation.

CONCLUSION

Although the primary outcome of this study (gastric tube removal) did not provide significant results, a significant benefit of vanilla olfactory stimulation for preterm infants was demonstrated in subgroup analysis above milk odor stimulation. Younger preterm infants seem to benefit from the stimulation.

Interventions for reducing late-onset sepsis in neonates: an umbrella review

OBJECTIVES

Neonatal sepsis is one of the leading causes of neonatal deaths in neonatal intensive care units. Hence, it is essential to review the evidence from systematic reviews on interventions for reducing late-onset sepsis (LOS) in neonates.

METHODS

PubMed and the Cochrane Central were searched from inception through August 2020 without any language restriction. Cochrane reviews of randomized clinical trials (RCTs) assessing any intervention in the neonatal period and including one or more RCTs reporting LOS. Two authors independently performed screening, data extraction, assessed the quality of evidence using Cochrane Grading of Recommendations Assessment, Development and Evaluation, and assessed the quality of reviews using a measurement tool to assess of multiple systematic reviews 2 tool.

RESULTS

A total of 101 high-quality Cochrane reviews involving 612 RCTs and 193,713 neonates, evaluating 141 interventions were included. High-quality evidence showed a reduction in any or culture-proven LOS using antibiotic lock therapy for neonates with central venous catheters (CVC). Moderate-quality evidence showed a decrease in any LOS with antibiotic prophylaxis or vancomycin prophylaxis for neonates with CVC, chlorhexidine for skin or cord care, and kangaroo care for low birth weight babies. Similarly, moderate-quality evidence showed reduced culture-proven LOS with intravenous immunoglobulin prophylaxis for preterm infants and probiotic supplementation for very low birth weight (VLBW) infants. Lastly, moderate-quality evidence showed a reduction in fungal LOS with the use of systemic antifungal prophylaxis in VLBW infants.

CONCLUSIONS

The overview summarizes the evidence from the Cochrane reviews assessing interventions for reducing LOS in neonates, and can be utilized by clinicians, researchers, policymakers, and consumers for decision-making and translating evidence into clinical practice.

Odor-active volatile compounds in preterm breastmilk

BACKGROUND

Volatile compounds in breastmilk (BM) likely influence flavor learning and, through the cephalic phase response, metabolism, and digestion. Little is known about the volatile compounds present in preterm BM. We investigated whether maternal or infant characteristics are associated with the profile of volatile compounds in preterm BM.

METHODS

Using solid-phase microextraction coupled with gas chromatography/mass spectrometry, we analyzed volatile compounds in 400 BM samples collected from 170 mothers of preterm infants.

RESULTS

Forty volatile compounds were detected, mostly fatty acids and their esters (FA and FAe), volatile organic compounds (VOCs), aldehydes, terpenoids, alcohols, and ketones. The relative concentration of most FA and FAe increased with advancing lactation and were lower in BM of most socially deprived mothers and those with gestational diabetes (p < 0.05), but medium-chain FAs were higher in colostrum compared to transitional BM (p < 0.001). Infant sex, gestational age, and size at birth were not associated with the profile of volatile compounds in preterm BM.

CONCLUSIONS

Sensory-active volatile FA and FAe are the major contributors to the smell of preterm BM. The associations between lactation stage, maternal characteristics, and volatile compounds, and whether differences in volatile compounds may affect feeding behavior or metabolism, requires further research.

IMPACT

Sensory-active volatile FAs are major contributors to the smell of preterm BM and are influenced by the lactation stage and maternal characteristics. Longitudinal analysis of volatile compounds in preterm BM found that FAs increased with advancing lactation. Colostrum had a higher concentration of medium-chain FAs compared to transitional BM and the concentration of these is associated with socioeconomic status, gestational diabetes, and ethnicity.

Effects on Growth of Smell and Taste of Milk During Tube Feeding of Preterm Infants: A Randomized Clinical Trial

IMPORTANCE

Smell and taste of food increase food anticipation, activate gut motility, and stimulate digestion and metabolism. Despite poor growth of many preterm infants in neonatal intensive care units, the smell and taste of milk with tube feeding are not generally considered a regular component of care.

OBJECTIVE

To determine the effect of smell and taste of milk with tube feeding on weight z scores at discharge from the hospital.

DESIGN, SETTING, AND PARTICIPANTS

A randomized, controlled, nonblinded, superiority trial was conducted at 2 perinatal centers between May 9, 2017, and February 1, 2020. Eligible infants (n = 659) were born at less than 29 weeks' postmenstrual age (PMA) and/or with a birth weight of less than 1250 g.

INTERVENTIONS

Infants were randomly assigned to receive either the smell and taste of milk with each tube feeding or routine care without the provision of smell and taste of milk.

MAIN OUTCOMES AND MEASURES

The primary outcome was weight z score at discharge from any hospital. Secondary outcomes included anthropometric measures at predefined time points, time to full enteral feeds, and other health outcomes associated with prematurity.

RESULTS

Of the 658 infants, a total of 396 infants were randomized; some parents had not been approached for consent (n = 144) or declined participation (n = 117), and 1 infant with consent was not randomized. Of the 396 infants, 196 were assigned to the treatment group (51% male; mean [SD] PMA at birth, 27.5 [2.2] weeks) and 200 were assigned to the control group (52% male; mean [SD] PMA at birth, 27.6 (2.3) weeks). Mean weight z scores at discharge were -0.87 (95% CI, -1.02 to -0.72) for the treatment group and -0.97 (95% CI, -1.11 to -0.83) for the control group (P = .40). The mean difference in z scores between the treatment and control groups at 36 weeks' PMA was 0.21 (95% CI, 0.01 to 0.4; P = .04) for head circumference and 0.26 (95% CI, 0.05 to 0.51; P = .04) for length. There were no clinically notable differences between the study groups for any other anthropometric, feeding, or health outcomes.

CONCLUSIONS AND RELEVANCE

In this randomized clinical trial, regular smell and taste of milk included with tube feeding did not improve weight at discharge in preterm infants. Secondary outcomes suggest exposure to smell and taste may improve head circumference and length at 36 weeks' PMA, but not at discharge. Regular exposure to the smell and taste of milk is a simple and inexpensive intervention with potential benefits and no apparent adverse effects.

TRIAL REGISTRATION

anzctr.org.au Identifier: ACTRN12617000583347.

Cortical Oxygenation Changes during Gastric Tube Feeding in Moderate- and Late-Preterm Babies: A NIRS Study

Smell and taste of food can trigger physiological responses facilitating digestion and metabolism of nutrients. Controlled experimental studies in preterm babies have demonstrated that smell activates the orbitofrontal cortex (OFC) but none have investigated the effect of taste stimulation. Using cotside Near-Infrared Spectroscopy (NIRS), we measured changes in OFC cerebral oxygenation in response to gastric tube feeds five and 10 days after birth in 53 assessments of 35 moderate- to late-preterm babies enrolled in a randomized trial. Babies were randomly assigned to receive smell and taste of milk before gastric tube feeds (intervention group, n = 16) or no exposure (control group, n = 19). The majority of babies were born at 33 weeks of gestation (range 32–34) and 69% were boys. No differences in OFC cerebral oxygenation were observed between control and intervention groups. Gastric tube feeds induced activation of the OFC (p < 0.05), but sensory stimulation alone with smell and taste did not. Boys, but not girls, showed activation of the OFC following exposure to smell of milk (p = 0.01). The clinical impact of sensory stimulation prior to tube feeds on nutrition of preterm babies, as well as the impact of environmental inputs on cortical activation, remains to be determined.

Olfactory Cues in Infant Feeds: Volatile Profiles of Different Milks Fed to Preterm Infants

Background: Smell is determined by odor-active volatile compounds that bind to specific olfactory receptors, allowing us to discriminate different smells. Olfactory stimulation may assist with digestion and metabolism of feeds in the neonate by activation of the cephalic phase response of digestion. Infants' physiological responses to the smell of different milks suggest they can distinguish between breastmilk and infant formula. We aimed to describe the profile of volatile compounds in preterm breastmilk and investigate how this differed from that of other preterm infant feeding options including pasteurized donor breastmilk, breastmilk with bovine milk-based fortifier, human milk-based products and various infant formulas. Methods: Forty-seven milk samples (13 different infant formulas and 34 human milk-based samples) were analyzed. Volatile compounds were extracted using Solid Phase Micro Extraction. Identification and relative quantification were carried out by Gas Chromatography with Mass Spectrometry. Principal Component Analysis (PCA) and one-way Analysis of Variance (ANOVA) with Tukey's HSD (parametric data) or Conover's post-hoc test (non-parametric data) were used as appropriate to explore differences in volatile profiles among milk types. Results: In total, 122 compounds were identified. Breastmilk containing bovine milk-based fortifier presented the highest number of compounds (109) and liquid formula the lowest (70). The profile of volatile compounds varied with 51 compounds significantly different (adjusted p < 0.001) among milk types. PCA explained 47% of variability. Compared to preterm breastmilk, the profile of volatile compounds in breastmilk with added bovine milk-based fortifier was marked by presence of fatty acids and their esters, ketones and aldehydes; infant formulas were characterized by alkyls, aldehydes and furans, and human milk-based products presented high concentrations of aromatic hydrocarbons, terpenoids and specific fatty acids. Conclusions: Sensory-active products of fatty acid oxidation are the major contributors to olfactory cues in infant feeds. Analysis of volatile compounds might be useful for monitoring quality of milk and detection of oxidation products and environmental contaminants. Further research is needed to determine whether these different volatile compounds have biological or physiological effects in nutrition of preterm infants.

The effect of smell and taste of milk during tube feeding of preterm infants (the Taste trial): a protocol for a randomised controlled trial

INTRODUCTION

Smell and taste of milk are not generally considered when tube feeding preterm infants. Preterm infants have rapid growth, particularly of the brain, and high caloric needs. Enteral feeding is often poorly tolerated which may lead to growth failure and long-term neurodevelopmental impairment. Smell and taste are strong stimulators of digestion and metabolism. We hypothesise that regular smell and taste during tube feeding will improve weight z-scores of very preterm infants at discharge from hospital.

METHODS AND ANALYSIS

Taste is a randomised, unblinded two-centre trial. Infants born at <29 weeks' gestation and/or <1250 g at birth and admitted to a participating neonatal intensive care unit are eligible. Randomisation occurs before infants receive two hourly feeds for 24 hours. Infants are randomised to either smell and taste of milk with each tube feed or tube feeding without the provision of smell and taste. The primary outcome is weight z-score at discharge. Secondary outcomes include: days to full enteral feeds, duration of parenteral nutrition, rate of late-onset sepsis, post menstrual age at removal of nasogastric tube and at discharge from hospital, anthropometric data and neurodevelopmental outcomes at 2 years of corrected age.

ETHICS AND DISSEMINATION

Human Research Ethics Committees of Mater Misericordiae (trial reference number: HREC/16/MHS/112) and the Royal Women's Hospital (trial reference number: 17/21) last approved the trial protocol (version 4.2; Date: 18 December 2018) and recruitment commenced in May 2017 and November 2017, respectively. The trial results will be published in a peer-reviewed journal and will be presented at national and international conferences.

TRIAL REGISTRATION NUMBER

ACTRN12617000583347.