Nurses' perception of milk temperature at delivery compared to actual practice in the neonatal intensive care unit

Temperature curve of raw human milk heated by different methods: experimental study

OBJECTIVE

To analyze the temperature curve of raw or pasteurized human milk exposed to different heating methods.

METHOD

Experiments with volumes of 5 ml to 100 ml of human milk were carried out between 2016 and 2021 and analyzed according to the exposure time by different heating methods. Descriptive statistics included the calculation of means, medians, minimum and maximum values, measures of dispersion and standard deviation.

RESULTS

The thermal curve made it possible to identify the heating of human milk close to body temperature when subjected to a water bath and microwaves. Milk exposed to room temperature (21°C) was unable to reach this temperature. When heated in a water bath at 40°C, smaller volumes reached body temperature between 3 and 5 minutes, while in a microwave at 50% power, practically all volumes reached temperature.

CONCLUSION

The temperature curves of raw or pasteurized human milk were constructed, and it was possible to verify its behavior using different heating methods for administering the food in a neonatal intensive care unit, considering the volume, type and time of heating and temperature.

Effects of the thawing rate and heating temperature on immunoglobulin A and lysozyme activity in human milk

Background

The percentage of infants receiving frozen human milk (HM) is increasing. The effects of thawing and warming on the secretory immunoglobulin A (SIgA) level and lysozyme activity in frozen HM should be investigated to identify optimal methods for preserving immune factors in frozen HM.

Methods

Milk samples were collected from 40 mothers with healthy full-term infants who had been lactating for one to six months. The baseline samples were analyzed within 24 h after collection, and the other samples were frozen at -18 °C before analyses. We compared two methods: placing the container overnight in a refrigerator at 4 °C before warming (slow thawing) and immediately thawing in warm water after removing the sample from the freezer (rapid thawing). Additionally, we investigated the effects of the warming temperature by comparing room temperature (25 °C) and physiological temperature (37 °C). The SIgA concentrations and lysozyme activities in the milk samples were determined using ELISA kits and fluorometric lysozyme activity assay kits, respectively.

Results

The SIgA concentrations and lysozyme activity in frozen HM were 16.5–52.1% and 16.8–39.3% lower than those in fresh HM, respectively. The SIgA concentrations in frozen HM were stable during slow thawing at 37 °C (p = 0.072) compared with those in fresh HM. The SIgA concentrations and lysozyme activity were maintained at significantly higher levels during slow thawing than during rapid thawing at 25 °C (p = 0.002 and p < 0.001, respectively). Slow thawing preserved higher SIgA concentrations and lysozyme activity than rapid thawing at 37 °C, but the difference was not significant.

Conclusions

The SIgA level in HM frozen at -18 °C for two months was stable after overnight thawing in the refrigerator (4 °C for 12 h) before warming to 37 °C compared with that in fresh milk. The thawing of HM in the refrigerator overnight (and then warming to 25 °C or 37 °C for 30 min) has the potential to preserve the SIgA concentration and lysozyme activity to a greater extent than heating immediately after removal from the freezer. Broader temperature ranges should be analyzed to determine the temperature that minimizes the losses in SIgA concentration and lysozyme activity in HM.

The Effect of a Continuous Milk Warming System on Weight Gain in Very Low Birth-Weight Infants: A Randomized Controlled Trial

BACKGROUND

Few studies support the practice of warming human milk before feeding. No studies have compared the method of warming milk and its effect on growth, particularly in preterm infants.

PURPOSE

To evaluate growth in preterm infants receiving continuously warmed human milk as compared with infants receiving human milk warmed in a hot water bath before feeding.

METHODS

Forty-four infants less than 32 weeks' gestation admitted to a regional referral level IV neonatal intensive care unit in south central United States were randomly assigned to either the experimental group (continuous warming: n = 22) or the control group (hot water bath: n =22) for 10 days. All infants were on full human milk feedings (120-130 kcal/kg/d) as part of a standardized feeding protocol. Tolerance and weight gain over the 10-day period were used to evaluate the effectiveness of continuous milk warming.

RESULTS

There was a significant difference in weight gain for infants receiving continuously warmed milk compared with infants receiving standard warmed milk (203.73 ± 70.71 vs 271.95 ± 67.40, P = .002).

IMPLICATIONS FOR PRACTICE

The use of continuous milk warming improves weight gain in very low birth-weight infants.

Preterm Infants May Better Tolerate Feeds at Temperatures Closer to Freshly Expressed Breast Milk: A Randomized Controlled Trial

PURPOSE

Feeding intolerance is one of the most frequent problems among preterm infants. These infants are fed with expressed breast milk or preterm formulas of which the temperature is not routinely measured. In this study, we aimed to examine the effects of feeds with warm milk versus room temperature milk in preterm infants.

MATERIALS AND METHODS

Infants with a birth weight ≤1,500 g or gestational age ≤34 weeks were included in the study and assigned to two different feeding temperature groups (22-24°C and 32-34°C). Some infants in both groups were exclusively breast milk-fed, and some received breast milk and artificial milk (mixed feeding). Feeding tolerance of infants in both groups and the consequences were evaluated.

RESULTS

In total, 80 preterm infants (group 1 fed with milk at 22-24°C, n = 40; group 2 fed with milk at 32-34°C, n = 40) were prospectively included in the study. There was a slight decrease in gastric residual frequency in infants fed with breast milk in group 2. Apnea was significantly more frequent in group 1 (p = 0.006), and these infants needed more anti-reflux treatment (p = 0.013).

CONCLUSION

According to our results, warming enteral feeds close to body temperature are encouraging especially due to the decrease in gastric residual frequency, apnea of prematurity, and need for anti-reflux treatment. More studies may confirm the positive effect of warm enteral feeds on feeding tolerance in preterm infants.