Cold Liquids Fed to Preterm Infants: Efficacy and Safety After 10 Minutes of Exposure

Swallowing dysfunction, medically defined as dysphagia, commonly occurs in infants born prematurely due to inadequate timing and coordination of the sensorimotor sequences required for safe swallowing. Approximately 70% of prematurely born infants will be diagnosed with oral, pharyngeal and/or esophageal phase dysphagia with an inverse relationship between severity and gestational age at birth.(1)

Swallowing is extremely important for the infant and child to meet the nutritional requirements for growth and development. When swallowing is dysfunctional, the consequences can be devastating for the infant, possibly resulting morbidity, with complications including pneumonia, respiratory disease, growth compromise or failure to thrive.(1-6) The implications of swallowing difficulty are, therefore, of considerable medical importance to the medical team working with these infants.

A videofluoroscopic swallow study (VFSS) is a widely used assessment for the diagnosis of neonatal dysphagia. VFSS is a definitive investigation to objectively assess the adequacy of airway protection during swallowing and allows simultaneous viewing of the bolus as it passes through the oral, pharyngeal and esophageal stages of swallowing.(7) For infants feeding from a bottle, the clinician relies on the VFSS to both identify and correct the swallowing dysfunction. Several therapeutic techniques or modifications are used during a VFSS to improve swallowing safety in infants, such as various nipple flow rates,(8,9) feeding positions,(10) or pacing the infant's sucking bursts.(11) The most frequently used modification is to thicken the infant's formula or breastmilk to a thicker consistency,(12-14) however, thickening causes some difficulty making it an undesirable option for young infants treated in the neonatal intensive care unit (NICU).(15) These difficulties have resulted in clinicians using alternate therapeutic techniques to treat dysphagia neonates. One alternate technique is to feed the infant cold liquids to stimulate a safer swallow.(16-20)

Original findings obtained by these investigators was the first to indicate that cold liquid swallows reduce airway compromise in dysphagic preterm infants when compared to room temperature liquid. Specifically, the occurrence of deep penetration (p=0.029), aspiration (0.017), mild penetration (p=0.044) and nasopharyngeal reflux (p=0.006) decreased significantly in the cold swallow (CS) condition when compared to the room temperature swallow (RTS) condition during VFSS. Similar findings are documented in adults with dysphagia.(21-35) These positive effects are theorized to occur due to the cold liquid providing the sensory receptors within the pharynx increased sensory information which triggers more efficient swallowing movements.(12,13,21-23)

The original study assessed 5 cold liquid swallows, which provided important information regarding the immediate effects of cold liquids on the pharyngeal swallowing mechanism in preterm infants with dysphagia. Further information regarding the duration of these positive effects is necessary to prove its reliability as a modification to be used at bedside. This study is designed to assess the swallowing mechanism of dysphagic preterm infants after feeding cold liquids for 10 minutes to objectively identify any changes over time.

In addition to the paucity of evidence regarding improved swallowing function over time, the safety of feeding cold liquids remains questionable in the preterm infant population. The greatest concern for these infants is the development of cold stress or altered digestive functioning due to the cold temperature of the liquid. The effects of cold stress in infants are observed in all body systems, including cool skin, tachypnea, respiratory distress, desaturation, increasing episodes of apnea and bradycardia, increased gastric residuals, and emesis.(36) Several older studies have assessed the effects of cold feeds in healthy term and healthy pre term infants, however, study populations may not be representative of todays preterm infant population due to significant medical advances and increased survival rates of extremely preterm infants.

Holt and colleagues(37) found no difference in sleep pattern, vocalizations, motility, intake, feeding behavior, weight gain, temperature or regurgitation in preterm infants with a weight of >1,500gm, when fed cold formula. Gonzalez and colleagues(38) found no significant differences in axillary temperature or gastric residuals in preterm infants fed cold (0-4°C) verses room temperature (25°C) milk. Participants included 14 preterm infants with a gestational age at birth (GAB) of 28-30w, and a mean corrected gestational age of 32 weeks. Anderson and Berseth(39) found no differences in infants' antral or duodenal motor activity as assessed via manometry, as well as gastric emptying among cold (6°C), room temperature (24°C), or body temperature (37°C) feeding groups. This study included preterm infants with GAB 25-36weeks, mean birth weights 915-2,455g. Corrected gestational age of 32-36 weeks at the time of the study. Feedings were given in random order for 3 liquid temperatures. Across all temperatures they found that all infants emptied approximately one third of the bolus feeding by 20 minutes. And across all temperatures approximately 10-20% of the bolus feeding remained in their stomach 2 hours post-prandially. The authors propose that thermo-receptors within the gastrointestinal tract do not appear to be functional in this age group.

Blumenthal and colleagues(40) found no statistical differences between stomach emptying rate in cold (0-4°C), room temperature (25°C) or body temperature (37°C) formula in 20 healthy preterm infants with a mean birth weight of 2.75 ± 0-18 (range 1.49-3.38) kg, and gestation 37-7 ± 0.6 (range 34-41) weeks. They also reported that in all infants the cold feeds were well tolerated and produced no obvious clinical effects.

To assess the potential risks of cold stress, each participant's body temperature will be obtained pre and post cold liquid exposure. To assess digestive functioning, the temperature of each participant's gastric contents will be obtained pre and post cold liquid exposure by extraction of the gastric content via a naso-gastric tube (NGT). If the child does not have a naso-gastric tube in place at the time of the study, the subjects will be enrolled but no documentation of the stomach content temperature will be obtained.