Enteral nutrition is the first-choice nutritional therapy for patients without gastrointestinal tract impairment [1]. Aspiration pneumonitis, caused by gastro-esophageal reflux (GER) of fed nutrients, is a frequent and life-threatening inflammatory event in patients who are fed enterally [2]. Semi-solid enteral nutrients are widely used in Japan and were developed as an alternative to conventional liquid enteral nutrients to prevent feeding-related GER [34]. Semi-solid enteral nutrients have a higher viscosity compared to liquid enteral nutrients and, therefore, are typically administered through a large-diameter percutaneous endoscopic gastrostomy (PEG) tube, rather than a nasogastric tube (NGT). In Japan, a pectin solution is used to semi-solidify liquid nutrients administered via small-diameter NGT. Low methoxide pectin in the presence of ionized calcium increases viscosity; therefore, the pectin solution increases the viscosity of liquid enteral nutrients, improving GER [56]. Because the pectin solution and liquid enteral nutrients are administered separately, it can be easily administered via NGT. A new formula (Mermed^®; Terumo Corporation, Tokyo, Japan) uses alginate, which behaves as a gelatin in acidic conditions, improving GER and diarrhea that result from enteral feeding [78]. Mermed^® is in a liquid state when administered through a NGT, and changes into a semi-solidified state in the stomach prior to reverting to a liquid state within the intestines [7]. We present a case where administration of Mermed Plus^® (with increased water content; Terumo Corporation, Tokyo, Japan) in a patient undergoing rehabilitation after cerebral infarction, reduced vomiting, thereby enabling the continuation of enteral nutrition. The ethics committee of Saiseikai Fukuoka General Hospital (2017-7-3) approved this case report and waived the requirement for informed consent.

The patient is an 86-year-old woman. Prior to entering our care, the patient performed usual daily living activities independently, including eating and toileting, albeit needing to use a cane for support. One month earlier, the patient developed an atherothrombotic cerebral infarction in the right anterior cerebral artery and right middle cerebral artery area, and was hospitalized at another hospital for 2 weeks before being transferring to our hospital. The clinical course of the patient is shown in Figure 1. On the first day of hospitalization, the patient experienced vomiting during enteral feeding via NGT and developed aspiration pneumonia. Enteral feeding was discontinued, and the patient was then changed to peripheral parenteral nutrition and antibiotics were administered. After 1 week, enteral feeding was restarted using 300 mL of water with no signs of vomiting. A liquid diet was slowly introduced beginning the next day. The patient started vomiting 3 hours later, and enteral feeding was discontinued once again.

REF-P1, a viscosity regulator, was introduced for use in combination with her liquid diet and enteral feeding was restarted using a 100 mL liquid diet but vomiting persisted. As a result, the patient was unable to continue enteral nutrition and was transferred to our hospital to resume nutritional therapy.

Computed tomography (CT) and esophagogastroduodenoscopy were performed on hospital day 2, and was negative for transit disorder, upper gastrointestinal ulcer, or feces accumulation. From hospital day 2, enteral feeding was resumed using a glutamine formulation, after which no vomiting was observed. Beginning from hospital day 4, the proton pump inhibitor was discontinued and Mermed Plus^® (300 mL/225 kcal, administered for 1 hour, 3 times a day) was started. No vomiting was observed after resuming enteral feedings with Mermed Plus^® and dietary intake of the patient was increased to 535 mL/400 kcal (administered for 1 hour, 3 times a day) beginning on hospital day 5, after which no vomiting was observed. Because the patient required enteral nutrition for more than 1 month, a PEG was performed on hospital day 7 after obtaining informed consent. The postoperative course of the patient was uneventful, and there was no vomiting while continuing with Mermed Plus^® (535 mL/400 kcal, administered for 1 hour, 3 times a day). On hospital day 14, the patient was transferred back to the previous hospital to continue rehabilitation.

Enteral nutrition is more affected by physiological parameters than parenteral nutrition. Enteral nutrition improves patient outcomes and decreases healthcare costs compared to parenteral nutrition [9]. GER is a common and serious complication in patients receiving enteral nutrition, potentially making continuation of enteral nutrition difficult. Our case report showed that a new semi-solid formula enabled continuation of enteral nutrition via NGT in a patient who had difficulty in tolerating enteral nutrition due to vomiting.

In our case, no vomiting occurred with the administration of water, but vomiting re-occurred when liquid enteral nutrients were administered. The oral rehydration solution was quickly discharged from the stomach, and its effect was applied before introducing general anesthesia [10]. Gastric emptying time is affected by the stomach expansion following the ingestion of a set volume load. Gastric emptying time increases in proportion to intake, up to a single intake of 600 mL [11]. In addition, chemical receptors in the stomach and the small intestine react to ingested substances then digestive juices are secreted and stimulate the movement of the gastrointestinal tract. This movement is affected by the type of digestive juices secreted from gastrointestinal wall [12]. Therefore, for enteral nutrients that contain proteins and lipids, gastric emptying time was prolonged and vomiting occurred.

On the contrary, “adaptive relaxation” modulates gastric tone in response to specific meal properties, promotes physiological movement within the stomach [1314] and is an important factor relating to enteral nutrient viscosity. Semi-solid enteral nutrients that appeared in recent years are more likely to exhibit adaptive relaxation than liquid enteral nutrients, potentially suppressing GER. Semi-solid enteral nutrients have high viscosity, and therefore are typically administered through a large-diameter PEG tube.

In our case, REF-P1 and Mermed Plus^®, which are easily administered via NGT, were used. Vomiting occurred when REF-P1 and 100 mL enteral nutrients were administered but did not occur with the administration of 300 mL Mermed Plus^®. To facilitate adaptive relaxation of the stomach, REF-P1 and the small amount of enteral nutrients were not sufficiently viscous; however, with Mermed Plus^®, we were able to achieve adequate viscosity and volume.

To prevent vomiting, it is common to slow the administration rate of enteral nutrients and/or use a duodenal tube [15], however these methods increase the burden on the patients and the medical staff. In the present case, Mermed Plus^® was easily administered via NGT, and the effect was quickly obtained. Therefore, its use may improve the patient's quality of life while reducing the burden on the medical staff.