Description of the condition
Lack of nutrition can be a serious obstacle to recovery in critically ill patients. Providing early nutrition support to these patients is an important therapy for attenuating disease severity, modulating the immune response, reducing complications, and improving patient outcomes (ASPEN 2009; ASPEN 2015).
Enteral nutrition is a common technique used to deliver nutritional sustenance to patients with a functioning gastrointestinal tract who are unable to eat. The method involves delivering nutrition directly to the gastrointestinal tract via a feeding tube. Several nutritional guidelines have recommended the method for preventing poor outcomes in critically ill patients who are unable to eat (ASPEN 2009; ASPEN 2015; ESPEN 2006). The technique is preferable to parenteral nutrition, which involves delivering calories via an intravenous tube (Seres 2013). Theoretical advantages include the preservation of mucosal architecture and immune function (Seres 2013).
Clinical studies show that enteral nutrition significantly reduces the risk of infection compared to parenteral nutrition (ASPEN 2009; ASPEN 2015; ESPEN 2006; Prieto 2011). A systematic review found that enteral nutrition resulted in a significant decrease in infectious complications in critically ill patients compared with parenteral nutrition (Gramlich 2004).
A routine technique for delivering enteral nutrition is post-pyloric feeding, which involves placing a tube through the nasal passage, past the pylorus, to the duodenum or jejunum. An alternative technique involves extending a gastric tube only to the stomach. Patients fed via post-pyloric nasoenteral tubes have a lower incidence of complications compared to those fed via nasogastric tubes because of their lower rate of gastroesophageal reflex, regurgitation, excessive salivation, and irritation of the mucosa. Nasogastric feeding tubes are easy to insert but frequently cause gastroesophageal reflex in children (Noviski 1999). Gastroesophageal reflex may lead to respiratory complications such as pulmonary aspiration, which occurs when food or liquid secretions go down the wrong way and enter the airways and lungs.
Compared with gastric tube insertion, post-pyloric feeding tubes can reduce the risk of pneumonia, and they have not been associated with epistaxis, pneumothoraces, or gastrointestinal bleeding. These results suggest that post-pyloric feeding increases the amount of nutrition delivered to the patient (Alkhawaja 2015).
Post-pyloric tube feeding is an important technique for preventing malnutrition in children with severe diseases. Malnutrition is a serious condition caused by a lack of the right amount or type of food (ESPEN 2006). Children have a lower percentage of muscle mass and fat than adults, which means that they have fewer energy reserves and higher energy expenditure, making them more prone to malnutrition (Prieto 2011). The prevalence of malnutrition among hospitalised children is 15% to 30% (Silva 2013), and the incidence of malnutrition in paediatric intensive care units (ICUs) varies between 25% and 70% (Prieto 2011). Higher rates of malnutrition have an impact on the length of hospitalisation, as well as on the number of deaths in a particular situation or period of time (mortality), and the occurrence of symptoms, diseases, or adverse effects caused by a medical intervention such as surgery (morbidity) (Silva 2013).
Critically ill children in the ICU are frequent candidates for post-pyloric feeding (ESPEN 2006), especially those who are prone to gastroesophageal reflex from nasogastric feeding. However, while post-pyloric feeding has some benefits over gastric feeding, the placement of post-pyloric tubes is technically challenging and often requires the use of subsidiary methods, such as imaging techniques (AGA 1995; ESPEN 2006). These difficulties, and a lack of expertise and resources in individual facilities, can cause delays in the insertion of post-pyloric feeding tubes (ESPEN 2006).
Description of the intervention
Several methods are used in clinical practice to insert feeding tubes through the pylorus, as well as to verify their placement (Marsland 2010).
The standard technique for inserting an enteral feeding tube involves first ensuring that the child is tilted at a 45-degree angle (if there is no contraindication), and inserting the lubricated tube into the nostril while at the same time gently bending back the child's head to facilitate easy movement through the pharynx (Leaes 2012).
The use of prokinetic agents, such as metoclopramide and erythromycin, prior to tube insertion can help to improve the success of the manual insertion procedure. Metoclopramide is a gastrointestinal stimulant and antiemetic drug used to treat gastroesophageal reflex, which increases gastric motility and the rate at which it empties. The contraction of the muscles helps to move the tube along (Simons 2012).
The proper placement of the feeding tube can be verified through auscultation, which involves using a syringe to fill the feeding tube with air while placing a stethoscope over the stomach to listen for rushing air (ASPEN 2009). Feeding tube placement can also be verified by measuring the pH of the fluid aspirated from the feeding tube (ASPEN 2009). Capnography can be used to verify that the feeding tube has been properly inserted through the oesophagus by measuring and displaying carbon dioxide levels in gas samples aspirated into a monitoring unit (Kindopp 2001).
For patients who cannot be moved, portable ultrasonographic units can be used to visualise and control the insertion of feeding tubes. In studies using the ultrasound technique, participants are placed in the supine and sniffing position with the left side down, if possible. A sonographic examination is performed from the neck to the abdomen. The feeding tube is directly visualised in the oesophagus and stomach (Hernandez-Socorro 1996).
Another technique involves the insertion of a feeding tube via endoscopic guidance. Endoscopes are thin and hollow tubes attached to a small video camera on the end, which can be inserted into the body to look inside. General anaesthesia is typically required in children during upper gastrointestinal endoscopy procedures.
A recently developed alternative to endoscopic guidance is electromagnetic-guided tube placement. This method uses a special stylet with a tip containing an electromagnetic transmitter that generates a real-time signal as the feeding tube is inserted and advanced to the desired position (October 2009).
The post-pyloric feeding tube can also be guided by fluoroscopy. Fluoroscopy is a type of medical imaging procedure that uses x-rays to acquire continuous, real-time images of the body. The image is continuously transmitted to a monitor, which enables the detailed observation of a moving instrument, such as a feeding tube, as it passes through the body (ASPEN 2009). Feeding is usually stopped several hours before the insertion procedure. The patient is brought into the procedure room and placed on the fluoroscopic table in the supine position, and sedated if necessary.
How the intervention might work
Prokinetic agents can aid the blind and manual placement of feeding tubes by stimulating the smooth muscle of the stomach and intestines. Metoclopramide stimulates gastrointestinal smooth muscle by blocking the neurotransmitter dopamine and triggering the release of the neurotransmitter acetylcholine. It facilitates peristalsis and gastric emptying. A previous Cochrane review described a study in which metoclopramide was found to be useful in post-pyloric catheter placement when administered before catheter introduction (Silva 2002). However, a more recent review has found that metoclopramide may cause drowsiness, anxiety, agitation, urticaria and, rarely, extrapyramidal symptoms (Silva 2015). Another gastrointestinal prokinetic agent is erythromycin, which belongs to a group of closely related antibiotics known as macrolides. Erythromycin activates receptors that bind to the hormone, motilin, located in gastric and duodenal smooth muscle. Its prokinetic properties also increase gastric motility and facilitate gastric emptying (AGA 1995; Leaes 2012). The use of erythromycin as an agent for treating gastric dysmotility, however, raises concerns about promoting macrolide resistance (Hawkyard 2007).
Ausculcation is not considered a reliable method for verifying the correct placement of a post-pyloric feeding tube. An experimental study demonstrated that auscultation could not determine where the tube had been placed (ASPEN 2009).
Measuring the pH of fluid aspirated from the feeding tube is considered a more useful technique for verifying the correct placement of a post-pyloric feeding tube. Gastric fluid usually has a pH less than or equal to 5 and the intestine has an approximate pH of 6.6, while respiratory secretions are almost always alkaline (Leaes 2012). However, as the pH level of the aspirated fluid is often elevated due to the presence of either medication or feeding formulas, pH testing is not always reliable (Simons 2012). The appearance of the aspirated gastric and small bowel fluid is usually different. Gastric fluid is typically clear and colourless or green, and small bowel fluid is typically bile-stained. The pH level of gastric fluid is often lower than that of small bowel secretions (ASPEN 2009).
Capnography is widely used in the ICU for confirming endotracheal tube placement, and can be used to verify exhaled CO2 if the enteral tube is placed in the tracheal position (Leaes 2012). Both capnography and colorimetric CO2 detection are easier to perform than the standard technique, and capnography is more time-efficient for tube insertion (Burns 2006). A calorimetric indicator is a disposable device which changes its colour from purple to yellow if it indicates the presence of carbon dioxide.
Sonographic guidance is a useful method for both inserting a tube and monitoring the tube's position. This technique has shown a high success rate for tube insertion compared with the blind manual method. It can also be used as an alternative to radiography in order to reduce exposure to radiation (Leaes 2012). While the ultrasound method has proved successful in adults, it could not confirm the feeding tube position in neonates (Tamhne 2006).
Endoscopy guidance allows placement under direct vision. This technique is simple but it requires a complete endoscopy system which increases the cost and procedure time, and has some risks related to sedation and complications associated with endoscopy such as perforation (Niv 2009).
Electromagnetic-guided tube placement is a new technique, with the first report of its use for post-pyloric enteral tube placement published about 15 years ago. The electromagnetic-guided system visualises the path of the feeding tube in the patient through the tip of a guide wire, which transmits an electromagnetic signal to a receiver placed on the abdomen of the patient. The system shows the position of the feeding tube on a monitor screen to facilitate steering of the tube. This method however, requires a trained operator and furthermore, electromagnetic tubes are more expensive than normal tubes (Koot 2011; October 2009).
Fluoroscopy is one of the most reliable methods for tube placement, however it exposes patients and operators to rather high levels of radiation.
Although both endoscopy and fluoroscopy provide accurate methods of tube placement, these procedures can be expensive, time-consuming, and cause additional risks, such as transporting the child to the imaging department, and in the case of fluoroscopy, exposure to radiation. Moreover, as feeding tubes frequently reposition or migrate back into the stomach, recurrent tube insertion can increase costs (AGA 1995; ASPEN 2009; Simons 2012).
Why it is important to do this review
In children with severe conditions who are admitted to the ICU, it is important to avoid complications related to tube feeding, such as aspiration pneumonia. Aspiration pneumonia is an inflammation of the lung and bronchial tubes caused by inhaling materials such as gastric contents. Feeding via a post-pyloric tube may be an appropriate technique for preventing these complications; however, placement of the transpyloric tube in children can be challenging and can take more time depending on the size of the child and the operator's skill. Furthermore, methods that do not involve radiation exposure are necessary for young children. It is therefore important to evaluate the efficacy and risks associated with methods of post-pyloric tube placement. This review will provide clinical evidence on initial placement of post-pyloric feeding tubes in children and focus on children aged under 18 years.