Pro/Con

Observe Standard NPO Times for Pediatric Patients Receiving Post-Pyloric Feeds

By Ashley Colletti, MD                                   
Seattle Children’s Hospital
University of Washington
Seattle, Washington

Children receiving gastric and jejunal feeds frequently present for procedures requiring anesthesia.  While gastric feeding is typically treated similar to oral intake in regards to NPO times, it is unclear whether post-pyloric duodenal or jejunal feeding should follow the same standards or should be considered differently.  The following discussion will suggest that children receiving post-pyloric feeds should follow the same, standard NPO guidelines as other patients prior to receiving anesthesia for procedures.

The indications for post-pyloric feeding in children include recurrent aspiration, gastroparesis, and tracheoesophageal fistula as well as severe pancreatitis, proximal enteric fistula, anastomotic gastric outlet stenosis, and hyperemesis1. The motivation to pursue post-pyloric feeding in this select group of patients is to deliver contents distal to the pyloric sphincter with the intent of reducing the likelihood of aspiration or vomiting caused by gastroesophageal reflux.  While aspiration is less common with post-pyloric feeding, it is not absolutely prevented.  Post-pyloric feeding is typically continuous, and clogging is frequent due to smaller tube diameter.  Utilizing post-pyloric feeding is not currently recommended outside of these indications as studies do not demonstrate benefit.  Interestingly, the location of the tip of a post-pyloric feeding tube (duodenum vs. small intestine) stimulates differing responses to feeding. Intraduodenal feeding actually causes a stronger gastrointestinal response than intragastric feeding, resulting in increased gallbladder contraction and stimulation, accelerated small bowel transit time, and increased cholecystokinin and pancreatic enzyme release.  On the other hand, jejunal feeding has not been found to stimulate pancreatic secretion in this way. Thus, from a purely physiologic standpoint, it may not make sense to group patients receiving duodenal and jejunal feeds together for purposes of NPO considerations.

The most recent American Society of Anesthesiology (ASA) practice guidelines describe perioperative fasting standards, which are designed to reduce the risk of pulmonary aspiration in healthy patients undergoing elective procedures2. These guidelines were not designed for nor studied in pediatric patients who receive their enteral intake via feeding tubes. These guidelines recommend a two-hour period of fasting for clear liquids, a four-hour period of fasting for breastmilk, and six hours for formula or solid foods comprising a light meal, with the acknowledgement that fried or fatty foods can delay gastric emptying and that eight hours should be observed in such cases.  For clear liquids, these recommendations are based on a meta-analysis of randomized controlled trials that report smaller gastric volumes and higher gastric pH when observed. For breast milk, the studies are observational and equivocal in regards to gastric volumes and pH post-fasting and for solids and nonhuman milk, randomized controlled trials found overnight fasting to be equivocal to a light meal four hours prior in terms of impact on gastric volumes and pH. Tube feed formulas are not specifically addressed, and may not have been studied in this context.  Children kept NPO for more than eight hours may have an increased risk of hypoglycemia.

The ASA guidelines clearly state that they may not apply to or may need to be modified for patients with diseases that may affect gastric emptying or fluid volume, which includes patients receiving enteral tube feeding2.  The authors acknowledge that following these guidelines does not guarantee complete gastric emptying; again, the supporting studies were primarily done in healthy patients having elective procedures.  It is emphasized that the anesthesiologist should recognize that these conditions can increase the likelihood of regurgitation and aspiration, and that additional or alternative strategies may be appropriate for such patients, such as rapid sequence induction or pharmacologic prophylaxis. 

Nonetheless, medically complex children with feeding tubes undergo frequent anesthetics and invasive procedures, and may undergo mask induction with pungent volatile anesthetics even when some mild gastrointestinal symptoms are present due to practicality or fear of needles.  Thus, based on these considerations, it is difficult to recommend less conservative NPO times in this group of patients determined to be at increased risk of aspiration.  Further, it may be difficult to identify which patients are at an especially high risk of aspiration, given that metrics such as residual volumes have been shown to have poor validity in determining aspiration risk3. 

The exact location of the tip of the feeding tube may be unknown. These patients in the ICU’s may be moved frequently and have dislodging of their feeding tubes. The feeding tube may have been initially placed trans-pyloric but have since unknowingly migrated to an intragastric position. In the intensive care unit (ICU), many patients are kept in a head of the bed elevated at 30-degree position. This has been shown to decrease the amount of aspiration pneumonia within ICU patients who are mechanically ventilated and/or being fed via a feeding tube4. There is also thought that that the feeding tube acts as a “wick” along which feeds may flow retrograde or that the tube may stent the upper and lower esophageal sphincter.

Substantial confusion already exists surrounding NPO guidelines among various hospital staff as well as for patient families, for example, what constitutes a “clear liquid”.  Any non-clear liquid, including tube feeds, is treated as a solid for these purposes.  Many scheduled procedures in pediatric patients inevitably end up delayed or cancelled due to misunderstanding and violation of the established guidelines, in both inpatients and outpatients, resulting in consumption of resources for both families and hospitals with busy operating rooms. 

This ultimately results in decreased efficiency and increased cost:  A recent study at a large children’s hospital estimated that 15% of day-of surgery cancellations were due to NPO violations5.  Further, preoperative calls to families giving NPO instructions are typically done in a standardized fashion by hospital staff, however, the ultimate decision to proceed is made by the individual anesthesiologist caring for a child on the day of the procedure, and may be based on history or physical exam findings elicited at that time.  Thus, following the standard, more conservative NPO guidelines would ensure the fewest number of cases are cancelled.  In conclusion, focus should be on simplification of NPO guidelines as much as possible to convey a consistent message to patients, families, and staff.  

References

1. Niv E., Vaisman V.  Post-pyloric feeding, World J Gastroenterol 2009 15(11): 1281-1288..
2. Apfelbaum JI, Caplan RA, Connis RT et al. and the American Society of Anesthesiologists Committee on Standards and Practice Parameters.  Practice Guidelines for Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration:  Application to Healthy Patients Undergoing Elective Procedures, Anesthesiology 2011 114(3): 495-511.
3. McClave SA, Lukan JK, Stefater JA et al.  Poor validity of residual volumes as a marker for risk of aspiration in critically ill patients, Crit Care Med 2005 33(2):  324-330.
4. Metheny NA, Davis-Jackson J, Stewart BJ. Effectiveness of an aspiration risk-reduction protocol. Nurs Res. 2010;59(1):18–25.
5. Pratap JN, Varughese AM, Mercurio P et al.  Reducing Cancelation on the Day of Scheduled Surgery at a Children’s Hospital, Pediatrics 2015 135(5):  e1292-1299.