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Enteral feeding is infrequently regarded as a source of infection in the specialised critical care setting. Pathogenic colonisation of enteral formula, ETF administration sets and associated equipment may potentially modulate the intestinal microflora leading to disequilibrium of intestinal bacteria homeostasis and diarrhoea. Enteral nutrition formula, administration sets and associated equipment present opportunistic portals of entry for contamination through poor equipment hygiene and variable daily management practices (Barrett, Shephard, & Gibson, 2009; Best, 2008; Mathus- Vliegen, Bredius, & Binnekade, 2006). Strategies are proposed to improve the nursing management of ETF formula and associated equipment to thereby minimise bacterial contamination that may result in intestinal microflora imbalance and diarrhoea in critically ill patients (see Table 2.7).

Improvements in the microbiological safety of ETF systems have occurred over the past two decades (Mathus-Vliegen et al., 2006). These improvements include ready- to-use liquid formulae, closed feeding systems with drip chambers in the delivery sets, collapsible plastic feeding bottles/bags, use of positive pressure mechanical infusion devices to administer feeds (Lau & Girard, 2011; Mathus-Vliegen et al., 2006; Williams & Leslie, 2005), improvements in the nutritional value of the formula (Skipper, 2012) and improvements with mechanical infusion pumps (Tepaske et al., 2006). Despite such improvements retrograde feeding set

contamination from health care professionals’ contaminated hands often remains overlooked as a cause of infection and diarrhoea in the ICU (Lloyd & Powell-Tuck. 2004). This occurs via contamination of the ETF set distal to the formula source

resulting in ETF formula contamination; for example, contamination of the Y-port during medication administration, feed set misconnection and routine daily use (Best, 2008; Lau & Girard, 2011). Infection and diarrhoea may ensue as enteral formulae provide an ideal environment for bacterial growth (Barrett et al., 2009; Lau & Girard, 2011).

Table 2.7

Strategies to Minimise Contamination of Enteral Feeding Tubes

Procedure Purpose

Aseptic technique Appropriate hand hygiene prior to/upon completion of preparing administration sets and changing of feed containers.

Use of non-sterile gloves to prepare administration sets is controversial with mixed results.

Equipment hygiene Day-to-day cleaning of ETF-associated equipment including feed pumps and prior to storage.

ETF administration sets and establishing feeding

Label administration sets with patient’s name, date, time the formula was opened.

Dispose of administration sets between intermittent feeding. Use single use administration sets/syringes to minimise human contact and contamination.

Flush feeding tubes regularly with tap water to prevent blockage and clear feeding tube luminal adherence of aspirated gastric contents.

ETF formula management

Store formula as per manufacturer’s recommendations to avoid fluctuations in temperature beyond 5–25°C.

Use smaller containers for bolus feeds to restrict the length of time container is exposed to environmental contamination.

Refrigerate opened and unused formula for ≤24 hours. Avoid decanting/reconstituting ETF.

Use only sterile containers, syringes, feed sets. Replace ETF container every 24 hours.

Avoid mixing additives into formula to reduce feed contamination and coagulation.

Administer medications via a designated injection port and avoid mixing directly with ETF formula.

Daily ETF management

Implement asepsis to prepare equipment and access feed sets. Change feed containers/administration sets every 24 hours. Use only single use, designated syringes for medication administration and tube aspiration.

Frequently flush feed tube with tap water and aspirate GRV. Regular assessment of bowel function.

Regular administration of medications.

Source: Bankhead et al., 2009; Best, 2008; Fletcher, 2010; Irish Clinical Resource Efficiency Support Team, 2004; Lau & Girard, 2011; Manchester NHS, 2010; Marshall & West, 2004; Mathus-Vliegen, Bredius, & Binnekade, 2006; NICE, 2003.

Feed tube site contamination was examined in an RCT of 37 ICU patients who received ETF via a glass bottle (with a sterile elastomer cap that was spiked by a feeding administration set) or plastic Pack feed system (a triple foil laminated collapsible bag without an air inlet) (Mathus-Vliegen et al., 2006). Bacteria were cultured in three of 112 glass bottles with one bottle suspended for more than eight hours and two of the 95 Pack systems. Contamination at the Y-port of the

administration sets increased to 48%. Exogenous contamination of ETF feed sets was less likely to occur compared with endogenous contamination from retrograde flow. Two strategies proposed to minimise the retrograde feed set contamination were the positive pressure exerted by the feeding pump and effective health care worker hand hygiene (Mathus-Vliegen et al., 2006). The significance of retrograde feed set contamination and diarrhoea was not measured in the Mathus-Vliegen et al. (2006) study. However, glass bottle enteral nutritional formulae are used less frequently in clinical practice.

International clinical practice guidelines recommend specific preparation and maintenance practices be implemented with the provision of enteral nutrition (Bankhead et al., 2009). These guidelines aim to minimise the risk of harm, such as feed contamination and infection among patients who receive ETF. Specific

recommendations include appropriate shelf-life of the enteral formulae and administration sets, refrigeration of the feed immediately it is opened, disposal of unused feed at 24 hours following opening, changing administration sets every 24 hours and labelling ETF formulae and administration sets with the patients’ name and date and time of opening to minimise the hanging time (Bankhead et al., 2009; Best, 2008; Lloyd & Powell-Tuck, 2004). The relationship between these guidelines and diarrhoea in critically ill patients was not reported.

Two methods of ETF preparation are routinely used in ICUs and include ready-to- hang packs and decanting of feed into flexi-containers (Skipper, 2012).

Contamination of ETF formulae has been demonstrated in the decanting of formula into a flexi-container in adult patients (Beattie & Anderton, 2001; Best, 2008). Microbiological risks were examined in the assemblage and running of four enteral feeding systems using prefilled nutrient containers and decanting ETF into flexi- containers in a simulated ward environment (Beattie & Anderton, 2001). Equipment

was prepared with hands encased in disposable gloves, or deliberately contaminated with a test organism, or contaminated hands deliberately touching the nutrient container top and administration set connector. No feed contamination was found when ready-to-hang feed systems were used. However, formulae contamination was found at 24 hours when feed was decanted from bottles, suggesting poor hygiene at the lip of the can. There is a clinically significant relationship between feed system contamination and preparation and maintenance techniques, however, the

relationships between diarrhoea and the variables were not examined.

Feed intolerance has been reported in 43–63% of ETF patients, with high GRV occurring in 30–51% of this patient population (MacLaren et al., 2008; McClave et al., 2004). The transient cessation of the ETF often accompanies clinical

management of feed intolerance. Patients who experience feed intolerance are more likely to encounter diarrhoea, more abdominal distension, nausea, vomiting, poor nutrition, increased lengths of ICU and hospital stays and higher mortality rates (Chan, 2010; MacLaren et al., 2008).

The use of GRV has become a barrier to effective nutrient delivery and potentially increases the risk to critically ill patients (Hurt & McClave, 2010). Intensive care nurses routinely aspirate GRV every two to four hours (Skipper, 2012). The practice and frequency of GRV remains contentiously reported in the literature over the past 20 years (Marshall & West, 2006; McClave et al., 1992; McClave et al., 2005). Practices surrounding GRV include the aspiration and/or the return of aspirated gastric contents and feed to the patient, versus the discarding of aspirated gastric contents. The reinfusion of aspirated gastric contents remains controversial. However, the discarding of aspirated feed and gastric contents may result in the underdelivery of nutritional requirements and the depletion of electrolytes (Williams & Leslie, 2004).

The practice of returning or discarding GRV and patient-associated complications was examined in a small RCT (n = 10) (Booker et al., 2000). No significant differences were observed between the two groups regarding acquiring aspiration pneumonia, electrolyte abnormalities and delays in feeding and tube replacements. These findings may be associated with the small sample size. Similar findings were observed in a larger RCT that also examined the returning (n = 63) or the discarding

of (n = 62) GRV (Juve-Udine et al., 2009). Delayed gastric emptying was

significantly lower in the reinfused GRV group. Both the Booker et al. (2000) and Juve-Udine et al. (2009) studies examined similar ETF intolerance endpoints

including diarrhoea, abdominal distension and nausea and vomiting. No statistically significant differences were found between the two groups in both studies (Booker et al., 2000; Juve-Udine et al., 2009). Consequently, it is recommended that GRVs less than 500 mL are reinfused. The noteworthy limitation of the Booker et al. (2000) and Juve-Udine et al. (2009) studies was that contamination of the ETF feed and

retrograde contamination of the administration sets were not measured.

Regular flushing of the feeding tube with cool boiled water, sterile water or tap water is recommended to maintain tube patency and to irrigate potentially harmful bacteria that may result from regular aspiration (Beattie & Anderton, 2001; Kenny &

Goodman, 2010; NHMRC, 2010; NICE, 2003). Evidence supporting the routine flushing of feeding tubes remains limited. Practice is often guided by the clinician’s experience or the health care facility’s local policy. Iatrogenic relationships between diarrhoea and ETF have variably been associated with the time to commencement of ETF following ICU admission, the method of ETF delivery, the osmolality and fibre content of ETF formula and the preparation and maintenance of ETF formula and systems.