The continuous infusion of ETF formulae via the nasogastric or orogastric routes was the method of ETF used in this study. Enteral nutritional formula was administered continuously over a 24-hour period as this method of tube-feeding is the most common method of enteral nutrition delivery in the critical care setting (ESICM Systematic Review Group, 2011; Skipper, 2012).
Enteral tube feeds were prepared and maintained as per the research setting’s ETF protocol (see Appendix 4). In this study, the ETF formula was delivered via a closed sterile system and the ETF formula and administration flow sets were changed every 24 hours. All patients were fed via continuous infusion. Diarrhoea associated with bolus feeding was therefore expected to be minimised in this study. Gastric residual volumes (GRVs) were routinely aspirated to assess patient tolerance to ETF. Gastric residual volumes greater than 200 mL were discarded. There is currently no
agreement regarding the accepted level of GRVs for the monitoring of ETF tolerance in critically ill patients (Johnson, 2009; Kattelman, Hise, Russell, Charney, Stokes, & Compher, 2006; McClave et al., 2009). The discarding of high GRVs at the research setting is consistent with other published reports (Hurt & McClave, 2010;
Landzinski, Kiser, Fish, Wischmeyer, & MacLaren, 2008; Williams & Leslie, 2005, 2010). The cleaning of medication injection ports with alcohol-based solution prior to the injection of medications was not routinely practiced at the research setting. This practice could potentially result in the patient developing infectious diarrhoea. There is currently no recommendation in international ETF clinical practice
guidelines to clean medication injection ports with alcohol-based solution prior to the injection of medications (Bankhead et al., 2009; Heyland et al., 2003; Kreymann et al., 2006; Martin et al., 2004; McClave et al., 2009; NICE, 2006). However,
disinfection of connection sites with isopropyl alcohol following manipulation of feed sets is suggested by Bankhead et al. (2009) as a strategy to minimise the introduction of feed set contamination. Of particular note is that no patient included in Study One developed infectious diarrhoea.
Nearly half of all patients audited in Study One were discharged to the ward with ETF insitu. Continuation of ETF at discharge from the ICU to the ward suggests that patients may have remained acutely unwell. Currently, the continuation or cessation
of ETF at ICU discharge is based upon the individual patient’s clinical needs. International ETF clinical practice guidelines have examined the continuation and cessation of ETF at ICU discharge with some variability enabling clinical decisions to be based upon patient need. Further, patients who have ETF continued at and following ICU discharge are potentially at risk of developing or continuing to experience diarrhoea. This relationship was not observed in Study One and is unlikely to be observed as the majority of research that examines diarrhoea in ETF critically ill patients stops once the patient is discharged from the ICU. A more accurate identification of ICU-associated diarrhoea requires future research to follow-up patients post ICU and possibly post hospital discharge.
4.7.3.3 Time to ETF commencement
In the current study, the commencement of ETF was measured in two ways: 1) ETF commenced within 24 hours of ICU admission; and 2) the exact time to ETF
commencement. International ETF clinical practice guidelines recommend that enteral nutrition be commenced within 24–48 hours of ICU admission (Heyland et al., 2003b; Kreymann et al., 2006; Martin et al., 2004; McClave et al., 2009; NICE, 2006). Consistent with these international ETF guidelines, the majority of
participants in Study One (n = 29, 58%,) had their ETF commenced within 24 hours of admission to the ICU, with the median time to commencement of ETF being 20 hours (range 2–86 hours) (Heyland et al., 2003a; Mehta & Compher, 2009; Woo et al., 2010). A notable relationship that has not been consistently examined in previous research is the relationship between diarrhoea and the timing to commencement of ETF following ICU admission. No association was observed between the occurrence and incidence rate of diarrhoea and the time to commencement of ETF following ICU admission. One explanation for the absence of an association could be the smaller sample size, which may have been inadequate to detect a statistically significant difference. While this study contributes to the ongoing development of knowledge of ETF-associated diarrhoea in critical illness, further research is required to clarify and explore this complex relationship and affirm the associations within the conceptual framework (see Figure 2.1, page 10).
4.7.3.4 Duration of ETF
In Study One, the median duration of ETF was 9 days (range 3–14 days). The later commencement and longer duration of ETF in Study One could be explained by the retrospective method of data collection and the minimum ICU LOS of five days. Often with prospective data collection, health care professionals are provided with information and education regarding the study protocol. The retrospective collection of data enabled researcher observation free of any intervention that could potentially change a clinician’s clinical practices.
Through medical chart audit higher proportions of patients (61%) with diarrhoea have been reported in patients who are ETF for longer periods of time (greater than 11 days) (Halmos et al., 2010). Current research examines the duration of ETF throughout the patient’s entire ICU stay compared with a period of time (Cahill et al., 2011; Hise, Halterman, Gajewski, Parkhurst, Moncure, & Brown, 2007), for
example, up to 14 days as seen in Study One. Of note within the current study was that the occurrence of diarrhoea and the incidence rate of diarrhoea were associated with the duration of ETF; thereby, supporting the association between the ICU patient with diarrhoea and ETF (commencement, duration, delivery and formula) in the conceptual framework (see Figure 2.1, page 10). The association between these variables might be explained by the longer period of data observation. Similar with the time to commencement of ETF following ICU admission, larger scale studies are required to further examine the association between the ICU patient with diarrhoea and time to ETF commencement as depicted in the conceptual framework (see Figure 2.1, page 10).
4.7.3.5 ETF formula
Patients in this study received standard polymeric enteral nutrition formulae (Jevity Plus, Jevity and Nepro) with the most common formulae being Jevity Plus (n = 37; 74%). The administration of standard polymeric enteral feed formulae is consistent with international practice (Heyland et al., 2003a, 2003b; Mehta & Compher, 2009; Skipper, 2012; Woo et al., 2010). These formulae contain energy, protein, fibre and fructooligosacchaarides with Jevity Plus containing higher concentrations of these formula components (Skipper, 2012). The research site had implemented a standard ETF protocol (see Appendix 4) which avoided the use of disease-specific ETF
formulae (Chen & Peterson, 2009; Skipper, 2012). Although Jevity Plus and Jevity contain the same concentrations of fibre, they differ in that Jevity Plus contains higher concentrations of fat and also has a higher osmolality than Jevity formula (477mOsm/L versus 365mOsm/L) (Dieticians Association of Australia, 2011; Skipper, 2012). The use of enteral nutritional formulae containing lower
concentrations of fibre, higher concentrations of fat and a higher osmolality (Jevity Plus) may partly explain the higher incidence rate of diarrhoea in this study, although statistical significance was not identified between diarrhoea and enteral nutritional formulae in this study (see Figure 2.1, page 10). This is because formulae with these characteristics (hyperosmolar liquid and calorie dense solutions) can lead to
diarrhoea and particularly when the critically ill patient experiences intestinal dysfunction (Bleichner, Thomas, & Sollet, 1993; Luft et al., 2008).
Interestingly, evidence on this point, that is, the association between diarrhoe and ETF formulae is contradictory. Some studies over the past 20 years (Bowling,
Raimundo, Grimble, & Silk, 1994; Btaiche et al., 2010; Lloyd & Powell-Tuck, 2004; Pessola et al., 1990) identified that there was no association between diarrhoea and the type or osmolality of the ETF formulae. It is important to note that contemporary practice is based on the findings of evidence dating from 1987 to 1990. Isotonic ETF formulae are routinely used in the critical care setting as a first line attempt to
minimise hyperosmolar diarrhoea in critically ill patients (Skipper, 2012). The absence of an association between ETF osmolality and diarrhoea in Study One is supported by Pessola et al. (1990) who demonstrated that the osmolality of ETF formulae did not increase the incidence of diarrhoea in healthy volunteers (n = 5) and ward (n = 10) and ICU patients (n = 24). Diarrhoea developed in only three ICU patients in the Pessola et al. study (1990) and these patients also had an average albumin level of 2.8 g/dL. This finding was not statistically significant (Pessola et al., 1990).