Table 2 Remaining areas of uncertainty in gastrointestinal dysfunction of critically ill patients (what we do not know) We describe these areas as high-level open-ended questions, to stimulate further research formulating specific questions. We highlight in bold the subjects that were chosen by the panel for needing consensus process and prioritized as the next tasks for the Working Group on GI function of the Section of MEN of ESICM
Subtopic | Remaining areas of uncertainties | |
|---|---|---|
Monitoring of GI dysfunction | ||
 i. | Clinical assessment | How are GI symptoms* associated with GI function? How to monitor GI function daily at bedside = what is the core set of daily monitoring of GI function? Which symptoms and when should trigger more complex diagnostics? Whether a combination of clinical assessment with specific diagnostics/monitoring methods could allow developing a reliable scoring system for GI dysfunction in critically ill? How to define feeding intolerance? What is the reference method to be used to measure gastric emptying in studies in critically ill patients? Can measurement of gastric residual volumes identify delayed gastric emptying? Can monitoring of gastric residual volumes help in avoiding complications in patients with feeding intolerance? |
 ii. | Imaging | What is the best abdominal ultrasound protocol for GI dysfunction? Needs collaboration with radiologists and gastroenterologists. Whether US image quality (which may be affected by air in the GI tract) can be further improved? What imaging technique is associated with high inter-operator and over time reproducibility? How to quantify bowel oedema? |
 iii. | Laboratory (including biomarkers) | Which biomarker(s) could be used as a marker of GI dysfunction? Which biomarker(s) could be used in decision-making regarding enteral nutrition? Which biomarkers could be used in decision-making regarding non-occlusive mesenteric ischaemia? |
 iv. | Absorption of nutrients | What is the reference method to be used to measure absorption of nutrients in studies in critically ill patients? What are the possible novel methods to measure absorption of nutrients at bedside? |
 v. | Barrier function | What is the reference method to be used to measure barrier dysfunction in studies in critically ill patients? How to differentiate between pathological and physiological GI mucosal permeability? What are the possible novel methods to measure/detect the presence of barrier dysfunction in studies in critically ill patients? What are the possible novel methods to estimate barrier dysfunction at bedside? What are the possible biomarkers that can rapidly detect barrier dysfunction caused by mesenteric ischaemia? (How) does the microbiome influence the gut-derived immunity? |
 vi. | Others | Which GI symptoms could identify the cohort of patients who would benefit from monitoring of intra-abdominal pressure? What are the other possible novel strategies to monitor/assist in monitoring of GI function? |
GI dysfunction: reporting and outcome | ||
|  |  | What is the natural course of GI dysfunction in survivors of critical illness? Which are the differences between primary and secondary GI injury? What is the core set of daily monitoring of GI function? What are the ‘core outcomes’ for GI dysfunction in critically ill patients? How to define non-occlusive mesenteric ischaemia (collaboration with radiologists, gastroenterologists and surgeons)? |
Management of GI dysfunction | ||
 vii. | Prokinetics | Which are the indications to use prokinetics? Which novel prokinetic agents with less side effects could be used in clinical practice? |
 viii. | Laxatives | Which are the indications for laxative agents? Which laxatives, when and in which dosage should be applied? |
 ix. | Post-pyloric feeding | Which are the indications to use post-pyloric feeding? How does post-pyloric feeding compare to gastric feeding with prokinetic drugs on patient-centred outcomes? Are there differences between duodenal and jejunal feeding? |
 x. | Others | Which other management options could be used to prevent and/or improve GI dysfunction? Could specific fluid resuscitation strategy reduce the prevalence and severity of GI dysfunction? Could achievement of high-normal levels of electrolytes (potassium and magnesium) improve GI motility? Could early mobilization improve GI function in ICU patients? Which sedation strategy associated with less GI dysfunction? |
xi. | GI function and nutrition | What is the optimal timing and duration for both trophic EN to ‘feed the mucosa and microbiome’ and ‘full feeding’ to match estimated energy expenditure? Does early EN benefits or harms GI function (e.g. absorptive capacity and barrier function of the gut) when compared to fasting or PN? Should intolerance of EN be accepted as a protective adaptive response to critical illness or treated to increase nutrient delivery? How and when should EN be initiated and/or increased to best maintain and/or improve GI function? |
Pathophysiological mechanisms in GI dysfunction relevant to the outcome | ||
 xii. | The role of the gut in multiple organ failure | What is the best definition and estimates of the prevalence of NOMI? How to achieve earlier identification of NOMI (e.g. with additional biomarkers or other tests of gut (hypo)perfusion)? What are the feeding strategies to reduce the rate of NOMI (e.g. early fasting vs early trophic EN)? What interventions are effective in conservative management of NOMI? When and how does GI injury cause multiple organ failure and vice versa? |
 xiii. | Microbiome | What mechanisms underlie changes in microbiota density, genus abundance, community structure and function during critical illness? Which role do microbiota-modulated metabolite function and inter-organ cross-talk play in critically ill patients? What are the causes and consequences of dysbiosis on gastrointestinal injury and organ dysfunction? Are there valid biomarkers for microbiome-related GI-dysfunction? Can personalized microbiome type- and function-directed interventions improve organ dysfunction and ICU-related outcomes? What are the best sampling methods for the specimen (e.g. stool vs rectal swabs)? |
 xiv. | Bacterial translocation /mucosal integrity | Which are the mechanistic approaches to protect mucosal integrity? Whether and how can/should the immune response on the loss of mucosal integrity be modulated? |
 xv. | GI hormones | Which GI hormones are inadequately secreted in critical illness? Quantify response to ‘normal’ endogenous or physiological concentrations? What is the effect of restoring secretion of hormones/levels of hormones to ‘normal’ endogenous or physiological concentrations? |
 xvi. | Bile acid signalling | Could plasma concentrations of bile acid signalling molecules be used as a marker of malabsorption? |
 xvii. | Others | How does development of bowel oedema impact GI motility and vice versa? What are the differences between the direct GI injury resulting in oedema vs GI injury due to generalized oedema? |