Feed intolerance in critical illness is associated with increased basal and nutrient-stimulated plasma cholecystokinin concentrations

The enteroendocrine axis and its effect on gastrointestinal function, nutrition, and inflammation

PURPOSE OF REVIEW

Gastrointestinal (GI) dysfunction limits enteral nutrition (EN) delivery in critical illness and contributes to systemic inflammation. The enteroendocrine (EE) axis plays an integral role in this interface between nutrition, inflammation, and GI function in critical illness. In this review, we present an overview of the EE system with a focus on its role in GI inflammation and function.

RECENT FINDINGS

Enteroendocrine cells have been primarily described in their role in macronutrient digestion and absorption. Recent research has expanded on the diverse functions of EE cells including their ability to sense microbial peptides and metabolites and regulate immune function and inflammation. Therefore, EE cells may be both affected by and contribute to many pathophysiologic states and interventions of critical illness such as dysbiosis , inflammation, and alternative EN strategies. In this review, we present an overview of EE cells including their growing role in nonnutrient functions and integrate this understanding into relevant aspects of critical illness with a focus on EN.

SUMMARY

The EE system is key in maintaining GI homeostasis in critical illness, and how it is impacted and contributes to outcomes in the setting of dysbiosis , inflammation and different feeding strategies in critical illness should be considered.

Multi-center study of residual gastric volume and bowel preparation after the usage of 1L and 2L polyethylene glycol in Korea

BACKGROUND

In colonoscopy, good bowel preparation is an important factor in determining the quality of colonoscopy. However, an increase in residual gastric volume (RGV) can lead to a higher risk of aspiration pneumonia. Therefore, the purpose of this study was to investigate the factors related to an increase in RGV with the usage of 1L polyethylene glycol (PEG).

METHODS

We prospectively analyzed 268 patients who underwent both gastroscopy and colonoscopy at 2 hospitals from May to October 2021. Bowel preparation was performed using 1L in 127 patients (47.4%) and 2L PEG in 141 patients (52.6%). We investigated the time taken for bowel preparation solutions, the last water intake, total water intake, and RGV, and conducted a survey on taking compliance and satisfaction.

RESULTS

The level of RGV was significantly increased in the 1L PEG group when compared to the 2L PEG group (1L, 52.26 ± 65.33 vs 2L, 23.55 ± 22.99; P < .001). There was no difference between the 2 groups in the degree of bowel preparation, but there were more bubbles formed in the 1L group (1L, 1.91 ± 2.74 vs 2L, 1.10 ± 2.02; P = .007). In the case of RGV ≥ 50 mL, in multivariate analysis, the risk was higher in water intake within 5 hours and the patients who think the dose is too high (all P < .05).

CONCLUSION

Therefore, since RGV is higher in 1L PEG than in 2L PEG, it is necessary to be careful not to take water for at least 5 hours before the test.

Gastrointestinal dysfunction during enteral nutrition delivery in intensive care unit (ICU) patients: Risk factors, natural history, and clinical implications. A post-hoc analysis of The Augmented versus Routine approach to Giving Energy Trial (TARGET)

BACKGROUND

Slow gastric emptying occurs frequently during critical illness and is roughly quantified at bedside by large gastric residual volumes (GRVs). A previously published trial (The Augmented versus Routine approach to Giving Energy Trial; TARGET) reported larger GRVs with energy-dense (1.5 kcal/mL) compared with standard (1.0 kcal/mL) enteral nutrition (EN), warranting further exploration.

OBJECTIVE

To assess the incidence, risk factors, duration, and timing of large GRVs (≥250 mL) and its relation to clinical outcomes in mechanically ventilated adults.

METHODS

A post-hoc analysis of TARGET data in patients with ≥1 GRV recorded. Data are n (%) or median [IQR].

RESULTS

Of 3876 included patients, 1777 (46%) had ≥1 GRV ≥250 mL, which was more common in males (50 compared with 39%; P < 0.001) and in patients receiving energy-dense compared with standard EN (52 compared with 40%; RR = 1.27 (95% CI: 1.19, 1.36); P < 0.001) in whom it also lasted longer (1 [0-2] compared with 0 [0-1] d; P < 0.001), with no difference in time of onset after EN initiation (day 1 [0-2] compared with 1 [0-2]; P = 0.970). Patients with GRV ≥250 mL were more likely to have the following: vasopressor administration (88 compared with 76%; RR = 1.15 [1.12, 1.19]; P < 0.001), positive blood cultures (16 compared with 8%; RR = 1.92 [1.60, 2.31]; P < 0.001), intravenous antimicrobials (88 compared with 81%; RR = 1.09 [1.06, 1.12]; P < 0.001), and prolonged intensive care unit (ICU) stay (ICU-free days to day 28; 12.9 [0.0-21.0] compared with 20.0 [3.9-24.0]; P < 0.001), hospital stay (hospital-free days to day 28: 0.0 [0.0-12.0] compared with 7.0 [0.0-17.6] d; P < 0.001), ventilatory support (ventilator-free days to day 28: 16.0 [0.0-23.0] compared with 22.0 [8.0-25.0]; P < 0.001), and a higher 90-d mortality (29 compared with 23%; adjusted: RR = 1.17 [1.05, 1.30]; P = 0.003).

CONCLUSION

Large GRVs were more common in males and those receiving energy-dense formulae, occurred early and were short-lived, and were associated with a number of negative clinical sequelae, including increased mortality, even when adjusted for illness severity. This trial was registered at clinicaltrials.gov as NCT02306746.

A new strategy of enteral nutrition intervention for ICU patients targeting intestinal flora

BACKGROUND

Enteral nutrition (EN) therapy is a routine supportive method for patients in the intensive care unit (ICU). However, the incidence of EN intolerance is prevalent, because most ICU patients suffer intestinal mucosal barrier damage and gastrointestinal motility disorder. There is no definite index to predict EN intolerance, and the current treatment methods are not effective in alleviating EN intolerance. Gut microbiota is an important component of the intestinal micro-ecological environment, and alterations in its structure and composition can reflect changes in intestinal function and microenvironment. The purpose of this study is to investigate the effect of EN on the gut microbiota of ICU patients by monitoring the dynamic alterations of gut microbiota and to screen out the microbial markers that can be used to predict the incidence of EN intolerance.

METHODS

One hundred ICU patients with trauma or in a period of acute stress after surgery will be enrolled, and their fecal samples will be collected at different timepoints for microbial sequencing and analysis. General clinical data (demographic information, surgical data, laboratory parameters, illness severity scores, and therapeutic drugs), nutritional status data (nutritional status assessment and nutrition therapy monitoring data), as well as clinical outcomes, will be recorded. The microbial and clinical data will be combined to analyze the baseline characteristics and dynamic alterations of gut microbiota along with the incidence of EN intolerance. Data related to the gut microbiota will be statistically analyzed by R software, and other data performed by SPSS23.0 software.

CONCLUSIONS

The effect of EN on gut microbiota and microbial markers predicting the intolerance of EN will lead us to develop a new nutrition intervention strategy for ICU patients. Furthermore, the results of this study will provide a basis for the discovery of potential probiotics used for the prevention and treatment of EN intolerance.

Effects of Standard vs Energy-Dense Formulae on Gastric Retention, Energy Delivery, and Glycemia in Critically Ill Patients

BACKGROUND

Energy-dense formulae are often provided to critically ill patients with enteral feed intolerance with the aim of increasing energy delivery, yet the effect on gastric emptying is unknown. The rate of gastric emptying of a standard compared with an energy-dense formula was quantified in critically ill patients.

METHODS

Mechanically ventilated adults were randomized to receive radiolabeled intragastric infusions of 200 mL standard (1 kcal/mL) or 100 mL energy-dense (2 kcal/mL) enteral formulae on consecutive days in this noninferiority, blinded, crossover trial. The primary outcome was scintigraphic measurement of gastric retention (percentage at 120 minutes). Other measures included area under the curve (AUC) for gastric retention and intestinal energy delivery (calculated from gastric retention of formulae over time), blood glucose (peak and AUC), and intestinal glucose absorption (using 3-O-methyl-D-gluco-pyranose [3-OMG] concentrations). Comparisons were undertaken using paired mixed-effects models. Data presented are mean ± SE.

RESULTS

Eighteen patients were studied (male/female, 14:4; age, 55.2 ± 5.3 years). Gastric retention at 120 minutes was greater with the energy-dense formula (standard, 17.0 ± 5.9 vs energy-dense, 32.5 ± 7.1; difference, 12.7% [90% confidence interval, 0.8%-30.1%]). Energy delivery (AUC₁₂₀ , 13,038 ± 1119 vs 9763 ± 1346 kcal/120 minutes; P = 0.057), glucose control (peak glucose, 10.1 ± 0.3 vs 9.7 ± 0.3 mmol/L, P = 0.362; and glucose AUC₁₂₀ 8.7 ± 0.3 vs 8.5 ± 0.3 mmol/L.120 minutes, P = 0.661), and absorption (3-OMG AUC₁₂₀ , 38.5 ± 4.0 vs 35.7 ± 4.0 mmol/L.120 minutes; P = .508) were not improved with the energy-dense formula.

CONCLUSION

In critical illness, administration of an energy-dense formula does not reduce gastric retention, increase energy delivery to the small intestine, or improve glucose absorption or glucose control; instead, there is a signal for delayed gastric emptying.

Impact of Intravenous Fluids and Enteral Nutrition on the Severity of Gastrointestinal Dysfunction: A Systematic Review and Meta-analysis

Introduction

Gastrointestinal dysfunction (GDF) is one of the primary causes of morbidity and mortality in critically ill patients. Intensive care interventions, such as intravenous fluids and enteral feeding, can exacerbate GDF. There exists a paucity of high-quality literature on the interaction between these two modalities (intravenous fluids and enteral feeding) as a combined therapy on its impact on GDF.

Aim

To review the impact of intravenous fluids and enteral nutrition individually on determinants of gut function and implications in clinical practice.

Methods

Randomized controlled trials on intravenous fluids and enteral feeding on GDF were identified by a comprehensive database search of MEDLINE and EMBASE. Extraction of data was conducted for study characteristics, provision of fluids or feeding in both groups and quality of studies was assessed using the Cochrane criteria. A random-effects model was applied to estimate the impact of these interventions across the spectrum of GDF severity.

Results

Restricted/ goal-directed intravenous fluid therapy is likely to reduce ‘mild’ GDF such as vomiting (p = 0.03) compared to a standard/ liberal intravenous fluid regime. Enterally fed patients experienced increased episodes of vomiting (p = <0.01) but were less likely to develop an anastomotic leak (p = 0.03) and peritonitis (p = 0.03) compared to parenterally fed patients. Vomiting (p = <0.01) and anastomotic leak (p = 0.04) were significantly lower in the early enteral feeding group.

Conclusions

There is less emphasis on the combined approach of intravenous fluid resuscitation and enteral feeding in critically ill patients. Conservative fluid resuscitation and aggressive enteral feeding are presumably key factors contributing to severe life-threatening GDF. Future trials should evaluate the impact of cross-interaction between conservative and aggressive modes of these two interventions on the severity of GDF.

Pathophysiology and Treatment of Gastrointestinal Motility Disorders in the Acutely Ill

Gastrointestinal dysmotility causes delayed gastric emptying, enteral feed intolerance, and functional obstruction of the small and large intestine, the latter functional obstructions being frequently termed ileus and Ogilvie syndrome, respectively. In addition to meticulous supportive care, drug therapy may be appropriate in certain situations. There is, however, considerable variation among individuals regarding what gastric residual volume identifies gastric dysmotility and would encourage use of a promotility drug. While the administration of either metoclopramide or erythromycin is supported by evidence it appears that, dual-drug therapy (erythromycin and metoclopramide) reduces the rate of treatment failure. There is a lack of evidence to guide drug therapy of ileus, but neither erythromycin nor metoclopramide appear to have a role. Several drugs, including ghrelin agonists, highly selective 5-hydroxytryptamine receptor agonists, and opiate antagonists are being studied in clinical trials. Neostigmine, when infused at a relatively slow rate in patients receiving continuous hemodynamic monitoring, may alleviate the need for endoscopic decompression in some patients.

In Search of the Ideal Promotility Agent: Optimal Use of Currently Available Promotility Agents for Nutrition Therapy of the Critically Ill Patient

PURPOSE OF REVIEW

Enteral nutrition therapy is essential in the management of critically ill patients. Prokinetic agents have been used successfully to aid in the delivery of nutrition and improve feeding tolerance in patients in the intensive care unit (ICU). The aim of this report is to review the existing promotility agents available for use in the critically ill as well as outline the role of potential investigative drugs in order to provide a guide to the management of this difficult and important clinical dilemma.

RECENT FINDINGS

While no single currently available agent currently meets all of the desired goals in the critical care setting, there are an increasing number of available agents from which to choose including motilin receptor agonists, 5HT4 receptor agonists, D2 receptor antagonists, and Mu opioid receptor antagonists. We recommend a multifaceted approach to optimizing enteral nutrition in the critical care setting which should include the early, prophylactic use of promotility agents and should focus on the management of reversible causes of impaired gastrointestinal motility.

Modified B-ultrasound method for measurement of antral section only to assess gastric function and guide enteral nutrition in critically ill patients

AIM

To establish a modified B-ultrasound method of measuring the antral section only to assess gastric motility in healthy people, and evaluate its application in guiding enteral nutrition (EN) in critically ill patients.

METHODS

First, 30 healthy volunteers were selected. The modified B-ultrasound method and the traditional B-ultrasound method were applied to assess gastric function. The correlation of indices of gastric function between the two groups was analyzed statistically. In addition, 64 critically ill patients were selected, and the modified B-ultrasound method and the gastric juice withdrawal method were applied to guide the implementation of EN. Daily caloric value, the time required to achieve complete EN, ICU stay, hospitalization time, and serum prealbumin and albumin levels were recorded and compared between the two groups. Kaplan-Meier survival curve was used to compare the complications of EN between the two groups.

RESULTS

In healthy subjects, there was a good correlation among gastric emptying time, antral contraction frequency and antral motility index between the two groups (r = 0.57, 0.61 and 0.54, respectively). The study on critically ill patients also revealed that a better effect of EN was achieved in the modified B-ultrasound method group, in which patients had shorter ICU stay and hospitalization time and higher levels of serum prealbumin and albumin. The Kaplan-Meier survival analysis revealed that the improved B-ultrasound method was associated with significantly fewer EN complications (P = 0.031).

CONCLUSION

The modified B-ultrasound method can provide a good real-time assessment of gastric function and has a better effect than the traditional method in guiding EN in critically ill patients.

Critical Illness Is Associated With Impaired Gallbladder Emptying as Assessed by 3D Ultrasound

OBJECTIVE

To quantify gallbladder dysfunction during critical illness.

DESIGN

Prospective observational comparison study of nutrient-stimulated gallbladder emptying in health and critical illness.

SETTING

Single-centre mixed medical/surgical ICU.

PATIENTS

Twenty-four mechanically ventilated critically ill patients suitable to receive enteral nutrition were compared with 12 healthy subjects.

INTERVENTIONS

Participants were studied after an 8-hour fast. Between 0 and 120 minutes, high-fat nutrient (20% intralipid) was infused via a postpyloric catheter into the duodenum at 2 kcal/min.

MEASUREMENTS AND MAIN RESULTS

Three-dimensional images of the gallbladder were acquired at 30-minute intervals from -30 to 180 minutes. Ejection fraction (%) was calculated as changes between 0 and 120 minutes. Blood samples were obtained at 30-minute intervals for plasma cholecystokinin. Data are mean (SD) or median [interquartile range]. In the critically ill, fasting gallbladder volumes (critically ill, 61 mL [36-100 mL] vs healthy, 22 mL [15-25] mL; p < 0.001] and wall thickness (0.45 mm [0.15 mm] vs 0.26 mm [0.08 mm]; p < 0.001] were substantially greater, and sludge was evident in the majority of patients (71% vs 0%). Nutrient-stimulated emptying was incomplete in the critically ill after 120 minutes but was essentially complete in the healthy individuals (22 mL [9-66 mL] vs 4 mL [3-5 mL]; p < 0.01]. In five critically ill patients (21%), there was no change in gallbladder volume in response to nutrient, and overall ejection fraction was reduced in the critically ill (50% [8-83%] vs 77 [72-84%]; p = 0.01]. There were no differences in fasting or incremental cholecystokinin concentrations.

CONCLUSIONS

Fasted critically ill patients have larger, thicker-walled gallbladders than healthy subjects and nutrient-stimulated gallbladder emptying is impaired with "gallbladder paresis" occurring in approximately 20%.

Energy-Dense Formulae May Slow Gastric Emptying in the Critically Ill

BACKGROUND

Enteral feed intolerance occurs frequently in critically ill patients and can be associated with adverse outcomes. "Energy-dense formulae" (ie, >1 kcal/mL) are often prescribed to critically ill patients to reduce administered volume and are presumed to maintain or increase calorie delivery. The aim of this study was to compare gastric emptying of standard and energy-dense formulae in critically ill patients.

METHODS

In a retrospective comparison of 2 studies, data were analyzed from 2 groups of patients that received a radiolabeled 100-mL "meal" containing either standard calories (1 kcal/mL) or concentrated calories (energy-dense formulae; 2 kcal/mL). Gastric emptying was measured using a scintigraphic technique. Radioisotope data were collected for 4 hours and gastric emptying quantified. Data are presented as mean ± SE or median [interquartile range] as appropriate.

RESULTS

Forty patients were studied (n = 18, energy-dense formulae; n = 22, standard). Groups were well matched in terms of demographics. However, patients in the energy-dense formula group were studied earlier in their intensive care unit admission (P = .02) and had a greater proportion requiring inotropes (P = .002). A similar amount of calories emptied out of the stomach per unit time (P = .57), but in patients receiving energy-dense formulae, a greater volume of meal was retained in the stomach (P = .045), consistent with slower gastric emptying.

CONCLUSIONS

In critically ill patients, the administration of the same volume of a concentrated enteral nutrition formula may not result in the delivery of more calories to the small intestine over time because gastric emptying is slowed.

A randomised controlled feasibility and proof-of-concept trial in delayed gastric emptying when metoclopramide fails: We should revisit nasointestinal feeding versus dual prokinetic treatment: Achieving goal nutrition in critical illness and delayed gastric emptying: Trial of nasointestinal feeding versus nasogastric feeding plus prokinetics

BACKGROUND & AIMS

Delayed gastric emptying (DGE) commonly limits the use of enteral nutrition (EN) and may increase ventilator-associated pneumonia. Nasointestinal feeding has not been tested against dual prokinetic treatment (Metoclopramide and Erythromycin) in DGE refractory to metoclopramide. This trial tests the feasibility of recruiting this 'treatment-failed' population and the proof of concept that nasointestinal (NI) feeding can increase the amount of feed tolerated (% goal) when compared to nasogastric (NG) feeding plus metoclopramide and erythromycin treatment.

METHODS

Eligible patients were those who were mechanically ventilated and over 20 years old, with delayed gastric emptying (DGE), defined as a gastric residual volume ≥250 ml or vomiting, and who failed to respond to first-line prokinetic treatment of 3 doses of 10 mg IV metoclopramide over 24 h. When assent was obtained, patients were randomised to receive immediate nasointestinal tube placement and feeding or nasogastric feeding plus metoclopramide and erythromycin (prokinetic) treatment.

RESULTS

Of 208 patients with DGE, 77 were eligible, 2 refused assent, 25 had contraindications to intervention, almost exclusively prokinetic treatment, and it was feasible to recruit 50. Compared to patients receiving prokinetics (n = 25) those randomised to nasointestinal feeding (n = 25) tolerated more of their feed goal over 5 days (87-95% vs 50-89%) and had a greater area under the curve (median [IQR] 432 [253-464]% vs 350 [213-381]%, p = 0.026) demonstrating proof of concept. However, nasointestinally fed patients also had a larger gastric loss (not feed) associated with the NI route but not with the fluid volume or energy delivered.

CONCLUSIONS

This is first study showing that in DGE refractory to metoclopramide NI feeding can increase the feed goal tolerated when compared to dual prokinetic treatment. Future studies should investigate the effect on clinical outcomes.

EU CLINICAL TRIALS REGISTER

EudraCT number: 2012-001374-29.

Upper gastrointestinal sensitivity to meal-related signals in adult humans - relevance to appetite regulation and gut symptoms in health, obesity and functional dyspepsia

Both the stomach and small intestine play important roles in sensing the arrival of a meal, and its physico-chemical characteristics, in the gastrointestinal lumen. The presence of a meal in the stomach provides a distension stimulus, and, as the meal empties into the small intestine, nutrients interact with small intestinal receptors, initiating the release of gut hormones, associated with feedback regulation of gastrointestinal functions, including gut motility, and signaling to the central nervous system, modulating eating behaviours, including energy intake. Lipid appears to have particularly potent effects, also in close interaction with, and modulating the effects of, gastric distension, and involving the action of gut hormones, particularly cholecystokinin (CCK). These findings have not only provided important, and novel, insights into how gastrointestinal signals interact to modulate subjective appetite perceptions, including fullness, but also laid the foundation for an increasing appreciation of the role of altered gastrointestinal sensitivities, e.g. as a consequence of excess dietary intake in obesity, or underlying the induction of gastrointestinal symptoms in functional dyspepsia (a condition characterized by symptoms, including bloating, nausea and early fullness, amongst others, after meals, particularly those high in fat, in the absence of any structural or functional abnormalities in the gastrointestinal tract). This paper will review the effects of dietary nutrients, particularly lipid, on gastrointestinal function, and associated effects on appetite perceptions and energy intake, effects of interactions of gastrointestinal stimuli, as well as the role of altered gastrointestinal sensitivities (exaggerated, or reduced) in eating-related disorders, particularly obesity and functional dyspepsia.

Gut Motility Issues in Critical Illness

Acute gastrointestinal injury (AGI) is common in critical illness and negatively affects outcome. A variety of definitions have been used to describe AGI, which has led to clinical confusion and hampered comparison of research studies across institutions. An international working group of the European Society of Intensive Care Medicine was convened to standardize definitions for AGI and provide current evidence-based understanding of its pathophysiology and management. This disorder is associated with a wide variety of signs and symptoms and may be difficult to detect, therefore a high index of suspicion is warranted.

Gastrointestinal dysmotility disorders in critically ill dogs and cats

OBJECTIVE

To review the human and veterinary literature regarding gastrointestinal (GI) dysmotility disorders in respect to pathogenesis, patient risk factors, and treatment options in critically ill dogs and cats.

ETIOLOGY

GI dysmotility is a common sequela of critical illness in people and small animals. The most common GI motility disorders in critically ill people and small animals include esophageal dysmotility, delayed gastric emptying, functional intestinal obstruction (ie, ileus), and colonic motility abnormalities. Medical conditions associated with the highest risk of GI dysmotility include mechanical ventilation, sepsis, shock, trauma, systemic inflammatory response syndrome, and multiple organ failure. The incidence and pathophysiology of GI dysmotility in critically ill small animals is incompletely understood.

DIAGNOSIS

A presumptive diagnosis of GI dysmotility is often made in high-risk patient populations following detection of persistent regurgitation, vomiting, lack of tolerance of enteral nutrition, abdominal pain, and constipation. Definitive diagnosis is established via radioscintigraphy; however, this diagnostic tool is not readily available and is difficult to perform on small animals. Other diagnostic modalities that have been evaluated include abdominal ultrasonography, radiographic contrast, and tracer studies.

THERAPY

Therapy is centered at optimizing GI perfusion, enhancement of GI motility, and early enteral nutrition. Pharmacological interventions are instituted to promote gastric emptying and effective intestinal motility and prevention of complications. Promotility agents, including ranitidine/nizatidine, metoclopramide, erythromycin, and cisapride are the mainstays of therapy in small animals.

PROGNOSIS

The development of complications related to GI dysmotility (eg, gastroesophageal reflux and aspiration) have been associated with increased mortality risk. Institution of prophylaxic therapy is recommended in high-risk patients, however, no consensus exists regarding optimal timing of initiating prophylaxic measures, preference of treatment, or duration of therapy. The prognosis for affected small animal patients remains unknown.

Disturbed release of cholecystokinin in pregnant women with hyperemesis gravidarum

AIMS

We aimed to investigate cholecystokinin (CCK) release in pregnant women with and without hyperemesis gravidarum (HG).

MATERIAL AND METHODS

In this case-control study including 40 pregnant women with HG and 40 women with healthy uncomplicated pregnancies, serum CCK levels in addition to hematological, biochemical and hormonal parameters were investigated.

RESULTS

Serum CCK values were found to be significantly lower in pregnant women with HG (P < 0.001). Additionally, while serum blood urea nitrogen and free thyroxine levels were significantly higher, sodium, potassium, and thyroid stimulating hormone levels were significantly lower in women with HG than in control women. No correlation was detected between CCK and other parameters like ketonuria and thyroid function tests.

CONCLUSIONS

CCK release has been found to be halved in pregnant women with HG, which supports the hypothesis that gastrointestinal motility is increased in pregnant women with HG. A causal effect remains to be confirmed.

Pharmacological therapy of feed intolerance in the critically ills

Feed intolerance in the setting of critical illness is associated with higher morbidity and mortality, and thus requires promptly and effective treatment. Prokinetic agents are currently considered as the first-line therapy given issues relating to parenteral nutrition and post-pyloric placement. Currently, the agents of choice are erythromycin and metoclopramide, either alone or in combination, which are highly effective with relatively low incidence of cardiac, hemodynamic or neurological adverse effects. Diarrhea, however, can occur in up to 49% of patients who are treated with the dual prokinetic therapy, which is not associated with Clostridium difficile infection and settled soon after the cessation of the drugs. Hence, the use of prokinetic therapy over a long period or for prophylactic purpose must be avoided, and the indication for ongoing use of the drug(s) must be reviewed frequently. Second line therapy, such as total parenteral nutrition and post-pyloric feeding, must be considered once adverse effects relating the prokinetic therapy develop.

Endogenous amylin and glucagon-like peptide-1 concentrations are not associated with gastric emptying in critical illness

BACKGROUND

In health, the hormones amylin and glucagon-like peptide-1 (GLP-1) slow gastric emptying (GE) and modulate glycaemia. The aims of this study were to determine amylin and GLP-1 concentrations in the critically ill and their relationship with GE, glucose absorption and glycaemia.

METHODS

In fasted critically ill and healthy subjects (n = 26 and 23 respectively), liquid nutrient, containing 100 mg (13) C-sodium octanoate and 3 g 3-O-methlyglucose (3-OMG), was administered via a nasogastric tube. Amylin, GLP-1, glucose and 3-OMG concentrations were measured in blood samples taken during fasting, and 30 min and 60 min after the 'meal'. Breath samples were taken to determine gastric emptying coefficient (GEC). Intolerance to intragastric feeding was defined as a gastric residual volume of ≥ 250 ml and/or vomiting within the 24 h prior to the study.

RESULTS

Although GE was slower (GEC: critically ill 2.8 ± 0.9 vs. health, 3.4 ± 0.2; P = 0.002), fasting blood glucose was higher (7.0 ± 1.9 vs. 5.7 ± 0.2 mmol/l; P = 0.005) and overall glucose absorption was reduced in critically ill patients (3-OMG: 9.4 ± 8.0 vs. 17.7 ± 4.9 mmol/l.60 min; P < 0.001), there were no differences in fasting or postprandial amylin concentrations. Furthermore, although fasting [1.7 (0.4-7.2) vs. 0.7 (0.3-32.0) pmol/l; P = 0.04] and postprandial [3.0 (0.4-8.5) vs. 0.8 (0.4-34.3) pmol/l; P = 0.02] GLP-1 concentrations were increased in the critically ill and were greater in feed intolerant when compared with those tolerating feed [3.7 (0.4-7.2) vs. 1.2 (0.7-4.6) pmol/l; P = 0.02], there were no relationships between GE and fasting amylin or GLP-1 concentrations.

CONCLUSION

In the critically ill, fasting GLP-1, but not amylin, concentrations are elevated and associated with feed intolerance. Neither amylin nor GLP-1 appears to substantially influence the rate of GE.

Effects of acute and longer-term dietary restriction on upper gut motility, hormone, appetite, and energy-intake responses to duodenal lipid in lean and obese men

BACKGROUND

A 4-d 70% energy restriction enhances gastrointestinal sensitivity to nutrients associated with enhanced energy-intake suppression by lipid. To our knowledge, it is unknown whether these changes occur with 30% energy restriction and are sustained in the longer term.

OBJECTIVES

We hypothesized that 1) a 4-d 30% energy restriction would enhance effects of intraduodenal lipid on gastrointestinal motility, gut hormones, appetite, and energy intake in lean and obese men and 2) a 12-wk energy restriction associated with weight loss would diminish effects of acute energy restriction on responses to lipid in in obese men.

DESIGN

Twelve obese males were studied before (day 0) and after 4 d (day 5), 4 wk (week 4), and 12 wk (week 12), and 12 lean males were studied before and after 4 d of consumption of a 30% energy-restricted diet. On each study day, antropyloroduodenal pressures, gut hormones, and appetite during a 120-min (2.86-kcal/min) intraduodenal lipid infusion and energy intake at a buffet lunch were measured.

RESULTS

On day 5, fasting cholecystokinin was less, and ghrelin was higher, in lean (P < 0.05) but not obese men, and lipid-stimulated cholecystokinin and peptide YY and the desire to eat were greater in both groups (P < 0.05), with no differences in energy intakes compared with on day 0. In obese men, a 12-wk energy restriction led to weight loss (9.7 ± 0.7 kg). Lipid-induced basal pyloric pressures (BPPs), peptide YY, and the desire to eat were greater (P < 0.05), whereas the amount eaten was less (P < 0.05), at weeks 4 and 12 compared with day 0.

CONCLUSIONS

A 4-d 30% energy restriction modestly affects responses to intraduodenal lipid in health and obesity but not energy intake, whereas a 12-wk energy restriction, associated with weight-loss, enhances lipid-induced BPP and peptide YY and reduces food intake, suggesting that energy restriction increases gastrointestinal sensitivity to lipid. This trial was registered at the Australian New Zealand Clinical Trials Registry (www.anzctr.org.au) as 12609000943246.

Review article: the role of gastrointestinal hormones in the treatment of delayed gastric emptying in critically ill patients

BACKGROUND

Delayed gastric emptying limits the administration of enteral nutrition, leading to malnutrition, which is associated with higher mortality and morbidity. Currently available prokinetics have limitations in terms of sustained efficacy and side effects.

AIM

To summarise the mechanisms of action and to discuss the possible utility of gastrointestinal hormones to prevent or treat delayed gastric emptying in critically ill patients.

METHODS

We searched PubMed for articles discussing 'delayed gastric emptying', 'enteral nutrition', 'treatment', 'gastrointestinal hormones', 'prokinetic', 'agonist', 'antagonist' and 'critically ill patients'.

RESULTS

Motilin and ghrelin receptor agonists initiate the migrating motor complex in the stomach, which accelerates gastric emptying. Cholecystokinin, glucagon-like peptide-1 and peptide YY have an inhibiting effect on gastric emptying; therefore, antagonising these gastrointestinal hormones may have therapeutic potential. Other gastrointestinal hormones appear less promising.

CONCLUSIONS

Manipulation of endogenous secretion, physiological replacement and administration of gastrointestinal hormones in pharmacological doses is likely to have therapeutic potential in the treatment of delayed gastric emptying. Future challenges in this field will include the search for candidates with improved selectivity and favourable kinetic properties.

Gastrointestinal dysmotility: evidence and clinical management

PURPOSE OF REVIEW

Gastrointestinal dysmotility and dysfunction underlie our difficulties in providing adequate nutrition by the enteral route to our critically ill patients.

RECENT FINDINGS

Recent studies have quantified gastric emptying and nutrient absorption. Slow gastric emptying is common and probably mediated by cholecystokinin and reduced active ghrelin concentrations. The cause of impaired nutrient absorption is not yet fully understood but may be related to small intestinal blood flow and/or mucosal factors. The absorption of the different macronutrients may be affected in different ways both by critical illness and by therapies. A better understanding of this may optimize the design of nutrient formulations in the future. New treatment modalities for gastrointestinal dysfunction are being investigated and include small intestinal feeding, nonpharmacological options such as acupuncture, and drugs including novel motilin receptor agonists, and opioid antagonists.

SUMMARY

We are gradually developing a better understanding of how the gut works during critical illness, which has implications for optimizing the delivery of nutrition and thereby improving nutritional and clinical outcomes.

Nutrition support in the critically ill

PURPOSE OF REVIEW

To highlight the recent developments in nutritional support for critically ill patients.

RECENT FINDINGS

Increasing data support the benefits of early initiation of enteral nutrition, with improvements in small intestinal absorption and clinical outcomes. In contrast to the previous belief, recent data suggest caloric administration of greater than 65-70% of daily requirement is associated with poorer clinical outcomes, especially when supplemental parenteral nutrition is used to increase the amount of caloric delivery. The role of supplementary micronutrients and anti-inflammatory lipids has been further evaluated but remains inconclusive, and is not currently recommended.

SUMMARY

Together, current findings indicate that intragastric enteral nutrition should be initiated within 24 h of admission to ICU and supplementary parenteral nutrition should be avoided. Future research should aim to clarify the optimal energy delivery for best clinical outcomes, and the role of small intestinal function and its flora in nutritional care and clinical outcomes.

Gastroparesis: pathogenesis, diagnosis and management

Gastroparesis is a prevalent condition that produces symptoms of delayed gastric emptying in the absence of physical blockage. The most common etiologies of gastroparesis are idiopathic, diabetic, and postsurgical disease, although some cases stem from autoimmune, paraneoplastic, neurologic or other conditions. Histologic examination of gastric tissues from patients with severe gastroparesis reveals heterogeneous and inconsistent defects in the morphology of enteric neurons, smooth muscle and interstitial cells of Cajal, and increased levels of inflammatory cells. Diagnosis is most commonly made by gastric emptying scintigraphy; however, wireless motility capsules and nonradioactive isotope breath tests have also been validated. A range of treatments have been used for gastroparesis including dietary modifications and nutritional supplements, gastric motor stimulatory or antiemetic medications, endoscopic or surgical procedures, and psychological interventions. Most treatments have not been subjected to controlled testing in patients with gastroparesis. The natural history of this condition is poorly understood. Active ongoing research is providing important insights into the pathogenesis, diagnosis, treatment and outcomes of this disease.

Enteral nutrition in patients with severe traumatic brain injury: reasons for intolerance and medical management

Approximately, 50% of patients with severe traumatic brain injury (TBI) exhibit intolerance to enteral nutrition (EN). This intolerance hampers the survival and rehabilitation of this subpopulation to a great extent, and poses various difficulties for clinicians due to its complex underlying mechanisms. This review discusses the possible reasons for intolerance to EN following severe TBI, current trends in medical management, as well as other related issues that are experienced by many clinicians.

Effects of acute dietary restriction on gut motor, hormone and energy intake responses to duodenal fat in obese men

BACKGROUND

Previous patterns of energy intake influence gastrointestinal function and appetite, probably reflecting changes in small-intestinal nutrient-mediated feedback. Obese individuals consume more fat and may be less sensitive to its gastrointestinal and appetite-suppressant effects than lean individuals.

OBJECTIVE

To evaluate the hypothesis that, in obese individuals, the effects of duodenal fat on gastrointestinal motor and hormone function, and appetite would be enhanced by a short period on a very-low-calorie diet (VLCD).

METHODS

Eight obese men (body mass index 34±0.6  kg  m(-2)) were studied on two occasions, before (V1), and immediately after (V2), a 4-day VLCD. On both occasions, antropyloroduodenal motility, plasma cholecystokinin (CCK), peptide-YY (PYY) and ghrelin concentrations, and appetite perceptions were measured during a 120-min intraduodenal fat infusion (2.86  kcal  min(-1)). Immediately afterwards, energy intake was quantified.

RESULTS

During V2, basal pyloric pressure and the number and amplitude of isolated pyloric pressure waves (PWs) were greater, whereas the number of antral and duodenal PWs was less, compared with V1 (all P<0.05). Moreover, during V2, baseline ghrelin concentration was higher; the stimulation of PYY and suppression of ghrelin by lipid were greater, with no difference in CCK concentration; and hunger and energy intake (kJ; V1: 4378±691, V2: 3634±700) were less (all P<0.05), compared with V1.

CONCLUSIONS

In obese males, the effects of small-intestinal lipid on gastrointestinal motility and some hormone responses and appetite are enhanced after a 4-day VLCD.

Practicalities of nutrition support in the intensive care unit: the usefulness of gastric residual volume and prokinetic agents with enteral nutrition

The provision of early nutrition therapy to critically ill patients is established as the standard of care in most intensive care units around the world. Despite the known benefits, tolerance of enteral nutrition in the critically ill varies and delivery is often interrupted. Observational research has demonstrated that clinicians deliver little more than half of the enteral nutrition they plan to provide. The main clinical tool for assessing gastric tolerance is gastric residual volume; however, its usefulness in this setting is debated. There are several strategies employed to improve the tolerance and hence adequacy of enteral nutrition delivery in the critically ill. One of the most widely used strategies is that of prokinetic drug administration, most commonly metoclopramide and erythromycin. Although there are new agents being investigated, none are ready for routine application in the critically ill and the benefits are still being established. This review investigates current practice and considers the literature on assessment of enteral tolerance and optimization of enteral nutrition in the critically ill.

Gastrointestinal hormonal dysfunction in gastroparesis and functional dyspepsia

BACKGROUND

Numerous hormones secreted by the gut, during both the fasted state and in response to a meal, influence gastrointestinal motor and/or sensory function, and appear to contribute to the pathogenesis of delayed gastric emptying associated with gastroparesis, functional dyspepsia (FD) and feed intolerance in critical illness. Gut hormones are, accordingly, potential targets for the management of these patients.

PURPOSE

This article will discuss the hypersensitivity to enteral fat and endogenous (nutrient-stimulated) and exogenous cholecystokinin (CCK) in patients with FD, and the elevation in both fasting and postprandial CCK levels evident in this group. It will review the use of pharmacological agonists of motilin and ghrelin, which accelerate gastric emptying, in the management of gastroparesis and FD. The frequent finding of markedly delayed gastric emptying in the critically ill will be examined; this is associated with elevated plasma CCK and peptide YY in both the fasted and postprandial states, which may account for the increase in small intestinal nutrient inhibitory feedback on gastric motility in this group. The concepts that the rate of gastric emptying is a major determinant of postprandial glycemic excursions in diabetes, and that modulation of gastric emptying may improve glycemic control, will be addressed; in type 1 and insulin-treated type 2 diabetic patients, co-ordination of insulin administration with nutrient delivery and absorption should be optimized, while type 2 patients who are not on insulin are likely to respond to dietary and/or pharmacological interventions which slow gastric emptying.

Current and future therapeutic prokinetic therapy to improve enteral feed intolerance in the ICU patient

Malnutrition is associated with poor outcomes in critically ill patients, and providing enteral feeding to those who cannot eat is considered best practice. Enteral feeding is often unsuccessful when there is delayed gastric emptying. Recent research has given additional insight into the mechanisms underlying delayed gastric emptying. Pharmacological strategies to improve the success of feeding include prokinetic drugs such as metoclopramide and erythromycin alone or in combination. When drug treatment fails, either parenteral nutrition or direct small intestinal feeding is indicated. Simpler methods to access the duodenum and distal small bowel for feed delivery are under investigation. This review summarizes current understanding of the mechanisms underlying enteral feeding intolerance in critical illness, together with the evidence for current treatment practices. Areas requiring further research are also described.

Bench-to-bedside review: the gut as an endocrine organ in the critically ill

In health, hormones secreted from the gastrointestinal tract have an important role in regulating gastrointestinal motility, glucose metabolism and immune function. Recent studies in the critically ill have established that the secretion of a number of these hormones is abnormal, which probably contributes to disordered gastrointestinal and metabolic function. Furthermore, manipulation of endogenous secretion, physiological replacement and supra-physiological treatment (pharmacological dosing) of these hormones are likely to be novel therapeutic targets in this group. Fasting ghrelin concentrations are reduced in the early phase of critical illness, and exogenous ghrelin is a potential therapy that could be used to accelerate gastric emptying and/or stimulate appetite. Motilin agonists, such as erythromycin, are effective gastrokinetic drugs in the critically ill. Cholecystokinin and peptide YY concentrations are elevated in both the fasting and postprandial states, and are likely to contribute to slow gastric emptying. Accordingly, there is a rationale for the therapeutic use of their antagonists. So-called incretin therapies (glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide) warrant evaluation in the management of hyperglycaemia in the critically ill. Exogenous glucagon-like peptide-2 (or its analogues) may be a potential therapy because of its intestinotropic properties.

[Promotility drugs use in critical care: indications and limits?]

Enteral feeding is often limited by gastric and intestinal motility disturbances in critically ill patients, particularly in patients with shock. So, promotility agents are frequently used to improve tolerance to enteral nutrition. This review summaries the pathophysiology, presents the available pharmacological strategies, the clinical data, the counter-indications and the principal limits. The clinical data are poor. No study demonstrates a positive effect on clinical outcomes. Metoclopramide and erythromycin seems to be the more effective. Considering the risk of antibiotic resistance, the first line use of erythromycin should be avoided in favor of metoclopramide.

A guide to enteral access procedures and enteral nutrition

The advent of total parenteral nutrition in the late 1960s meant that no situation remained in which a patient could not be fed. Unfortunately, total parenteral nutrition was complicated by serious infective and metabolic side effects that undermined the beneficial effects of nutrient repletion. Consequently, creative ways of restoring upper gut function were designed, based on semielemental diets and novel feeding tube systems. The employment of specific protocols and acceptance of increased gastric residual volumes has allowed most patients in intensive care to be fed safely and early by nasogastric tube. However, nasogastric feeding is unsuitable for patients with severely compromised gastric emptying owing to partial obstruction or ileus. Such patients require postpyloric tube placement with simultaneous gastric decompression via double-lumen nasogastric decompression and jejunal feeding tubes. These tubes can be placed endoscopically 40-60 cm past the ligament of Treitz to enable feeding without pancreatic stimulation. In patients whose disorders last more than 4 weeks, tubes should be repositioned percutaneously, by endoscopic, open or laparoscopic surgery. Together, the advances in enteral access have improved patients' outcomes and led to a 70-90% reduction in the demand for total parenteral nutrition.

Motility disorders in the ICU: recent therapeutic options and clinical practice

PURPOSE OF REVIEW

Motility disturbances often occur in critically ill patients resulting in an increased rate of morbidity and mortality. Only limited options for treatment of gastrointestinal dysfunction have been introduced. Factors contributing to motility disorders in the ICU patient, and recent therapeutic approaches are reviewed in the following.

RECENT FINDINGS

Despite the growing use of early enteral nutrition in the ICU and improvements in patients' outcome, feed intolerance and motility disorders in critical illness remain unsolved. Evaluation of pathophysiological patterns such as antro-pyloric dysfunction has led to a better knowledge of gut function, whereas development of new prokinetic agents is scarce, and enthusiasm has been cut by the withdrawal of some propulsive agents from the market.

SUMMARY

The complexity of gastrointestinal motor function poses a challenge to the pharmacological modulation of gut motility. There has been progress in the understanding of pathophysiologic patterns, whereas therapeutic options are still rare. Metoclopramide and erythromycin are the best evaluated and still the most promising prokinetic agents. Only a few studies in critical illness are available, and the definite value of novel propulsive agents such as motilin agonists and mu-receptor antagonists is unclear due to small patient populations. The most reasonable approach of motility disorders in critical illness seems to be an individual assessment of all associated risk factors combined with early enteral nutrition and use of prokinetic agents.

Evidence-based nutrition support in the intensive care unit: an update on reported trial quality

PURPOSE OF REVIEW

Meta-epidemiological reviews report that trials of nutritional support in critical illness rarely fulfil basic quality requirements, with overall quality rated as 'worse than poor'. This update reviews recently published trials to determine whether current evidence meets or exceeds basic quality requirements.

RECENT FINDINGS

Although recent trials were significantly more likely to report blinding, there is a concerning trend towards a decrease in overall trial quality. Many recent trials fail to report the use of 'any' of three key validity criteria: use of blinding, presentation of intention-to-treat analysis and the maintenance allocation concealment.

SUMMARY

Future researchers must improve the quality with which trials are conducted and reported. Submitting a clinical trial to an approved registry prior to enrolling patients provides transparency of conduct. Investigators must ensure that an intention-to-treat analysis is reported, especially when a subset efficacy analysis is presented, even if the intention-to-treat analysis requires imputing missing data values. Investigators also need to improve reporting details concerning allocation concealment and blinding. Finally, until investigators, editors and reviewers embrace these measures, we strongly recommend that readers should become familiar with the appropriate evidence-based medicine users' guides so that they can base clinical decisions on valid studies.

Gastric Residual Volume and Aspiration in Critically Ill Patients Receiving Gastric Feedings

Background The helpfulness of bedside assessment of gastric residual volume in the prediction of aspiration has been questioned, as has the volume that signals increased risk of aspiration.

Objective To describe the association between gastric residual volumes and aspiration of gastric contents.

Methods In a prospective study of 206 critically ill patients receiving gastric tube feedings for 3 consecutive days, gastric residual volumes were measured with 60-mL syringes every 4 hours. Measured volumes were categorized into 3 overlapping groups: at least 150 mL, at least 200 mL, and at least 250 mL. Patients were categorized as frequent aspirators if 40% or more of their tracheal secretions were positive for pepsin and as infrequent aspirators if less than 40% of their secretions were positive for pepsin. Gastric residual volumes were compared between the 2 aspiration groups.

Results Approximately 39% of the 206 patients had 1 or more gastric residual volumes of at least 150 mL, 27% had 1 or more volumes of at least 200 mL, and 17% had 1 or more volumes of at least 250 mL. Large-bore tubes identified most of the high volumes. Eighty-nine patients were frequent aspirators. Volumes less than 150 mL were common in both aspiration groups. However, the frequent aspirators had a significantly greater frequency of 2 or more volumes of at least 200 mL and 1 or more volumes of at least 250 mL.

Conclusions No consistent relationship was found between aspiration and gastric residual volumes. Although aspiration occurs without high gastric residual volumes, it occurs significantly more often when volumes are high.

Year in review 2007: Critical Care--shock

The research papers on shock published in Critical Care throughout 2007 are related to three major subjects: the modulation of the macrocirculation and microcirculation during shock, focusing on arginine vasopressin, erythropoietin and nitric oxide; studies on metabolic homeostasis (acid–base status, energy expenditure and gastrointestinal motility); and basic supportive measures in critical illness (fluid resuscitation and sedation, and body-temperature management). The present review summarizes the key results of these studies and provides a brief discussion in the context of the relevant scientific and clinical background.

The impact of delaying enteral feeding on gastric emptying, plasma cholecystokinin, and peptide YY concentrations in critically ill patients

BACKGROUND

Enteral nutrient (EN) deprivation slows gastric emptying (GE) and increases plasma cholecystokinin (CCK) concentrations in healthy humans and may potentially contribute to the delayed GE in the critically ill. This study examined the impact of delayed feeding on GE, plasma CCK, and peptide YY (PYY) concentrations in the critically ill.

DESIGN

Randomized controlled trial.

SETTING

Mixed medical and surgical intensive care unit (ICU).

INTERVENTIONS

Twenty-eight critically ill patients were randomized to receive EN either within 24 hrs of admission ("early feeding": 54.9 +/- 3.3 yrs; Acute Physiology and Chronic Health Evaluation (APACHE) II = 23.0 +/- 1.8) or on day 4 of admission after GE assessment ("delayed feeding": 56.1 +/- 4.2 yrs, APACHE II = 21.7 +/- 1.8). GE of 100 ml of Ensure was measured using scintigraphy on day 4 of admission. Blood was sampled for measurement of plasma CCK, PYY, and glucose concentrations.

RESULTS

Demographics, APACHE II score, use of inotrope and morphine sedation were similar between the groups. The mean administered/prescribed caloric ratio in the "early feeding" group was 72 +/- 4%. There were no differences in the retention of meal, intragastric meal distribution, proportion of patients with delayed GE (9/14 vs. 9/14), and plasma CCK and PYY concentrations during fasting and postprandially between the two groups. There was no relationship between the number of calories received and percentage of meal retention at 240 min (p > .05). However, delayed feeding was associated with longer duration of mechanical ventilations (13.7 +/- 1.9 vs. 9.2 +/- .9 days, p = .049) and length of stay in ICU (15.9 +/- 1.9 vs. 11.3 +/- 0.8 days, p = .048), but no difference in mortality.

CONCLUSIONS

In critical illness, delayed enteral feeding appears to have little impact on either GE or the enterogastric feedback hormones. However, the association between delayed feeding and increased duration of ventilation and length of stay in the ICU supports the current recommendation that enteral nutrition should be commenced early.

Diminished functional association between proximal and distal gastric motility in critically ill patients

OBJECTIVE

This study examined the effects of critical illness on the relationship between proximal and distal gastric motor activity during fasting and duodenal nutrient stimulation.

DESIGN

Prospective, case-controlled study.

PATIENTS AND PARTICIPANTS

Ten critically ill patients and ten healthy volunteers.

INTERVENTIONS

Concurrent proximal gastric (barostat) and antro-pyloro-duodenal (manometry) motility were recorded during fasting and during two 60-min duodenal nutrient infusions (Ensure at 1 kcal/min and 2 kcal/min) in random order, separated by a 2-h wash-out period.

RESULTS

Baseline proximal gastric volumes were similar between the two groups. At 10 min nutrient-induced fundic relaxation was lower in patients than healthy subjects (45 +/- 26 vs. 196 +/- 29 ml). In patients the frequency and volume amplitude of fundic waves were also lower. There were fewer propagated antral waves in patients than in healthy subjects during both fasting and nutrient infusion. These were more retrograde, shorter in length and associated with a pyloric contraction. The proportion of fundic waves followed by a distally propagated antral wave was significantly less in patients (0%, 0-8%) than controls 36% (11-44%).

CONCLUSIONS

In critical illness, in addition to impairment of proximal and distal gastric motor activity, the association between the two gastric regions is abnormal. This disturbance may interfere with meal distribution and further contribute to slow gastric emptying in these patients.

The relationship between blood glucose control and intolerance to enteral feeding during critical illness

OBJECTIVE

To assess the relationship between blood glucose concentrations (BSL) and intolerance to gastric feeding in critically ill patients.

DESIGN

Prospective, case-controlled study.

PATIENTS AND PARTICIPANTS

Two-hourly BSL and insulin requirements over the first 10 days after admission were assessed in 95 consecutive feed-intolerant (NG aspirate > 250 ml during feed) critically ill patients and 50 age-matched, feed-tolerant patients who received feeds for at least 3 days. Patients with diabetes mellitus were excluded. A standard insulin protocol was used to maintain BSL at 5.0-7.9 mmol.

MEASUREMENTS AND RESULTS

The peak BSLs were significantly higher before and during enteral feeding in feed-intolerant patients. The mean and trough BSLs were, however, similar between the two groups on admission, 24 h prior to feeding and for the first 4 days of feeding. The variations in BSLs over 24 h before and during enteral feeding were significantly greater in feed-intolerant patients. A BSL greater than 10 mmol/l was more prevalent in patients with feed intolerance during enteral feeding. The time taken to develop feed intolerance was inversely related to the admission BSL (r= -0.40). The amount of insulin administered before and during enteral feeding was similar between the two groups.

CONCLUSIONS

Feed intolerance in critically ill patients is associated with a greater degree of glycaemic variation, with a greater number of patients with transient hyperglycaemia. These data suggest more intensive insulin therapy may be required to minimize feed intolerance, an issue that warrants further study.