Proximal gastric response to small intestinal nutrients is abnormal in mechanically ventilated critically ill patients

Lack of gastric emptying at autopsy eleven days after heat trauma in the sauna- a forensic autopsy case report

A man in his mid-70s passed out in a public 90-degree sauna and remained unconscious for at least half an hour. He suffered third-degree burns to approximately 50% of his body surface area. Despite immediate transport to a burn center and intensive care therapy, he did not regain consciousness and died eleven days later.When the body was opened, the lungs, liver, kidneys, and spleen showed changes consistent with the burns, intensive care therapy, and clinically suspected septic shock. The stomach contained approximately 200 ml of thickened chyme with coarse vegetable components. Such food components were not seen in the duodenum or in the following intestinal segments.Considering the overall circumstances, the stomach contents must have been the last meal the man had eaten before the sauna session. The problem of reduced gastrointestinal motility in burn patients is clinically recognized. Nevertheless, a complete failure of gastric emptying for eleven days after intensive care therapy has not been described before and shows that the use of gastric contents in forensic practice is inappropriate for drawing conclusions about the time interval between last food intake and death and thus for estimating the time of death.

Intermittent versus continuous enteral nutrition in critically ill children: A pre-planned secondary analysis of an international prospective cohort study

BACKGROUND & AIMS

Intermittent enteral nutrition (EN) may have physiologic benefits over continuous feeding in critical illness. We aimed to compare nutrition and infection outcomes in critically ill children receiving intermittent or continuous EN.

METHODS

International, multi-center prospective observational study of mechanically ventilated children, 1 month to 18 years of age, receiving EN. Percent energy or protein adequacy (energy or protein delivered/prescribed × 100) and acquired infection rates were compared between intermittent and continuous EN groups using adjusted-multivariable and 4:1 propensity-score matched (PSM) analyses. Sensitivity analyses were performed after excluding patients who crossed over between intermittent and continuous EN.

RESULTS

1375 eligible patients from 66 PICUs were included. Patients receiving continuous EN (N = 1093) had a higher prevalence of respiratory illness and obesity, and lower prevalence of neurologic illness and underweight status on admission, compared to those on intermittent EN (N = 282). Percent energy or protein adequacy, proportion of patients who achieved 60% of energy or protein adequacy in the first 7 days of admission, and rates of acquired infection were not different between the 2 groups in adjusted-multivariable and propensity score matching analyses (P > 0.05).

CONCLUSION

Intermittent versus continuous EN strategy is not associated with differences in energy or protein adequacy, or acquired infections, in mechanically ventilated, critically ill children. Until further evidence is available, an individualized feeding strategy rather than a universal approach may be appropriate.

Occult upper gastrointestinal mucosal abnormalities in critically ill patients

BACKGROUND

The objectives of this study were to estimate the frequency of occult upper gastrointestinal abnormalities, presence of gastric acid as a contributing factor, and associations with clinical outcomes.

METHODS

Data were extracted for study participants at a single centre who had an endoscopy performed purely for research purposes and in whom treating physicians were not suspecting gastrointestinal bleeding. Endoscopic data were independently adjudicated by two gastroenterologists who rated the likelihood that observed pathological abnormalities were related to gastric acid secretion using a 3-point ordinal scale (unlikely, possible or probable).

RESULTS

Endoscopy reports were extracted for 74 patients [age 52 (37, 65) years] undergoing endoscopy on day 5 [3, 9] of ICU admission. Abnormalities were found in 25 (34%) subjects: gastritis/erosions in 10 (14%), nasogastric tube trauma in 8 (11%), oesophagitis in 4 (5%) and non-bleeding duodenal ulceration in 3 (4%). The contribution of acid secretion to observed pathology was rated 'probable' in six subjects (rater #1) and five subjects (rater #2). Prior to endoscopy, 39 (53%) patients were receiving acid-suppressive therapy. The use of acid-suppressive therapy was not associated with the presence of an endoscopic abnormality (present 15/25 (60%) vs. absent 24/49 (49%); P = 0.46). Haemoglobin concentrations, packed red cells transfused and mortality were not associated with mucosal abnormalities (P = 0.83, P > 0.9 and P > 0.9 respectively).

CONCLUSIONS

Occult mucosal abnormalities were observed in one-third of subjects. The presence of mucosal abnormalities appeared to be independent of prior acid-suppressive therapy and was not associated with reduced haemoglobin concentrations, increased transfusion requirements, or mortality.

Post-pyloric versus gastric tube feeding for preventing pneumonia and improving nutritional outcomes in critically ill adults

BACKGROUND

Nutritional support is an essential component of critical care. Malnutrition has been associated with poor outcomes among patients in intensive care units (ICUs). Evidence suggests that in patients with a functional gut, nutrition should be administered through the enteral route. One of the main concerns regarding use of the enteral route is the reduction in gastric motility that is often responsible for limited caloric intake. This increases the risk of aspiration pneumonia as well. Post-pyloric feeding, in which the feed is delivered directly into the duodenum or the jejunum, could solve these issues and provide additional benefits over routine gastric administration of the feed.

OBJECTIVES

To evaluate the effectiveness and safety of post-pyloric feeding versus gastric feeding for critically ill adults who require enteral tube feeding.

SEARCH METHODS

We searched the following databases: Cochrane Central Register of Controlled Trials (CENTRAL;2013 Issue 10), MEDLINE (Ovid) (1950 to October 2013), EMBASE (Ovid) (1980 to October 2013) and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) via EBSCO host (1982 to October 2013). We reran the search on 4 February 2015 and will deal with the one study of interest when we update the review.

SELECTION CRITERIA

Randomized or quasi-randomized controlled trials comparing post-pyloric versus gastric tube feeding in critically ill adults.

DATA COLLECTION AND ANALYSIS

We extracted data using the standard methods of the Cochrane Anaesthesia, Critical and Emergency Care Group and separately evaluated trial quality and data extraction as performed by each review author. We contacted trials authors to request missing data.

MAIN RESULTS

We pooled data from 14 trials of 1109 participants in a meta-analysis. Moderate quality evidence suggests that post-pyloric feeding is associated with low rates of pneumonia compared with gastric tube feeding (risk ratio (RR) 0.65, 95% confidence interval (CI) 0.51 to 0.84). Low-quality evidence shows an increase in the percentage of total nutrient delivered to the patient by post-pyloric feeding (mean difference (MD) 7.8%, 95% CI 1.43 to 14.18).Evidence of moderate quality revealed no differences in duration of mechanical ventilation or in mortality. Intensive care unit (ICU) length of stay was similar between the two groups. The effect on the time required to achieve the full nutrition target was uncertain (MD -1.99 hours 95% CI -10.97 to 6.99) (very low-quality evidence). We found no evidence suggesting an increase in the rate of complications during insertion or maintenance of the tube in the post-pyloric group (RR 0.51, 95% CI 0.19 to 1.364; RR1.63, 95% CI 0.93 to 2.86, respectively); evidence was assessed as being of low quality for both.Risk of bias was generally low in most studies, and review authors expressed concern regarding lack of blinding of the caregiver in most trials.

AUTHORS' CONCLUSIONS

We found moderate-quality evidence of a 30% lower rate of pneumonia associated with post-pyloric feeding and low-quality evidence suggesting an increase in the amount of nutrition delivered to these participants. We do not have sufficient evidence to show that other clinically important outcomes such as duration of mechanical ventilation, mortality and length of stay were affected by the site of tube feeding.Low-quality evidence suggests that insertion of a post-pyloric feeding tube appears to be safe and was not associated with increased complications when compared with gastric tube insertion. Placement of the post-pyloric tube can present challenges; the procedure is technically difficult, requiring expertise and sophisticated radiological or endoscopic assistance.We recommend that use of a post-pyloric feeding tube may be preferred for ICU patients for whom placement of the post-pyloric feeding tube is feasible. Findings of this review preclude recommendations regarding the best method for placing the post-pyloric feeding tube. The clinician is left with this decision, which should be based on the policies of institutional facilities and should be made on a case-by-case basis. Protocols and training for bedside placement by physicians or nurses should be evaluated.

Comparison of postpyloric tube feeding and gastric tube feeding in intensive care unit patients: a meta-analysis

BACKGROUND AND OBJECTIVE

Enteral feeding is vital in the critical care setting; however, the optimal route of enteral feeding (postpyloric vs gastric feeding) remains debated. We aimed to systematically review the current evidence to see whether postpyloric feeding could provide additional benefits to intensive care unit (ICU) patients.

METHOD

Randomized controlled trials (RCTs) comparing the efficacy and safety of postpyloric feeding vs gastric feeding were included in our systematic review. Odds ratio (OR) was used for binary outcome data and weighted mean difference (WMD) was used for continuous outcome data. Summary effects were pooled using a fixed or random effects model as appropriate.

RESULTS

Seventeen RCTs were included in our meta-analysis. Postpyloric tube feeding could deliver higher proportions of estimated energy requirement (WMD, 12%; 95% confidence interval [CI], 5%-18%) and reduce the gastric residual volume (GRV) (WMD, -169.1 mL; 95% CI, -291.995 to -46.196 mL). However, the meta-analysis failed to demonstrate any benefits to critically ill patients with postpyloric tube feeding in terms of mortality (OR, 1.05; 95% CI, 0.77-1.44), new-onset pneumonia (OR, 0.77; 95% CI, 0.53-1.13), and aspiration (OR, 1.20; 95% CI, 0.64-2.25). There was no significant publication bias as represented by an Egger's bias coefficient of 0.21 (95% CI, -1.01 to 1.43; P = .7).

CONCLUSION

As compared with gastric feeding, postpyloric feeding is able to deliver higher proportions of the estimated energy requirement and can help reduce the GRV.

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.

Motility disorders of the upper gastrointestinal tract in the intensive care unit: pathophysiology and contemporary management

Upper gastrointestinal (GI) dysmotility, an entity commonly found in the intensive care unit setting, can lead to insufficient nutrient intake while increasing the risk of infection and mortality. Further, overcoming the altered motility with early enteral feeding is associated with a reduced incidence of infectious complications in intensive care unit patients. Upper GI dysmotility in critical care patients is a common occurrence, and there are many causes for this problem, which affects a very heterogenous population with a multitude of underlying medical abnormalities. Therefore, it is of utmost importance to identify this widespread problem and subsequently institute a proper therapy as rapidly as possible. Prokinetic pharmacotherapies are currently the mainstay for the management of disordered upper GI motility. Future therapies, aimed at the underlying pathophysiology of this complex problem, are under investigation. These aim is to reduce the side effects of the currently available options, while improving on nutrition delivery in the critically ill. This review discusses the pathophysiology, clinical manifestations, diagnosis, and treatment of upper GI motility disturbances in the critically ill.

Gastrointestinal dysmotility: clinical consequences and management of the critically ill patient

Gastrointestinal dysmotility is a common feature of critical illness, with a number of significant implications that include malnutrition secondary to reduced feed tolerance and absorption, reflux and aspiration resulting in reduced lung function and ventilator-associated pneumonia, bacterial overgrowth and possible translocation causing nosocomial sepsis. Prokinetic agent administration can improve gastric emptying and caloric delivery, but its effect on nutrient absorption and clinical outcomes is, as yet, unclear. Postpyloric delivery of nutrition has not yet been demonstrated to increase caloric intake or improve clinical outcomes.

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.

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.

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.

Gastric emptying and the organization of antro-duodenal pressures in the critically ill

The motor dysfunctions underlying delayed gastric emptying (GE) in critical illness are poorly defined. Our aim was to characterize the relationship between antro-duodenal (AD) motility and GE in critically ill patients. AD pressures were recorded in 15 mechanically ventilated patients and 10 healthy volunteers for 2 h (i) during fasting, (ii) following an intragastric nutrient bolus with concurrent assessment of GE using the (13)C-octanoate breath test and (iii) during duodenal nutrient infusion. Propagated waves were characterized by length and direction of migration. Critical illness was associated with: (i) slower GE (GEC: 3.47 +/- 0.1 vs 2.99 +/- 0.2; P = 0.046), (ii) fewer antegrade (duodenal: 44%vs 83%, AD: 16%vs 83%; P < 0.001) and more retrograde (duodenal: 46%vs 12%, AD: 38%vs 4%; P < 0.001) waves, (iii) shorter wave propagation (duodenal: 4.7 +/- 0.3 vs 6.0 +/- 0.4 cm; AD: 7.7 +/- 0.6 vs 10.9 +/- 0.9 cm; P = 0.004) and (iv) a close correlation between GE with the percentage of propagated phase 3 waves that were antegrade (r = 0.914, P = 0.03) and retrograde (r = -0.95, P = 0.014). In critical illness, the organization of AD pressure waves is abnormal and associated with slow GE.

The effects of sedation on gastric emptying and intra-gastric meal distribution in critical illness

OBJECTIVE

To evaluate the effects of sedation with morphine and midazolam (M&M) versus propofol on gastric emptying in critically ill patients.

DESIGN

Descriptive study.

SETTING

Mixed medical and surgical intensive care unit.

PATIENTS

Thirty-six unselected, mechanically ventilated, critically ill patients.

INTERVENTIONS

Gastric scintigraphic data were analysed retrospectively according to whether patients were receiving M&M (n=20; 14M, 6F) or propofol (n=16; 7M, 9F). Measurements were performed over 4 h after administration of 100 ml of Ensure, labelled with 20 MBq Tc99m.

MEASUREMENTS AND RESULTS

Gastric half-emptying time (t1/2) and total and regional (proximal and distal stomach) meal retention (%) were assessed. The median t1/2 of patients receiving M&M (153 (IQR: 72-434) min) was significantly longer than that of patients receiving propofol (58 (34-166) min, p=0.02). Total gastric retention was greater in patients receiving M&M compared to those receiving propofol (p<0.01). Proximal (p=0.02) but not distal (p=0.80) gastric retention was greater in patients who received M&M. Patients who received M&M were more likely to have >or=5% meal retention at 240 min than those treated with propofol (95% (19/20) vs. 56% (9/16); p=0.01). Changes in blood glucose concentrations during the study were similar in the two groups.

CONCLUSIONS

In critical illness, patients receiving M&M for sedation are more likely to have slow gastric emptying, and proximal meal retention than those receiving propofol. The apparent beneficial effects of propofol-based sedation need confirmation by a prospective randomised controlled study.

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.

Mechanisms underlying feed intolerance in the critically ill: Implications for treatment

Malnutrition is associated with poor outcomes in critically ill patients. Although nutritional support is yet to be proven to improve mortality in non-malnourished critically ill patients, early enteral feeding is considered best practice. However, enteral feeding is often limited by delayed gastric emptying. The best method to clinically identify delayed gastric emptying and feed intolerance is unclear. Gastric residual volume (GRV) measured at the bedside is widely used as a surrogate marker for gastric emptying, but the value of GRV measurement has recently been disputed. While the mechanisms underlying delayed gastric emptying require further investigation, recent research has given a better appreciation of the pathophysiology. A number of pharmacological strategies are available to improve the success of feeding. Recent data suggest a combination of intravenous metoclopramide and erythromycin to be the most successful treatment, but novel drug therapies should be explored. Simpler methods to access the duodenum and more distal small bowel for feed delivery are also under investigation. This review summarises current understanding of the factors responsible for, and mechanisms underlying feed intolerance in critical illness, together with the evidence for current practices. Areas requiring further research are also highlighted.

The impact of admission diagnosis on gastric emptying in critically ill patients

Introduction

Disturbed gastric emptying (GE) occurs commonly in critically ill patients. Admission diagnoses are believed to influence the incidence of delayed GE and subsequent feed intolerance. Although patients with burns and head injury are considered to be at greater risk, the true incidence has not been determined by examination of patient groups of sufficient number. This study aimed to evaluate the impact of admission diagnosis on GE in critically ill patients.

Methods

A retrospective review of patient demographics, diagnosis, intensive care unit (ICU) admission details, GE, and enteral feeding was performed on an unselected cohort of 132 mechanically ventilated patients (94 males, 38 females; age 54 ± 1.2 years; admission Acute Physiology and Chronic Health Evaluation II [APACHE II] score of 22 ± 1) who had undergone GE assessment by ¹³C-octanoic acid breath test. Delayed GE was defined as GE coefficient (GEC) of less than 3.20 and/or gastric half-emptying time (t50) of more than 140 minutes.

Results

Overall, 60% of the patients had delayed GE and a mean GEC of 2.9 ± 0.1 and t50 of 163 ± 7 minutes. On univariate analysis, GE correlated significantly with older age, higher admission APACHE II scores, longer length of stay in ICU prior to GE measurement, higher respiratory rate, higher FiO₂ (fraction of inspired oxygen), and higher serum creatinine. After these factors were controlled for, there was a modest relationship between admission diagnosis and GE (r = 0.48; P = 0.02). The highest occurrence of delayed GE was observed in patients with head injuries, burns, multi-system trauma, and sepsis. Delayed GE was least common in patients with myocardial injury and non-gastrointestinal post-operative respiratory failure. Patients with delayed GE received fewer feeds and stayed longer in ICU and hospital compared to those with normal GE.

Conclusion

Admission diagnosis has a modest impact on GE in critically ill patients, even after controlling for factors such as age, illness severity, and medication, which are known to influence this function.

Practicalities of nutrition support in the intensive care unit

PURPOSE OF REVIEW

Nutrition support improves clinical outcomes in the critically ill and our understanding of its effects has advanced significantly over the last few years. Three recently published evidence-based guidelines have made generally consistent and thorough recommendations to assist clinicians in providing nutrition support. This review will focus on various aspects of these recommendations, concentrating on the practicalities of nutrition support in the intensive care unit, such as its optimal mode and composition.

RECENT FINDINGS

Enteral nutrition is preferred to parenteral nutrition unless there is a major gut condition which will delay commencement of enteral nutrition. Nasogastric feeding should begin within 24 h, but if intolerance develops, small bowel feeding or pro-motility drugs (erythromycin or metoclopramide) should be attempted before resorting to supplementary parenteral nutrition. Enteral nutrition should not routinely be supplemented with arginine or glutamine, but it should contain a package of eicosapentaenoic acid, gamma-linolenic acid and antioxidants if the patient has acute lung injury or sepsis. Parenteral nutrition should be glutamine supplemented and the prescription should be limited in energy to avoid hyperglycemia. Whether using enteral nutrition or parenteral nutrition, most patients should receive intravenous selenium, and may also need zinc and copper supplementation.

SUMMARY

Intensive care unit patients should have nutrition support based on recent evidence-based guidelines with a preference for nasogastric feeding. If intolerance occurs, pro-motility drugs and small bowel feeding should be attempted. Clinicians should also consider carefully the composition of the nutrition support regimen with regard to lipid content (especially eicosapentaenoic acid and gamma-linolenic acid), antioxidants, glutamine and other micronutrients.

Gastrointestinal motility and prokinetics in the critically ill

PURPOSE OF REVIEW

Enteral nutrition is frequently unsuccessful in the critically ill due to gastrointestinal dysfunction. Current treatment strategies are often disappointing. In this article upper gastrointestinal function in health together with abnormalities seen during critical illness are reviewed, and potential therapeutic options summarized.

RECENT FINDINGS

Reflux oesophagitis occurs frequently due to reduced or absent lower oesophageal sphincter tone. In the stomach a number of motor patterns contribute to slow gastric emptying. The fundus has reduced compliance, there are less frequent contractions in both the proximal and distal stomach, isolated pyloric activity is increased and the organization of duodenal motor activity is abnormal. In response to nutrients, enterogastric feedback is enhanced, fundic relaxation and subsequent recovery is delayed, antral motility is further reduced and localized pyloric contractions stimulated. Elevated concentrations of hormones such as cholecystokinin and peptide YY are potential mediators for these phenomena. Rapid tachyphylaxis occurs with the commonly used prokinetics, metoclopramide and erythromycin, and novel agents are under investigation. Independent of gastric emptying, nutrient absorption is reduced.

SUMMARY

There has been considerable progress in understanding the pathogenesis of mechanisms causing feed intolerance in critical illness, but this is yet to be translated into therapeutic benefit.

Proximal gastric motility in critically ill patients with type 2 diabetes mellitus

AIM: To investigate the proximal gastric motor response to duodenal nutrients in critically ill patients with long-standing type 2 diabetes mellitus.

METHODS: Proximal gastric motility was assessed (using a barostat) in 10 critically ill patients with type 2 diabetes mellitus (59 ± 3 years) during two 60-min duodenal infusions of Ensure^® (1 and 2 kcal/min), in random order, separated by 2 h fasting. Data were compared with 15 non-diabetic critically ill patients (48 ± 5 years) and 10 healthy volunteers (28 ± 3 years).

RESULTS: Baseline proximal gastric volumes were similar between the three groups. In diabetic patients, proximal gastric relaxation during 1 kcal/min nutrient infusion was similar to non-diabetic patients and healthy controls. In contrast, relaxation during 2 kcal/min infusion was initially reduced in diabetic patients (p < 0.05) but increased to a level similar to healthy humans, unlike non-diabetic patients where relaxation was impaired throughout the infusion. Duodenal nutrient stimulation reduced the fundic wave frequency in a dose-dependent fashion in both the critically ill diabetic patients and healthy subjects, but not in critically ill patients without diabetes. Fundic wave frequency in diabetic patients and healthy subjects was greater than in non-diabetic patients.

CONCLUSION: In patients with diabetes mellitus, proximal gastric motility is less disturbed than non-diabetic patients during critical illness, suggesting that these patients may not be at greater risk of delayed gastric emptying.

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

OBJECTIVE

Delayed gastric emptying and intolerance to gastric feeding occur frequently in the critically ill. In these patients, gastric motor responses to nutrients are disturbed. Cholecystokinin (CCK) slows gastric emptying. The aim of this study was to determine plasma CCK concentrations during fasting and in response to small-intestine nutrient infusion in critically ill patients.

DESIGN

Randomized, controlled trial.

SETTING

Level 3, mixed medical and surgical intensive care unit.

SUBJECTS

A total of 31 mechanically ventilated, critically ill patients (23 men, 51 +/- 3 yrs) and 28 healthy subjects (21 men, 43 +/- 2 yrs).

INTERVENTIONS

Subjects received two 60-min duodenal infusions of Ensure (complete balanced nutrition), at 1 and 2 kcal/min, in a randomized, single-blind fashion. The nutrient infusions were separated by a 2-hr "washout" period. Blood samples for measurement of plasma CCK concentrations were obtained immediately before and every 20 mins during nutrient infusion.

MEASUREMENTS AND MAIN RESULTS

Baseline and nutrient-stimulated plasma CCK concentrations were higher in critically ill patients compared with healthy subjects (p < .001). The magnitude of the rise in plasma CCK in response to nutrients was also greater in the critically ill (p < .01). Of the 23 patients who received enteral nutrition before the study, nine were intolerant of gastric feeding. In these patients, both the baseline plasma CCK concentration and the magnitude of CCK increase during nutrient infusions were greater than in patients with feed tolerance (p < .002). Impaired renal function was associated with an increased baseline CCK concentration but had no effect on the CCK response to nutrients.

CONCLUSIONS

Both fasting and nutrient-stimulated plasma CCK concentrations are increased in critically ill patients, particularly in those with feed intolerance. This may provide a humoral mechanism for delayed gastric emptying seen in critical illness.

The relationship between gastric emptying, plasma cholecystokinin, and peptide YY in critically ill patients

BACKGROUND

Cholecystokinin (CCK) and peptide YY (PYY) are released in response to intestinal nutrients and play an important physiological role in regulation of gastric emptying (GE). Plasma CCK and PYY concentrations are elevated in critically ill patients, particularly in those with a history of feed intolerance. This study aimed to evaluate the relationship between CCK and PYY concentrations and GE in critical illness.

METHODS

GE of 100 mL of Ensure meal (106 kcal, 21% fat) was measured using a 13C-octanoate breath test in 39 mechanically ventilated, critically ill patients (24 males; 55.8 +/- 2.7 years old). Breath samples for 13CO2 levels were collected over the course of 4 hours, and the GE coefficient (GEC) (normal = 3.2 to 3.8) was calculated. Measurements of plasma CCK, PYY, and glucose concentrations were obtained immediately before and at 60 and 120 minutes after administration of Ensure.

RESULTS

GE was delayed in 64% (25/39) of the patients. Baseline plasma CCK (8.5 +/- 1.0 versus 6.1 +/- 0.4 pmol/L; P = 0.045) and PYY (22.8 +/- 2.2 versus 15.6 +/- 1.3 pmol/L; P = 0.03) concentrations were higher in patients with delayed GE and were inversely correlated with GEC (CCK: r = -0.33, P = 0.04, and PYY: r = -0.36, P = 0.02). After gastric Ensure, while both plasma CCK (P = 0.03) and PYY (P = 0.02) concentrations were higher in patients with delayed GE, there was a direct relationship between the rise in plasma CCK (r = 0.40, P = 0.01) and PYY (r = 0.42, P < 0.01) from baseline at 60 minutes after the meal and the GEC.

CONCLUSION

In critical illness, there is a complex interaction between plasma CCK, PYY, and GE. Whilst plasma CCK and PYY correlated moderately with impaired GE, the pathogenetic role of these gut hormones in delayed GE requires further evaluation with specific antagonists.

Fasting and nutrient-stimulated plasma peptide-YY levels are elevated in critical illness and associated with feed intolerance: an observational, controlled study

INTRODUCTION

Delayed gastric emptying and feed intolerance occur frequently in the critically ill. In these patients, gastric motor responses to nutrients are disturbed. Peptide YY (PYY) slows gastric emptying. The aim of this study was to determine fasting and nutrient-stimulated plasma PYY concentrations and their relationship to cholecystokinin (CCK) in critically ill patients.

METHODS

Studies were performed in 19 unselected mechanically ventilated critically ill patients (12 males; 48 +/- 7 years old) in a randomised, single-blind fashion. Subjects received a 60-minute duodenal infusion of Ensure at either 1 or 2 kcal/minute. Blood samples were collected at baseline and at 20, 40, 60, and 180 minutes following commencement of the nutrient infusion for the measurement of plasma PYY and CCK concentrations (using radioimmunoassay). Patient data were compared to 24 healthy subjects (17 males; 43 +/- 2 years old).

RESULTS

Fasting PYY concentration was higher in patients (P < 0.05), particularly in those with feed intolerance (P < 0.05). Plasma PYY concentrations were higher in patients during nutrient infusion (area under the curve [AUC] at 1 kcal/minute: 2,265 +/- 718 versus 1,125 +/- 138 pmol/l.min, P < 0.05; at 2 kcal/minute: 2,276 +/- 303 versus 1,378 +/- 210 pmol/l.min, P = 0.01) compared to healthy subjects. The magnitude of PYY elevation was greater in patients during the 1 kcal/minute infusion (AUC: 441 +/- 153 versus 186 +/- 58 pmol/l.min, P < 0.05), but not the 2 kcal/minute infusion. Fasting and nutrient-stimulated plasma CCK concentrations were higher in patients (P < 0.05). There was a relationship between plasma PYY and CCK concentrations during fasting (r = 0.52, P < 0.05) and nutrient infusion (r = 0.98, P < 0.0001).

CONCLUSION

In critical illness, both fasting and nutrient-stimulated plasma PYY concentrations are elevated, particularly in patients with feed intolerance, in conjunction with increased CCK concentrations.