Gastrointestinal promotility drugs in the critical care setting: a systematic review of the evidence

Gastrointestinal motility in acute illness

Critical illness affects gastrointestinal motility - not only as a primary problem, which brings the patient to the intensive care unit (ICU), but also as a complication consecutive to the ICU stay. Motility disturbances may result from impaired function of gastrointestinal muscle, pacemaker cell function and nerve activity. The most important neural control system is the enteric nervous system that contains the largest collection of neurons (10(8) cells) outside the central nervous system. Through its organization it can operate independently of the brain and generate motility patterns according to need: a postprandial motility pattern starting after food intake, and an interdigestive motility pattern starting several hours after a meal. Undisturbed intestinal motility depends critically on a balanced interaction between inhibition and excitation, and a disturbance in this balance leads to severe derangements of intestinal motility. These motility disturbances differ in clinical appearance and location but can affect all parts of the gastrointestinal tract. This review focuses on select motility disturbances such as gastroparesis, postoperative ileus, and Ogilvie's syndrome. Generally effective methods to treat these conditions are given. Finally, we focus on special management options to prevent such motility disturbances or to reduce their severity.

Standardized concept for the treatment of gastrointestinal dysmotility in critically ill patients--current status and future options

Inhibition of gastrointestinal motility is a major problem in critically ill patients. Motor stasis gives rise to subsequent complications including intolerance to enteral feeding, enhanced permeability of the atrophic intestinal mucosa and conditions as severe as systemic inflammatory response syndrome, sepsis and multiple organ failure. Although the diagnosis of motility disturbances in critically ill patients is difficult, the type and site of the disturbance are important to consider in the analysis of the condition and in the choice of therapeutic approach. The pharmacological treatment of impaired gastrointestinal motility is difficult to handle for the clinician, because the underlying mechanisms are complex and not fully understood and the availability of pharmacological treatment options is limited. In addition, there is a lack of controlled studies on which to build an evidence-based treatment concept for critically ill patients. Notwithstanding this situation, there has been remarkable progress in the understanding of the integrated regulation of gastrointestinal motility in health and disease. These advances, which largely relate to the organization of the enteric nervous system and its signaling mechanisms, enable the intensivist to develop a standardized concept for the use of prokinetic agents in the treatment of impaired gastrointestinal motility in critically ill patients.

Decisions to be made when initiating enteral nutrition

Enteral nutrition support is preferred to parenteral or no nutritional support, but many patients who could benefit receive inadequate enteral feeding. Many decisions must be made before initiating enteral nutrition support; including if and when enteral nutrition should be started, which formula should be used, and how enteral nutrition support should be monitored. The gastroenterologist should be able to understand and evaluate these decisions in all patients potentially requiring nutritional support.

Gastric versus postpyloric feeding

Feeding into the small bowel is often recommended to improve nutrient delivery for critically ill patients, and thus improve outcome and reduce complications associated with enteral feeding. Risks and benefits of gastric feeding, use of motility agents, postpyloric feeding, and obtaining small bowel access are discussed here. Randomized clinical trials directly comparing postpyloric with gastric feeds are also evaluated. These small, underpowered studies demonstrate small but clinically important differences in important outcomes (pneumonia), but are weakened by significant heterogeneity. Current evidence does not support routine use of postpyloric feeding in the critically ill. A standardized approach to optimizing benefits and minimizing risks with enteral nutrition delivery will help clinicians identify patients who would benefit from small bowel feeding.

Nutrition support and treatment of motility disorders in critically ill patients - results of a survey on German intensive care units

BACKGROUND AND OBJECTIVE

To evaluate the current clinical attitude in enteral nutrition support and motility disorders in adult critically ill patients on German intensive care units.

METHODS

A total of 1493 questionnaires, including 25 items on the medical environment, treatment of motility disorders and enteral nutrition, were sent to German intensive care units in September 2005. Responses were collected during a 2-month period.

RESULTS

A total of 593 questionnaires were returned (response rate 41%). The intensive care units were mainly led by anaesthesiologists (63%) or internists (17%). Standard nutrition protocols were used in 44%. Feeding was mainly started as a combined enteral-parenteral regimen (70%). Early enteral nutrition was performed in 58% using a volume of 250-500 mL (66%) and increased by 200-400 mL day-1 (55%). It was mainly delivered by gastric tube (76%) via continuous pump systems (72%) with short interruption intervals of <4 h (86%). Enteral nutrition solutions were mainly standard polymeric formulae (86%). Modified solutions for diabetics and those with renal or liver failure were uncommonly used; immunonutrition did not play a role. Prokinetic agents, especially metoclopramide, laxatives and neostigmine, were routinely used (39%). Further therapeutic options in motility dysfunction included purgative enemas (96%), gastrografin (72%) and colon massage (39%).

CONCLUSIONS

The concept of early enteral nutrition has been well established and approved in German intensive care units, though the recommendations only meet level C criteria in the current ESPEN guidelines. The current survey may serve for further updates on practical nutrition support in intensive care medicine.

Enteral access options and management in the patient with intestinal failure

Intestinal failure refers to a condition in which inadequate digestion and/or absorption of nutrients leads to malnutrition and/or dehydration. Enteral access is occasionally used in patients with intestinal failure either for the purpose of providing nutrition or decompressing the gut. As a consequence, it is important that clinicians caring for these highly complex patients be knowledgeable in enteral access options and experienced in the subsequent care of these tubes. In this review, enteral access options and the potential complications associated with their use will be reviewed. Importantly, this information is relevant to both the pediatric and adult patient with intestinal failure.

Risk of aspiration in patients on enteral nutrition: frequency, relevance, relation to pneumonia, risk factors, and strategies for risk reduction

Upper digestive feeding intolerance, as evidenced by high gastric residual volume and vomiting, is the most common complication among hospitalized patients receiving enteral nutrition. These patients are at high risk of developing aspiration pneumonia, which in turn is associated with prolonged hospital stay and increased mortality. Most episodes of aspiration are small in volume and do not lead to pneumonia. The likelihood of pneumonia increases with multiple aspirations. Pneumonia is also more common in critically ill patients who have bacterial colonization of the oropharynx. Gastric residual volume is commonly used as a means to assess aspiration risk during tube feeding. However, recent studies have demonstrated that this measurement has limited sensitivity. The approach to minimizing the frequency of aspiration during tube feeding involves assessment of the patient's degree of risk and initiation of appropriate measures directed at risk reduction.

Erythromycin is more effective than metoclopramide in the treatment of feed intolerance in critical illness

OBJECTIVE

This study aimed to a) compare the efficacy of metoclopramide and erythromycin in the treatment of feed intolerance in critical illness; and b) determine the effectiveness of "rescue" combination therapy in patients who fail monotherapy.

DESIGN

Randomized controlled trial.

SETTING

Level III mixed medical and surgical intensive care unit.

PATIENTS

Ninety mechanically ventilated, medical patients with feed-intolerance (gastric residual volume>or=250 mL).

INTERVENTIONS

Patients received either metoclopramide 10 mg intravenously four times daily (n=45) or erythromycin 200 mg intravenously twice a day (n=45) in a double-blind, randomized fashion. After the first dose, nasogastric feeding was commenced and 6-hourly nasogastric aspirates were performed. If a gastric residual volume>or=250 mL recurred on treatment, open-label, combination therapy was given. Patients were studied for 7 days. Successful feeding was defined as 6-hourly gastric residual volume<250 mL with a feeding rate>or=40 mL/hr.

MEASUREMENTS AND MAIN RESULTS

Demographic data, blood glucose levels, and use of inotropes, opioids, and benzodiazepines were similar between the two groups. After 24 hrs of treatment, both monotherapies reduced the mean gastric residual volume (metoclopramide, 830+/-32 mL to 435+/-30 mL, p<.0001; erythromycin, 798+/-33 mL to 201+/-19 mL, p<.0001) and improved the proportion of patients with successful feeding (metoclopramide=62% and erythromycin=87%). Treatment with erythromycin was more effective than metoclopramide, but the effectiveness of both treatments declined rapidly over time. In patients who failed monotherapy, rescue combination therapy was highly effective (day 1=92%) and maintained its effectiveness for the study duration (day 6=67%). High pretreatment gastric residual volume was associated with poor response to prokinetic therapy.

CONCLUSIONS

In critical illness, erythromycin is more effective than metoclopramide in treating feed intolerance, but the rapid decline in effectiveness renders both treatments suboptimal. Rescue combination therapy is highly effective, and further study is required to examine its role as the first-line therapy.

The use of erythromycin as a gastrointestinal prokinetic agent in adult critical care: benefits versus risks

Erythromycin A, the first macrolide, was introduced in the 1950s and after years of clinical experience it still remains a commonly relied upon antibiotic. In the past, pharmacodynamic characteristics of macrolides beyond antimicrobial action such as anti-inflammatory and immune-modulating properties have been of scientific and clinical interest. The function of erythromycin as a prokinetic agent has also been investigated for a range of gastrointestinal motility disorders and more recently within the context of critically ill patients. Prokinetic agents are drugs that increase contractile force and accelerate intraluminal transit. Whilst the anti-inflammatory action may be a desirable side effect to its antibiotic action, using erythromycin A merely for its prokinetic effect alone raises the concern about promoting emergence of macrolide resistance. The objectives of this review article are: (i) to briefly summarize the modes and epidemiology of macrolide resistance, particularly in respect to that found in the Streptococcus species (a potential reservoir for the dissemination of macrolide resistance on the critical care unit); (ii) to discuss in this context the evidence for conditions promoting bacterial resistance against macrolides; and (iii) to assess the potential clinical benefit of using erythromycin A as a prokinetic versus the risks of promoting emergence of macrolide resistance in the clinical setting. We conclude, that in view of the growing weight of evidence demonstrating the potential epidemiological impact of the increased use of macrolides upon the spread of resistance, versus a lack of sufficient and convincing evidence that erythromycin A is a superior prokinetic agent to potential alternatives in the critically ill patient population, at this stage we do not advocate the use of erythromycin A as a prokinetic agent in critically ill patients unless they have failed all other treatment for impaired gastrointestinal dysmotility and are intolerant of metoclopramide. Further large and methodologically robust studies are needed to ascertain the effectiveness of erythromycin A and other alternative agents in the critically ill.

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.

Intestinal motility disturbances in intensive care patients pathogenesis and clinical impact

BACKGROUND

Gastrointestinal motility disturbances in critically ill patients are frequent in the ICU setting, causing considerable discomfort and are associated with increased rates of morbidity and mortality. This review focuses on the pathophysiological basis of intestinal motility, the major patterns of pathological motility alterations, the impact on patient outcome, and current therapeutic options.

DISCUSSION

Intestinal motility is controlled by the enteric nervous system, modulated by hormones and extrinsic afferent and efferent neurons. Pathological motility disturbances can affect the stomach, small bowel, and colon separately or in combination. Changes in esophageal motor activity contribute to the aspiration of gastric juice, whereas early enteral feeding most frequently fails due to gastric intolerance. Disturbances in digestive and interdigestive motility patterns and the inability to switch motor activity from the interdigestive to the digestive pattern also contribute to feeding disability and thus to increased morbidity and mortality as well.

CONCLUSIONS

The therapeutic options for motility disturbances in critically ill patients include the adjustment of electrolyte imbalances, tailored fluid management, early enteral feeding, appropriate management of catecholamines and drugs used for analgosedation, and prokinetic drugs. Unfortunately, the therapeutic options for treating motility disturbances in ICU patients are still limited. This situation requires careful assessment of ICU patients with respect to gut motility disturbances and their pathophysiological mechanisms and an individually tailored treatment to prevent further aggravation of existing motility disturbances.

Erythromycin for prokinesis: imprudent prescribing?

Problems with antibiotic resistant bacteria are increasing in the hospital and particularly in the intensive care unit. Methicillin-resistant Staphylococcus aureus, Acinetobacter baumanii and extended spectrum beta-lactamase producing Gram-negative bacilli constitute a therapeutic and infection control challenge. Early enteral feeding improves survival in patients in the intensive care unit. Prokinetic agents are routinely used in patients with inappropriate gastrointestinal motility. The use of erythromycin at sub-therapeutic doses as a prokinetic agent is a cause of concern for the following reasons: it can increase the emergence and spread of antibiotic resistance and the likelihood of Clostridium difficile disease. The use of an antibiotic as a prokinetic agent does not constitute prudent antimicrobial prescribing and should be avoided. Alternative agents, whenever possible, should be used.

Risks and benefits of nutritional support during critical illness

Critically ill patients who depend on intensive care for more than a few days reveal profound erosion of lean body mass, which is thought to contribute to high morbidity and mortality. Despite a shortfall of evidence that supplemental feeding actually alters clinical outcome of these life-threatening disease states, this observation evoked an almost universal, albeit often inappropriate, use of nutritional support (NS) in the critically ill, administered via the parenteral or the enteral route. Lack of knowledge and overenthusiasm subsequently resulted in complications associated with both parenteral nutrition (PN) and enteral nutrition (EN), which led to the standing controversy over which should be preferred. With time, however, it became clear that EN and PN are not mutually exclusive and that critically ill patients requiring NS should be fed according to the functional status of the gastrointestinal tract. In addition, tight blood glucose control with insulin is advised in fed critically ill patients because overall metabolic control appears to surpass any outcome benefit attributed to the route of feeding. Recently, various special nutritional formulas have been suggested to prevent or treat multiorgan failure in the critically ill, among other pathways via modulation of immune function. Although special nutritional formulas may be promising in a variety of clinical settings, based on currently available data, these cannot be recommended for routine use in critically ill patients.

Use of novel prokinetic agents to facilitate return of gastrointestinal motility in adult critically ill patients

PURPOSE OF REVIEW

Intolerance of enteral feeding due to impaired gastrointestinal motility is common in critically ill patients. Strategies to prevent or treat gastrointestinal hypomotility include the use of prokinetic agents. Many currently employed prokinetic agents are associated with serious adverse drug reactions. The novel prokinetic agents - alvimopan, tegaserod, and dexloxiglumide - are reviewed.

RECENT FINDINGS

Alvimopan exerts mixed, but generally favorable, effects on restoration of gastrointestinal motility in patients with postoperative ileus. The observation of increased opioid requirements (without increased pain scores) and associated clinical ramifications requires further study. Tegaserod stimulates the peristaltic reflex and improves motility in multiple sites along the gastrointestinal tract. Its efficacy in improving gastrointestinal hypomotility in the critically ill population has not yet been determined. Furthermore, its use has been associated with the development of ischemic colitis and increased requirement for abdominal/pelvic surgery. Dexloxiglumide may be beneficial for improving gastric emptying in critically ill patients, especially those receiving lipid-enriched enteral feeds.

SUMMARY

Novel prokinetic agents show promise for management of gastrointestinal hypomotility in the critically ill population. However, further study is required before these agents can be recommended for use.

Preliminary Evidence for a Medical Nutrition Therapy Protocol: Enteral Feedings for Critically Ill Patients

The objective of this study was to evaluate the evidence behind specific but common patient care decisions in support of enteral feedings for patients admitted to intensive care units. Six specific questions were developed and refined to address clinical outcomes specific to clinical practice decisions pertinent to enteral feeding of critically ill patients. The data sources consisted of an intensive literature review from five databases, using standardized search terms. Randomized controlled clinical trials, meta-analyses, consensus statements, reviews, US Food and Drug Administration alerts, and case reports were selected for study. Research reports were abstracted in detail and evaluated for research quality using the criteria developed by the American Dietetic Association. Consensus statements regarding the influence of specific enteral feeding methods on key clinical outcomes (ie, infectious complications, cost, length of hospital stay, and mortality) were developed and graded based on the quality of the available evidence. The data support the use of enteral over parenteral nutrition to reduce infectious complications and cost, and the initiation of enteral feedings within 24 to 48 hours of injury or admission to an intensive care unit to reduce infectious complications and length of hospital stay in head injury and trauma patients. Postpyloric tube placement is associated with reduced gastric residual volume and reflux, but adequately powered trials are not available to support prevention of aspiration pneumonia. Acceptance of gastric residual volumes of up to 250 mL may increase volume of formula delivered. Promotility agents are associated with reduced gastric residual volume. Feeding patients in the semirecumbent rather than supine position is associated with reduced aspiration pneumonia and pharyngoesophageal formula reflux. Actual delivery of 14 to 18 kcal/kg/day or 60% to 70% of goal is associated with improved outcomes, whereas greater intake may not be in some populations. Blue food coloring should not be used with enteral feedings due to its limited sensitivity for aspiration and some risk of mortality. Well-designed, adequately powered, randomized controlled clinical trials are needed to evaluate any benefit of tube tip position on aspiration pneumonia or mortality, and of early enteral feedings on mortality.

ESPEN Guidelines on Enteral Nutrition: Intensive care

Enteral nutrition (EN) via tube feeding is, today, the preferred way of feeding the critically ill patient and an important means of counteracting for the catabolic state induced by severe diseases. These guidelines are intended to give evidence-based recommendations for the use of EN in patients who have a complicated course during their ICU stay, focusing particularly on those who develop a severe inflammatory response, i.e. patients who have failure of at least one organ during their ICU stay. These guidelines were developed by an interdisciplinary expert group in accordance with officially accepted standards and are based on all relevant publications since 1985. They were discussed and accepted in a consensus conference. EN should be given to all ICU patients who are not expected to be taking a full oral diet within three days. It should have begun during the first 24h using a standard high-protein formula. During the acute and initial phases of critical illness an exogenous energy supply in excess of 20-25 kcal/kg BW/day should be avoided, whereas, during recovery, the aim should be to provide values of 25-30 total kcal/kg BW/day. Supplementary parenteral nutrition remains a reserve tool and should be given only to those patients who do not reach their target nutrient intake on EN alone. There is no general indication for immune-modulating formulae in patients with severe illness or sepsis and an APACHE II Score >15. Glutamine should be supplemented in patients suffering from burns or trauma.

Intestinal failure

PURPOSE OF REVIEW

The gastrointestinal tract plays a major role in critical illness. We will review four common problem areas pertaining to the gut and abdominal compartment that intensivists managing critically ill patients must deal with on an everyday basis.

RECENT FINDINGS

In the area of enteral nutrition, there have been concerns that early feeding in hemodynamically unstable patients might cause bowel infarction by increasing the gut oxygen consumption beyond splanchnic oxygen delivery. The most recent data suggest that early enteral feeding, even when patients are receiving vasopressors, is safe and may actually protect the gut by increasing gut perfusion. Although there are no new treatments for ileus, in most critically ill patients ileus primarily affects the stomach and large intestine, and most patients who are diagnosed with ileus may still be fed enterally as long as they are fed distal to the stomach. Diarrhea is a common occurrence in the intensive care unit, particularly in patients who are being fed enterally. Of most import is the realization that Clostridium difficile infection is ubiquitous and must be considered in virtually every case of diarrhea. Abdominal compartment syndrome is usually a result of shock, and its resuscitation with increased intra-abdominal pressure results in many untoward hemodynamic and respiratory events. Early recognition and treatment seem to be associated with improved outcome.

SUMMARY

Continued progress in the areas of optimal nutritional support, understanding the implications of alterations in immune function of the gut, and the avoidance of such morbid complications as abdominal compartment syndrome are expected.

Nutrition support for patients in the intensive care unit

Enteral nutrition (EN) is the mainstay of nutrition delivery within intensive care seeking to capitalise on its benefits for the gastrointestinal tract and associated immune system, but this has brought new challenges in delivery to the sick. The hoped for benefit has led to the mistaken belief by some that parenteral nutrition (PN) is no longer required. However, a greater appreciation of the risks of EN delivery in the sick patient combined with improvements in PN formulation and use help explain why PN is not as risky as some have believed. Real outcome benefits have been described with the new glutamine containing PN formulations. PN remains important in the presence of gastrointestinal feed intolerance or failure.

Important Facts About Intestinal Feeding Tube Placement

Enteral feeding is desirable when the gastrointestinal tract is functional because it allows better use of nutrients, is safer, and is more cost-effective than parenteral nutrition. Feeding through a gastric tube, however, is often not feasible in severely ill adults and children because of gastric paresis leading to recurrent episodes of gastroesophageal reflux with the risk of subsequent aspiration. Feeding into the small intestine (duodenum or jejunum) through a nasointestinal tube, therefore, is preferred. Unfortunately, no method of enteral feeding is risk free. This literature review addresses the following 10 topics: (a) the reasons why nasointestinal tube feeding is better tolerated by some patients, (b) candidates for nasointestinal tube feeding, (c) options for selecting nasointestinal tubes, (d) recommended methods for predicting the distance to insert nasointestinal tubes, (e) recommended methods for placing nasointestinal tubes, (f) how promotility medications work and whether they facilitate nasointestinal tube placement, (g) nasointestinal tube placement error rate, (h) methods of determining the internal location of nasointestinal tubes, (i) complications associated with nasointestinal tube use, and (j) other pertinent issues surrounding feeding through nasointestinal tubes. The available research evidence is summarized and recommendations for future work are suggested.

Enteral access for nutrition in the intensive care unit

PURPOSE OF REVIEW

Enteral nutrition is the preferred route for nutrition support in the intensive care unit setting. This is usually delivered through nasoenteric feeding tubes in patients with an otherwise functional gastrointestinal tract. Placement of nasoenteric feeding tubes, however, may be difficult in this setting. Nasoenteric feeding tubes may be placed by multiple methods, each with their particular advantages and disadvantages. This review summarizes the recent literature on different methods of nasoenteric feeding tube placement with emphasis on critically ill patients.

RECENT FINDINGS

Bedside assisted methods using electromyogram, electrocardiogram, and magnetic fields to provide immediate positional feedback to help guide tube advancement appear promising. Bedside methods using specific protocols, modified feeding tubes, prokinetics or magnetic assistance were also successfully reported. None of these methods has been prospectively compared with more commonly practiced methods in large studies. Endoscopic nasoenteric tube placement methods including transnasal approaches using ultra-thin endoscopes have been recently described and appear to be equivalent to fluoroscopic placement. All these recently reported techniques, however, may require more specialized equipment or training than is currently widely available.

SUMMARY

Feeding tubes can be placed using bedside, fluoroscopic, and endoscopic means. Novel bedside methods have been recently described using immediate positional feedback or new assistive methods. Endoscopic techniques have similar success rates to fluoroscopic techniques and provide data on upper gastrointestinal abnormalities. There is no clear universal standard method. When feeding tube placement is required the technique used depends on local institutional resources and expertise.

Enteral feeding in the critically ill: are nursing practices contributing to hypocaloric feeding?

INTRODUCTION

Enteral feeding is the preferred method of nutritional support for the critically ill; however, a significant number of these patients are under-fed. It is possible that common nursing practices associated with the delivery of enteral feeding may contribute to under-feeding although there is little data available describing nursing practice in this area.

METHOD

A descriptive survey-based design was used to explore the enteral feeding practices of 376 critical care nurses (response rate 50.5%). Participants completed a 57-item survey that focused on general enteral feeding practice and the management of feeding intolerance and complications.

RESULTS

The enteral feeding practice of critical care nurses varied widely and included some practices that could contribute to under-feeding in the critically ill. Practices associated with the measurement of gastric residual volumes (GRV) were identified as the most significant potential contributor to under-feeding. GRV measurements were commonly used to assess feeding tolerance (n = 338; 89.9%) and identified as a reason to delay feeding (n = 246; 65.4%). Delayed gastric emptying was frequently managed by prokinetic agents (n = 237; 63%) and decreasing the rate of feeding (n = 247; 65.7%) while nursing measures, such as changing patient position (n = 81; 21.5%) or checking tube placement (n = 94; 25%) were less frequently reported.

CONCLUSION

The findings of this survey support the contention that nursing practices associated with the delivery of enteral feeds may contribute to under-feeding in the critically ill patient population.

Basic and clinical pharmacology of new motility promoting agents

Recent research has provided new information about drugs that could be used to treat functional motility disorders. Promotility drugs accelerate gastric emptying or colonic transit and these properties may contribute to their efficacy in treating symptoms associated with gastroparesis, functional dyspepsia or constipation. 5-Hydroxytryptamine4 receptors are targets for drugs (tegaserod, renzapride) that treat symptoms in constipated irritable bowel syndrome patients and in gastroparesis. Drugs acting at motilin (erythromycin) and cholecystokinin-1 (dexloxiglumide) receptors accelerate gastric emptying. Dexloxiglumide might be useful in the treatment of functional dyspepsia particularly that associated with lipid intake. Alvimopan is a mu-opioid receptor antagonist that does not cross the blood brain barrier. Alvimopan is effective in treating postsurgical ileus and perhaps opiate-induced bowel dysfunction. Successes and failures of recent efforts to develop promotility agents revealed opportunities and challenges for developing new promotility drugs. The pharmacological properties of partial agonists might be exploited to develop effective promotility drugs. However, opposing actions of promotility agents on motility (increased contraction vs decreased accommodation) limit the clinical efficacy of drugs with these opposing actions. Selection of appropriate patient populations for evaluation of new drugs is also critical.

Does enteral nutrition compared to parenteral nutrition result in better outcomes in critically ill adult patients? A systematic review of the literature

OBJECTIVE

Nutritional support is part of the standard of care for the critically ill adult patient. In the average patient in the intensive care unit who has no contraindications to enteral nutrition (EN) or parenteral nutrition (PN), the choice of route for nutritional support may be influenced by several factors. Because EN and PN are associated with risks and benefits, we systematically reviewed and critically appraised the literature to compare EN with PN the critically ill patient.

METHODS

We searched computerized bibliographic databases, personal files, and relevant reference lists to identify potentially eligible studies. Only randomized clinical trials that compared EN with PN in critically ill patients with respect to clinically important outcomes were included in this review. In an independent fashion, relevant data on the methodology and outcomes of primary studies were abstracted in duplicate. The studies were subsequently aggregated statistically.

RESULTS

There were 13 studies that met the inclusion criteria and, hence, were included in our meta-analysis. The use of EN as opposed to PN was associated with a significant decrease in infectious complications (relative risk = 0.64, 95% confidence interval = 0.47 to 0.87, P = 0.004) but not with any difference in mortality rate (relative risk = 1.08, 95% confidence interval = 0.70 to 1.65, P = 0.7). There was no difference in the number of days on a ventilator or length of stay in the hospital between groups receiving EN or PN (Standardized Mean Difference [SMD] = 0.07, 95% confidence interval = -0.2 to 0.33, P = 0.6). PN was associated with a higher incidence of hyperglycemia. Data that compared days on a ventilator and the development of diarrhea in patients who received EN versus PN were inconclusive. In the EN and PN groups, complications with enteral and parenteral access were seen. Four studies documented cost savings with EN as opposed to PN.

CONCLUSION

The use of EN as opposed to PN results in an important decrease in the incidence of infectious complications in the critically ill and may be less costly. EN should be the first choice for nutritional support in the critically ill.

Endemic multidrug-resistant Pseudomonas aeruginosa in critically ill patients

OBJECTIVE

To describe the epidemiology of endemic multidrug-resistant Pseudomonas aeruginosa colonizations and infections in critically ill patients.

DESIGN

Prospective study on bacterial strain typing and retrospective cohort study of charts of patients in the intensive care unit (ICU).

PATIENTS

Fifty-three patients with P. aeruginosa isolated from clinical cultures in 2001 were selected, divided into those with P. aeruginosa in vitro resistant to at least two classes of antibiotics (multidrug-resistant, n = 18) and those susceptible to all or resistant to only one antibiotic (susceptible, n = 35).

RESULTS

Risk factors for multidrug-resistant P. aeruginosa included maxillary sinusitis, long-dwelling central venous catheters, prolonged use of certain antibiotics, a high lung injury score, and prolonged mechanical ventilation and duration of stay. The frequency of colonization (approximately 50%) versus infection (ie, ventilator-associated pneumonia) did not differ between the groups. On amplified fragment-length polymorphism analysis, 64% of the multidrug-resistant strains had been potentially transmitted via cross-colonization and 36% had probably originated endogenously. ICU mortality was 22% in the multidrug-resistant group and 23% in the susceptible group, although the duration of mechanical ventilation was longer in the former.

CONCLUSIONS

Patients with sinusitis who stayed in the ICU longer, were ventilated longer because of acute lung injury, received antibiotics for longer durations, and had long-dwelling central venous catheters ran an elevated risk of acquiring multidrug-resistant P. aeruginosa. These patients did not have a higher mortality than patients with susceptible P. aeruginosa. Prevention of the emergence of multidrug-resistant strains requires changes in infection control measures and antibiotic policies in our ICU.

A review of the nursing care of enteral feeding tubes in critically ill adults: part I

Enteral tubes are frequently used in critically ill patients for feeding and gastric decompression. Many of the nursing guidelines to facilitate the care of patients with enteral tubes have not been based on current research, but on ritual and opinion. Using a computerised literature search and an evidence-based classification system as described by the Joanna Briggs Institute for Evidence Based Nursing and Midwifery (JBI), a comprehensive review was undertaken of enteral tube management. Several nursing practices related to enteral tube management are described. Evidence to support alternate methods of tube placement assessment other than abdominal X-ray was inconclusive. Enteral feeding should continue if gastric residual volumes are not considered excessive, as feeding is often withheld unnecessarily. Frequency of checking gastric residual volumes is largely opinion based and varies considerably, but prokinetics that aid gastric emptying should be used if absorption of feeds is problematic. Other recommendations include continuous rather than intermittent feeding, semi-recumbent positioning to reduce the risk of airway aspiration and diligent artificial airway cuff management. Contamination of feeds can be minimised by minimal, meticulous handling and the use of closed rather than open systems. Generally, there was little high quality evidence to support practice recommendations leaving significant scope for further research by nurses in the management of patients with enteral tubes.

Effect of gastrointestinal motility and feeding tube site on aspiration risk in critically ill patients: a review

OBJECTIVE

The purpose of this literature review is to examine the effect of the interaction between gastrointestinal motility and feeding site on the aspiration risk in critically ill, tube-fed patients.

METHODS AND RESULTS

A single answer to the question of the preferred feeding site is not likely to be found because the degree of aspiration risk varies significantly according to individual variations in gastrointestinal motility and multiple pre-existing and treatment-related risk factors. However, regardless of the feeding site, it is ultimately regurgitated gastric contents that are aspirated into the lungs. For this reason, the clinical assessment of greatest interest is the evaluation of gastric emptying, usually monitored clinically by measuring gastric residual volumes.

CONCLUSION

Current recommendations for monitoring residual volumes and preventing aspiration are provided.

Evaluation of Gastric pH and Guaiac Measurements in Neonates Receiving Acid Suppression Therapy During Extracorporeal Membrane Oxygenation

STUDY OBJECTIVES

To assess gastric pH measurements, evaluate the frequency of guaiac-positive gastric aspirates, and characterize the appearance of gastric aspirates in neonates receiving acid suppression therapy during extracorporeal membrane oxygenation (ECMO).

DESIGN

Retrospective, observational study.

SETTING

Intensive care unit in a 225-bed tertiary care pediatric referral hospital.

SUBJECTS

Thirteen neonates receiving ECMO.

MEASUREMENTS AND MAIN RESULTS

Gastric pH measurements, guaiac test results, appearance of gastric aspirates, and ranitidine and antacid dosing were recorded. On ECMO day 1, mean+/-SD gastric pH was 4.3+/-2.8 in the five neonates whose pH was documented. Intravenous ranitidine 2.9+/-0.4 mg/kg/day was started in all neonates by ECMO day 2. Gastric pH was less than 4.0 in seven neonates; these low pH values accounted for only 10% of gastric pH measurements. The frequency of positive guaiac results in neonates with pH measurements below 4.0 was 27% compared with 41% for neonates with a gastric pH of 4.0 or greater (p=0.125). Guaiac tests were positive in 69 (42%) aspirates in 11 neonates. Of the guaiac-positive aspirates that had a corresponding pH measurement, 94% had a pH of 4.0 or greater. Guaiac-positive aspirates had evidence of bile (49%), antacid (17%), and blood (7%) in gastric fluid. In six patients, ranitidine dosages were increased to 3.9+/-0.6 mg/kg/day due to low pH and/or positive guaiac results. In two of these neonates, gastric pH remained below 4.0 in nine of 35 pH measurements despite increased ranitidine dosing. Guaiac results remained positive in all subsequent aspirates in five out of six of these neonates. No neonates developed clinically significant upper gastrointestinal bleeding (UGIB).

CONCLUSIONS

Gastric pH is variable in neonates receiving histamine2-receptor antagonist and antacid therapy during ECMO, and gastric pH of 4.0 or greater does not decrease the frequency of guaiac-positive aspirates. Higher gastric pH measurements are confounded by duodenogastric reflux and the presence of blood and/or antacid in gastric fluid. Motility agents in combination with acid suppression therapy for prevention of UGIB may be necessary in this setting based on gastric pH measurements, appearance of gastric aspirates, and guaiac testing.

Establishment of enteral nutrition: prokinetic agents and small bowel feeding tubes

PURPOSE OF REVIEW

Nutritional support is vital to improving the clinical outcomes in patients in the intensive care unit. Enteral nutrition should be administered early and aggressively, thereby reducing the need for parenteral nutrition. Because nasogastric feeding is often associated with gastrointestinal intolerance, recent research has focused on the use of prokinetic agents or small bowel feeding tubes to enhance the successful establishment and maintenance of enteral nutrition.

RECENT FINDINGS

Prokinetic agents (such as metoclopramide and erythromycin) improve markers of gastric emptying and appear to improve tolerance of enteral nutrition, although their effects on clinical outcomes are not as well established. In comparison with nasogastric feeding, small bowel feeding allows the dysfunctional stomach of the critically ill to be bypassed, thereby reducing the rate of gastrointestinal complications and probably the risk of pneumonia. Small bowel tubes are more difficult to place than nasogastric tubes, although the new Tiger tube appears very promising.

SUMMARY

Nasogastric feeding is preferred for almost all patients in the intensive care unit. Metoclopramide is the preferred prokinetic agent, although whether it or erythromycin should be administered to all patients in the intensive care unit or only those with gastrointestinal intolerance remains unknown. Small bowel feeding is not currently recommended for all patients in the intensive care unit because the benefits do not appear to outweigh the logistic and cost considerations. Nevertheless, when gastrointestinal intolerance develops in a nasogastrically fed patient, a small bowel feeding tube should be inserted at the earliest opportunity.

Nutrition given to critically ill patients during high level/complex care (on Italian ICUs)

BACKGROUND & AIMS

Within a prospective study on costs in 45 Italian intensive units we reviewed nutrition support practice given during critical illness.

METHODS

From June to October 1999, patients with an ICU stay longer than 47 h were studied. Nutrition (i.e. fasting, parenteral, enteral and mixed) and calorie supply by the enteral route were monitored during the first consecutive days (up to seven) of invasive support of organ failure (high-care).

RESULTS

388 patients received high-care for at least 1 day, 200 patients had seven consecutive high-care-days. Some form of nutrition was given in 90.7% of patients, 9.3% were never fed (25.8% of the cardiac patients). Parenteral nutrition was given in 13.9% of patients (78.9% of the abdominal surgery patients), 39.7% received only enteral nutrition, and 36.4% received mixed nutrition. Finally, 77.1% of the patients received nutrient by gut. Nutrition was given in 78.5% of 2115 collected days, 44.1% of the first high-care-days and 93.5% of the 7th days were positive for nutrition. Enteral calorie load on the first day was similar for enteral and mixed nutrition (range 8-14 kcal/kg), it was higher for exclusive enteral nutrition between the 4th and the 7th day (15-19 vs. 11-14 kcal/kg). It differed according to diagnosis group.

CONCLUSIONS

In Italian ICUs, in complex critically ill patients, nutrition is consistently given in critical illness, gut is widely used except in abdominal surgery patients.

Outcomes in critically ill patients before and after the implementation of an evidence-based nutritional management protocol

OBJECTIVE

To determine whether the implementation of a nutritional management protocol in the ICU leads to the increased use of enteral nutrition, earlier feeding, and improved clinical outcomes in patients.

DESIGN

Prospective evaluation of critically ill patients before and after the introduction of an evidence-based guideline for providing nutritional support in the ICU.

SETTING

The medical-surgical ICUs of two teaching hospitals.

PATIENTS

Two hundred critically ill adult patients who remained npo > 48 h after their admission to the ICU. One hundred patients were enrolled into the preimplementation group, and 100 patients were enrolled in the postimplementation group.

INTERVENTION

Implementation of an evidence-based ICU nutritional management protocol.

MEASUREMENT AND RESULTS

Nutritional outcome measures included the number of patients who received enteral nutrition, the time to initiate nutritional support, and the percent caloric target administered on day 4 of nutritional support. Clinical outcomes included the duration of mechanical ventilation, ICU and in-hospital length of stay (LOS), and in-hospital mortality rates. Patients in the postimplementation group were fed more frequently via the enteral route (78% vs 68%, respectively; p = 0.08), and this difference was statistically significant after adjusting for severity of illness, baseline nutritional status, and other factors (odds ratio, 2.4; 95% confidence interval [CI], 1.2 to 5.0; p = 0.009). The time to feeding and the caloric intake on day 4 of nutritional support were not different between the groups. The mean (+/- SD) duration of mechanical ventilation was shorter in the postimplementation group (17.9 +/- 31.3 vs 11.2 +/- 19.5 days, respectively; p = 0.11), and this difference was statistically significant after adjusting for age, gender, severity of illness, type of admission, baseline nutritional status, and type of nutritional support (p = 0.03). There was no difference in ICU or hospital LOS between the two groups. The risk of death was 56% lower in patients who received enteral nutrition (hazard ratio, 0.44; 95% CI, 0.24 to 0.80; p = 0.007).

CONCLUSION

An evidence-based nutritional management protocol increased the likelihood that ICU patients would receive enteral nutrition, and shortened their duration of mechanical ventilation. Enteral nutrition was associated with a reduced risk of death in those patients studied.

Is parenteral nutrition really that risky in the intensive care unit?

PURPOSE OF REVIEW

Although enteral nutrition is now the mainstay of nutrition delivery within intensive care, there is a blind faith in its benefits and a disregard of its risks. This has led to the belief that parenteral nutrition is no longer required as it is fraught with risks to the patient. This review attempts to dispel these myths and compares and contrasts the risks of enteral nutrition with those of parenteral nutrition in the critically ill.

RECENT FINDINGS

A greater appreciation of the failings and risks associated with the delivery of enteral nutrition combined with improvements in the formulation and use of parenteral nutrition help explain why parenteral nutrition is not as risky as some have believed. Recent evidence has suggested that enteral nutrition in a few selected circumstances may even carry a higher mortality risk. Real outcome benefits have been described with the new glutamine-containing parenteral nutrition formulations.

SUMMARY

Parenteral nutrition remains a valuable yet challenging weapon in our therapeutic armoury in the presence of gastrointestinal feed intolerance or failure. However, it should be used wisely and not indiscriminately because the majority of intensive care unit patients with a fully functional gastrointestinal tract may be fed safely with enteral nutrition.

Early enteral nutrition in mechanically ventilated patients in the prone position

OBJECTIVE

To assess the tolerance of early enteral nutrition in critically ill patients receiving invasive mechanical ventilation in the prone position.

DESIGN

Prospective, comparative study.

SETTING

General intensive care unit in a university-affiliated hospital.

PATIENTS

A total of 71 consecutive patients receiving invasive mechanical ventilation with early nasogastric enteral nutrition were studied for 5 days while being treated continuously in the supine position (supine position group, n = 37) or with intermittent prone positioning for severe hypoxemia (prone position group, n = 34).

INTERVENTIONS

Inclusion occurred within 24 hrs of mechanical ventilation initiation. Daily 18-hr enteral nutrition via a 14F gastric tube was initiated. Prone position patients were turned every 6 hrs as long as PaO2/FiO2 remained at <150, with a FiO2 of 0.6 and positive end-expiratory pressure of 10; the head was slightly elevated. When supine, patients in both groups were semirecumbent. Residual gastric volume was measured every 6 hrs, and enteral nutrition was discontinued if it exceeded 250 mL or vomiting occurred.

MEASUREMENTS AND MAIN RESULTS

The groups were similar for age, sex, Simplified Acute Physiology Score II, mortality, and risk factors for enteral nutrition intolerance. At baseline, PaO2/FiO2 was lower in prone position patients than in supine position patients (127 +/- 55 vs. 228 +/- 102; p <.001). As compared with supine position patients, prone position patients had significantly greater residual gastric volumes on days 1, 2, and 4 and experienced more vomiting episodes (median, 1 [interquartile range, 0-2] vs. 0 [interquartile range, 0-1]; p <.05). Enteral nutrition was stopped in 82% of prone position patients and 49% of supine position patients (p <.01) so that daily enteral nutrition volumes were lower with prone position patients. In the prone position group, vomiting occurred more frequently in the prone than in the supine position (relative risk, 2.5; 95% confidence interval, 1.5-4.0; p <.001).

CONCLUSION

In critically ill patients receiving invasive mechanical ventilation in the prone position, early enteral nutrition is poorly tolerated. Prokinetic agents or transpyloric feeding and semirecumbency should be considered to enhance gastric emptying and to prevent vomiting in patients receiving mechanical ventilation in the prone position.

The problem of gastric atony

Normal gastrointestinal motility is crucial for maintaining an appropriate balance of microorganisms within the gut. Disruption of this system results in bacterial overgrowth and associated complications such as bacterial translocation, aspiration pneumonia, and sepsis. Critically ill animals are at increased risk of developing gastroparesis caused by primary gastrointestinal disturbances or severe metabolic derangements that impact gastrointestinal function. In the intensive-care setting, delayed gastric emptying complicates enteral nutrition, and the catabolic effects of severe illness further deplete the patient's caloric reserves, resulting in impaired wound healing, decreased immune function, and increased morbidity and mortality. The use of promotility drugs in critically ill patients is a safe, effective means to circumvent the problem of gastric atony and improve patient recovery. Understanding the drugs available and their interaction with the receptors involved in neuromuscular transmission within the gastrointestinal tract will aid the clinician in selecting the optimal prokinetic therapy.

Nutritional support in critical care

Despite the key role of nutrition in health and the almost universal use of supplemental feeding in the ICU, there is a lack of high-quality evidence to guide clinical practice. Enteral nutrition is superior to TPN in almost all circumstances and most patients in the ICU can be fed successfully by this route. There is little evidence to support the use of special feeds and the role of immunonutrients remains unproven. Nutritional support cannot completely prevent the adverse effects of catabolic illness and overfeeding should be avoided.

Specialized nutrition support in critically ill patients

How nutritional therapy may affect real clinical outcomes is not readily apparent from a superficial reading of current data. Despite great claims in reducing infectious incidence, many studies show little difference in meaningful clinical outcomes. This has led to confusion over the role of nutrition and nutrition practice in intensive care. However, the role that nutrition plays in preventing infection and later how nutrition aids long-term recovery perhaps explain many of the misconceptions and difficulty in understanding the evidence. Encouraging new evidence is starting to show that outcome can be improved by implementing relatively simple therapies well that have an impact on nutrition and metabolic control.

Gastrointestinal disorders of the critically ill. Systemic consequences of ileus

Ileus refers to the partial or complete blockage of the small and/or large intestine either by functional (adynamic or paralytic ileus) or mechanical bowel obstruction. The diffuse gastrointestinal dysmotility during functional and mechanical ileus may result in intestinal dilatation, increased luminal pressure and gut wall ischaemia which may lead to increased intra-abdominal pressure (IAP). Any type of ileus may promote abdominal fluid sequestration with severe systemic hypovolaemia, intestinal bacterial overgrowth with the evolution of bacterial translocation and systemic invasive infections and inflammation of the intestinal wall with concomitant release of cytokines and the development of the systemic inflammatory response syndrome. The most serious complications of ileus are mediated by an increase in IAP. Intra-abdominal hypertension has been found in up to 20% of critically ill patients and may lead to a broad pattern of systemic consequences with multiple organ dysfunction, including cardiovascular, hepatic, pulmonary, renal and neurological function. The abdominal compartment syndrome is an emergency condition which is defined as elevation of IAP above 20 to 25 mmHg and the presence of systemic consequences. Therapeutic considerations include the maintenance of adequate hydration status, avoidance of drugs known to impair intestinal perfusion, stimulation of gastric and intestinal motility and various nutritional aspects. Colonic tube placement after decompressive colonoscopy may be effective in reducing intestinal dilatation. In the abdominal compartment syndrome the 'open abdominal approach' with decompressive laparotomy by opening the peritoneal cavity and temporary abdominal closure is the therapy of choice.

Nutrition support in critically ill septic patients

PURPOSE OF REVIEW

Infection and sepsis remain major challenges in the critically ill. How nutritional therapy can effect real clinical outcomes is not easily apparent from the clinical data. Despite reducing infectious incidence, many studies show little difference in meaningful clinical outcomes.

RECENT FINDINGS

Confusion over the role that nutrition and nutrition practice in intensive care plays in preventing infection, and later how nutrition aids recovery from sepsis perhaps explains many of the misconceptions and difficulties with the evidence.

SUMMARY

Encouraging new evidence will help our decision making and shows that outcome can be improved by performing relatively simple therapies well.

Prokinetic agents in critical care

Prokinetic agents are commonly used in intensive care, mainly to aid in early enteral feeding. The present commentary reviews some of the recently published papers and highlights the lack of a sizable evidence base, as well as the possible importance of euglycaemia in this important clinical area.