The paracetamol absorption test: a useful addition to the enteral nutrition algorithm?

Impact of GLP-1 Receptor Agonists in Gastrointestinal Endoscopy: An Updated Review

Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) have become one of the most popular medications for patients with diabetes and obesity. Due to their effects on gut motility via central or parasympathetic pathways, there have been concerns about an increased incidence of retained gastric contents and risk of aspiration in the perioperative period. Hence, the American Society of Anesthesiologists (ASA) recommends holding GLP-1 RAs on the procedure day or a week before the elective procedure based on the respective daily or weekly formulations, regardless of the dose, indication (obesity or diabetes), or procedure type. On the contrary, the American Gastroenterological Association (AGA) advises an individualized approach, stating that more data are needed to decide if and when the GLP-1 RAs should be held prior to elective endoscopy. Several retrospective and prospective studies, along with meta-analyses, have been published since then evaluating the role of GLP-1 RAs in patients scheduled for endoscopic procedures. In this review, we discuss the current clinical guidelines and available studies regarding the effect of GLP-1 RAs on GI endoscopies.

Impact of glucagon-like peptide receptor agonists on endoscopy and its preoperative management: Guidelines, challenges, and future directions

Glucagon-like peptide receptor agonists (GLP-1RA) are used to treat type 2 diabetes mellitus and, more recently, have garnered attention for their effectiveness in promoting weight loss. They have been associated with several gastrointestinal adverse effects, including nausea and vomiting. These side effects are presumed to be due to increased residual gastric contents. Given the potential risk of aspiration and based on limited data, the American Society of Anesthesiologists updated the guidelines concerning the preoperative management of patients on GLP-1RA in 2023. They included the duration of mandated cessation of GLP-1RA before sedation and usage of "full stomach" precautions if these medications were not appropriately held before the procedure. This has led to additional challenges, such as extended waiting time, higher costs, and increased risk for patients. In this editorial, we review the current societal guidelines, clinical practice, and future directions regarding the usage of GLP-1RA in patients undergoing an endoscopic procedure.

Clinical Experience, Characteristics, and Performance of an Acetaminophen Absorption Test in Critically Ill Patients

BACKGROUND

Altered drug and nutrient absorption presents a unique challenge in critically ill patients. Performing an acetaminophen absorption test (AAT) has been used as a marker for gastric motility and upper small bowel absorption; thus, it may provide objective data regarding enteral absorptive ability in critically ill patients.

STUDY QUESTION

What is the clinical experience with AAT when used as a surrogate marker for enteral absorption in critically ill patients?

STUDY DESIGN

This single-center, retrospective, cohort study evaluated serum acetaminophen concentrations within 180 minutes following 1-time enteral administration of an AAT. Patients admitted to the surgical and medical intensive care units and medical intensive care units over a 7-year period were evaluated. Groups were defined as positive (acetaminophen concentration of ≥10 mg/L) or negative (acetaminophen concentration of <10 mg/L) AAT.

MEASURES AND OUTCOMES

The outcomes were to describe the clinical experience, characteristics, and performance of AAT.

RESULTS

Forty-eight patients were included. Patients were 58.5 ± 14 years of age, mostly male (58.3%), and admitted to the surgical intensive care unit (66.7%). Median hospital length of stay was 47.5 (27-78.8) days. Thirty-four patients (70.8%) had a positive AAT [median concentration, 14 (12-18) mg/L]. Median time to first detectable concentration was 37 (33-64) minutes. AAT characteristics were similar between the groups including total dose, weight-based dose, time to first and second assays, drug formulation, and site of administration between groups. There were no independent risk factors identified on regression analysis for negative AAT.

CONCLUSIONS

An acetaminophen dose of 15 mg/kg with 2 coordinated serum concentrations approximately 30 and 60 minutes after administration is a reasonable construct for AAT. Future research is needed to assess AAT utility, safety, and clinical outcomes for predicting patient ability to absorb enteral feeds and medications.

An examination of gastrointestinal absorption using the acetaminophen absorption test in critically ill patients with COVID-19: A retrospective cohort study

OBJECTIVE

Gastrointestinal (GI) dysfunction is prevalent in critically ill patients with coronavirus disease 2019 (COVID-19). The acetaminophen absorption test (AAT) has been previously described as a direct method for assessment of GI function. Our study determines whether the AAT can be used to assess GI function in critically ill COVID-19 patients, compared with traditional measures of GI function.

DESIGN

Retrospective observational study of critically ill patients with COVID-19.

SETTING

Three intensive care units at a tertiary care academic medical center.

PATIENTS

Twenty critically ill patients with COVID-19.

INTERVENTIONS

The results of AAT and traditional measures for assessing GI function were collected and compared.

MEASUREMENTS AND MAIN RESULTS

Among the study cohort, 55% (11 of 20) of patients had evidence of malabsorption by AAT. Interestingly, all patients with evidence of malabsorption by AAT had clinical evidence of bowel function, as indicated by stool output and low gastric residuals during the prior 24 h. When comparing patients with a detectable acetaminophen level (positive AAT) with those who had undetectable acetaminophen levels (negative AAT), radiologic evidence of ileus was less frequent (20 vs 88%; P = .03), tolerated tube-feed rates were higher (40 vs 10 ml/h; P =.01), and there was a trend toward lower gastric residual volumes (45 vs 830 ml; P =.11).

CONCLUSION

Malabsorption can occur in critically ill patients with COVID-19 despite commonly used clinical indicators of tube-feeding tolerance. The AAT provides a simple, rapid, and cost-effective mechanism by which enteral function can be efficiently assessed in COVID-19 patients.

The efficacy and safety of itopride in feeding intolerance of critically ill patients receiving enteral nutrition: a randomized, double-blind study

BACKGROUND

Enteral feeding intolerance (EFI) is a frequent problem in the Intensive care unit (ICU) and is associated with poor clinical outcomes leading to worse prognosis in terms of mortality and ICU stay. Nowadays, prokinetic drugs are the mainstay of therapy in EFI. However, available prokinetics have uncertain efficacy and safety profiles. Itopride, is a prokinetic agent which is different and unique from the available prokinetics because of its dual mode of action as well as its tolerability and safety. The current study compared the efficacy and safety of Itopride against metoclopramide for EFI in critically ill patients. Moreover, it tested the utility and applicability of ultrasonography to measure gastric residual volume (GRV) in this population.

METHODS

This randomized, double-blind study included 76 EFI patients who were randomly assigned to either Itopride or metoclopramide group. The primary outcome was to measure GRV by ultrasonography. Secondary outcomes included the percentage ratio of enteral feed volume, energy and protein received by patients over 7 days of treatment, ICU length of stay, safety parameters and occurrence of infectious complications or vomiting.

RESULTS

Thirty-five patients of each group completed the study. At day 7, itopride significantly decreased GRV compared with metoclopramide group (p = 0.001). Moreover, there was a significant increase in the ratios of received enteral nutrition feed volume, calories, and protein after the one-week therapy in the itopride group more than the metoclopramide group (p = 0.001), (p = 0.002), (p = 0.01), respectively and there were no differences in any secondary outcomes or adverse events between the two groups.

CONCLUSION

In critically ill patients with EFI, itopride was well tolerated with superior efficacy to metoclopramide. In addition, we demonstrated that ultrasonography is a simple, non-invasive, inexpensive, and undemanding method for GRV measurements and can offer reliable assessments in the gastric emptying modality.

TRIAL REGISTRATION

The trial was registered in ClinicalTrials.gov (NCT03698292). Date: October 5, 2018.

How to choose the best route of feeding during critical illness

Increased and specific nutritional requirements occurring during critical illness need to be covered by appropriate administration of energy, nitrogen and micronutrients, especially in case of pre-existing malnutrition, chronic insufficient oral intakes or expected delay before recovery of eating. The use of artificial nutrition (enteral or parenteral) is recommended whenever the oral intakes are insufficient, in order to avoid the detrimental consequences of malnutrition and promote the best possible outcome of severely ill patients. This paper aims to provide an overview and practical recommendations of artificial nutrition therapy in the ICU setting.

Gastrointestinal Dysfunction and Feeding Intolerance in Critical Illness: Do We Need an Objective Scoring System?

PURPOSE OF REVIEW

Efforts to provide early enteral nutrition in critical illness are thwarted by gastrointestinal dysfunction and feeding intolerance. While many of the signs and symptoms of this dysfunction reflect gastroparesis and intestinal dysmotility, other symptoms which may or may not be related are often included such as diarrhea, bleeding, and intra-abdominal hypertension. This paper discusses the need to monitor tolerance of nutritional therapy in the critical care setting and reviews the results of those clinical trials which have helped establish objective measures, define feeding intolerance, and provide a tool to guide continued delivery of the enteral regimen.

RECENT FINDINGS

While definitions vary, the presence of gastrointestinal dysfunction and feeding intolerance correlates with adverse clinical outcomes, including prolonged duration of mechanical ventilation, greater length of stay in the intensive care unit, and increased mortality. Despite their prognostic value, it is not clear to what extent these scoring systems should direct nutritional therapy. The clinician should be astute in the careful selection of monitors, in identifying and addressing signs and symptoms of intolerance, and by responding appropriately with feeding strategies that are effective and safe. Early enteral feeding in critical illness has been shown to be optimized by following protocols which allow monitoring patient tolerance while providing individualized care.

Gastrointestinal Hormone Profiles Associated With Enteral Nutrition Tolerance and Gastric Emptying in Pediatric Critical Illness: A Pilot Study

BACKGROUND

Enteral nutrition (EN) intolerance and delayed gastric emptying are prevalent in pediatric critical illness and limit EN delivery. Gastrointestinal (GI) hormones may be associated with EN intolerance and delayed gastric emptying in this cohort.

METHODS

We determined GI hormone levels, time to achieve 50% of EN goal, and gastric emptying in critically ill children. Total amylin, active ghrelin, total glucagon-like peptide-1 (GLP-1), total gastric inhibitory polypeptide, glucagon, and total peptide-YY (PYY) were measured by multiplex assay and cholecystokinin by ELISA. Lower concentrations of acetaminophen at 1 hour (C1h, µg/mL) using the acetaminophen absorption test defined delayed gastric emptying. Correlation, regression analyses, and a principal component analysis were used to examine the association between GI hormones and time to 50% EN goal and C1h.

RESULTS

GI hormones were measured in 14 of 21 patients with gastric emptying testing; median age of 11.2 years (6.74-16.3) and 50% male. Increasing hormone levels from GI hormone profile 1 (GLP-1, glucagon, and amylin) correlated with greater time to reach 50% EN goal (R² = 0.296, P = 0.04). Decreasing hormone levels from GI hormone profile 2 (PYY and ghrelin) correlated with lower C1h and slower gastric emptying (R² = 0.342, P = 0.02).

CONCLUSION

GI hormone profiles are associated with time to achieve 50% of EN goal and gastric emptying in critically ill children. We have described a feasible model to study the role of GI hormones in this cohort, including the potential clinical applicability of GI hormone measurement in the management of delayed gastric emptying.

Enteral tolerance in critically ill patients

Enteral nutrition (EN) can maintain the structure and function of the gastrointestinal mucosa better than parenteral nutrition. In critically ill patients, EN must be discontinued or interrupted, if gastrointestinal complications, particularly vomiting and bowel movement disorders, do not resolve with appropriate management. To avoid such gastrointestinal complications, EN should be started as soon as possible with a small amount of EN first and gradually increased. EN itself may also promote intestinal peristalsis. The measures to decrease the risk of reflux and aspiration include elevation the head of the bed (30° to 45°), switch to continuous administration, administration of prokinetic drugs or narcotic antagonists to promote gastrointestinal motility, and switch to jejunal access (postpyloric route). Moreover, the control of bowel movement is also important for intensive care and management. In particular, prolonged diarrhea can cause deficiency in nutrient absorption, malnutrition, and increase in mortality. In addition, diarrhea may cause a decrease the circulating blood volume, metabolic acidosis, electrolyte abnormalities, and contamination of surgical wounds and pressure ulcers. If diarrhea occurs in critically ill patients on EN management, it is important to determine whether diarrhea is EN-related or not. After ruling out the other causes of diarrhea, the measures to prevent EN-related diarrhea include switch to continuous infusion, switch to gastric feeding, adjustment of agents that improve gastrointestinal peristalsis or laxative, administration of antidiarrheal drugs, changing the type of EN formula, and semisolidification of EN formula. One of the best ways to success for EN management is to continue as long as possible without interruption and discontinuation of EN easily by appropriate measures, even if gastrointestinal complications occur.

Gastrointestinal dysmotility in critically ill patients

Gastrointestinal (GI) motility disorders are commonly present in critical illness. Up to 60% of critically ill patients have been reported to experience GI dysmotility of some form necessitating therapeutic intervention. It has been attributed to various factors, related to both the underlying disease and the therapeutic interventions undertaken. The assessment of motility disturbances can be challenging in critically ill patients, as the available tests used to detect abnormal motility have major limitations in the setting of an Intensive Care Unit. Critically ill patients with GI dysmotility require a multifaceted treatment approach that addresses multiple causes and utilizes multiple pharmacological pathways. In this review, we discuss the pathophysiology, assessment and management of GI dysmotility in critically ill patients.

Gastric Emptying in Critically Ill Children

BACKGROUND

Delayed gastric emptying (GE) impedes enteral nutrient (EN) delivery in critically ill children. We examined the correlation between (a) bedside EN intolerance assessments, including gastric residual volume (GRV); (b) delayed GE; and (c) delayed EN advancement.

MATERIALS AND METHODS

We prospectively enrolled patients ≥1 year of age, eligible for gastric EN and without contraindications to acetaminophen. Gastric emptying was determined by the acetaminophen absorption test, specifically the area under the curve at 60 minutes (AUC₆₀). Slow EN advancement was defined as delivery of <50% of the prescribed EN 48 hours after study initiation. EN intolerance assessments (GRV, abdominal distension, emesis, loose stools, abdominal discomfort) were recorded.

RESULTS

We enrolled 20 patients, median 11 years (4.4-15.5), 50% male. Sixteen (80%) patients had delayed GE (AUC₆₀ <600 mcg·min/mL) and 7 (35%) had slow EN advancement. Median GRV (mL/kg) for patients with delayed vs normal GE was 0.43 (0.113-2.188) vs 0.89 (0.06-1.91), P = .9635. Patients with slow vs rapid EN advancement had median GRV (mL/kg) of 1.02 mL/kg (0.20-3.20) vs 0.27 mL/kg (0.06-1.62), P = .3114, and frequency of altered EN intolerance assessments of 3/7 (42.9%) vs 5/13 (38.5%), P = 1. Median AUC₆₀ for patients with slow vs rapid EN advancement was 91.74 mcg·min/mL (53.52-143.1) vs 449.5 mcg·min/mL (173.2-786.5), P = .0012.

CONCLUSIONS

A majority of our study cohort had delayed GE. Bedside EN intolerance assessments, particularly GRV, did not predict delayed GE or rate of EN advancement. Delayed gastric emptying predicted slow EN advancement. Novel tests for delayed GE and EN intolerance are needed.

Effect of Feeding-Tube Properties on Residual Volume Measurements in Tube-Fed Patients

BACKGROUND

The effect of feeding tube size and port configuration on the ability to measure gastric residual volume (GRV) is poorly understood. In addition, there is confusion about the need to measure GRVs during feedings into the small bowel. This study sought to (1) compare the volume of gastric contents obtained from small-diameter feeding tubes and large-diameter sump tubes concurrently positioned in the stomach and (2) describe the distribution of GRVs during small-bowel feedings.

METHODS

For the first objective, GRV measurements were made from 10-Fr tubes (n = 645) and 14-Fr or 18-Fr sump tubes (n = 645) concurrently present in 62 critically ill patients. Sixty-milliliter syringes were used to measure GRVs from the 10-Fr tubes; the fluid was returned to the stomach and measurements were repeated from the large-diameter sump tubes. To address the second research objective, 890 GRV measurements were made from 14-Fr or 18-Fr gastric sump tubes (not connected to suction) in 75 critically ill patients who were receiving small-bowel feedings.

RESULTS

When GRVs were >50 mL, a linear regression equation indicated that volumes obtained from the large-diameter sump tubes were about 1.5 times greater than those obtained from the small-diameter tubes concurrently present in the stomach, p < .001. Gastric volumes > or =100 mL were found in 11.6% of the 890 measurements made in patients receiving small-bowel feedings; volumes > or =150 mL were found in 5.4% of the measurements.

CONCLUSIONS

The findings suggest that GRVs obtained from large-diameter sump tubes are about 1.5 times greater than those obtained from 10-Fr tubes. Large GRVs occur in at least 5% of patients receiving postpyloric feedings.

Measurement of gastric emptying in the critically ill

BACKGROUND & AIMS

Enteral nutrition is important in critically ill patients and is usually administered via a nasogastric tube. As gastric emptying is frequently delayed, and this compromises the delivery of nutrient, it is important that the emptying rate can be quantified.

METHODS

A comprehensive search of MEDLINE/PubMed, of English articles, from inception to 1 July 2014. References of included manuscripts were also examined for additional studies.

RESULTS

A number of methods are available to measure gastric emptying and these broadly can be categorised as direct- or indirect-test and surrogate assessments. Direct tests necessitate visualisation of the stomach contents during emptying and are unaffected by liver or kidney metabolism. The most frequently used direct modality is scintigraphy, which remains the 'gold standard'. Indirect tests use a marker that is absorbed in the proximal small intestine, so that measurements of the marker, or its metabolite measured in plasma or breath, correlates with gastric emptying. These tests include drug and carbohydrate absorption and isotope breath tests. Gastric residual volumes (GRVs) are used frequently to quantify gastric emptying during nasogastric feeding, but these measurements may be inaccurate and should be regarded as a surrogate measurement. While the inherent limitations of GRVs make them less suitable for research purposes they are often the only technique that is available for clinicians at the bedside.

CONCLUSIONS

Each of the available techniques has its strength and limitations. Accordingly, the choice of gastric emptying test is dictated by the particular requirement(s) and expertise of the investigator or clinician.

Prokinetic drugs for gastric emptying in critically ill ventilated patients: Analysis through breath testing

PURPOSE

The prupose was to identify, through the BreathID automatic breath-testing device, the best prokinetic therapy to enhance gastric-emptying rate (GER) in ventilated intensive care unit patients.

MATERIALS AND METHODS

This was a prospective, crossover, nonrandomized study. Consecutive ventilated patients who could be fed enterally and expected to require 5 days of ventilation were included. (13)C-labeled-acetate in 100 mL Osmolite (BreathID; Exalenz Bioscience Ltd, Jerusalem, Israel) was administered intragastrically and followed by a 4-hour continuous recording of expiratory (13)CO2 by the BreathID. Prokinetics were changed daily: (1) baseline (no prokinetic), (2) intravenous (IV) metoclopramide (10 mg every 6 hours), (3) IV metoclopramide (10 mg every 6 hours) and continuous low-dose erythromycin (10 mg/h), (4) IV continuous low-dose erythromycin alone (10 mg/h), and (5) IV bolus erythromycin (200 mg every 12 hours). Gastric-emptying rate was assessed by the percentage dose recovered (PDR)-change from time 0 of the recording in the ratio of (13)CO2/(12)CO2 in exhaled gases (%/h). We used PDR peak values and time to peak (minutes to reach PDR peak) to express GER.

RESULTS

In the first 17 patients (group A), baseline GER measurements preceded prokinetic therapy. In the subsequent 14 patients (group B), 2 prokinetic regimens preceded baseline. No order-time effect was observed, justifying pooled analysis of all 31 patients. Combined metoclopramide-continuous low-dose erythromycin yielded significantly higher PDR peak and shorter time to peak vs baseline (P = .0001, P = .005, respectively). The PDR peak was also significantly higher from baseline during continuous low-dose administration of erythromycin alone (P = .004). Metoclopramide alone did not improve GER significantly.

CONCLUSIONS

Combined metoclopramide-continuous low-dose erythromycin was found to be the best protocol in the current study to increase GER in ventilated patients. It should be tested as a first-line prokinetic therapy in ventilated patients with poor gastric emptying in further randomized controlled studies. The breath-test device presented in this study can be a user-friendly and practical method to monitor GER, enabling individual tailoring of prokinetic therapy. Further studies to explore its utility are warranted.

Corticotropin-releasing factor is present in intestinal tissue of patients with gastrointestinal dysfunction following shock and abdominal surgery

OBJECTIVE

Corticotropin-releasing factor (CRF) is implicated in stress-related gastrointestinal dysfunction, possibly causing gut dysfunction following trauma and surgery. We investigated plasma and intestinal tissue CRF levels and gut function in patients with traumatic shock or those undergoing elective abdominal surgery.

RESEARCH METHODS AND PROCEDURES

In a prospective, parallel, observational study in a university hospital surgical intensive care unit (ICU), 8 shocked patients (systolic blood pressure <90 mmHg and/or acidosis and/or urine output <1 mL/kg/hr and/or requiring >2 L of intravenous fluid resuscitation) undergoing small bowel resection during emergency laparotomy following abdominal injury and 17 stable patients undergoing elective hepatobiliary surgery were included if they required postoperative ICU management. Serial plasma and intestinal CRF was measured and postoperative gastric emptying and intestinal permeability were evaluated.

RESULTS

Plasma CRF was significantly increased in the shocked patients compared with the elective surgery patients at all times. CRF peptide was quantified in intestinal tissue at similar levels in both groups. Intestinal permeability was increased and associated with shock and resuscitation fluid volume. Gastric emptying was retarded and correlated significantly with shock but not with plasma CRF. Delayed gastric emptying in shocked patients was associated with longer ICU stay.

CONCLUSIONS

The novel finding is the presence of CRF in the small bowel of both elective and emergency gastrointestinal surgery patients with concomitant gastrointestinal dysfunction. Circulating CRF is associated with poor gastric emptying, which prolongs ICU stay, whereas shock significantly impairs gastric emptying and gut permeability.

Gastric residual volumes in critical illness: what do they really mean?

The practice of measuring gastric residual volumes (GRVs) has become a routine part of enteral feeding protocols in the critical care setting. However, little scientific evidence indicates that their use improves patient outcomes. The use of GRVs is more of a tradition, which unfortunately guides the delivery of enteral nutrition (EN). The practice of GRVs is predicated on several flawed assumptions. Using GRVs in hospitalized patients assumes that the practice is well standardized, that GRVs reliably and accurately measure gastric contents, and that they sufficiently distinguish normal from abnormal emptying. The practice also assumes that GRVs are easy to interpret, that a tight correlation exists between GRVs and aspiration, and that continuing EN after a high value for GRV is obtained leads to pneumonia and adverse patient outcomes. And finally, clinicians assume that GRVs are an inexpensive "poor man's test" for determining tolerance of EN. This article reviews studies showing the fallacies of these assumptions. Although clinicians are unlikely to stop using GRVs, interpretation of these must be modified so as not to interrupt the delivery of EN. Using a protocol that directs appropriate responses to elevated GRVs should promote the delivery of EN and improve patient outcome.

Altered GI motility in critically Ill patients: current understanding of pathophysiology, clinical impact, and diagnostic approach

Gastrointestinal (GI) motility disturbances are common in critically ill patients. GI tract dysmotility has been linked to increased permeability of intestinal mucosa and bacterial translocation, contributing to systemic inflammatory response syndrome, sepsis, and multiple organ dysfunction syndrome. A key issue in providing nutrition to critically ill patients is intolerance of enteral feeding as a result of impaired GI motility. Remarkable progress has been made in the understanding of the regulation of GI motility in critical illness. Predominant motility abnormalities seen in ICU patients include antral hypomotility, delayed gastric emptying, and reduced migrating motor complexes. The diagnosis of motility disturbances can be challenging to establish in critically ill patients. The available tests used for detection of abnormal motility have major limitations in the ICU setting. Recognition of the type and site of intestinal motility disorder is important to guide the therapy and improve the outcome.

Methods for the assessment of gastric emptying in critically ill, enterally fed adults

Critically ill patients may experience delayed gastric emptying. Patients receiving enteral feeding are monitored closely to detect a delay of gastric emptying, assess feeding tolerance, and prevent aspiration pneumonia. The most common practice for assessing gastric emptying is to measure the aspirated gastric residual volume; however, this is an unreliable method that lacks standardization, fails to differentiate normal digestive secretions from enteral formula, and results in unnecessary interruptions of enteral nutrition. The aim of this review is to identify an alternative method to assess gastric emptying, which should be reliable, sensitive, harmless, feasible, and inexpensive. Several techniques are discussed: scintigraphy, paracetamol absorption test, breath tests, refractometry, ultrasound, and gastric impedance monitoring. Refractometry seems to be the most appropriate tool for the regular assessment of enteral nutrition; however, standardization and validation of this method are needed before it can be routinely used to monitor critically ill patients receiving enteral nutrition.

Gastric emptying: a comparison of three methods

OBJECTIVE

A better understanding of the clinical relevance of delayed gastric emptying (e.g. in diabetes) requires a simple, easily accessible and inexpensive method for measuring it. Two "new" methods for measuring gastric emptying of liquids (the paracetamol absorption test and the 13C-acetate breath test) are compared with the gold standard (gastric emptying scintigraphy (GES)).

MATERIAL AND METHODS

The three techniques were used simultaneously in 10 healthy subjects. A gastric emptying time-retention curve was drawn for each technique and the results were compared at the 75%, 50% and 25% retention quartiles.

RESULTS

Agreement was found between the paracetamol absorption test and GES (p=0.95; Hotelling's T 2 test). Using the Wagner-Nelson one compartment correction produced a retention curve for the 13C-acetate breath test statistically significantly below GES (p<0.01).

CONCLUSION

In healthy subjects, the paracetamol absorption test produced results comparable to those of liquid GES, but not to the results of the 13C-acetate breath test.

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.

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.

The effect of metoclopramide on gastric emptying in traumatic brain injury

OBJECTIVE

Gastric paresis in traumatic brain injury (TBI) hinders the effectiveness of enteral support in this patient group. In this study we have investigated the effect of metoclopramide on gastric emptying in TBI patients.

METHOD

In this prospective, randomized, controlled, double-blind study, 19 TBI patients with Glasgow Coma Scale scores of 3-11 were included. In all patients, enteral nutrition was commenced with a nasogastric feeding tube within 48 hours of trauma. Patients were randomized into two groups. In the metoclopramide (M) group, 10 mg metoclopramide was delivered intravenously three times daily for 5 days. In the control (C) group, an equal volume of saline was administered. Besides demographics, gastric emptying according to a paracetamol absorption test at days 0 and 5, time to reach target nutritional requirements, gastric residues, intolerance to feeding, nutritional complications, and clinical outcomes were recorded for each patient.

RESULTS

The gastric residue rates were 2.7+/-7.4 mL and 8.1+/-17.7 mL per 100 patient days for groups C and M respectively (p=0.408). Similarly, feeding intolerance and complication rates did not significantly differ between groups C and M, (respectively p=0.543 and 0.930). Gastric emptying parameters also were similar between the study groups.

CONCLUSION

We were unable to document any advantage to using metoclopramide in TBI patients. Simple intragastric enteral feeding with close monitoring of the possible complications seems to be sufficient with acceptable morbidity rates.

Nutrition support in acute pancreatitis

The benefit of early enteral nutrition (EN) for the disease process and for patient outcome in severe acute pancreatitis is dramatic. A narrow window of opportunity exists during which there is potential for EN to decrease disease severity and reduce overall complications. Most patients with severe pancreatitis tolerate enteral feeds. Any signs of symptom exacerbation or increasing inflammation in response to EN may be ameliorated by subtle adjustments in the feeding strategy. In this manner, provision of EN represents primary therapy in the management of the patient with acute pancreatitis and is emerging as the gold standard of therapy in nutrition support for this disease process.

Preventing Respiratory Complications of Tube Feedings: Evidence-Based Practice

The most dreaded complication of tube feedings is tracheobronchial aspiration of gastric contents. Strong evidence indicates that most critically ill tube-fed patients receiving mechanical ventilation aspirate gastric contents at least once during their early days of tube feeding. Those who aspirate frequently are about 4 times more likely to have pneumonia develop than are those who aspirate infrequently. Although a patient’s illness might not be modifiable, some risk factors for aspiration can be controlled; among these are malpositioned feeding tubes, improper feeding site, large gastric volume, and supine position. A review of current research-based information to support modification of these risk factors is provided.

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.

Gastric residual volumes in critically ill paediatric patients: a comparison of feeding regimens

This study examined the effect of gastric feeding regimens, either continuous or intermittent, on fourth hourly gastric residual volumes (GRV) in a group of critically ill paediatric patients where delayed gastric emptying is defined as a GRV greater than 5ml/kg. A randomised controlled trial was conducted in a tertiary paediatric intensive care unit (PICU), with 45 participants being randomly assigned to either the continuous (n=22) or intermittent (n=23) gastric feeding groups. Participants remained in the assigned group for the duration of the study and, fourth hourly, GRV were assessed to monitor the incidence of delayed gastric emptying. Both groups were similar in age, weight, gender, diagnosis, paediatric index mortality (PIM) score, and usage of pharmacological agents known to affect the gastrointestinal tract. No differences emerged in study duration or the volume of administered enteral formula (ml/kg/day). The intermittent feeding group commenced enteral feeding earlier in the PICU admission (13.0 hours versus 18.5 hrs, p=0.05). Repeated measures analysis revealed no overall difference in median GRV/kg values between treatment groups over the 72 hour study period. Additionally, the incidence of fourth hourly GRV, greater than 5ml/kg, was not different between the continuous and intermittent feeding groups. The provision of enteral nutrition via the gastric route is a common treatment in the PICU, and GRV are frequently used as a measure of gastric tolerance. The result of this analysis provides some support for the theoretical definition of delayed gastric emptying being >5ml/kg. However, further work is required to confirm this finding and to determine its relevance when providing enteral nutrition to the critically ill paediatric patient.

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.

Effect of food on gastrointestinal transit of liquids in cynomolgus monkeys

We investigated the gastrointestinal transit of liquids, as well as various gastric pH profiles, in fed cynomolgus monkeys. Twelve grams of a biscuit-type solid food were provided 1 h before the test. The acetaminophen method was used to determine the gastric half-emptying time (t(50%)), which provided an estimate of the gastric emptying rate. The gastric emptying rate of liquids was significantly reduced after food intake in monkeys. The mean t(50%) value was 143.5 min and comparable to that of humans after eating. However, there was a large variability in the t(50%) between individual animals as shown by the coefficient of variance of approximately 80%. Next, the median oro-caecal transit time in fed monkeys was determined to be 1.8 h, using the sulfasalazine-sulfapyridine method. There was no significant difference in oro-caecal transit time between unfed and fed monkeys; thus, food intake has no significant effect on the oro-caecal transit time of liquids in either monkeys or humans. However, the oro-caecal transit time in humans is about 2 h longer than that in monkeys. Our experiments using several different foods suggested that the typical human gastric pH profile could not be simulated in fed monkeys.

Clinical use of gastric residual volumes as a monitor for patients on enteral tube feeding

BACKGROUND

The use of gastric residual volumes (GRVs) as a clinical monitor for patients receiving enteral tube feeding (ETF) is based on presumptions that are not physiologically sound and practice that is poorly standardized.

METHODS

This systematic review of the medical literature summarizes results from studies that evaluate the practice, interpretation, and impact on patient outcome from use of GRV.

RESULTS

Little data exist to support a correlation of GRV with gastric emptying, volume of gastric contents, or changes in the infusion of ETF. GRVs do not correlate to regurgitation or aspiration, and their use cannot be relied on to protect patients against aspiration pneumonia. Although recent reports suggest that elevated GRVs correlate to "intolerance" of ETF, use as a marker of impending clinical deterioration is limited by the fact that the timing of increases in GRV is unpredictable and high GRVs do not correlate independently to adverse outcome. The practice of GRV may in fact impede delivery of ETF by promoting inappropriate cessation and reducing potential infusion time.

CONCLUSIONS

Modifying interpretation and the response by healthcare providers to GRV data are needed to preserve any clinical use for this practice.

Use of enteral nutrition for stress ulcer prophylaxis

OBJECTIVE

To review the controversies involving the use of enteral nutrition support for stress ulcer prophylaxis and formulate recommendations.

DATA SOURCES

A MEDLINE search (1966-December 2000) was conducted using the MeSH of nutrition, ulcer, critical care, and acid to identify relevant articles. References of selected articles were reviewed, and relevant abstracts from critical care or gastrointestinal journals identified.

DATA EXTRACTION

Animal and human data from prospective studies, retrospective studies, and case series were evaluated for the effects of enteral nutrition on gastric pH, intramucosal pH, gastrointestinal blood flow, development of macroscopic mucosal erosions, and hemorrhage.

DATA SYNTHESIS

Intragastric administration of enteral nutrition has variable effects on gastric pH, enhances regional distribution of gastrointestinal blood flow, and may lower intramucosal pH. All substrates (carbohydrate, lipid, amino acid), when administered into the stomach, reduce the occurrence of mucosal erosions but do not entirely prevent their development. Few studies of stress ulcer prophylaxis regimens have reported use of enteral nutrition. Limited retrospective data suggest enteral nutrition support may be effective for preventing gastrointestinal hemorrhage, but the results of prospective studies are confounded by poor study design.

CONCLUSIONS

Definitive recommendations regarding the role of enteral nutrition for stress ulcer prophylaxis are not possible due to the lack of prospective, randomized studies. Therefore, the use of enteral nutrition as the only therapeutic agent for stress ulcer prophylaxis should be discouraged until definitive data are available. Initiation and discontinuation of pharmacologic stress ulcer prophylaxis should be independent of enteral nutrition.

Comparison of cisapride and metoclopramide for facilitating gastric emptying and improving tolerance to intragastric enteral nutrition in critically III, mechanically ventilated adults

BACKGROUND

Placebo-controlled studies have indicated that both cisapride and metoclopramide promote gastric motility in critically ill patients.

OBJECTIVE

This study was conducted to compare cisapride and metoclopramide for facilitating gastric emptying and improving tolerance to intragastric enteral nutrition (EN) and to evaluate the relationship between aspirated gastric residual volume and gastric emptying function in this patient population.

METHODS

In this double-blind study, critically ill, mechanically ventilated patients with an aspirated gastric residual volume > or = 150 mL while receiving intragastric EN were randomized to receive enteral cisapride 10 mg or metoclopramide 10 mg every 6 hours for a total of 7 doses. The acetaminophen-absorption method was used to assess gastric emptying at baseline and 30 minutes after the seventh dose by determining the area under the plasma concentration-time curve at 240 minutes (AUC240), maximum concentration (Cmax), and time to Cmax (Tmax). Gastric residual volume was measured every 6 hours before dosing.

RESULTS

Fourteen patients were included in the study, 7 in each group. Patient characteristics were similar in the 2 groups. Compared with baseline, metoclopramide significantly accelerated Tmax (39.00 +/- 15.56 min with metoclopramide vs 103.71 +/- 47.35 min at baseline; P = 0.018) and increased Cmax (12.94 +/- 6.68 mg/L vs 6.97 +/- 4.78 mg/L; P = 0.018) and AUC240 (1,421.43 +/- 780.31 mg/L x min vs 839.00 +/- 545.58 mg/L x min; P = 0.043). Cisapride increased Cmax from baseline (12.27 +/- 8.95 mg/L vs 4.53 +/- 2.37 mg/L, respectively), but the difference was not statistically significant. Gastric residual volume was significantly reduced from baseline after 3 doses of metoclopramide (from 268.7 +/- 112.3 mL to 57.0 +/- 23.1 mL; P < 0.05) and was significantly lower after the seventh dose of metoclopramide than after the seventh dose of cisapride (5.3 +/- 8.2 mL vs 41.4 +/- 39.7 mL, respectively; P = 0.05). Cmax at baseline and residual volume at study entry were inversely correlated (r = -0.50; P = 0.049).

CONCLUSIONS

Both cisapride and metoclopramide enhanced gastric motility and improved tolerance to intragastric EN. Metoclopramide reduced gastric residual volume to a significantly greater extent than did cisapride. Only Cmax at baseline was inversely associated with residual volume.