Effect of Critical Illness on Triglyceride Absorption

BACKGROUND

Adequate nutrition support for critically ill patients optimizes outcome, and enteral feeding is the preferred route of nutrition. Small intestinal glucose absorption is frequently impaired in critical illness. Despite lipid being a major constituent of liquid nutrient administered, there is little information about lipid absorption during critical illness.

OBJECTIVES

To determine small intestinal lipid, as well as glucose, absorption in critical illness compared with health.

MATERIALS AND METHODS

Twenty-nine mechanically ventilated critically ill patients and 16 healthy volunteers were studied. Liquid nutrient (60 mL, 1 kcal/mL), containing 200 µL (13)C-triolein and 3 g 3-O-methyl-glucose (3-OMG), was infused directly into the duodenum at a rate of 2 kcal/min. Exhaled (13)CO2 and serum 3-OMG concentrations were measured at timed intervals over 360 minutes. Lipid absorption was measured as the cumulative percentage dose (cPDR) of (13)CO2 recovered at 360 minutes. Glucose absorption was measured as the area under the 3-OMG concentration curve. Data are median (range) and analyzed using the Mann-Whitney U and Pearson correlation tests.

RESULTS

Lipid absorption was markedly less in the critically ill (cPDR(13)CO2: patients, 22.6% [0%-100%] vs healthy participants, 40.7% [5.3%-84.7%]; P = .018). While glucose absorption was less at 60 minutes in the critically ill (3-OMG60: 13.2 [3.5-29.5] vs 21.1 [9.3-31.9] mmol/L·min; P = .003), this was not apparent at 360 minutes (3-OMG360: 92.7 [54.5-147.9] vs 107.9 [64.0-168.7] mmol/L·min; P = .126). There was no relationship between lipid and glucose absorption.

CONCLUSION

Small intestinal absorption of lipid is diminished during critical illness.

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.

Effects of exogenous glucagon-like peptide-1 on blood pressure, heart rate, gastric emptying, mesenteric blood flow and glycaemic responses to oral glucose in older individuals with normal glucose tolerance or type 2 diabetes

AIMS/HYPOTHESIS

A postprandial fall in BP occurs frequently in older individuals and in patients with type 2 diabetes. The magnitude of this decrease in BP is related to the rate of gastric emptying (GE). Intravenous administration of glucagon-like peptide-1 (GLP-1) attenuates the hypotensive response to intraduodenal glucose in healthy older individuals. We sought to determine the effects of exogenous GLP-1 on BP, GE, superior mesenteric artery (SMA) flow and glycaemic response to oral ingestion of glucose in healthy older individuals and patients with type 2 diabetes.

METHODS

Fourteen older volunteers (six men, eight women; age 72.1 ± 1.1 years) and ten patients with type 2 diabetes (six men, four women; age 68.7 ± 3.4 years; HbA1c 6.6 ± 0.2% [48.5 ± 2.0 mmol/mol]; nine with blood glucose managed with metformin, two with a sulfonylurea and one with a dipeptidyl-peptidase 4 inhibitor) received an i.v. infusion of GLP-1 (0.9 pmol kg(-1) min(-1)) or saline (154 mmol/l NaCl) for 150 min (t = -30 min to t = 120 min) in randomised order. At t = 0 min, volunteers consumed a radiolabelled 75 g glucose drink. BP was assessed with an automated device, GE by scintigraphy and SMA flow by ultrasonography. Blood glucose and serum insulin were measured.

RESULTS

GLP-1 attenuated the fall in diastolic BP after the glucose drink in older individuals (p < 0.05) and attenuated the fall in systolic and diastolic BP in patients with type 2 diabetes (p < 0.05). GE was faster in patients with type 2 diabetes than in healthy individuals (p < 0.05). In both groups, individuals had slower GE (p < 0.001), decreased SMA flow (p < 0.05) and a lower degree of glycaemia (p < 0.001) when receiving GLP-1.

CONCLUSIONS/INTERPRETATION

Intravenous GLP-1 attenuates the hypotensive response to orally administered glucose and decreases SMA flow, probably by slowing GE. GLP-1 and 'short-acting' GLP-1 agonists may be useful in the management of postprandial hypotension.

Management of critically ill patients with type 2 diabetes: The need for personalised therapy

Critical illness in patients with pre-existing diabetes frequently causes deterioration in glycaemic control. Despite the prevalence of diabetes in patients admitted to hospital and intensive care units, the ideal management of hyperglycaemia in these groups is uncertain. There are data that suggest that acute hyperglycaemia in critically ill patients without diabetes is associated with increased mortality and morbidity. Exogenous insulin to keep blood glucose concentrations < 10 mmol/L is accepted as standard of care in this group. However, preliminary data have recently been reported that suggest that chronic hyperglycaemia may result in conditioning, which protects these patients against damage mediated by acute hyperglycaemia. Furthermore, acute glucose-lowering to < 10 mmol/L in patients with diabetes with inadequate glycaemic control prior to their critical illness appears to have the capacity to cause harm. This review focuses on glycaemic control in critically ill patients with type 2 diabetes, the potential for harm from glucose-lowering and the rationale for personalised therapy.

Hyperglycemia potentiates the slowing of gastric emptying induced by exogenous GLP-1

OBJECTIVE

Acute hyperglycemia markedly slows gastric emptying. Exogenous GLP-1 also slows gastric emptying, leading to diminished glycemic excursions. The primary objective was to determine whether hyperglycemia potentiates the slowing of gastric emptying induced by GLP-1 administration.

RESEARCH DESIGN AND METHODS

Ten healthy participants were studied on 4 separate days. Blood glucose was clamped at hyperglycemia using an intravenous infusion of 25% dextrose (∼12 mmol/L; hyper) on 2 days, or maintained at euglycemia (∼6 mmol/L; eu) on 2 days, between t = -15 and 240 min. During hyperglycemic and euglycemic days, participants received intravenous GLP-1 (1.2 pmol/kg/min) and placebo in a randomized double-blind fashion. At t = 0 min, subjects ingested 100 g beef mince labeled with 20 MBq technetium-99m-sulfur colloid and 3 g 3-O-methyl-glucose (3-OMG), a marker of glucose absorption. Gastric emptying was measured scintigraphically from t = 0 to 240 min and serum 3-OMG taken at regular intervals from t = 15 to 240 min. The areas under the curve for gastric emptying and 3-OMG were analyzed using one-way repeated-measures ANOVA with Bonferroni-Holm adjusted post hoc tests.

RESULTS

Hyperglycemia slowed gastric emptying (eu/placebo vs. hyper/placebo; P < 0.001) as did GLP-1 (eu/placebo vs. eu/GLP-1; P < 0.001). There was an additive effect of GLP-1 and hyperglycemia, such that gastric emptying was markedly slower compared with GLP-1 administration during euglycemia (eu/GLP-1 vs. hyper/GLP-1; P < 0.01).

CONCLUSIONS

Acute administration of exogenous GLP-1 profoundly slows gastric emptying during hyperglycemia in excess of the slowing induced by GLP-1 during euglycemia. Studies are required to determine the effects of hyperglycemia on gastric emptying with the subcutaneously administered commercially available GLP-1 agonists in patients with type 2 diabetes.

Gastrointestinal dysfunction relating to the provision of nutrition in the critically ill

PURPOSE OF REVIEW

During critical illness, enteral nutrition remains central to clinical care and an understanding of gut dysfunction is therefore important. Contemporary data have contributed to our knowledge in this area and this review will concentrate on recently published studies.

RECENT FINDINGS

It is difficult to precisely measure gastric emptying and nutrient absorption as part of routine clinical care. However, techniques for the measurement of these parameters for research purposes have been refined, studied and validated. These methodologies allow the evaluation of novel treatments that modulate gastric emptying. Quantification and an understanding of the mechanisms of nutrient malabsorption may facilitate the development of therapeutic agents to improve absorption and/or formulae, which are more readily absorbed, thereby improving nutritional and clinical outcomes.

SUMMARY

Improved understanding of gut pathophysiology in critical illness provides opportunities for the development and testing of novel and targeted treatment strategies, with the objective to improve clinical outcomes in this group.

Accelerated intestinal glucose absorption in morbidly obese humans: relationship to glucose transporters, incretin hormones, and glycemia

CONTEXT

Intestinal glucose absorption is mediated by sodium-dependent glucose transporter 1 (SGLT-1) and glucose transporter 2 (GLUT2), which are linked to sweet taste receptor (STR) signaling and incretin responses.

OBJECTIVE

This study aimed to examine intestinal glucose absorption in morbidly obese humans and its relationship to the expression of STR and glucose transporters, glycemia, and incretin responses.

DESIGN/SETTING/PARTICIPANTS

Seventeen nondiabetic, morbidly obese subjects (body mass index [BMI], 48 ± 4 kg/m(2)) and 11 lean controls (BMI, 25 ± 1 kg/m(2)) underwent endoscopic duodenal biopsies before and after a 30-minute intraduodenal glucose infusion (30 g glucose and 3 g 3-O-methylglucose [3-OMG]).

MAIN OUTCOME MEASURES

Blood glucose and plasma concentrations of 3-OMG, glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide 1 (GLP-1), insulin, and glucagon were measured over 270 minutes. Expression of duodenal SGLT-1, GLUT2, and STR (T1R2) was quantified by PCR.

RESULTS

The increase in plasma 3-OMG (P < .001) and blood glucose (P < .0001) were greater in obese than lean subjects. Plasma 3-OMG correlated directly with blood glucose (r = 0.78, P < .01). In response to intraduodenal glucose, plasma GIP (P < .001), glucagon (P < .001), and insulin (P < .001) were higher, but GLP-1 (P < .001) was less in the obese compared with lean. Expression of SGLT-1 (P = .035), but not GLUT2 or T1R2, was higher in the obese, and related to peak plasma 3-OMG (r = 0.60, P = .01), GIP (r = 0.67, P = .003), and insulin (r = 0.58, P = .02).

CONCLUSIONS

In morbid obesity, proximal intestine glucose absorption is accelerated and related to increased SGLT-1 expression, leading to an incretin-glucagon profile promoting hyperinsulinemia and hyperglycemia. These findings are consistent with the concept that accelerated glucose absorption in the proximal gut underlies the foregut theory of obesity and type 2 diabetes.

Attenuated platelet aggregation in patients with septic shock is independent from the activity state of myosin light chain phosphorylation or a reduction in Rho kinase-dependent inhibition of myosin light chain phosphatase

Background

Impaired coagulation contributes to the morbidity and mortality associated with septic shock. Whether abnormal platelet contraction adds to the bleeding tendency is unknown. Platelets contract when Ca²⁺-dependent myosin light chain kinase (MLCK) phosphorylates Ser19 of myosin light chain (MLC₂₀), promoting actin-myosin cross-bridge cycling. Contraction is opposed when myosin light chain phosphatase (MLCP) dephosphorylates MLC₂₀. It is thought that Rho kinase (ROK) inhibits MLCP by phosphorylating Thr855 of the regulatory subunit MYPT, favouring platelet contraction. This study tested the hypotheses that in septic shock, (i) platelet function is inversely correlated with illness severity and (ii) ROK-dependent MLCP inhibition and myosin light chain phosphorylation are reduced.

Methods

Blood was sampled from non-septic shock patients and patients in the first 24 h of septic shock. Platelet function was assessed using whole blood impedance aggregation induced by 1) ADP (1.6 and 6.5 μM), 2) thrombin receptor-activating protein (TRAP; 32 μM), 3) arachidonic acid (500 μM) and 4) collagen (3.2 μg/ml). Arachidonic acid-induced aggregation was measured in the presence of the ROK inhibitor Y27632. Illness severity was evaluated using sequential organ failure assessment (SOFA) and acute physiology and chronic health evaluation (APACHE) II scores. Western blot analysis of [Ser19]MLC₂₀ and [Thr855]MYPT phosphorylation quantified activation and inhibition of platelet MLC₂₀ and MLCP, respectively. Data were analysed using Spearman's rank correlation coefficient, Student's t-test and Mann-Whitney test; p < 0.05 was considered significant.

Results

Agonist-induced aggregation was attenuated in septic shock patients (n = 22 to 34; p < 0.05). Aggregation correlated inversely with SOFA and APACHE II scores (n = 34; p < 0.05). Thr855 phosphorylation of MYPT from unstimulated platelets was not decreased in patients with septic shock (n = 22 to 24). Both septic shock and ROK inhibition attenuated arachidonic acid-induced platelet aggregation independent of changes in [Ser19]MLC₂₀ and [Thr855]MYPT phosphorylation (n = 14).

Conclusions

Impairment of whole blood aggregation in patients within the first 24 h of septic shock was correlated with SOFA and APACHE II scores. Attenuated aggregation was independent of molecular evidence of diminished platelet contraction or reduced ROK inhibition of MLCP. Efforts to restore platelet function in septic shock should therefore focus on platelet adhesion and degranulation.

Gastric emptying and glycaemia in health and diabetes mellitus

The rate of gastric emptying is a critical determinant of postprandial glycaemia and, accordingly, is fundamental to maintaining blood glucose homeostasis. Disordered gastric emptying occurs frequently in patients with longstanding type 1 diabetes mellitus and type 2 diabetes mellitus (T2DM). A complex bidirectional relationship exists between gastric emptying and glycaemia--gastric emptying accounts for ∼35% of the variance in peak postprandial blood glucose concentrations in healthy individuals and in patients with diabetes mellitus, and the rate of emptying is itself modulated by acute changes in glycaemia. Clinical implementation of incretin-based therapies for the management of T2DM, which diminish postprandial glycaemia, in part by slowing gastric emptying, is widespread. Other therapies for patients with T2DM, which specifically target gastric emptying include pramlintide and dietary-based treatment approaches. A weak association exists between upper gastrointestinal symptoms and the rate of gastric emptying. In patients with severe diabetic gastroparesis, pathological changes are highly variable and are characterized by loss of interstitial cells of Cajal and an immune infiltrate. Management options for patients with symptomatic gastroparesis remain limited in their efficacy, which probably reflects the heterogeneous nature of the underlying pathophysiology.

Effects of glucose-dependent insulinotropic polypeptide on gastric emptying, glycaemia and insulinaemia during critical illness: a prospective, double blind, randomised, crossover study

INTRODUCTION

Insulin is used to treat hyperglycaemia in critically ill patients but can cause hypoglycaemia, which is associated with poorer outcomes. In health glucose-dependent insulinotropic polypeptide (GIP) is a potent glucose-lowering peptide that does not cause hypoglycaemia. The objectives of this study were to determine the effects of exogenous GIP infusion on blood glucose concentrations, glucose absorption, insulinaemia and gastric emptying in critically ill patients without known diabetes.

METHODS

A total of 20 ventilated patients (Median age 61 (range: 22 to 79) years, APACHE II 21.5 (17 to 26), BMI 28 (21 to 40) kg/m(2)) without known diabetes were studied on two consecutive days in a randomised, double blind, placebo controlled, cross-over fashion. Intravenous GIP (4 pmol/kg/min) or placebo (0.9% saline) was infused between T = -60 to 300 minutes. At T0, 100 ml of liquid nutrient (2 kcal/ml) containing 3-O-Methylglucose (3-OMG), 100 mcg of Octanoic acid and 20 MBq Tc-99 m Calcium Phytate, was administered via a nasogastric tube. Blood glucose and serum 3-OMG (an index of glucose absorption) concentrations were measured. Gastric emptying, insulin and glucagon levels and plasma GIP concentrations were also measured.

RESULTS

While administration of GIP increased plasma GIP concentrations three- to four-fold (T = -60 23.9 (16.5 to 36.7) versus T = 0 84.2 (65.3 to 111.1); P <0.001) and plasma glucagon (iAUC300 4217 (1891 to 7715) versus 1232 (293 to 4545) pg/ml.300 minutes; P = 0.04), there were no effects on postprandial blood glucose (AUC300 2843 (2568 to 3338) versus 2819 (2550 to 3497) mmol/L.300 minutes; P = 0.86), gastric emptying (AUC300 15611 (10993 to 18062) versus 15660 (9694 to 22618) %.300 minutes; P = 0.61), glucose absorption (AUC300 50.6 (22.3 to 74.2) versus 64.3 (9.9 to 96.3) mmol/L.300 minutes; P = 0.62) or plasma insulin (AUC300 3945 (2280 to 6731) versus 3479 (2316 to 6081) mU/L.300 minutes; P = 0.76).

CONCLUSIONS

In contrast to its profound insulinotropic effect in health, the administration of GIP at pharmacological doses does not appear to affect glycaemia, gastric emptying, glucose absorption or insulinaemia in the critically ill patient.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry ACTRN12612000488808. Registered 3 May 2012.

Comparison of different definitions of feeding intolerance: A retrospective observational study

BACKGROUND & AIMS

While feeding intolerance (FI) is clinically important in the critically ill it is inconsistently defined. By evaluating definitions of FI based on relationships between symptoms and signs of gastrointestinal (GI) dysfunction and mortality the objective was to define FI using the definition that was most strongly associated with subsequent mortality.

METHODS

Data from all adult patients admitted to a single ICU between 2004 and 2011, and who were receiving enteral nutrition (EN), were analysed. The amount of EN administered, presence of absent bowel sounds (BS), vomiting and/or regurgitation, diarrhoea, bowel distension, and large gastric residual volumes (GRVs) were documented daily. A GRV ≥500 ml/day was considered as large and the sum of gastrointestinal (GI) symptoms including large GRV was calculated daily. Various definitions of FI were modelled. Definitions using only GRV, or GRV with other GI symptoms, or GRV and failure to reach preset EN targets were evaluated. The predictive power of FI on mortality was tested by adding the presence of FI (different definitions were tested one-by-one) into multiple regression analyses together with admission day demographic and severity of illness variables.

RESULTS

Of the 1712 patients included, 221 (12.9%) died in ICU and 495 (28.9%) had died within 90 days after ICU admission. The definition of FI based on the presence of at least three out of five GI symptoms was most strongly related to ICU-mortality (6.3% prevalence in survivors vs. 23.5% in non-survivors, p < 0.001, odds ratio (95%CI) 3.39 (2.23-5.14)), whereas EN <23% of caloric target was the strongest predictor for mortality 90 days after admission (50.7% prevalence among survivors vs 75.2% in non-survivors, p < 0.001, odds ratio (95% CI) 2.34 (1.80-3.04)).

CONCLUSIONS

FI is associated with increased mortality but the strength of this relationship depends on the definition used. The 'best' definition of FI for prediction of ICU-mortality is based on a complex assessment of GI symptoms (including large GRV), whereas enteral underfeeding is the definition of FI that is the strongest predictor of death within 90 days of admission. Our 'best' definitions are not immediately generalizable, but should help building up future studies.

International observational study of nutritional support in mechanically ventilated patients following burn injury

INTRODUCTION

It has been proposed that nutritional therapy in critically ill patients after major burn reduces mortality. However, the actual practice of nutrient delivery, and the effect on outcome, has not been described.

STUDY OBJECTIVES

To evaluate international practices related to nutritional support and outcomes in mechanically ventilated patients with burn injury.

METHODS

Data from the International Nutrition Surveys (2007-2011) for patients with a primary diagnosis of burn were extracted and analysed.

RESULTS

Eighty-eight of 90 patients (aged 16-84 years) received enteral nutrition. The median time for initiation of enteral feeding was 17 h [range 0-65]. Fifty patients (57%) had interruptions to nutrient delivery, most often these interruptions were fasting for operative procedures. There were substantive energy and protein deficits [943 (654) kcal/day and 49 (41) g/day, respectively; mean (SD)]. Nineteen (21%) patients died within 60 days of admission, and the energy and protein deficits were greater in those that died compared with survivors [died vs. survived, energy: 1251 (742) vs. 861 (607) kcal/d; p=0.02; and protein 67(42) vs. 44(39) g/d; p=0.03]. Energy and protein deficits were associated with increased mortality with the greater the deficit, the stronger the association with death (odds ratio for death: energy deficit/100 kcal 1.10 (1.01, 1.19); p=0.028 and protein/10 g 1.16 (1.01, 1.33); p=0.037). Results were similar and remained significant after adjusting for severity of illness.

CONCLUSIONS

Mechanically ventilated patients following burn develop substantial energy and protein deficits, with lesser deficits observed in survivors.

Upregulation of intestinal glucose transporters after Roux-en-Y gastric bypass to prevent carbohydrate malabsorption

OBJECTIVE

To determine the effect of Roux-en-Y gastric bypass (RYGB) on the expression of intestinal sweet taste receptors (STRs), glucose transporters (GTs), glucose absorption, and glycemia.

METHODS

Intestinal biopsies were collected for mRNA expression of STR (T1R2) and GTs (SGLT-1 and GLUT2) from 11 non-diabetic RYGB, 13 non-diabetic obese, and 11 healthy subjects, at baseline and following a 30 min small intestinal (SI) glucose infusion (30 g/150 ml water with 3 g 3-O-methyl-d-glucopyranose (3-OMG)). Blood glucose, plasma 3-OMG, and insulin were measured for 270 min.

RESULTS

In RYGB patients, expression of both GTs was ∼2-fold higher at baseline and after glucose infusion than those of morbidly obese or healthy subjects (P < 0.001). STR expressions were comparable amongst the groups. Peak plasma 3-OMG in both RYGB (r = 0.69, P = 0.01) and obese (r = 0.72, P = 0.005) correlated with baseline expression of SGLT-1, as was the case with peak blood glucose in RYGB subjects (r = 0.69, P = 0.02).

CONCLUSIONS

The upregulated intestinal GTs in RYGB patients are associated with increased glucose absorption when glucose is delivered at a physiological rate, suggesting a molecular adaptation to prevent carbohydrate malabsorption from rapid intestinal transit after RYGB.

Impact of delirium and suture-less securement on accidental vascular catheter removal in the ICU

The objectives were to describe the incidence of accidental vascular catheter removal (AVCR) in an Australian Intensive Care Unit (ICU) and evaluate whether the fixation method or patient delirium increased the risk of AVCR. This prospective observational study was based in a tertiary level ICU between April 2011 and October 2012. All vascular catheters were secured either by sutures or by a suture-less securement device (STATLOCK(™), Bard Medical, Covington, GA, USA) as per the treating clinician. Data were obtained from bedside nursing staff, with daily screening for delirium completed by the ICU medical team using the Confusion Assessment Method-ICU. 2361 patients were admitted during this period with 1032 patients screened and data available for 322 patients (452 vascular catheters). AVCR occurred in 15 patients (16 vascular catheters) (5.0%) with an incidence of AVCR of 2.77 per 100 catheter-days. Delirious patients were 13-fold more likely to have an AVCR event (odds ratio=13.3; 95% confidence interval 4.36, 40.52; P <0.0001). There was a non-significant trend to an increase in AVCR when using the suture-less securement device (odds ratio=2.6; 95% confidence interval 0.87, 7.8; P=0.09) but delirious patients were no more likely to have an AVCR episode when a suture-less securement device was used (P=0.95). In this study the use of suture-less securement did not seem to increase the risk of AVCR. However, there was a non-significant trend towards increased AVCR when using suture-less securement devices, which may reflect a ß error.

Use of a concentrated enteral nutrition solution to increase calorie delivery to critically ill patients: a randomized, double-blind, clinical trial

BACKGROUND

Critically ill patients typically receive ∼60% of estimated calorie requirements.

OBJECTIVES

We aimed to determine whether the substitution of a 1.5-kcal/mL enteral nutrition solution for a 1.0-kcal/mL solution resulted in greater calorie delivery to critically ill patients and establish the feasibility of conducting a multicenter, double-blind, randomized trial to evaluate the effect of an increased calorie delivery on clinical outcomes.

DESIGN

A prospective, randomized, double-blind, parallel-group, multicenter study was conducted in 5 Australian intensive care units. One hundred twelve mechanically ventilated patients expected to receive enteral nutrition for ≥2 d were randomly assigned to receive 1.5 (n = 57) or 1.0 (n = 55) kcal/mL enteral nutrition solution at a rate of 1 mL/kg ideal body weight per hour for 10 d. Protein and fiber contents in the 2 solutions were equivalent.

RESULTS

The 2 groups had similar baseline characteristics (1.5 compared with 1.0 kcal/mL). The mean (±SD) age was 56.4 ± 16.8 compared with 56.5 ± 16.1 y, 74% compared with 75% were men, and the Acute Physiology and Chronic Health Evaluation II score was 23 ± 9.1 compared with 22 ± 8.9. The groups received similar volumes of enteral nutrition solution [1221 mL/d (95% CI: 1120, 1322 mL/d) compared with 1259 mL/d (95% CI: 1143, 1374 mL/d); P = 0.628], which led to a 46% increase in daily calories in the group given the 1.5-kcal/mL solution [1832 kcal/d (95% CI: 1681, 1984 kcal/d) compared with 1259 kcal/d (95% CI: 1143, 1374 kcal/d); P < 0.001]. The 1.5-kcal/mL solution was not associated with larger gastric residual volumes or diarrhea. In this feasibility study, there was a trend to a reduced 90-d mortality in patients given 1.5 kcal/mL [11 patients (20%) compared with 20 patients (37%); P = 0.057].

CONCLUSIONS

The substitution of a 1.0- with a 1.5-kcal/mL enteral nutrition solution administered at the same rate resulted in a 46% greater calorie delivery without adverse effects. The results support the conduct of a large-scale trial to evaluate the effect of increased calorie delivery on clinically important outcomes in the critically ill.

Dysglycaemia in the critically ill and the interaction of chronic and acute glycaemia with mortality

PURPOSE

Hyperglycaemia is common in the critically ill. The objectives of this study were to determine the prevalence of critical illness-associated hyperglycaemia (CIAH) and recognised and unrecognised diabetes in the critically ill as well as to evaluate the impact of premorbid glycaemia on the association between acute hyperglycaemia and mortality.

METHODS

In 1,000 consecutively admitted patients we prospectively measured glycated haemoglobin (HbA1c) on admission, and blood glucose concentrations during the 48 h after admission, to the intensive care unit. Patients with blood glucose ≥7.0 mmol/l when fasting or ≥11.1 mmol/l during feeding were deemed hyperglycaemic. Patients with acute hyperglycaemia and HbA1c <6.5% (48 mmol/mol) were categorised as 'CIAH', those with known diabetes as 'recognised diabetes', and those with HbA1c ≥6.5% but no previous diagnosis of diabetes as 'unrecognised diabetes'. The remainder were classified as 'normoglycaemic'. Hospital mortality, HbA1c and acute peak glycaemia were assessed using a logistic regression model.

RESULTS

Of 1,000 patients, 498 (49.8%) had CIAH, 220 (22%) had recognised diabetes, 55 (5.5%) had unrecognised diabetes and 227 (22.7%) were normoglycaemic. The risk of death increased by approximately 20% for each increase in acute glycaemia of 1 mmol/l in patients with CIAH and those with diabetes and HbA1c levels <7% (53 mmol/mol), but not in patients with diabetes and HbA1c ≥7%. This association was lost when adjusted for severity of illness.

CONCLUSIONS

Critical illness-associated hyperglycaemia is the most frequent cause of hyperglycaemia in the critically ill. Peak glucose concentrations during critical illness are associated with increased mortality in patients with adequate premorbid glycaemic control, but not in patients with premorbid hyperglycaemia. Optimal glucose thresholds in the critically ill may, therefore, be affected by premorbid glycaemia.

Glucagon-like peptide 1 attenuates the acceleration of gastric emptying induced by hypoglycemia in healthy subjects

OBJECTIVE

Exogenous GLP-1 slows gastric emptying in health and diabetes leading to diminished glycemic excursions. Gastric emptying is markedly accelerated by hypoglycemia. The primary objective was to determine whether GLP-1 attenuates the acceleration of gastric emptying induced by hypoglycemia.

RESEARCH DESIGN AND METHODS

Ten healthy volunteers were studied on four separate days in a randomized double-blind fashion. Blood glucose was stabilized using a glucose/insulin clamp at hypoglycemia (2.6 mmol/L on two occasions [hypo]) or euglycemia (6.0 mmol/L on two occasions [eu]) between T = -15 and 45 min before clamping at 6.0 mmol/L until 180 min. During hypoglycemia and euglycemia, subjects received intravenous GLP-1 (1.2 pmol/kg/min) or placebo. At T = 0 min, subjects ingested 100 g beef mince labeled with 20 MBq (99m)Tc-sulfur-colloid and 3 g of 3-O-methyl-glucose (3-OMG), a marker of glucose absorption. Gastric emptying was measured scintigraphically from T = 0 to 180 min and serum 3-OMG taken at 15-min intervals. The areas under the curve for gastric emptying and 3-OMG concentration were analyzed using one-way repeated-measures ANOVA with Bonferroni-Holm adjusted post hoc tests.

RESULTS

Gastric emptying was accelerated during hypoglycemia (hypo/placebo vs. eu/placebo; P < 0.001), as was glucose absorption (P < 0.03). GLP-1 slowed emptying during euglycemia (eu/placebo vs. eu/GLP-1; P < 0.001). However, hypoglycemia-induced acceleration of gastric emptying on placebo was markedly diminished by GLP-1 (hypo/placebo vs. hypo/GLP-1; P < 0.008), as was glucose absorption (P < 0.01).

CONCLUSIONS

Acute administration of exogenous GLP-1 attenuates, but does not abolish, the acceleration of gastric emptying by insulin-induced hypoglycemia in healthy subjects.

Intensivists under threat: who's in charge here?

The model currently used in public hospitals in Australia and New Zealand - of closed, mixed medical-surgical ICUs, led by consultant intensivists who remain in charge but collaborate closely across multiple specialties and disciplines and are supported by well trained junior medical staff- is internationally admired and has provided cost-effective care. Careful workforce planning is essential to ensure that intensivists retain their identity and that an efficient model persists into the future.

Prevalence, risk factors, clinical consequences, and treatment of enteral feed intolerance during critical illness

BACKGROUND

We aimed to determine the incidence of enteral feed intolerance and factors associated with intolerance and to assess the influence of intolerance on nutrition and clinical outcomes.

METHODS

We conducted a retrospective analysis of data from an international observational cohort study of nutrition practices among 167 intensive care units (ICUs). Data were collected on nutrition adequacy, ventilator-free days (VFDs), ICU stay, and 60-day mortality. Intolerance was defined as interruption of enteral nutrition (EN) due to gastrointestinal (GI) reasons (large gastric residuals, abdominal distension, emesis, diarrhea, or subjective discomfort). Logistic regression was used to determine risk factors for intolerance and their clinical significance. A sensitivity analysis restricted to sites specifying a gastric residual volume ≥200 mL to identify intolerance was also conducted.

RESULTS

Data from 1,888 ICU patients were included. The incidence of intolerance was 30.5% and occurred after a median 3 days from EN initiation. Patients remained intolerant for a mean (±SD) duration of 1.9 ± 1.3 days . Intolerance was associated with worse nutrition adequacy vs the tolerant (56% vs 64%, P < .0001), fewer VFDs (2.5 vs 11.2, P < .0001), increased ICU stay (14.4 vs 11.3 days, P < .0001), and increased mortality (30.8% vs 26.2, P = .04). The sensitivity analysis demonstrated that intolerance remained associated with negative outcomes. Although mortality was greater among the intolerant patients, this was not statistically significant.

CONCLUSIONS

Intolerance occurs frequently during EN in critically ill patients and is associated with poorer nutrition and clinical outcomes.

Incretins and the intensivist: what are they and what does an intensivist need to know about them?

Hyperglycaemia occurs frequently in the critically ill, even in those patients without a history of diabetes. The mechanisms underlying hyperglycaemia in this group are complex and incompletely defined. In health, the gastrointestinal tract is an important modulator of postprandial glycaemic excursions and both the rate of gastric emptying and the so-called incretin hormones, glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide, are pivotal determinants of postprandial glycaemia. Incretin-based therapies (that is, glucagon-like peptide- 1 agonists and dipeptidyl-peptidase-4 inhibitors) have recently been incorporated into standard algorithms for the management of hyperglycaemia in ambulant patients with type 2 diabetes and, inevitably, an increasing number of patients who were receiving these classes of drugs prior to their acute illness will present to ICUs. This paper summarises current knowledge of the incretin effect as well as the incretin-based therapies that are available for the management of type 2 diabetes, and provides suggestions for the potential relevance of these agents in the management of dysglycaemia in the critically ill, particularly to normalise elevated blood glucose levels.

Comparative effects of prolonged and intermittent stimulation of the glucagon-like peptide 1 receptor on gastric emptying and glycemia

Acute administration of glucagon-like peptide 1 (GLP-1) and its agonists slows gastric emptying, which represents the major mechanism underlying their attenuation of postprandial glycemic excursions. However, this effect may diminish during prolonged use. We compared the effects of prolonged and intermittent stimulation of the GLP-1 receptor on gastric emptying and glycemia. Ten healthy men received intravenous saline (placebo) or GLP-1 (0.8 pmol/kg ⋅ min), as a continuous 24-h infusion ("prolonged"), two 4.5-h infusions separated by 20 h ("intermittent"), and a 4.5-h infusion ("acute") in a randomized, double-blind, crossover fashion. Gastric emptying of a radiolabeled mashed potato meal was measured using scintigraphy. Acute GLP-1 markedly slowed gastric emptying. The magnitude of the slowing was attenuated with prolonged but maintained with intermittent infusions. GLP-1 potently diminished postprandial glycemia during acute and intermittent regimens. These observations suggest that short-acting GLP-1 agonists may be superior to long-acting agonists when aiming specifically to reduce postprandial glycemic excursions in the treatment of type 2 diabetes.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

The effects of critical illness on intestinal glucose sensing, transporters, and absorption

OBJECTIVES

Providing effective enteral nutrition is important during critical illness. In health, glucose is absorbed from the small intestine via sodium-dependent glucose transporter-1 and glucose transporter-2, which may both be regulated by intestinal sweet taste receptors. We evaluated the effect of critical illness on glucose absorption and expression of intestinal sodium-dependent glucose transporter-1, glucose transporter-2, and sweet taste receptors in humans and mice.

DESIGN

Prospective observational study in humans and mice.

SETTING

ICU and university-affiliated research laboratory.

SUBJECTS

Human subjects were 12 critically ill patients and 12 healthy controls. In the laboratory 16-week-old mice were studied.

INTERVENTIONS

Human subjects underwent endoscopy. Glucose (30 g) and 3-O-methylglucose (3 g), used to estimate glucose absorption, were infused intraduodenally over 30 minutes. Duodenal mucosa was biopsied before and after infusion. Mice were randomized to cecal ligation and puncture to model critical illness (n = 16) or sham laparotomy (control) (n = 8). At day 5, mice received glucose (100 mg) and 3-O-methylglucose (10 mg) infused intraduodenally prior to mucosal tissue collection.

MEASUREMENTS AND MAIN RESULTS

Quantitative polymerase chain reaction was performed to measure absolute (human) and relative levels of sodium-dependent glucose transporter-1, glucose transporter-2, and taste receptor type 1 member 2 (T1R2) transcripts. Blood samples were assayed for 3-O-methylglucose to estimate glucose absorption. Glucose absorption was three-fold lower in critically ill humans than in controls (p = 0.002) and reduced by a similar proportion in cecal ligation and puncture mice (p = 0.004). In critically ill patients, duodenal levels of sodium-dependent glucose transporter-1, glucose transporter-2, and T1R2 transcript were reduced 49% (p < 0.001), 50% (p = 0.009), and 85% (p = 0.007), whereas in the jejunum of cecal ligation and puncture mice sodium-dependent glucose transporter-1, glucose transporter-2, and T1R2 transcripts were reduced by 55% (p < 0.001), 50% (p = 0.002), and 69% (p = 0.004).

CONCLUSIONS

Critical illness is characterized by markedly diminished glucose absorption, associated with reduced intestinal expression of glucose transporters (sodium-dependent glucose transporter-1 and glucose transporter-2) and sweet taste receptor transcripts. These changes are paralleled in cecal ligation and puncture mice.

The effect of exogenous glucose-dependent insulinotropic polypeptide in combination with glucagon-like peptide-1 on glycemia in the critically ill

OBJECTIVE

Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) have additive insulinotropic effects when coadministered in health. We aimed to determine whether GIP confers additional glucose lowering to that of GLP-1 in the critically ill.

RESEARCH DESIGN AND METHODS

Twenty mechanically ventilated critically ill patients without known diabetes were studied in a prospective, randomized, double-blind, crossover fashion on 2 consecutive days. Between T0 and T420 minutes, GLP-1 (1.2 pmol/kg·min(-1)) was infused intravenously with either GIP (2 pmol/kg·min(-1)) or 0.9% saline. Between T60 and T420 minutes, nutrient liquid was infused into the small intestine at 1.5 kcal/min.

RESULTS

Adding GIP did not alter blood glucose or insulin responses to small intestinal nutrient. GIP increased glucagon concentrations slightly before nutrient delivery (P=0.03), but not thereafter.

CONCLUSIONS

The addition of GIP to GLP-1 does not result in additional glucose-lowering or insulinotropic effects in critically ill patients with acute-onset hyperglycemia.

Modulation of individual components of gastric motor response to duodenal glucose

AIM: To evaluate individual components of the antro-pyloro-duodenal (APD) motor response to graded small intestinal glucose infusions in healthy humans.

METHODS: APD manometry was performed in 15 healthy subjects (12 male; 40 ± 5 years, body mass index 26.5 ± 1.6 kg/m²) during four 20-min intraduodenal infusions of glucose at 0, 0.5, 1.0 and 1.5 kcal/min, in a randomised double-blinded fashion. Glucose solutions were infused at a rate of 1 mL/min and separated by 40-min “wash-out” period. Data are mean ± SE. Inferential analyses are repeated measure analysis of variance with Bonferroni post-hoc testing.

RESULTS: At 0 kcal/min frequency of pressure waves were: antrum (7.5 ± 1.8 waves/20 min) and isolated pyloric pressure waves (IPPWs) (8.0 ± 2.3 waves/20 min) with pyloric tone (0.0 ± 0.9 mmHg). Intraduodenal glucose infusion acutely increased IPPW frequency (P < 0.001) and pyloric tone (P = 0.015), and decreased antral wave frequency (P = 0.007) in a dose-dependent fashion. A threshold for stimulation was observed at 1.0 kcal/min for pyloric phasic pressure waves (P = 0.002) and 1.5 kcal/min for pyloric tone and antral contractility.

CONCLUSION: There is hierarchy for the activation of gastrointestinal motor responses to duodenal glucose infusion. An increase in IPPWs is the first response observed.

Dysglycaemia in the critically ill - significance and management

Hyperglycaemia frequently occurs in the critically ill, in patients with diabetes, as well as those who were previously glucose-tolerant. The terminology 'stress hyperglycaemia' reflects the pathogenesis of the latter group, which may comprise up to 40% of critically ill patients. For comparable glucose concentrations during acute illness outcomes in stress hyperglycaemia appear to be worse than those in patients with type 2 diabetes. While several studies have evaluated the optimum glycaemic range in the critically ill, their interpretation in relation to clinical recommendations is somewhat limited, at least in part because patients with stress hyperglycaemia and known diabetes were grouped together, and the optimum glycaemic range was regarded as static, rather than dynamic, phenomenon. In addition to hyperglycaemia, there is increasing evidence that hypoglycaemia and glycaemic variability influence outcomes in the critically ill adversely. These three categories of disordered glucose metabolism can be referred to as dysglycaemia. While stress hyperglycaemia is most frequently managed by administration of short-acting insulin, guided by simple algorithms, this does not treat all dysglycaemic categories; rather the use of insulin increases the risk of hypoglycaemia and may exacerbate variability. The pathogenesis of stress hyperglycaemia is complex, but hyperglucagonaemia, relative insulin deficiency and insulin resistance appear to be important. Accordingly, novel agents that have a pathophysiological rationale and treat hyperglycaemia, but do not cause hypoglycaemia and limit glycaemic variability, are appealing. The potential use of glucagon-like peptide-1 (or its agonists) and dipeptyl-peptidase-4 inhibitors is reviewed.

The gut-brain axis in the critically ill: is glucagon-like peptide-1 protective in neurocritical care?

Enteral nutrient is a potent glucagon-like peptide-1 (GLP-1) secretagogue. In vitro and animal studies indicate that GLP-1 has immune-modulatory and neuroprotective effects. To determine whether these immune-modulatory and neuroprotective effects of GLP-1 are beneficial in the critically ill, studies achieving pharmacological GLP-1 concentrations are warranted.

Comparisons between intragastric and small intestinal delivery of enteral nutrition in the critically ill: a systematic review and meta-analysis

Introduction

The largest cohort of critically ill patients evaluating intragastric and small intestinal delivery of nutrients was recently reported. This systematic review included recent data to compare the effects of small bowel and intragastric delivery of enteral nutrients in adult critically ill patients.

Methods

This is a systematic review of all randomised controlled studies published between 1990 and March 2013 that reported the effects of the route of enteral feeding in the critically ill on clinically important outcomes.

Results

Data from 15 level-2 studies were included. Small bowel feeding was associated with a reduced risk of pneumonia (Relative Risk, RR, small intestinal vs. intragastric: 0.75 (95% confidence interval 0.60 to 0.93); P = 0.01; I² = 11%). The point estimate was similar when only studies using microbiological data were included. Duration of ventilation (weighted mean difference: -0.36 days (-2.02 to 1.30); P = 0.65; I² = 42%), length of ICU stay (WMD: 0.49 days, (-1.36 to 2.33); P = 0.60; I² = 81%) and mortality (RR 1.01 (0.83 to 1.24); P = 0.92; I² = 0%) were unaffected by the route of feeding. While data were limited, and there was substantial statistical heterogeneity, there was significantly improved nutrient intake via the small intestinal route (% goal rate received: 11% (5 to 16%); P = 0.0004; I² = 88%).

Conclusions

Use of small intestinal feeding may improve nutritional intake and reduce the incidence of ICU-acquired pneumonia. In unselected critically ill patients other clinically important outcomes were unaffected by the site of the feeding tube.

Gastrointestinal dysmotility: evidence and clinical management

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Mesenteric blood flow, glucose absorption and blood pressure responses to small intestinal glucose in critically ill patients older than 65 years

PURPOSE

To compare nutrient-stimulated changes in superior mesenteric artery (SMA) blood flow, glucose absorption and glycaemia in individuals older than 65 years with, and without, critical illness.

METHODS

Following a 1-h 'observation' period (t (0)-t (60)), 0.9 % saline and glucose (1 kcal/ml) were infused directly into the small intestine at 2 ml/min between t (60)-t (120), and t (120)-t (180), respectively. SMA blood flow was measured using Doppler ultrasonography at t (60) (fasting), t (90) and t (150) and is presented as raw values and nutrient-stimulated increment from baseline (Δ). Glucose absorption was evaluated using serum 3-O-methylglucose (3-OMG) concentrations during, and for 1 h after, the glucose infusion (i.e. t (120)-t (180) and t (120)-t (240)). Mean arterial pressure was recorded between t (60)-t (240). Data are presented as median (25th, 75th percentile).

RESULTS

Eleven mechanically ventilated critically ill patients [age 75 (69, 79) years] and nine healthy volunteers [70 (68, 77) years] were studied. The magnitude of the nutrient-stimulated increase in SMA flow was markedly less in the critically ill when compared with healthy subjects [Δt (150): patients 115 (-138, 367) versus health 836 (618, 1,054) ml/min; P = 0.001]. In patients, glucose absorption was reduced during, and for 1 h after, the glucose infusion when compared with health [AUC(120-180): 4.571 (2.591, 6.551) versus 11.307 (8.447, 14.167) mmol/l min; P < 0.001 and AUC(120-240): 26.5 (17.7, 35.3) versus 40.6 (31.7, 49.4) mmol/l min; P = 0.031]. A close relationship between the nutrient-stimulated increment in SMA flow and glucose absorption was evident (3-OMG AUC(120-180) and ∆SMA flow at t (150): r (2) = 0.29; P < 0.05).

CONCLUSIONS

In critically ill patients aged >65 years, stimulation of SMA flow by small intestinal glucose infusion may be attenuated, which could account for the reduction in glucose absorption.

Comparative effects on glucose absorption of intragastric and post-pyloric nutrient delivery in the critically ill

INTRODUCTION

Studies in the critically ill that evaluate intragastric and post-pyloric delivery of nutrient have yielded conflicting data. A limitation of these studies is that the influence in the route of feeding on glucose absorption and glycaemia has not been determined.

METHODS

In 68 mechanically ventilated critically ill patients, liquid nutrient (100 ml; 1 kcal/ml containing 3 g of 3-O-Methyl-D-glucopyranose (3-OMG), as a marker of glucose absorption), was infused into either the stomach (n = 24) or small intestine (n = 44) over six minutes. Blood glucose and serum 3-OMG concentrations were measured at regular intervals for 240 minutes and the area under the curves (AUCs) calculated for 'early' (AUC60) and 'overall' (AUC240) time periods. Data are presented as mean (95% confidence intervals).

RESULTS

Glucose absorption was initially more rapid following post-pyloric, when compared with intragastric, feeding (3-OMG AUC60: intragastric 7.3 (4.3, 10.2) vs. post-pyloric 12.5 (10.1, 14.8) mmol/l.min; P = 0.008); however, 'overall' glucose absorption was similar (AUC240: 49.1 (34.8, 63.5) vs. 56.6 (48.9, 64.3) mmol/l.min; P = 0.31). Post-pyloric administration of nutrients was also associated with greater increases in blood glucose concentrations in the 'early' period (AUC60: 472 (425, 519) vs. 534 (501, 569) mmol/l.min; P = 0.03), but 'overall' glycaemia was also similar (AUC240: 1,875 (1,674, 2,075) vs. 1,898 (1,755, 2,041) mmol/l.min; P = 0.85).

CONCLUSIONS

In the critically ill, glucose absorption was similar whether nutrient was administered via a gastric or post-pyloric catheter. These data may have implications for the perceived benefit of post-pyloric feeding on nutritional outcomes and warrant further investigation.

Randomized double-blind crossover study to determine the effects of erythromycin on small intestinal nutrient absorption and transit in the critically ill

BACKGROUND

The gastrokinetic drug erythromycin is commonly administered to critically ill patients during intragastric feeding to augment small intestinal nutrient delivery. However, erythromycin has been reported to increase the prevalence of diarrhea, which may reflect reduced absorption and/or accelerated small intestinal transit.

OBJECTIVE

The objective was to evaluate the effects of intravenous erythromycin on small intestinal nutrient absorption and transit in the critically ill.

DESIGN

On consecutive days, erythromycin (200 mg in 20 mL 0.9% saline) or placebo (20 mL 0.9% saline) were infused intravenously between -20 and 0 min in a randomized, blinded, crossover fashion. Between 0 and 30 min, a liquid nutrient containing 3-O-methylglucose (3-OMG), [13C]triolein, and [(99m)Tc]sulfur colloid was administered directly into the small intestine at 2 kcal/min. Serum 3-OMG concentrations and exhaled (13)CO2 (indices of glucose and lipid absorption, respectively) were measured. Cecal arrival of the infused nutrient was determined by scintigraphy. Data are medians (ranges) and were analyzed by using Wilcoxon's signed-rank test.

RESULTS

Thirty-two mechanically ventilated patients were studied. Erythromycin increased small intestinal glucose absorption [3-OMG AUC360: 105.2 (28.9-157.0) for erythromycin compared with 91.8 (51.4-147.9) mmol/L · min for placebo; P = 0.029] but tended to reduce lipid absorption [cumulative percentage dose (13)CO2 recovered: 10.4 (0-90.6) compared with 22.6 (0-100) %; P = 0.06]. A trend to slower transit was observed after erythromycin [300 (39-360) compared with 228 (33-360) min; P = 0.07].

CONCLUSIONS

Acute administration of erythromycin increases small intestinal glucose absorption in the critically ill, but there was a tendency for the drug to reduce small intestinal lipid absorption and slow transit. These observations have implications for the use of erythromycin as a gastrokinetic drug in the critically ill. This trial was registered in the Australian New Zealand Clinical Trials Registry as ACTRN 12610000615088.

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

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

Glucose absorption and small intestinal transit in critical illness

OBJECTIVES

Although enteral nutrition is standard care for critically ill patients, nutrient absorption has not been quantified in this group and may be impaired due to intestinal dysmotility. The objectives of this study were to measure small intestinal glucose absorption and duodenocecal transit and determine their relationship with glycemia in the critically ill.

DESIGN

Prospective observational study of healthy and critically ill subjects.

SETTING

Tertiary mixed medical-surgical adult intensive care unit.

SUBJECTS

Twenty-eight critically ill patients and 16 healthy subjects were studied. MATERIALS AND MAIN RESULTS: Liquid feed (100 kcal/100 mL), labeled with Tc-sulfur colloid and including 3 g of 3-O-methylglucose, was infused into the duodenum. Glucose absorption and duodenocecal transit were measured using the area under the 3-O-methylglucose concentration curve and scintigraphy, respectively. Data are median (range).

RESULTS AND DISCUSSION

Glucose absorption was reduced in critical illness when compared to health (area under the concentration curve: 16 [1-32] vs. 20 [14-34] mmol/L·min; p = .03). Small intestinal transit times were comparable in patients and healthy subjects (192 [9-240] vs. 168 [6-240] min; p = .99) and were not related to glucose absorption. Despite higher fasting blood glucose concentrations (6.3 [5.1-9.3] vs. 5.7 [4.6-7.6] mmol/L; p < .05), the increment in blood glucose was sustained for longer in the critically ill (Δ glucose at t = 60; 1.9 [-2.1-5.0] mmol/L vs. -0.2 [-1.3-2.3] mmol/L; p < .01).

CONCLUSIONS

Critical illness is associated with reduced small intestinal glucose absorption, but despite this, the glycemic response to enteral nutrient is sustained for longer.

Exogenous glucagon-like peptide-1 attenuates the glycaemic response to postpyloric nutrient infusion in critically ill patients with type-2 diabetes

INTRODUCTION

Glucagon-like peptide-1 (GLP-1) attenuates the glycaemic response to small intestinal nutrient infusion in stress-induced hyperglycaemia and reduces fasting glucose concentrations in critically ill patients with type-2 diabetes. The objective of this study was to evaluate the effects of acute administration of GLP-1 on the glycaemic response to small intestinal nutrient infusion in critically ill patients with pre-existing type-2 diabetes.

METHODS

Eleven critically ill mechanically-ventilated patients with known type-2 diabetes received intravenous infusions of GLP-1 (1.2 pmol/kg/minute) and placebo from t = 0 to 270 minutes on separate days in randomised double-blind fashion. Between t = 30 to 270 minutes a liquid nutrient was infused intraduodenally at a rate of 1 kcal/min via a naso-enteric catheter. Blood glucose, serum insulin and C-peptide, and plasma glucagon were measured. Data are mean ± SEM.

RESULTS

GLP-1 attenuated the overall glycaemic response to nutrient (blood glucose AUC30-270 min: GLP-1 2,244 ± 184 vs. placebo 2,679 ± 233 mmol/l/minute; P = 0.02). Blood glucose was maintained at < 10 mmol/l in 6/11 patients when receiving GLP-1 and 4/11 with placebo. GLP-1 increased serum insulin at 270 minutes (GLP-1: 23.4 ± 6.7 vs. placebo: 16.4 ± 5.5 mU/l; P < 0.05), but had no effect on the change in plasma glucagon.

CONCLUSIONS

Exogenous GLP-1 in a dose of 1.2 pmol/kg/minute attenuates the glycaemic response to small intestinal nutrient in critically ill patients with type-2 diabetes. Given the modest magnitude of the reduction in glycaemia the effects of GLP-1 at higher doses and/or when administered in combination with insulin, warrant evaluation in this group.

TRIAL REGISTRATION

ANZCTR:ACTRN12610000185066.

Intrasubject variability of gastric emptying in the critically ill using a stable isotope breath test

BACKGROUND AND AIMS

Isotope breath tests are increasingly used to evaluate the effects of prokinetic drugs on gastric emptying. The aim was to assess intrasubject variability in gastric emptying, when using an isotope breath test in the critically ill.

METHODS

A retrospective analysis of data was undertaken in 12 patients who had gastric emptying measurements on consecutive days using a (13)C-octanoic acid breath test. The gastric emptying coefficient--GEC (a global index for the gastric emptying rate), and the t(50) (calculated time for 50% of meal to empty) were calculated, together with the coefficient of variability for these parameters. Data are mean (SD).

RESULTS

Neither GEC (day 1: 3.3 (0.8) vs. day 2: 3.1 (0.6); P = 0.31) nor t(50) (day 1: 127 (43) min vs. day 2: 141 (48) min; P = 0.46) were significantly different between the two days. Intrasubject variability was less for GEC (15.6%) than for t(50) (31.8%).

CONCLUSION

There is only modest intrasubject variability in GEC measurements using the (13)C-octanoic acid breath test in critically ill patients. As such, it may be an acceptable measurement tool to assess the effects of prokinetic drugs in this group.

Effects of exogenous glucagon-like peptide-1 on gastric emptying and glucose absorption in the critically ill: relationship to glycemia

OBJECTIVE

To determine the acute effects of exogenous glucagon-like peptide-1 on gastric emptying, glucose absorption, glycemia, plasma insulin, and glucagon in critically ill patients.

DESIGN

Randomized, double-blind, crossover study.

SETTING

Intensive care unit.

SUBJECTS

Twenty-five mechanically ventilated patients, without known diabetes, studied on consecutive days.

INTERVENTIONS

Intravenous glucagon-like peptide-1 (1.2 pmol/kg/min) or placebo was infused between -30 and 330 mins. At 0 min, 100 mL liquid nutrient (1 kcal/mL) including 100 microg of 13C-octanoic acid and 3 grams of 3-O-methyl-glucose was administered.

MEASUREMENTS AND MAIN RESULTS

Blood glucose, serum 3-O-methyl-glucose (as an index of glucose absorption), insulin and glucagon concentrations, as well as exhaled 13CO2 were measured. The gastric emptying coefficient was calculated to quantify gastric emptying. Data are presented as mean (sd). There was a nonsignificant trend for glucagon-like peptide-1 to slow gastric emptying (gastric emptying coefficient) (glucagon-like peptide-1, 2.45 [0.93] vs. placebo, 2.75 [0.83]; p = .09). In 11 of the 25 patients, gastric emptying was delayed during placebo infusion and glucagon-like peptide-1 had no detectable effect on gastric emptying in this group (1.92 [0.82] vs. 1.90 [0.68]; p = .96). In contrast, in patients who had normal gastric emptying during placebo, glucagon-like peptide-1 slowed gastric emptying substantially (2.86 [0.58] vs. 3.41 [0.37]; p = .006). Glucagon-like peptide-1 markedly reduced the rate of glucose absorption (3-O-methyl-glucose area under the curve(0-330), 37 [35] vs. 76 [51] mmol/L/min; p < .001), decreased preprandial glucagon (at 0 min change in glucagon, -15 [15] vs. -3 [14] pmol/L; p < .001), increased the insulin/glucose ratio throughout the infusion (area under the curve(-30-330), 1374 [814] vs. 1172 [649] mU/mmol/min; p = .041), and attenuated the glycemic response to the meal (glucose area under the curve(0-330), 2071 [353] vs. 2419 [594] mmol/L/min; p = .001).

CONCLUSIONS

Exogenous glucagon-like peptide-1 lowers postprandial glycemia in the critically ill. This may occur, at least in part, by slowing gastric emptying when the latter is normal but not when it is delayed.

Ureteric bupivicaine infusion for loin pain haematuria syndrome

INTRODUCTION

Loin pain haematuria syndrome is a common problem with complications including opiate dependence. Morbidity treatments include intra-ureteric capsaicin infusion, nephrectomy, autotransplantation and nephrolysis. We explored the use of flexible cystoscopic infusion of intra-ureteric bupivicaine.

PATIENTS AND METHODS

Patients presenting with chronic loin pain underwent urological and nephrological evaluation. Bupivicaine (0.5%, 20 ml) was infused via an intra-ureteric catheter under flexible cystoscopic guidance. Repeat infusions were offered if indicated.

RESULTS

Sixteen of 17 patients with 1-year follow-up responded and were satisfied. Twelve of these required repeat infusions (mean, 2.9 infusions). The procedures were well tolerated by all patients without adverse effects.

CONCLUSIONS

Intra-ureteric bupivicaine infusion has a place in the management of patients with chronic renal pain. It offers a minimally invasive alternative to other treatments. This procedure warrants further investigation within a randomised, controlled trial setting.