A prospective randomised study comparing oral 13C-bicarbonate tracer technique versus indirect calorimetry for measurement of energy expenditure in adults.

BACKGROUND AND AIMS: Accurate assessment of energy expenditure (EE) is important in guiding nutritional therapy but current methods are unsatisfactory. This study compared the oral 13C-bicarbonate tracer (BT) technique using the IRIS® system (Wagner, Germany) against indirect calorimetry (IC, ventilated-hood) to measure CO2 output (VCO2) and thus estimate EE. METHODS: Ten overnight-fasted healthy male volunteers were randomised to studies at rest or mild exercise in a crossover manner. During each study BT-IRIS® and IC were used simultaneously to measure VCO2 and thus EE. Participants ingested a drink labelled with 50mg 13C-bicarbonate and breath samples were collected every 5 min for 180 min and analysed using IRIS®. Bland-Altman plots were used to assess agreement between the two techniques in measurements of VCO2 (L/day) and estimates of EE (kJ/day). RESULTS: Mean ± SE age and BMI of participants were 21.1 ± 1.1 yrs and 23.6 ± 0.6 kg/m2. Both at rest and exercise, there was small bias but overall poor agreement between the two techniques as evident by the wide 95% limits of agreement in measurements of VCO2 and EE: rest VCO2 (bias 1.4, SD 93, 95% limits of agreement -180 to 183), rest EE (-8.3, 1830, -3595 to 3578), exercise VCO2 (49.3, 66.1, -80.4 to 178.9) and exercise EE (1083, 1944, -2727 to 4893). Furthermore, there was also evidence of systematic error in these measurements. CONCLUSION: Prior to clinical application, further optimisation of the BT-IRIS® system should be undertaken, given the poor agreement with IC in measuring VCO2 and estimating EE.

A randomized crossover study of the effects of glutamine and lipid on the gastric emptying time of a preoperative carbohydrate drink.

BACKGROUND & AIMS: Supplementing preoperative carbohydrate drinks with glutamine may lead to benefits in addition to reducing insulin resistance, but amino acids may delay gastric emptying (GE). The effects of supplementing a preoperative carbohydrate drink (CCD) with glutamine or lipid on GE were studied. METHODS: Ten healthy male volunteers ingested 410 ml of one of three isocaloric-isovolumetric carbohydrate-based drinks labelled with (99m)Tc-DTPA: CCD (preOp(®), Nutricia, UK, 50 g carbohydrate), CCD/G (preOp(®), 36 g carbohydrate + 15 g glutamine) or CCD/L (preOp(®), 36 g carbohydrate + 7 g lipid) in this randomized, blinded, three-way crossover study. After baseline measurements, GE was measured scintigraphically and blood sampled for insulin, glucose and glucagon-like peptide 1 (GLP-1) at 20 min intervals for 240 min. RESULTS: Mean (95% CI) T(90) GE times for CCD, CCD/G and CCD/L were 101 (87-115), 95 (84-107) and 87 (72-102) min, respectively. At 40 min postprandially, mean (SEM) concentrations of glucose (mmol/l) and insulin (mIU/l) were 7.5 (0.5) and 35 (5) for CCD; 6.2 (0.2) and 28 (4) for CCD/G; and 7 (0.3) and 31 (5) for CCD/L, respectively. There were no differences in postprandial GLP-1 concentrations. CONCLUSIONS: Glutamine and lipid supplementation did not prolong the GE of CCD but did 'blunt' postprandial glucose and insulin responses, independent of GLP-1 concentrations. Registered under ClinicalTrials.gov Identifier no. NCT00943020.

Gastric emptying of three liquid oral preoperative metabolic preconditioning regimens measured by magnetic resonance imaging in healthy adult volunteers: a randomised double-blind, crossover study.

BACKGROUND & AIMS: Preoperative starvation has many undesirable effects but the minimum length of fasting is limited by gastric emptying, which may be dependent on nutrient content, viscosity and osmolarity of the feed. We compared the gastric emptying of two types of preoperative metabolic preconditioning drinks [Oral Nutritional Supplement (ONS) (Fresenius Kabi, Germany) and preOp (Nutricia Clinical Care, UK)] in healthy volunteers. METHODS: Twenty (10 male, 10 female) healthy adult volunteers were studied on 3 separate occasions in a randomised crossover manner. Volunteers ingested 400 ml preOp, which is a clear carbohydrate drink (CCD) (50 g carbohydrate, 0 g protein), 70 g ONS (50 g carbohydrate and 15 g glutamine) dissolved in water to a total volume of 400 ml (ONS400) and 300 ml (ONS300). Gastric emptying time was measured using magnetic resonance imaging. RESULTS: Mean (95% CI) T(50) and T(100) gastric emptying times for CCD were significantly lower (p<0.001) compared with ONS400 and ONS300. T(50) was 47 (39-55), 78 (69-87) and 81 (70-92)min for CCD, ONS400 and ONS300 respectively. Correspondingly T(100) was 94 (79-110), 156 (138-173) and 162 (140-184)min. Residual gastric volumes returned to baseline 120 min after CCD and 180 min after ONS400 and ONS300. CONCLUSIONS: The faster gastric emptying for CCD compared to ONS400 and ONS300 signifies that gastric emptying may be more dependent on nutrient load than volume or viscosity in healthy volunteers. While it is safe to give CCD 2h preoperatively, ONS400 and ONS300 should be given at least 3h preoperatively.

The effects of bolus and continuous nasogastric feeding on gastro-oesophageal reflux and gastric emptying in healthy volunteers: a randomised three-way crossover pilot study.

BACKGROUND & AIMS: Nasogastric feeding may result in gastro-oesophageal reflux and, therefore, increase the risk of aspiration. This may be greater when feeds are administered via a bolus than by infusion. We aimed to measure gastric emptying time and quantify gastro-oesophageal reflux in healthy volunteers given a liquid feed via an oral bolus (OB), a nasogastric tube bolus (TB) and a nasogastric tube drip (TD). METHODS: Twelve male volunteers participated in three separate studies (OB, TB and TD) in random order, each 3 days apart. The feed consisted of 220 ml Ensure Plus (1.5 kcal/ml), labelled with 12 MBq (99m)Tc DTPA. The OB and TB were given over 5 min and the infusion rate for the TD was 55 ml/h. Gastric emptying time was measured using gamma scintigraphy. Gastro-oesophageal reflux was observed continuously until the stomach was empty, using a multichannel intraluminal impedance catheter. RESULTS: Mean (95% CI) T(50) gastric emptying times for the OB and TB studies were 41.3 (36.5-46.2) min and 36.2 (30.6-41.8) min respectively (p=0.19). The stomach emptied at a rate equal to the infusion rate in the TD studies. Median (IQR) number of reflux episodes for the OB, TB and TD studies were 4.5 (2.0-6.0), 3.0 (2.0-4.75) and 2.0 (0.25-6.25) respectively. Median (IQR) total duration of reflux for the OB, TB and TD studies were 38 (20-242), 49 (17-71) and 36 (1-125) s respectively (p=NS). CONCLUSIONS: The lack of difference in gastro-oesophageal reflux between bolus and continuous feeding indicates that in healthy volunteers both methods are equally safe with respect to the risk of aspiration.