Does Adding Milk to Tea Delay Gastric Emptying?

Study Overview
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Brief Summary
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Most pre-operative fasting regimes dictate that if there is any milk added to tea or coffee, the preoperative fasting time should be extended from 2 to 6 hours. The purpose of this study is to demonstrate whether there is really a delay in gastric emptying time associated with the inclusion of milk in a cup of tea.

Detailed Description
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This was a randomised controlled crossover study conducted in ten healthy volunteers. The paracetamol absorption technique and real-time ultrasound measurement of the cross-sectional area (CSA) of the gastric antrum were used to assess gastric emptying following ingestion of 300ml of black tea or 300ml of tea with milk (250ml black tea plus 50ml of full fat milk) Each participant took part in both arms of the trial, drinking black tea and tea with milk, the order of which was determined by a computerised random number generator and concealed from the investigators by opaque brown paper envelopes. In each arm of the study the procedure was as follows. The subject sat in a semi-reclined position at a 45 angle, a 16g intravenous cannula was sited in an upper limb and baseline blood samples taken. The initial cross-sectional area of the gastric antrum was then measured by ultrasound. The investigating anaesthetist then left the room, the subject opened their randomisation envelope and drank, as directed, either 300ml of black tea or 300ml of tea with milk (250ml black tea plus 50ml of full fat milk) over 3 minutes, followed by 1.5 g of dispersible paracetamol dissolved in 30ml of water. Blood samples were taken every 10 minutes for the first hour, then every 30 minutes until 150 minutes had elapsed. Paracetamol concentrations in each sample were measured using an enzymatic assay. Time to peak concentration (tmax) was thus determined. The CSA of the gastric antrum was measured by ultrasound in real-time (RUS) at baseline, every ten minutes for 60 minutes and then at 30-minute intervals for 150 minutes. Antral CSA was plotted against time and gastric emptying expressed as half-time to gastric emptying (T½). This was defined as the time from baseline to the time the gastric antrum returns to half the maximal value. The primary outcome was tmax. Previous studies have shown mean or median tmax values for paracetamol to vary from 25 to 60 minutes following ingestion of clear fluids, with standard deviation up to 38 minutes. In this study we considered that a delay of gastric emptying of under 60 minutes would not be clinically important; and that we would be able to declare that the two regimes were equivalent if the (two sided) 95% confidence interval for the mean difference in tmax, between black tea and tea with milk included only times less than 60 minutes. Using these assumptions and taking (pessimistically) a correlation between repeated measurements of 0.0, power analysis determined nine participants would be required (with 90% power) to show equivalence. A 95% confidence interval for the mean difference in tmax that lay entirely within 60 minutes of no effect would confirm the hypothesis that tea with milk was clinically equivalent to black tea.

Official Title
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Gastric Emptying of Tea With Milk, Compared With Tea Without Milk. Does Milk Delay Gastric Emptying?

Conditions
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Gastric Emptying

Intervention / Treatment
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* Other: Black tea
* Other: Tea with milk


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy non-pregnant volunteers Exclusion Criteria: medical conditions with a predisposition to delayed gastric emptying (e.g. diabetes or gastric disease) ingestion of paracetamol within the previous 24 hours ingestion of solids or non-clear liquids in the previous six hours ingestion of clear liquids in the previous two hours.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 40 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Black Tea<br> | Other: Black tea<br>* 300ml of tea without milk<br>|
| Active Comparator: Tea with Milk<br> | Other: Tea with milk<br>* 250ml of black tea with 50ml of full fat milk<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Tmax | tmax = the time taken to reach peak paracetamol concentration. The blood samples were analysed for the level of paracetamol, from which the time taken to reach peak paracetamol concentration was subsequently calculated. Blood samples were taken at the same time points as the ultrasound measurements. | Blood samples taken every 10 minutes for 1 hour and then 30 minute intervals until 150 minutes had elapsed. Each participant spent approximately 3 hours for each arm of the trial separated by no less than 24 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| T½ | T½ = time from baseline to the time the cross-sectional surface area (CSA) of the gastric antrum, measured using realtime ultrasound, returned to half the maximal value (CSA½max ). CSA ½ max calculated as below: CSA½max = CSAmax - [(CSAmax - CSAbaseline)/2] | Measurments taken every 10 minutes for 1 hour and then 30 minute intervals until 150 minutes had elapsed. Each participant spent approximately 3 hours for each arm of the trial separated by no less than 24 hours. | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Gastrointestinal tract emptying, Pre-operative fasting, Ultrasound, Paracetamol Absorption