Gastric Emptying
Conditions
Keywords
Gastrointestinal tract emptying, Pre-operative fasting, Ultrasound, Paracetamol Absorption
Brief summary
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
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.
Interventions
OTHERBlack tea
300ml of tea without milk
OTHERTea with milk
250ml of black tea with 50ml of full fat milk
Sponsors
Guy's and St Thomas' NHS Foundation Trust
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
SINGLE (Investigator)
Eligibility
Sex/Gender
ALL
Age
18 Years to 40 Years
Healthy volunteers
Yes
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.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Tmax | 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 | 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. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| T½ | 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. | 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 - \[(CSAmax - CSAbaseline)/2\] |
Countries
United Kingdom
Participant flow
Recruitment details
Recruitment took place from november 2011 until january 2012 at St Thomas' Hospital, London
Participants by arm
| Arm | Count |
|---|---|
| Entire Study Population Includes all participants in this crossover trial | 10 |
| Total | 10 |
Baseline characteristics
| Characteristic | Entire Study Population |
|---|---|
| Age, Categorical <=18 years | 0 Participants |
| Age, Categorical >=65 years | 0 Participants |
| Age, Categorical Between 18 and 65 years | 10 Participants |
| Age, Continuous | 36 years STANDARD_DEVIATION 4 |
| Region of Enrollment United Kingdom | 10 participants |
| Sex: Female, Male Female | 5 Participants |
| Sex: Female, Male Male | 5 Participants |
Adverse events
| Event type | EG000 affected / at risk |
|---|---|
| deaths Total, all-cause mortality | — / — |
| other Total, other adverse events | 0 / 10 |
| serious Total, serious adverse events | 0 / 10 |
Outcome results
Primary
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.
Time frame: 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
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Black Tea | Tmax | 38 minutes | Standard Deviation 17.6 |
| Tea With Milk | Tmax | 30 minutes | Standard Deviation 23.9 |
Secondary
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 - \[(CSAmax - CSAbaseline)/2\]
Time frame: 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.
Population: It was difficult to visualise under ultrasound the gastric antrum in one patient after they drank both black tea and tea with milk, so they were exlcuded from final analysis of the US data only.
| Arm | Measure | Value (GEOMETRIC_MEAN) |
|---|---|---|
| Black Tea | T½ | 22.7 minutes |
| Tea With Milk | T½ | 23.6 minutes |