Prevalence and Measurement of Delayed Gastric Emptying in Patients Receiving Extracorporeal Membrane Oxygenation

When patients are very unwell and admitted to the intensive care unit (ICU), they may need support for their breathing through a breathing machine (known as mechanical ventilation). Patients with severe heart or lung illness may also require life support using 'extracorporeal membrane oxygenation' (ECMO), a machine that takes over the role of the lungs and heart to keep them alive.

These patients are primarily given nutrition in the liquid form, through a tube placed into their stomach via the nose or mouth ('gastric tube'). While gastric tube feeding is commonly used for patients requiring mechanical ventilation and ECMO, current research shows that these patients often do not receive enough nutrition through their gastric tubes.

Slow stomach emptying (often referred to as 'delayed gastric emptying') and other stomach or bowel problems ('gastrointestinal' complications) are thought to be common reasons for not receiving enough nutrition in patients receiving ECMO. Several factors may put these patients at higher risk of delayed gastric emptying, including their high level of illness, complex sedation, unstable blood pressure, and poor blood flow to the gut. Despite this, there is limited research on delayed gastric emptying in patients receiving ECMO.

Not receiving enough nutrition has been associated with longer hospital stays and higher risk of death in patients receiving ECMO, and poorer physical recovery from ICU. Health professionals need to know if the stomach is emptying adequately to ensure that patients receive the nutrition they need.

A common way to measure how much liquid nutrition is in a patients' stomach is by removing liquid nutrition left in the stomach with a syringe through the gastric tube ('residual volumes'). While this is a quick and inexpensive method that can be used on the bedside, it has been shown to be imprecise in identifying delayed gastric emptying.

Another method is stomach ultrasound, a painless scan which is commonly available and has shown promising results in healthy individuals and general ICU patients. However, this has not yet been tested in patients receiving ECMO.

The standard research method for measuring how fast or slow the stomach empties is called 'scintigraphy'. Scintigraphy uses a small, safe amount of radioactivity mixed in the patient's liquid nutrition and a special camera to scan the stomach. However, this is more expensive, labour-intensive and requires portable equipment not available in most hospitals. Therefore, it is only used for research purposes in ICU.

Without a suitable bedside method to measure stomach emptying, there is a risk that delayed gastric emptying may not be properly managed in clinical practice. This may lead to delays in treatment, such as giving medications or changing feeding strategies, or unnecessary interruptions of gastric tube feeding resulting in poor nutritional intake.

This study has two stages:

• Stage A aims to observe whether the stomach takes longer to empty in patients receiving ECMO compared to patients receiving mechanical ventilation but not receiving ECMO, and whether this relates to the nutrition patients receive and how well or unwell they become in ICU.
• Stage B aims to identify the most appropriate method ('residual volumes' or stomach ultrasound) for measuring stomach emptying in ICU for this patient population.

Stage A will aim to recruit 72 participants in total (36 receiving ECMO; 36 not receiving ECMO). Stomach emptying will be measured within four days of ICU admission using 'residual volumes' and stomach ultrasound, and differences between patients receiving ECMO versus no ECMO will be assessed. The study will also check whether delayed gastric emptying and any other gastrointestinal complications experienced by patients relate to how much nutrition patients receive during the first 14 days of their ICU stay, how well-nourished they are on ICU admission and discharge (nutritional status), and how well or unwell they become while in ICU (clinical outcomes).

In stage B, scintigraphy will also be undertaken in a subgroup of 27 patients receiving ECMO from stage A to measure the rate of stomach emptying (how fast or slow the stomach empties) and stomach retention (the amount of liquid nutrition remaining in the stomach), and results from 'residual volumes' and stomach ultrasound will be compared with this.

The investigators believe that findings from this study may help to better measure stomach emptying in clinical practice, inform timely management of delayed gastric emptying and in turn improve the nutrition patients receive and their clinical recovery.