Trial Summary

Carbogen for Status Epilepticus in Children Trial. Seizure control via pH manipulation: a phase II double blind RCT of inhaled carbogen as adjunctive treatment of paediatric convulsive status epilepticus.


An epileptic seizure that is not stopping is a medical emergency. The longer it lasts the greater the risk of brain damage or even, occasionally, death. We need better ways to stop long seizures sooner. We believe creating a slightly more acidic environment within the brain may help this. One convenient and safe way to alter brain acidity is to give someone a different gas mixture to breathe. Our bodies take oxygen out of the air we breathe in; we then breathe out carbon dioxide as a “waste” gas. Carbon dioxide is very slightly acidic: if you mix a small amount (5%) with oxygen it makes the body and brain slightly acidic. This mixture is called Carbogen. It still has much more oxygen in it than room air (95% compared to 21%), and only the same amount of carbon dioxide as in the air we normally breathe out.

Why are we doing this research?

A lot of scientific evidence suggests that if we make the blood slightly acidic for a short time this may help stop an ongoing seizure. Adding a small amount of carbon dioxide in the oxygen gas achieves this.

If it was effective, carbogen inhalation would have a number of advantages over current treatments in that it does not make a child or young person drowsy or risk causing chest infections. The results from the CRESCENT study will be used to help us improve treatments for children with ongoing long-lasting seizures.

What is involved when someone takes part?

When a child or young person attends a paediatric emergency department whilst exhibiting the signs of Convulsive Status Epilepticus (CSE), they will be assessed for inclusion into the CRESCENT study. There are no additional assessment procedures or tests required, other than those given as part of standard care. If the child or young person satisfies all the eligibility criteria, they will be enrolled in to the CRESCENT study.

Once a child or young person has been enrolled into CRESCENT, they will be given a medical gas to inhale for 10 minutes. This medical gas will either consist of 100% oxygen or Carbogen. The medical gas will be given through a normal hospital face mask. Whilst the medical gas is being inhaled, the emergency department staff treating the child or young person will record some study data. At the end of the 10 minutes, the medical gas will be stopped and the child or young person will receive their normal standard care. There are no follow-up medical procedures of appointments related to the CRESCENT study after the medical gas has been administered.

Researcher’s at the site where the child or young person was treated will collect additional data from the person’s medical notes for up to 30-days after they were treated. This data will help to work out whether the use of 100% oxygen or Carbogen can help in the treatment of CSE.

Do I have to give my consent for my child/young person to take part?

As CSE is a medical emergency we cannot delay giving the study treatment to a child/young person. Usually consent for involvement in a study is sought before the treatments are given and covers study treatment and ongoing data collection. In this study, treatment is given before it is possible to seek consent. After the participating child’s/young person’s condition has stabilized, a member of the research team will come and talk to the parent(s)/legal representative(s) of the child/young person and explain what treatment the child/young person has received, what sort of data will be collected as part of the CRESCENT study and will answer any questions; the research staff member will then ask for consent from the child’s/young person’s parent(s)/legal representative(s). Asking for consent after a study procedure has already been performed is known as “deferred consent”. The team who are running the CRESCENT study have already completed another study looking at the impact and opinions of families involved with deferred consent procedures. The results of this study showed that families understood and supported the reasons for not being able to seek consent during a medical emergency.

If my child takes part, what will happen to my child’s information?

The Newcastle upon Tyne Hospitals NHS Foundation Trust (NUTH) and University of Liverpool are the joint Data Controllers for this study and will need to use information from participating child/young person’s medical records for this research project. If consent is received, then the additional data we will be collect is the participating child/young person’s initials/name, data of birth and contact details.

Individuals from NUTH, the Liverpool Clinical Trials Centre (LCTC) and regulatory organisations may look at medical and research records for participants, and any consent forms to check the accuracy of the research study. People who do not need to know who the child/young person is, will not be able to see their name or contact details; The child/young persons’ data will have a code number instead. Data will be sent from the treating hospital to the LCTC. We will notify the child/young person’s GP that they will be taking part in the study for their information. All the confidential information about any child/young person participation in this study will be kept confidential. We will keep all information about any participants safe and secure. Once we have finished the study, we will keep the data for 25 years, so we can check the results. We will write our reports in a way that no-one can work out who took part in the study.


NIHR Medical Research Council
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Hospital departments taking part

To see if your hospital is taking part please visit the list of open sites in recruiting centres.

Study funder

This study has been funded by the the NIHR Efficacy and Mechanism Evaluation Programme (NIHR129875), with additional operational support received from the NIHR Clinical Research Network. The views expressed are those of the author(s) and not necessarily those of the NIHR, Clinical Research Network or the Department of Health and Social Care.

Study organiser

Sponsor - The Newcastle upon Tyne Hospitals NHS Foundation Trust. Clinical Trials Unit – Liverpool Clinical Trials Centre.

Study review and approval

This study has been reviewed and approved within the UK by the Health Research Authority (HRA), the National Research Ethics Service (NRES) and the Medicines & Healthcare Products Regulatory Agency (MHRA).

Recruiting Centres


CRESCENT Central Trial Team
Liverpool Clinical Trials Centre
University of Liverpool
2nd Floor – Institute in the Park
Alder Hey Children's NHS Foundation Trust
Eaton Road
L12 2AP
+44 (0)151 794 0250