Your child is having a CT scan under general anaesthetic

CT scanner

A CT scan (Computed Tomography) uses x-rays and computers to take pictures of the internal structures of your child’s body. This page from Great Ormond Street Hospital (GOSH) explains about having a CT scan at, how to prepare for it and what care your child will need afterwards.

The CT scanner is a large doughnut-shaped machine with a hole in the centre through which a special bed can move. The scan can last anywhere from five minutes to 20 minutes, depending on the area and complexity of the scan. Although the bed will move through the scanner, it will not come into contact with your child.

Some children need to have injection of ‘contrast’ a liquid that shows up as a different colour on the scan. If your child is likely to need contrast, we will put local anaesthetic cream on their skin to make it numb before the injection.

If your child is apprehensive or scared of needles or injections or the scan itself, please telephone the Radiology play specialist before the appointment.

Why does my child need a general anaesthetic for the CT scan?

Some children find it difficult to lie still for the scan – either because of their age or their medical condition – so we might suggest they have a general anaesthetic for the CT scan. We assess all children to see if they might benefit from general anaesthesia. Your appointment letter will state whether your child is having a general anaesthetic so you can follow the instructions below to prepare them.

Are there any alternatives?

Your child may need this scan to show the doctors detailed pictures of part of their body. Various types of scan such as ultrasound and x-rays can show the size and shape of parts of your child’s body but not in as much detail as a CT scan. The information from the scan is then used to help with diagnosis and plan their treatment.

When you receive your appointment letter

If you are unable to keep this appointment, please inform the department as soon as possible beforehand. Sometimes, we can offer the appointment to another child on the waiting list.

As so many children and young people need to use our services, we have had to introduce a policy where if a child cancels or does not attend two appointments in a row, we will close their referral and inform their GOSH consultant.

Before the appointment

If you are pregnant or think you could be pregnant, please let us know. The x-rays used in the CT scan could harm your unborn baby, so we would advise bringing another adult to come into the scanning room with your child.

If your daughter is 12 years old or older, we will ask her about her periods and any possibility that she could be pregnant.

Preparing for the general anaesthetic

Our ‘list’ for CT scans under general anaesthetic is in the afternoon. It is important that your child does not eat or drink anything for a few hours before the anaesthetic. This reduces the risk of stomach contents entering the lungs during and after the procedure.

You will be informed the night before the procedure of the time that your child should be ‘nil by mouth’ – in other words, have nothing to eat or drink before the anaesthetic. It is equally important to keep giving your child food and drink until those times to ensure they are not thirsty or hungry. This may involve waking your child in the night to give them a drink which we recommend.


The person bringing your child to the scan should have ‘Parental Responsibility’ for them. Parental Responsibility refers to the individual who has legal rights, responsibilities, duties, power and authority to make decisions for a child. If the person bringing your child does not have Parental Responsibility, we may have to cancel the scan.

The day of the scan

You will need to be at the hospital at 11.30am. Your child will be admitted to a ward where they will be seen by a doctor or nurse specialist to assess that they are fit for anaesthesia.

We will ask you to give permission for the CT scan under general anaesthetic by signing a consent form if this has not been done previously. The anaesthetist will decide the order of the list on the day itself. This will be based on the clinical diagnosis and condition of all the children due to have a scan.

The scan

We will give your child a hospital gown to wear – wearing clothes containing metal such as zips or buttons can interfere with the scan. Your child will either have an anaesthetic gas to breathe or an injection. The anaesthetist will closely monitor your child’s blood pressure, pulse, temperature and breathing throughout the scan, ensuring that they are safe and fully asleep. Once your child is under anaesthetic, we will ask you to wait on the ward until the scan is completed.

Your child will need to lie on the scanner bed, either head towards the scanner or feet first, depending on the part of their body being scanned. Once your child is in the correct position, the radiographer will go into the control room to operate the scanner. They will move the bed into the scanner – it will not touch your child – and the scan will start. The scanner makes some quiet whirring noises as it takes the pictures.

A radiologist (doctor who specialises in imaging) may come into the control room to check the pictures and confirm they are good enough. When the scan has finished, the radiographer will move the bed out of the scanner so your child can be moved to the recovery area to wake up from the anaesthetic.

Next they will be taken back to the ward to recover. We will call you back at this point so that you can be with them when they start to wake up. You should be prepared to stay in the hospital until your child is fully awake and has had something to eat and drink. Most families are able to go home a couple of hours or so after the scan.

Radiation and risk

It is our legal duty to tell you about the potential risk of having a CT scan.

CT scans are only ever requested if the benefits outweigh the risks involved. CT does use radiation, but the dose is kept as low as possible. This is because the radiographers are specially trained to obtain the best quality pictures while using the lowest amount of radiation possible.

After the scan

When your child has recovered fully from the anaesthetic and has had something to eat and drink, you will be able to go home. A radiologist will send a report about the scan to your child’s doctor in time for your next appointment. If you have not been given a follow up appointment to see your consultant, please contact their secretary after two weeks.

When you get home

  • After the anaesthetic, your child may feel sick for 24 hours. You should encourage your child to drink but do not force them to do so. As long as your child is drinking, it does not matter if they do not feel like eating for the first couple of days.
  • Children are generally sleepier than usual for 24 hours after a scan under anaesthetic. This is because the effects of the anaesthetic medicine last for about a day.
  • If your child is unduly sleepy or difficult to rouse, make sure they are in a safe position on their side and ring your family doctor (GP).
  • Keep a close watch on your child until they are back to normal. Do not leave them with an inexperienced carer.
  • Your child may be tired and a little clumsy for 24 hours after the anaesthetic, so do not let them do anything that might lead to a fall.
  • You should keep your child away from school or nursery for one day until they have recovered from the anaesthetic. 
  • Your child may have mood changes which can make them irritable. This is temporary. 
  • If your child is taking any medications, please give this as normal.
Compiled by:
The Radiology department in collaboration with the Child and Family Information Group This information does not constitute health or medical advice and will not necessarily reflect treatment at other hospitals
Last review date:
March 2019