This page explains about having an MRI scan under general anaesthetic, and what to expect when your child comes to Great Ormond Street Hospital (GOSH) to have this procedure.
An MRI (magnetic resonance imaging) scan uses a magnetic field rather than x-rays to take pictures of your child’s body. The MRI scanner is a hollow machine with a tube running horizontally through its middle. 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 the MRI scan under general anaesthetic.
Watch our short video about having an MRI scan or listen to our audio podcast. If you would like further advice about preparing your child for the scan, please ring the department’s play specialist on the numbers below.
We assess all children to see if they might benefit from having the scan under anaesthetic. Your appointment letter will state whether your child is having an anaesthetic so you can follow the instructions below to prepare them.
Are there any alternatives?
Your child may need this scan so that their doctors can get detailed pictures of the size and shape of part of your child’s body. Various types of scan such as CT, ultrasound and x-rays can show the size and shape of parts of your child’s body but not in as much detail as an MRI scan. The information from the scan is then used to help with a 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.
Preparing for the general anaesthetic
We operate two ‘lists’ for MRI scans under general anaesthetic – one in the morning and one in the afternoon. Your child’s admission letter will state whether your child is on the morning list or the afternoon list.
It is important that your child does not eat or drink anything for a few hours before the anaesthetic. This is called ‘fasting’ or ‘nil by mouth’. Fasting 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. Fasting times are provided in your admissions letter – in broad terms, this is six hours for food (including milk), four hours for breast feeding and two hours for clear fluids before the procedure.
On the day of the scan
You will need to be at the hospital at 7.30am for a morning list and 11.30am for an afternoon list. Your child will be admitted to a ward where they will be seen by a doctor or nurse specialist and be assessed as fit for anaesthesia.
We will also ask you to give permission for the MRI 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 placed on that list.
Your child should wear clothes without zips or metal poppers for the scan – otherwise they will need to change into a gown.
Before the scan starts, the nurse or radiographer will check your child does not have a pacemaker, metal implants or clips, dental braces, a history of metal fragments in the eyes or any allergies. We will ask you to sign a form to confirm this.
If your daughter is 12 years old or older, we will ask her about her periods and any possibility she could be pregnant.
What does the scan involve?
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, they will be transferred to the scanning room and we will ask you to wait on the ward until the scan is completed.
Your child will need to lie on the bed for the scan. Depending on the part of their body being scanned, they may need to have a coil over part of their body or wear a head coil (this will not touch their head). When your child is in the correct position, the radiographer will move the bed inside the scanner and then go into the control room. The anaesthetist will monitor your child throughout the scan.
When the scan has finished, the radiographer will move the bed out of the scanner. They will then move your child into the recovery area to wake up from the anaesthetic. Some children are 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.
Medicines given during an MRI scan
We may give your child some medicine during the MRI scan to make the image clearer. The radiographer will tell you which medicines your child has had in case of later side effects. The medicines we use most often at GOSH include:
Secretin – this is a naturally occurring hormone that increases the volume of juice within the duct of the pancreas. It is given as an injection. Possible side effects include: loose or runny poo, cramp-like stomach ache, headache, skin itching and a rash.
Hyoscine butylbromide (Buscopan®) – this medicine relaxes the smooth muscle of the intestine. Possible side effects immediately after the injection include: dilated pupils, dry mouth, flushing of the skin, dislike of bright light and palpitations. In the hours following the injection, other side effects may occur: constipation, urinary retention and urinary urgency.
Furosemide – this medicine increases the production of urine immediately after injection. Possible side effects include: low blood pressure and dehydration. You can reduce these side effects by encouraging your child to drink plenty of fluids in the hours after the scan.
Mannitol – this medicine is drunk and allows clear imaging of the wall of the bowel. A common side effect is loose or runny poo, so in the first few hours after the scan, your child should have access to a toilet. Dehydration may also occur, so ensure plenty of fluids in the hours following the scan.
Gadoteric acid (Dotarem®) – this is a ‘dye’ that makes blood vessels and any inflammation show up more clearly on the pictures. It is given as an injection. A possible side effect is hypersensitivity, but this will normally be an immediate effect. There are no reported long-term side effects of gadoteric acid.
Are there any risks?
There are no risks associated with MRI scans. They are painless and generally quick with no lasting effects. The scanner does not touch your child during the scan. MRI scans are not suitable for people with certain metal implants inside them (such as pacemakers) because the scanner emits a strong magnetic field. This is why we carry out a thorough metal check before your child has the scan.
Every anaesthetic carries a risk of complications, but this is very small. Your child’s anaesthetist is a very experienced doctor who is trained to deal with any complications.
What happens afterwards?
When your child has recovered fully from the anaesthetic and has had something to eat and drink, you will be able to go home. The radiologist (doctor specialising in scans) will send a report of the scan to your child’s doctor in time for their 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 him or her irritable. This is temporary.
If your child is taking any medications, please give this as normal.
Please note this is a generic GOSH information sheet. If you have specific questions about how this relates to your child, please ask your doctor. Please note this information may not necessarily reflect treatment at other hospitals.