An auditory brainstem response (ABR) is a computerised hearing test that records your child’s response to sound. The response is recorded by placing a number of sticky electrode pads on your child’s head. The electrodes send the response to the computer where it is recorded.
The test takes about two hours. Children must be asleep for the test so normal muscle movement isn’t recorded (which prevents an audiologist from seeing the hearing responses). Your child may be given sedation medicine (to make them sleepy) or a general anaesthetic.
Note: If your child is having sedation or general anaesthetic for their ABR they will need to fast (go without food or drink) before the procedure. You will receive instructions and information about this before the day.
ABR using sedation
If your child is having sedation for their ABR, they will usually be given a medicine called chloral hydrate to drink (it has strong peppermint taste). It is important that the whole dose is taken and nurses will assist you and your child with this. It will then take between 10 and 30 minutes for your child to become drowsy.
Sometimes Chloral Hydrate is not successful, and another medicine Midazolam may be required. Midazolam is taken intranasally (via the nose).
Some children become upset before going off to sleep – this is a normal effect of the sedation medicine and will pass. Once your child is asleep, a monitor will be attached to their hand or foot to monitor their oxygen level and pulse during the procedure. You and your child will then be escorted to the ABR room in the Day Unit. A nurse will stay with your child and monitor them while they are asleep. You can stay with your child during the test if you wish.
Sedation fails in approximately 1 in 5 cases. If the sedation fails completely, with no sleep time obtained on the first visit, your child will be re-booked to have the procedure undertaken with general anaesthetic. In cases where sleep is achieved with sedation, but not long enough to complete a full hearing assessment with ABR, a second sedation ABR appointment will be booked.
After the ABR
When the ABR is finished and your child is awake, they will be offered some food and drink. Breastfed or bottle-fed babies can be fed as soon as they are awake. Once your child has had food and drink and is alert, you will be able to take them home.
Care at home
Chloral hydrate can affect your child for between four and eight hours and they should be watched during this time. Quiet inside play is recommended for the rest of the day. They can return to normal activity the following day.
ABR using general anaesthetic
If your child is having their test under general anaesthetic, it will take place in the operating theatre and they will be cared for by an anaesthetist. One parent can usually stay with them until they are asleep (at your anaesthetist’s discretion).
After the ABR
When the ABR is finished and your child is awake, they will be offered some food and drink. Breastfed or bottle-fed babies can be fed as soon as they are awake. After approximately 1 hour, and once your child has had food and drink and is alert, you will be able to take them home.
Care at home
Quiet inside play is recommended for the rest of the day. They can return to normal activity the following day. Some children may feel nauseous and vomit after- an anaesthetic – this is a normal side-effect. If your child vomits, give them sips of clear fluids, and encourage them to eat a piece of dry toast or a cracker biscuit until the vomiting settles. If the vomiting continues, seek medical advice.
The audiologist will discuss the results of the ABR with you on the day of the test. A follow-up appointment with the doctor who asked for the ABR may be required.