MRI Sedation Information


Some patients undergoing an MRI scan who are claustrophobic may require Sedation (Hypnovel) to help relax and feel comfortable to have their scan completed.

Hypnovel contains the active substance midazolam, which belongs to a group of medicines known as benzodiazepines. It is a short-acting medicine that is used to induce sedation (a very relaxed state of calm, drowsiness, or sleep) and relieves anxiety and muscle tension. This is given intravenously usually through a vein in the arm.

Although we would like this service to be available to everyone, we must be very careful of the patients that receive this drug as there are risks associated with the administration of it. If we feel you are at high risk of a reaction or complication your sedation may be cancelled and be better suited in a hospital environment.

To be aware of the risks prior to the scan, we would like to inform you that possible side effects include:

  • Anaphylactic shock (a life-threatening allergic reaction). Signs may include a sudden rash, itching or lumpy rash (hives) and swelling of the face, lips, tongue, or other parts of the body. You may also have shortness of breath, wheezing or trouble breathing, or a pale skin, a weak and rapid pulse, or feeling of loss of consciousness. Additionally, you may experience chest pain, which can be a sign of a potentially serious allergic reaction called Kounis syndrome.
  • Heart attack (cardiac arrest). Signs may include chest pain which may spread to your neck and shoulders and down your left arm.
  • Breathing problems or complications (sometimes causing the breathing to stop).
  • Choking and sudden blockage of the airway (laryngospasm).

Other possible side effects include:

  • Effects on behaviour: restlessness, agitation, irritability, nervousness, anxiety, hostility, anger or aggression, excitement, hyperactivity, changes in libido.
  • Muscle problems: muscle spasms and muscle tremors (shaking of your muscles that you cannot control).
  • Mental and Nervous system problems: confusion, disorientation, emotional and mood disturbances, involuntary movements, nightmares, abnormal dreams, hallucinations.
  • Heart and circulation problems: low blood pressure, slow heart rate, redness of the face and neck (flushing), fainting or headache.
  • Breathing problems: shortness of breath, hiccup.
  • Stomach, gut and mouth problems: feeling sick or being sick, constipation, dry mouth.
  • Skin problems: rash, hives (lumpy rash), itchiness.
  • Injury: Patients taking benzodiazepine medicines are at risk of falling and breaking bones. This risk is increased in the elderly and those taking other sedatives (including alcohol).
  • General: tiredness (fatigue).
  • Elderly patients: Life-threatening side effects are more likely to occur in adults over 60 years of age and those who already have breathing difficulties or heart problems, particularly when the injection is given too quickly or at a high dose.
  • Patients with severe kidney disease: Patients with severe kidney disease are more likely to experience side effects.

How to Prepare for an MRI with Sedation?

To ensure the scan runs as smooth and as safe as possible it is very important to:

  • Fast for 6 hours before your appointment time, including food, drink, alcohol, and cigarettes.
  • Organise a friend or family member to attend the appointment with you. You will not be able to drive for 24 hours and will not be able to take a taxi or Uber home. For safety reasons you will need to leave the practice in the care of someone who will accompany you home.
  • Stop taking any anti-anxiety (e.g. Valium), anti-depressants (e.g. Zoloft), or sleeping tablets (e.g. Temazepam) 24 hours before your appointment.

Post Care after having Sedation.

To ensure the safety of the sedated patient, after the scan you will:

  • Remain on site for a minimum of 1 hour until you have returned to a baseline of consciousness.
  • Will only be permitted to leave under the care and supervision of a friend or family member who will be provided with verbal and written care instructions.
  • Not be able to drive or operate any machinery for 24 hours after sedation.