Liquid meal test with head-up tilt (Autonomic Unit)

The Autonomic Nervous System (ANS) is an important system that controls many of the bodily functions that we have unconscious control of. This includes: heart rate, blood pressure, temperature control, the bladder, digestion and bowel movements.

When one or more parts of this system are impaired, it can result in a variety of disorders.

In the Autonomic Unit, we focus on testing how well the ANS is functioning, using various tests, to be able to diagnose these conditions.

A Liquid Meal Test is a specific clinical test that is used to aid the diagnosis of disorders related to falls in blood pressure when digesting food. This test allows us to monitor your blood pressure and heart rate before and after you consume a liquid meal. Post-prandial hypotension is when there is a drop in blood pressure following the ingestion of a meal. It is thought to be related to the pooling of blood to the gut during the process of digestion.

Due to this impairment of the ANS, this then reduces the amount of blood that is available to the rest of the body, causing a drop in blood pressure.

Common symptoms include: dizziness, light headedness and falls. This test can be beneficial as it provides us with blood pressure and heart rate changes related to meal consumption, which can aid diagnosis and treatment.

During the test, the blood pressure cuff may get uncomfortably tight. Sometimes the cuff can irritate or chafe the skin. If this happens during the test, please let the Clinical Autonomic Scientist (CAS) know as the cuff can be adjusted to make it more comfortable. If you have any issues with swallowing, then let us know during the test.

The drink used in the test consists of a meal replacement supplement (Complan) and powdered glucose dissolved in full fat milk. If you are lactose intolerant, please let us know as we can provide an alternative drink (composed of glucose and water).

If you are diabetic, please take into account that the liquid meal used is high in sugar (consists of 20 grams of powdered glucose and the Complan used has 44.7g of carbohydrates). The glucose content that is used will be explained to you by the CAS on the day of your test.

If you are someone who experiences low blood pressure following the ingestion of a meal, you may experience symptoms such as dizziness and light headedness during and after the test. However, the equipment that is used during testing will allow the CAS to closely monitor your blood pressure and heart rate.

After the test is completed, the CAS may take a few blood pressure recordings to ensure your blood pressure is at a safe level before leaving the department.

Before testing, the CAS will explain what is involved in a Liquid Meal Test, and will also answer any queries you may have. The decision to have a Liquid Meal Test is entirely yours.

If you decide not to take part in this treatment, this will not affect our attitude or influence any other aspect of your care. It may mean, however, that your consultant cannot be as certain or specific about any future treatment or diagnosis.

Your consultant or clinical nurse specialist (CNS) will have taken into account the potential risks and benefits of having a Liquid Meal Test during your initial referral. There are some alternative methods that may be available under certain circumstances, although the possibility of these should be discussed with your referring doctor or CNS.

We are able to provide an alternative drink for patients that are lactose intolerant. This drink will be made up of glucose and water only. The amount of glucose used will be equivalent to your body weight in grams i.e., one gram of glucose for each kg of body weight.

Please wear suitable clothes which will allow access to the upper arms to apply a blood pressure cuff.

Please do not eat four hours prior to testing; you may drink water only. It is advisable to stay hydrated prior to testing.

Please ensure your hands are kept warm in preparation for this test. You may need to stop certain medications prior to testing, although the consultant or CNS should be able to advise you during your initial consultation; if you are unsure, please call us directly or ask us when you confirm your appointment.

Testing can take up to two hours.

Consenting to treatment means that a patient must give their permission to take part in any medical treatment, test or examination. Therefore, before any treatment can take place, by law we must obtain your consent. This confirms that you understand what is involved and agree to have the procedure.

If you change your mind at any point, you are free to withdraw your consent at any time. In some cases, we like to video record the test, which the CAS will explain to you on the day of your appointment. We ask for your written consent if you wish to proceed with the test being video recorded (which will only be seen by anyone involved in your direct care).

We also ask for your written consent if you are happy for the video recording to be used for teaching purposes; which you are free to decline and will not affect your treatment. If you have any queries or are unsure about any part of the proposed treatment, please do not hesitate to get in touch and speak to one of our senior members of staff.

The Liquid Meal Test will be carried out by a CAS and only the patient being tested will be allowed in the room (any family members/carers will be asked to wait outside the testing room).

During the Liquid Meal Test, your blood pressure and heart rate will be monitored whilst you lie on your back and when you change your posture before and after you consume a milky drink. Firstly, you will be asked to lie down on the tilt table.

The CAS will fit you up with the following equipment

• A blood pressure cuff which will take recordings of your blood pressure at certain points during testing
• Respiratory belt that goes around your chest which will measure your breathing activity
• Electrocardiogram (ECG) which will measure your heart rate activity (on both shoulders and one on your ankle)
• A finger cuff attached to a small device that sits on your wrist which will measure your blood pressure and heart rate continuously throughout testing.

Once the equipment is on and is working as it should, we then tilt you to 60° head-up (safety belts will be put in place that go Blood pressure cuff ECG tab A finger cuff to monitor your blood pressure and heart rate Safety belts for the 60° head-up tilt 10 across your knees and abdomen during the tilt). The pre-meal tilt can last up to 10 minutes.

Once the first tilt has been completed, we then provide you with a 300ml milky drink (alternatively, glucose and water if you are lactose intolerant). After consuming the liquid meal, we leave you lying down with all the equipment still applied for 45 minutes to allow the liquid meal to digest. After the rest period is complete, a repeat 60° head-up post-meal tilt is performed which can last up to 10 minutes.

After all of your clinical treatments have taken place with us, the results will be analysed and discussed in a multi-disciplinary team (MDT) meeting. A brief summary letter will then be sent to you by post and to the doctor who referred you for testing (normally your GP) detailing the results of your tests.

You will be sent a letter that will include a follow up plan and you will then be contacted by one of our consultants or CNS for a follow up appointment to explain the results in more detail, and to also answer any queries you may have.

Address: National Hospital of Neurology and Neurosurgery
The Autonomic Unit 2nd Floor
Queen Mary Wing
Queen Square
London WC1N 3BG

Direct tel: 0203 448 3079
Switchboard: 0203 456 7890
Fax: 0203 448 3878
Email: uclh.enquiry.autonomic.secretaries@nhs.net

The Autonomic Unit is located on the second floor of the Queen Mary Wing at the National Hospital for Neurology & Neurosurgery, Queen Square.

Please follow signs from the main entrance towards the Queen Mary Wing and you should find the appropriate set of lifts/stairs on your right-hand side. Head to the second floor and use the intercom to contact our admin team who will let you in once you have confirmed your identity.