NICE opens consultation on draft guidance for depth of anaesthesia monitors
Draft guidance from NICE's Diagnostics Assessment Programme issued for consultation today recommends the use of the Bispectral Index (BIS) depth of anaesthesia monitor as an option for reducing adverse outcomes from anaesthesia in patients receiving total intravenous anaesthesia and in patients who are at higher risk of complications from any type of general anaesthesia such as unintended awareness, cognitive dysfunction, and the adverse physiological effects of deep anaesthesia. Although there is more uncertainty about the E-Entropy (GE Healthcare), and Narcotrend-Compact M (MT MonitorTechnik GmbH & Co) depth of anaesthesia monitors, the draft guidance also recommends them as options for the same patient groups.
General anaesthesia is a reversible state of controlled unconsciousness achieved with drugs used to prevent awareness, recall, distress and movement in patients during surgery. It is estimated that 2.4 million people needed a general anaesthetic in England in 2007. Individual variation in response to anaesthetics can lead to occasional complications associated with inadequate or excessively deep levels of anaesthesia. These include patient awareness during surgery and recall after surgery which can cause post-traumatic stress disorder as a result of inadequate levels of anaesthesia during surgery, and potentially fatal cardiac and respiratory collapse, prolonged recovery and cognitive dysfunction as a result of excessively deep anaesthesia.
In current NHS clinical practice, a patient's response to anaesthesia during surgery is assessed by clinical observations such as crying, sweating, pupillary size and reactivity, and by the use of supplementary monitoring devices. These include an electrocardiograph (ECG) to measure the speed and rhythm of the heart, a non-invasive blood pressure monitor, and a pulse oximeter to detect the pulse and calculate the amount of oxygen in the blood. The monitors that NICE is currently assessing measure electrical brain activity, providing a further indication of how the patient is reacting to the anaesthetic.
Patients who are considered at higher risk of complications from general anaesthesia include older patients, those with a high body mass index, patients with airway problems, patients who have comorbidities and those undergoing certain types of surgery in which lower levels of anaesthetic are often used (for example, cardiac surgery, airway surgery, obstetric surgery or emergency surgery for major trauma). The use of muscle relaxants can also increase the risk of patient awareness because they allow a lower level of anaesthetic to be used and prevent patients from moving. This limits the patient's ability to communicate with the surgical team about any awareness that may develop. This assessment focuses on three depth of anaesthesia monitors that are based on algorithms using EEG (electroencephalography) data and compares them, in combination with standard clinical monitoring, to current NHS clinical practice.
Professor Carole Longson, NICE Health Technology Evaluation Centre Director, said: "Although relatively rare, inadequate or excessively deep levels of anaesthetic can be traumatic and have far-reaching consequences for patients, including post-traumatic stress disorder, cognitive dysfunction and an increase in the incidence of stroke and heart attack. The Committee considered that whilst additional research on the benefits and costs of the products is desirable, they concluded that the size, complexity, cost, and time requirements of such studies could unduly delay the uptake by the NHS of a technology that is likely to be of benefit to patients at high risk of the complications of anaesthesia."
The draft diagnostics guidance for depth of anaesthesia monitors is available on the NICE website at http://guidance.nice.org.uk/DT/7. The closing date for comments on the draft guidance is 22 June 2012.
Notes to Editors
About the draft guidance
1. The combination of standard clinical observation (of pupillary size and reactivity, crying and sweating) and measurement of one or more clinical markers such as pulse, blood pressure and end-tidal anaesthetic gas concentration (for inhaled anaesthesia) constitutes standard clinical monitoring and is the comparator for this assessment.
2. Some common side effects of general anaesthesia include vomiting, headaches and dizziness.
3. Awareness during anaesthesia is a less common side-effect and results from under-dosing of anaesthetic. It is more likely during certain types of surgery in which lower levels of anaesthetic may be indicated, such as cardiac, airway, obstetric or emergency surgery for major trauma. For those who are aware during anaesthesia there can be long-term effects such as anxiety, nightmares, flashbacks, clinical depression and in some cases post-traumatic stress disorder.
4. Studies suggest that between 1 and 2 people in 1000 experience awareness or recall during general anaesthesia, with a third of these also experiencing pain and prolonged recovery.
5. The use of muscle relaxants can increase the risk of patient awareness because they are used with a lower level of anaesthetic. Muscle relaxants also prevent patients from moving. This limits the patient's ability to communicate with the surgical team and means that the anaesthetist has to use other clinical information to judge the patient's state of consciousness.
6. Side effects of excessively deep general anaesthesia include prolonged recovery and, in severe cases, cardiovascular collapse and respiratory depression (which can be fatal without cardiovascular and respiratory support). Postoperative cognitive dysfunction is another side effect and is most common in older people. There is some evidence to suggest a link between longer term morbidity and mortality, and the length and depth of anaesthesia.
7. Current NHS clinical practice for monitoring the depth of anaesthesia consists of clinical observations such as crying and sweating, and the use of supplementary monitoring devices. These include an electrocardiograph (ECG) to measure the speed and rhythm of the heart, a non-invasive blood pressure monitor, a pulse oximeter to detect the pulse and calculate the amount of oxygen in the blood, a method of patient temperature control, a device to monitor volatile agent concentration and provide a MAC value (measure of potency of inhalational general anaesthetics), a nerve stimulator (if a muscle relaxant is used) and a capnograph to monitor the inhaled and exhaled concentration of carbon dioxide. Additional monitoring equipment such as a cardiac output monitor may be used for some patients or certain types of surgery.
About the NICE Diagnostics Assessment Programme
8. Further information about the NICE diagnostics assessment programme can be found at: www.nice.org.uk/diagnostics
9. Topics to be considered by the Programme are routed through the related Medical Technologies Assessment Programme. Further information about this can be found at: www.nice.org.uk/mt
10. The National Institute for Health and Care Excellence (NICE) is the independent organisation responsible for providing national guidance and standards on the promotion of good health and the prevention and treatment of ill health.
11. NICE produces guidance in three areas of health:
- public health - guidance on the promotion of good health and the prevention of ill health for those working in the NHS, local authorities and the wider public and voluntary sector
- health technologies - guidance on the use of new and existing medicines, treatments, medical technologies (including devices and diagnostics) and procedures within the NHS
- clinical practice - guidance on the appropriate treatment and care of people with specific diseases and conditions within the NHS.
12. NICE produces standards for patient care:
- quality standards - these reflect the very best in high quality patient care, to help healthcare practitioners and commissioners of care deliver excellent services
- Quality and Outcomes Framework - NICE develops the clinical and health improvement indicators in the QOF, the Department of Health scheme which rewards GPs for how well they care for patients
13. NICE provides advice and support on putting NICE guidance and standards into practice through its implementation programme, and it collates and accredits high quality health guidance, research and information to help health professionals deliver the best patient care through NHS Evidence.
This page was last updated: 01 June 2012