Evaluation and Application of Bispectral Index Monitoring (BIS)

Introduction:

The majority of individuals admitted to critical care are very ill and require a lot of invasive treatments. Various drugs and medications are given to help the patients tolerate this treatments. Such patients are normally attached to a lot of necessary monitoring equipment. I have chosen the use of Bispectral Index monitoring (BIS) as the focus for this entry. This device measures the awareness of patients during procedures, such as surgical intervention and other invasive treatments. This entry aims to give a deeper knowledge about the use of this tool and to share the information with others who may need it. Neuromuscular blocking agents(muscle relaxants) are frequently used in the Intensive Care Unit to facilitate tracheal intubation and the application of continuous paralysis(Sharpe 1992),due to the complex nature of the critically ill patients, the effects of neuromuscular blocking agents are unpredictable (Sharpe 1992),hence a monitoring device such as BIS will help both nurses and doctors in assessing the adequacy of medications given. The Intensive Therapy Unit (ITU) at my place of work has only started using this monitoring tool, in the last few years. Previously to this, vital signs and subjective sedation scales were utilised and often resulted in the over sedation of patients due to their inaccuracies. This off course has a direct effect on post anaesthesia care, and in a study of patients aged over 60 in Berlin delirium was found to be lower in patients who had the BIS monitoring (Davidson et al, 2013).Furthermore, with the direct correlation between over-sedation and post intensive care syndrome , which can affect patients physically and cognitively (Gautam et al, 2017) the effective use of such tool can aid Medical and Nursing staff in titrating muscle relaxants, anaesthetic medication, and other drugs that induce sleep (Gilrado et al, 2017).Essentially, this could then help hasten the weaning of medication and reduce the possible side effects of prolonged use of sedatives on patients, while lowering costs to the NHS budgets (Gilrado et al, 2017).

The National Institute for Health and Care Excellence (NICE) (2012) has assessed 3 electroencephalography (EEG)-based depth of anaesthesia monitors - Bispectral Index (BIS), E-Entropy and Narcotrend-Compact M - to help the NHS decide whether to use these products. There is more uncertainty about the clinical benefits of the E-Entropy and Narcotrend-Compact M monitors than the BIS monitor (NICE 2012).

Experience:

During one of my shifts on ITU, I looked after a patient who was sedated but was struggling to synchronize with the ventilator. The Doctor decided to paralyse them using muscle relaxants to give them the time to receive the best therapy for their chest. Assessment of awareness in individuals can be complex, particularly with regards to sedated patients (Gurudatt 2011).According to Gurudatt (2011),because the majority of the sedation scales are subjective , an objective monitor of sedation is preferable in adequately assessing the status of a patient. The Richmond Agitation Sedation Scale (RASS) (Curtis et al 2002)is one such subjective method, which is currently used in our clinical area. Because this patient was paralysed, I struggled to use the RASS tool, which is essentially a scale in determining how deeply sedated a patient is through movements, so when the patient was paralysed such a tool becomes limited. I then resorted to using BIS monitor, which analysed the patient's brain activity and displayed the results as numbers on the screen to determine how deeply sedated they were. Although I have been shown how and had set up this monitoring before, I wasn't confident in assessing the wakefulness and the brains state of consciousness from a number, particularly as the limits were set by Doctors, and they were satisfied as long as the muscle relaxant had the desired effect of allowing the patient to synchronize with the ventilator. This made it hard for me to understand and to act on the number displayed by the BIS monitoring, and essentially the size of their pupils and movements during intervention such as suctioning were still being used more to determine whether they were heavily sedated or not.

Issue:

I was limited in the understanding of how BIS worked. As I relied on the set limits by Doctors, I was not aware of the significance of the set range and as such still relied on the RASS score to determine whether the patient was deeply sedated or not, and this was only effective when the patient was actually moving rather than when they were sedated enough. This meant that I effectively would not know when to titrate or begin to wean off the muscle relaxants if the patient was heavily sedation. The idea is for practitioners to be aware of sedation levels and ensure that patient who are on muscle relaxants should not be awake and practitioners can be alerted if wakefulness is assessed.

Questions:

What is BIS? Why use BIS monitoring, and which patients would you use it on? And What does this mean for practice?

Bispectral Index ( BIS) monitor (Sandham 1994) is a technology device that was introduced as a novel measure of the level of consciousness by algorithmic analysis of patients electroencephalogram during anaesthesia. This has been used in conjunction with other monitors to help assess the depth of common anaesthetic medications given to a patient.

The goal of BIS is to help balance anaesthesia which is achieved by three factors: hypnosis, analgesia and immobility (Kyoungho et al 2017). This off course is not as straight forward as theorised, for instance when it comes to the use of BIS and monitoring hypnosis, several studies including that written by Sengubta et al (2011), show that BIS monitoring had a positive response to standardized local anaesthesia such as propofol in terms of hypnosis , but had no effect in the use of ketamine. This would suggest a distinct limitation in the use of BIS, depending on the form of anaesthesia used. Nonetheless, arguably hypnosis is signified by BIS during the sedation of patients on propofol making it useful, for patients on such measures. Furthermore, apart from being a validated measure of hypnosis, BIS is also useful in predicting light and deep sedation in patients, which ultimately also helps in ensuring the right levels of analgesic effect. In a study by Tasaka et al (2016), on the use of BIS to measure paralysis, the results showed that there was a correlative sensitivity and predictive value on the BIS with regards to level of sedation , and where 3 of the participants were inadequately sedated, the BIS monitoring was able to show definitive changes, in correlation with physical signs, observed using the RASS score. Off course pain is one the main issues that BIS tries to monitor, and studies have shown that it is sensitive in detecting nociceptive stimulation , which refers to the sensory nervous systems response to certain harmful stimuli (Dublin 2010) .However according to Gruenewald M et al(2013) despite BIS sensitivity in detecting nociceptive stimulation , the increase in the values on BIS are yet to be demonstrated as sufficient to be used clinically as a pain measuring tool in ITU’s. Perhaps this is an interesting area of study that requires further research, although debatably, if BIS shows that a patient is deeply sedated, it could be assumed that they are not in pain.

Ultimately using the device will help Nurses and Doctors wean the depth of anaesthetic drugs which would then give the option to titrate the drugs to avoid giving too much or too little effects to the patient. National Institute for Health and Care Excellence (NICE) have created a guideline (DG6) in November 2012.The machine gives a number which is from 0 to 99, where 100 means patients are awake and 0 means no brain activity. The target range of BIS values during general anaesthesia is 40–60; this range indicates a low probability of awareness with recall( NICE 2012)..Understanding the NICE guidelines would benefit Nursing and Medical staff to use BIS safely .

Clinical sedation assessment becomes insufficient in deeply sedated patients (Riess et al, 2002). Assessment of sedation is vital in Intensive Care, over sedating and under sedating patients can put the patient at risk of complications . Over sedating patients can lead to increased length of stay in hospital, it prolongs mechanical ventilation, it will cost more, increases risk of delirium, decreases wound healing and GI motility, it can impair the reliability of neurological assessment(EBME, Covidien 2010). On the other hand, if the sedation is not enough it can lead to fear, anxiety ,agitation, unpleasant recall, prolonged nursing care and an increase in hospital cost (EBME ,Covidien 2019). It is therefore important for patients to get the right dose of sedations and muscle relaxants. However, when a patient is on a muscle relaxant infusion, monitoring patients wakefulness is also necessary to avoid Postoperative Cognitive Dysfunction (POCD)(Rundshagen,I. 2014).

 The BIS Index range chart says that a 100 shows that patient is awake and responds to normal voice, while 80 shows a light to moderate sedation where patient can still respond to loud commands or mild prodding and shaking while 40-60 is the acceptable where patient is on deep hypnotic state or on general anaesthesia and patient will probably have low recall or have unresponsive to verbal stimuli, and 20 -0 means that patient is too flat or no brain activity.(EBME and Covidien ,2019).My understanding of the BIS chart range and NICE guideline is very important to allow me in titration of muscle relaxant infusion.). A study has suggested that more than 69 per cent of ICU patients were found inappropriately sedated(Kaplan L.J., Bailey H. 2018).

Monitoring patients by using sedation scale and attachment to an electroencephalogram (EEG) monitor to know their brain (cerebral cortex) activity is needed to guide in titrating medications (Crippen, D.1997). Monitoring with the BIS can be justified because it allows advantages from reducing the recovery time after waking, mainly by reducing the administration of general anaesthetics as well as the risk of adverse events such as reduction of cognitive impairment, reduced time of extubation, delirium ,nausea, vomiting, intra operative memory loss ( Oliveira et al 2017). If these patients are under sedated or over sedated, they are at risks of developing cognitive impairment, delirium, trauma, prolonged hospitalization, higher mortality and morbidity, and other side effects (Girard,T.2008).

According to the NICE guidelines (2012) the use of BIS is monitoring is recommended as an option during any type of general anaesthesia in patients considered at higher risk of adverse outcomes. This would include patients at a higher risk of unintended awareness, particularly those being kept sedated for prolonged periods such as ventilated patient as well as those more at risk of excessively deep anaesthesia. General anaesthesia requires multiple agent administration to achieve unconsciousness (hypnotics), muscle relaxation, analgesia and hemodynamic control ( Punjasawadwong Y,et al 2014). Many anaesthesiologists rely on clinical signs alone to guide anaesthetic management ( PunjasawadwongY,et al 2014). Such a subjective method could arguably lead to the over sedation of patients, particularly if it is signs of clinical wakefulness being used. Although titration of analgesia and sedation is very important to prevent pain and discomfort in these patients, over sedation has been associated with an increase in mortality and morbidity (Kress J, et al 2000).However, despite the correlation between over sedation and increased morbidity in ventilated critically ill patients, a recent trial by the SRLF trail group (2018), could not definitively conclude that strategies to prevent over sedation significantly reduced mortality. This could raise questions on the effectiveness of BIS monitoring in preventing mortality. Nevertheless, the trial which used a randomized control method and split its participants into two groups, found that the time to first spontaneous breathing trial and time to successful extubating were significantly shorter in the intervention group than in the control group. This shows that despite the lack of evidence to show an overall decreased risk of mortality, the use of such methods is effective in lessening the time patients stay sedated, which has its own benefits. However caution should be used on the last results of this trial due to its limitations, such as early termination, which the trial prudently alerts to.

Furthermore, though studies have shown that BIS guided anaesthesia can decrease postoperative delirium and cognitive decline ( Chan et al 2013) while Radtke F.M. et al (2013) argues that monitoring depth of anaesthesia decreases the rate of postoperative delirium and not cognitive dysfunction which may be due to anaesthetic agents which are harmful to aged brains in comparison to a young one. Also a great number of post operative patients developed delirium and cognitive deficit (Diener et al 2009) anyway due to numerous reasons, such as infection, hypoxemia, drug withdrawals and others.ICU delirium is multifactorial. Such results though unsupportive of the effectiveness of BIS monitoring are such to highlight the limitations of any form of monitoring method. Essentially monitoring will not prevent all adverse incidents or accidents. Ultimately the presence of an appropriately trained and experienced anaesthetist is the main determinant of patient safety during anaesthesia, and the effective use of monitoring kits such as BIS are essential in early detection wakefulness or over sedation. This makes the effective use and interpretation by practitioners essential in trying to prevent harm of patients.

However, there is substantial evidence that such preventative methods of monitoring can reduce the risks of incidents and accidents both by detecting the consequences of errors, and by giving early warning that the condition of a patient is deteriorating. For instance the use of BIS as a prevention of sedation may reduce the duration of mechanical ventilation and ITU length of stay resulting in reduced cost and improved resource utilization(Jackson et al 2010). It is recommended to use scales and scoring based on clinical criteria (Jacobi et al 2002). BIS-guided anaesthesia reduced anaesthetic exposure and decreased the risk of POCD at 3 months after surgery. For every 1000 elderly patients undergoing major surgery(Chan et al 2013), anaesthetic delivery titrated to a range of BIS between 40 and 60 would prevent 23 patients from POCD and 83 patients from delirium.( Chan., et al 2013).

 The NICE guidelines (2012) though aware of the limitations of such forms of monitoring in preventing certain adverse reactions, have nonetheless recommended the use of BIS on patients who are considered at higher risk of unintended awareness during general anaesthesia including patients with high opiate or high alcohol use, and patients with previous experience of accidental awareness during surgery. Debatably safety is ultimately at the forefront of all Nursing practice, and ‘doing no harm’ as stipulated by the NMC code (date), should underpin our practice. For that one patient who experiences unintended awareness, the use of BIS monitoring can offer the opportunity to impact many facets of patients' outcome, and so is still relevant to practice despite the evidence, as it offers early detection of over sedation or wakefulness under the right circumstances .

Practice

All the multidisciplinary members have one goal and that is to provide an excellent service to all those who need the care. The Medical and Nursing team faces so many challenges in providing comfort, the safety and the quality of care given. Critically ill patients are one of the most vulnerable individuals that need extra care. Sedatives, muscle relaxants and anaesthetics are common medication in ITU. High technology monitors can be used but this should not supplement the nursing skill, the clinical assessment remained to be a very important tool in giving the appropriate care.

Adequate monitoring of critically ill patients who are receiving intravenous medications such as sedatives, muscle relaxants, anaesthetics and any other treatment needs clinical guidance. Making sure that the practitioners looking are aware of the NICE guidelines. This trust have no policy about BIS but we can are guided by NICE guidance.

It is still very important to assess the neurological state of the patients. When it is appropriate we have to do a sedation hold (Reschreiter,H. 2008) in line with ICS guidelines, where we stop all the medication to induced coma and anaesthetics including muscle relaxants and wait for patients to wake up and follow commands, at times it can be a sign that the patient can be extubated but things sometimes go wrong that the patient becomes more agitated, restless, intolerant with the invasive treatment and becomes unstable then the decision to re sedate will most probably be the right thing to do. Sedation breaks is encouraged by Intensive Care Society. Systematic interventions to improve sedation practice and maintain patients at an optimal sedation level in the ICU may improve patient outcomes and optimize resource usage(Jackson D.2010). Daily sedation holding in mechanically-ventilated ICU patients is part of the UK ventilator care bundle( Lomas ,C. 2010).Our unit practice ventilator care bundles daily, therefore I am able to practice such assessment.

But again it has been an issue that prolonged hospitalization will cost the NHS Trust more money. Therefore the earliest we can wean off these drugs and other invasive treatment, the quickest we can move patients, the less trauma it brings to them and their family and of course it will save the budget of NHS Trust.

Looking closely at the BIS guidance index chart and titrating the medication will be up to medical and nursing staff. It will lead us to optimize the clinical care we give to these poorly patients. Weaning the medications at the earliest opportunity will provide our patients with fewer complications and thus saves the NHS trust money which can probably be spent on other important things. The sooner we can transfer patients to the ward, can make a better outcome, it can reduce the possible mortality and morbidity of these individuals(Zhou,Y. 2018) .

Conclusion:

The skills learned in the nursing course is one of the most important tools in giving care to a patient. There are different adjuncts that we can use to optimize these care such as the use of medications, new technologies, new guidelines and even experiences.

The Bispectral Index monitor has the computer power to sense waves from the cerebral cortex to give us the signal of how aware and awake patients are when receiving mixtures of intravenous anaesthetic, muscle relaxant sedative drugs while being treated invasively or having a surgical procedure. It provides an advantage to the medical and nursing team. Although this monitoring alone will not help with the care, it needs manpower to read and interpret its meaning. It can even produce a wrong reading as it is prone to artefacts, and it cannot be relied on all the time. Therefore the skills of the clinician are still very valid.

The role of nurses remains to be one of the most important aspects of giving extra care and attention to give excellent care to the public. Teaching and cascading new information will help new staff to gain more knowledge. Assessment, monitoring, documentation, communications are the keys to better nursing care. This will prevent and help reduce any errors in practice and will promote a better outcome.

The BIS Index monitor does help in reducing the recalls of patient but the monitor alone is not enough, it is still a computer based machine and therefore it can still fail. Despite the high technology the world has got, the multidisciplinary team should not always rely on these computers, I believe that it is still important that we practitioners have the basic skills to assess patients, new technology can help make things easier but the basics remain to be one of the important tools in nursing these patients.

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