Bispectral index-guided management of anaesthesia in permanent vegetative state

General anaesthesia in end-of-life care: extending the indications for anaesthesia beyond surgery

In this article, we describe an extension of general anaesthesia – beyond facilitating surgery – to the relief of suffering during dying. Some refractory symptoms at the end of life (pain, delirium, distress, dyspnoea) might be managed by analgesia, but in high doses, adverse effects (e.g. respiratory depression) can hasten death. Sedation may be needed for agitation or distress and can be administered as continuous deep sedation (also referred to as terminal or palliative sedation) generally using benzodiazepines. However, for some patients these interventions are not enough, and others may express a clear desire to be completely unconscious as they die. We summarise the historical background of an established practice that we refer to as ‘general anaesthesia in end‐of‐life care’. We discuss its contexts and some ethical and legal issues that it raises, arguing that these are largely similar issues to those already raised by continuous deep sedation. To be a valid option, general anaesthesia in end‐of‐life care will require a clear multidisciplinary framework and consensus practice guidelines. We see these as an impending development for which the specialty should prepare. General anaesthesia in end‐of‐life care raises an important debate about the possible role of anaesthesia in the relief of suffering beyond the context of surgical/diagnostic interventions.

A Review of Bispectral Index Utility in Neurocritical Care Patients

Context: Bispectral Index (BIS) was introduced in 1960 to monitor the depth of anesthesia in the operating rooms. It has been recently used to monitor the sedation in the critically ill patients hospitalized in intensive care and neurocritical care units (NCCU). Evidence Acquisition: Patients in the NCCU, particularly those with prolonged mechanical ventilation require appropriate adjustments in the administration of sedative drugs. Similarly, those who require neuro protection with barbiturates need to be closely monitored in the depth of their coma. Results: BIS may be a useful tool in this situation, and it can also help shorten the duration of mechanical ventilation by determining the appropriate time to eliminate patients from mechanical ventilation. We conducted a literature search to evaluate the utility of BIS monitoring in the NCCU patients with subarachnoid hemorrhage, intracranial hemorrhage, coma, cerebral hypoxia, status epilepticus and traumatic brain injury. Conclusions: BIS monitoring may be a useful adjunct to take care of the patients. However, further studies with a larger population and better design are required to substantiate the role of BIS monitoring in the care of NCCU patients.

Use of ADMS™ during sedation for dental treatment of an intellectually disabled patient: a case report

Dental treatment is often performed under general anesthesia or sedation when an intellectually disabled patient has a heightened fear of treatment or has difficulty cooperating. When it is impossible to control the patient due to the severity of intellectual disability, conscious sedation is not a viable option, and only deep sedation should be performed. Deep sedation is usually achieved by propofol infusion using the target controlled infusion (TCI) system, with deep sedation being achieved at a slightly lower concentration of propofol in disabled patients. In such cases, anesthesia depth monitoring using EEG, as with a Bispectral Index (BIS) monitor, can enable dental treatment under appropriate sedation depth. In the present case, we performed deep sedation for dental treatment on a 27-year-old female patient with mental retardation and severe dental phobia. During sedation, we used BIS and a newly developed Anesthetic Depth Monitor for Sedation (ADMS™), in addition to electrocardiography, pulse oximetry, blood pressure monitoring, and capnometry for patient safety. Oxygen was administered via nasal prong to prevent hypoxemia during sedation. The BIS and ADMS™ values were maintained at approximately 70, and dental treatment was successfully performed in approximately 30 min..

Insights from neuroenergetics into the interpretation of functional neuroimaging: an alternative empirical model for studying the brain's support of behavior

Functional neuroimaging measures quantitative changes in neurophysiological parameters coupled to neuronal activity during observable behavior. These results have usually been interpreted by assuming that mental causation of behavior arises from the simultaneous actions of distinct psychological mechanisms or modules. However, reproducible localization of these modules in the brain using functional magnetic resonance imaging (MRI) and positron emission tomography (PET) imaging has been elusive other than for sensory systems. In this paper, we show that neuroenergetic studies using PET, calibrated functional magnetic resonance imaging (fMRI), (13)C magnetic resonance spectroscopy, and electrical recordings do not support the standard approach, which identifies the location of mental modules from changes in brain activity. Of importance in reaching this conclusion is that changes in neuronal activities underlying the fMRI signal are many times smaller than the high ubiquitous, baseline neuronal activity, or energy in resting, awake humans. Furthermore, the incremental signal depends on the baseline activity contradicting theoretical assumptions about linearity and insertion of mental modules. To avoid these problems, while making use of these valuable results, we propose that neuroimaging should be used to identify observable brain activities that are necessary for a person's observable behavior rather than being used to seek hypothesized mental processes.

Glutamatergic function in the resting awake human brain is supported by uniformly high oxidative energy

Rodent (13)C magnetic resonance spectroscopy studies show that glutamatergic signaling requires high oxidative energy in the awake resting state and allowed calibration of functional magnetic resonance imaging (fMRI) signal in terms of energy relative to the resting energy. Here, we derived energy used for glutamatergic signaling in the awake resting human. We analyzed human data of electroencephalography (EEG), positron emission tomography (PET) maps of oxygen (CMR(O2)) and glucose (CMR(glc)) utilization, and calibrated fMRI from a variety of experimental conditions. CMR(glc) and EEG in the visual cortex were tightly coupled over several conditions, showing that the oxidative demand for signaling was four times greater than the demand for nonsignaling events in the awake state. Variations of CMR(O2) and CMR(glc) from gray-matter regions and networks were within ±10% of means, suggesting that most areas required similar energy for ubiquitously high resting activity. Human calibrated fMRI results suggest that changes of fMRI signal in cognitive studies contribute at most ±10% CMR(O2) changes from rest. The PET data of sleep, vegetative state, and anesthesia show metabolic reductions from rest, uniformly >20% across, indicating no region is selectively reduced when consciousness is lost. Future clinical investigations will benefit from using quantitative metabolic measures.

Correlation between BIS and GCS in patients suffering from head injury

OBJECTIVES AND BACKGROUND

Glasgow coma scale (GCS) is considered an important parameter to predict the clinical outcome in head injury; however, in some cases such as the use of sedative drugs the estimate of GCS would not be precise. Bispectral index (BIS) is an electrophysiological parameter to determine the clinical state of anesthesia. The aim of the present study is to evaluate correlation between GCS and BIS in patients suffering from head injury and to see if we can use BIS values as a prognostic factor in head trauma.

METHODS

In this analytic study 61 consecutive patients with traumatic head injury admitted to the intensive care unit from January till June 2010 were examined. In each case the GCS and BIS values were measured and compared regarding different degrees of head injuries.

RESULTS

Mean BIS in mild injury group was 96.20 ± 3.27 and in moderate injury group was 45.57 ± 1.28 and in severe injury group was 31.37 ± 2.08. There was a significant correlation between GCS and mean BIS (r = 0.88; P < 0.05). Mean BIS values were significantly different between mild, moderate and severe head injuries (96.2 ± 3.2, 45.5 ± 1.2, and 31.3 ± 2.08, respectively; P < 0.05).

CONCLUSION

We found significant correlation between GCS and BIS in patients with traumatic head injury, so BIS can be used in addition to GCS for prediction of outcome in these patients specially in patients who are sedated or are intubated or in other case in whom GCS values cannot be determined accurately.

When the bispectral index (bis) can give false results

BACKGROUND AND OBJECTIVES

The bispectral index (BIS) is a multifactorial parameter derived from the electroencephalogram (EEG), which allows monitoring of the hypnotic component of anesthesia. It was obtained from the algorithm based on the analysis of a large number of EEGs from volunteers and patients undergoing sedation and general anesthesia with different anesthetic agents. The use of BIS to monitor the depth of anesthesia reduces the incidence of intraoperative awakening and recall, among other benefits. The objective of this review was to present clinical situations in which the BIS gives false results, either elevated or decreased, due to conditions related to the patient or anesthetic actions unforeseen when the algorithm was elaborated.

CONTENTS

The bispectral index can be altered and influenced in different clinical situations in which abnormal EEG patterns are present; the effects of different anesthetics and other drugs not included when the algorithm was elaborated; interference from electrical equipment; as well as peculiarities of the monitor.

CONCLUSIONS

Although the BIS algorithm underwent several changes since its first version, the anesthesiologist should be aware of situations that cause false BIS readings to avoid complications, may it be secondary to anesthetic overdose or underdosing, which might cause intraoperative awakening and recall.

Different Conditions That Could Result in the Bispectral Index Indicating an Incorrect Hypnotic State

Since its introduction in 1996, the Bispectral Index (BIS) has gained increasing popularity in daily anesthesia practice. However, numerous reports have been appearing in the literature of paradoxical BIS changes and inaccurate readings. The purpose of this review is to assess the utility of BIS monitoring through examining the various published reports of all BIS values not coinciding with a clinically judged sedative-hypnotic state, whether arising from an underlying pathophysiology of electroencephalographic (EEG) cerebral function or because of shortcomings in the performance and design of the BIS monitor. High electromyographic activity and electric device interference could create subtle artifact signal pollution without their necessarily being displayed as artifacts. This would be misinterpreted by the BIS algorithm as EEG activity and assigned a spuriously increased BIS value. Numerous clinical conditions that have a direct effect on EEG cerebral function could also directly influence the BIS value.