Cerebral state index vs. bispectral index during sevoflurane–nitrous oxide anaesthesia:

Depth of sedation during drug induced sedation endoscopy monitored by BiSpectral Index® and Cerebral State Index®

PURPOSE

Drug induced sedation endoscopy (DISE) is performed to investigate patterns and sites of obstruction in patients with sleep-disordered breathing (SDB). During DISE the patients are sedated to obtain a muscular relaxation of the upper airway which mimics the relaxation during natural sleep. Different sleep stages are intended to be simulated by drug induced sedation, and it is helpful to measure the depth of sedation. The BiSpectral Index® (BIS) is often used for this procedure. Besides the BIS, other means of sedation depth monitoring exist in anaesthesiology but have not yet been investigated with respect to DISE. Monitoring of the Cerebral State Index® (CSI) is one of these methods. The aim of the study was to compare the BIS and CSI for sedation depth monitoring during DISE.

METHODS

Sixty patients underwent DISE monitored by the BIS and CSI in parallel. The BIS and CSI values were compared using the Bland-Altman analysis.

RESULTS

The BIS and CSI values differed during the course of sedation during DISE by a mean of - 6.07. At light sedation (BIS 60-80), lower values by 10 scale points of CSI compared with BIS were detectable. At deeper sedation levels (BIS 40-50), the CSI turned to present equal and even higher values compared with the BIS.

CONCLUSION

Sedation depth measurement during DISE can be performed by the BIS or CSI, but the differences should be interpreted carefully as comparable data for sleep stages in natural sleep are available only for BIS.

Comparison between cerebral state index and bispectral index during desflurane anesthesia

Background

Cerebral state index (CSI) is an anesthesia depth monitor alternative to bispectral index (BIS). Published comparative studies have used propofol or sevoflurane. However, studies using desflurane have not been reported yet. Different volatile anesthetics have different electroencephalography signatures. The performance of CSI may be different in desflurane anesthesia. Therefore, the objective of this study was to compare CSI and BIS during desflurane anesthesia.

Methods

Thirty-three patients were recruited. Desflurane and remifentanil were used to maintain general anesthesia. BIS and CSI were recorded simultaneously every minute. End-tidal concentration of desflurane was maintained at 4% from the beginning of surgery for 5 minutes. Pairwise data of CSI and BIS were obtained five times at one-minute intervals. This process was repeated in the order of 6%, 8%, and 10%.

Results

BIS and CSI were negatively correlated with the end-tidal concentration of desflurane with a similar degree of correlation (correlation coefficient BIS: –0.847, CSI: –0.844). The relationship between CSI and BIS had a good linearity with a slope close to 1 (R² = 0.905, slope = 1.01). For the relationship between CSI and BIS at each end-tidal concentration of desflurane, CSI and BIS showed good linearity in 4% and 10% (R² = 0.559, 0.540). However, the linearity and slope were decreased in 6% and 8% (R² = 0.163, 0.014).

Conclusions

CSI showed an equivalent degree of overall performance compared to BIS in desflurane anesthesia. Accounting for previous literature, CSI can be used as a good substitute for BIS regardless of the kind of anesthetics used.

Anesthetic influence on occurrence and treatment of the trigemino-cardiac reflex: a systematic literature review

Trigeminocardiac reflex (TCR) is defined as sudden onset of parasympathetic dysrhythmia including hypotension, apnea, and gastric hypermotility during stimulation of any branches of the trigeminal nerve. Previous publications imply a relation between TCR and depth of anesthesia. To gain more detailed insights into this hypothesis, we performed a systematic literature review.Literature about occurrence of TCR was systematically identified through searching in Cochrane Central Register of Controlled Trials (CENTRAL), PubMed (MEDLINE), EMBASE (Ovid SP), and the Institute for Scientific Information (ISI Web of Sciences) databases until June 2013, as well as reference lists of articles for risk calculation. In this study, TCR was defined as drop in mean arterial blood pressure and heart rate, both >20% to baseline. We calculated intraoperative cerebral state index (CSI) of each TCR-case using a newly developed method. These data were further divided into 3 subgroups: CSI <40 (deep anesthesia), CSI 40-60 (regular anesthesia), and CSI >60 (slight anesthesia).Including 45 studies with 910 patients, 140 (15%) presented with TCR, and 770 (85%) without TCR during operation. TCR occurrence showed a 1.2-fold higher pooled risk slighter anesthesia (CSI <40: 13%, at CSI 40-60: 21%, and at CSI >60: 27%) compared with deeper anesthesia. In addition, we could discover a 1.3-fold higher pooled risk of higher MABP drop with a strong negative correlation (r = -0.935; r = 0.89) and a 4.5-fold higher pooled risk of asystole during TCR under slight anesthesia compared with deeper anesthesia.Our work is the first systematic review about TCR and demonstrates clear evidence for TCR occurrence and a more severe course of the TCR in slight anesthesia underlying the importance of skills in anesthesia management during skull base surgery. Furthermore, we have introduced a new standard method to calculate the depth of anesthesia.

Agreement of cerebral state index and glasgow coma scale in brain-injured patients

Background:

Variables derived from electroencephalogram like cerebral state index (CSI) have been used to monitor the anesthesia depth during general anesthesia. Observed evidences show such variables have also been used as a detector of brain death or outcome predictor in traumatic brain-injured (TBI) patients.

Objectives:

The current study was designed to determine the correlation between Glasgow coma score (GCS) and CSI among TBI patients.

Patients and Methods:

In 60 brain-injured patients who did not need and receive sedatives, GCS and CSI were daily measured during the first ten days of their hospital stay. Correlation between GCS and CSI was studied using the Pearson's correlation test. The Gamma agreement coefficient was also calculated between the two variables for the first day of hospitalization.

Results:

A significant correlation coefficient of 0.611-0.796 was observed between CSI and GCS in a ten-day period of the study (P < 0.001). Gamma agreement coefficient was 0.79 (P < 0.001) for CSI and GCS for the first day of hospitalization. An increased daily correlation was observed in both CSI and GCS values. However, this increase was less significant in CSI compared with the GCS.

Conclusions:

A statistically significant correlation and agreement was found between GCS and CSI in the brain-injured patients and GCS was also found to be more consistent and reliable compared with CSI.

Electroencephalography during out-of-hospital cardiopulmonary resuscitation

BACKGROUND

At the present time there is no parameter that can estimate the quality of cerebral perfusion and possible success of cerebral resuscitation during advanced cardiac life support (ACLS) efforts. In recent years, various attempts have been made to use electroencephalography (EEG)-based cerebral neuromonitoring to assess the effectiveness of cardiopulmonary resuscitation (CPR).

OBJECTIVES

The Cerebral State Monitor M3 (Danmeter A/S, Odense, Denmark) is a portable, single-channel EEG monitor that provides the user with different EEG-based parameters and the raw waveform EEG to measure cerebral activity.

CASE REPORT

We report two cases of out-of-hospital CPR with single-channel EEG monitoring conducted parallel to ACLS with external chest compressions. We demonstrate an artifact in waveform EEG recordings that is caused by the external chest compressions, and that leads to a miscalculation of the Burst Suppression Ratio and Cerebral State Index.

CONCLUSION

These cases suggest that digitally processed EEG-monitoring is not a useful tool during CPR.

Administration and monitoring of intravenous anesthetics

PURPOSE OF REVIEW

The importance of accuracy in controlling the dose-response relation for intravenous anesthetics is directly related to the importance of optimizing the efficacy and quality of anesthesia while minimizing adverse drug effects. Therefore, it is important to measure and control all steps of the pharmacokinetic and dynamic cascade influencing this dose-effect relationship.

RECENT FINDINGS

The ultimate goal when administering a particular dose of a drug is to obtain the desired clinical effect, taking into account interindividual pharmacokinetic and dynamic variability. Recent findings suggest that effect compartment-controlled target-controlled infusion systems and measurement of (surrogate) clinical drug effects might be helpful in an attempt to optimize the administration intravenous anesthetics and opioids. Additionally, recent findings suggest that the pharmacokinetic and dynamic interaction between anesthetics and opioids is important and such be taking into account when optimizing drug administration. Hereby, feedback control technology and advisory displays depicting these interactions have been studied.

SUMMARY

Anesthetic drug administration might be optimized by applying knowledge from clinical pharmacokinetics and dynamics.

Recent advance in patient monitoring

Recent advance in technology has developed a lot of new aspects of clinical monitoring. We can monitor sedation levels during anesthesia using various electroencephalographic (EEG) indices, while it is still not useful for anesthesia depth monitoring. Some attempts are made to monitor the changes in sympathetic nerve activity as one of the indicators of stress, pain/analgesia, or anesthesia. To know the balance of sympathetic and parasympathetic activity, heart rate or blood pressure variability is investigated. For trend of cardiac output, low invasive monitors have been investigated. Improvement of ultrasound enables us to see cardiac structure and function continuously and clearer, increases success rate and decreases complication of central venous puncture and various kinds of nerve blocks. Without inserting an arterial catheter, trends of arterial oxygen tension or carbon dioxide tension can be monitored. Indirect visualization of the airway decreases difficult intubation and makes it easier to teach tracheal intubation. The changes in blood volume can be speculated non-invasively. Cerebral perfusion and metabolism are not ordinary monitored yet, but some studies show their usefulness in management of critically ill. This review introduces recent advances in various monitors used in anesthesia and critical care including some studies of the author, especially focused on EEG and cardiac output. However, the most important is that these new monitors are not almighty but should be used adequately in a limited situation where their meaning is confirmed.

Cerebral state index versus bispectral index during propofol-fentanyl-nitrous oxide anesthesia

PURPOSE

The aim of this study was to compare the cerebral state index (CSI) and bispectral index (BIS) during propofol-fentanyl-nitrous oxide anesthesia.

METHODS

Thirty patients scheduled for abdominal surgery, with a mean age of 30-70 years, were enrolled. Anesthesia was induced with propofol and fentanyl and was maintained with propofol, fentanyl, epidural mepivacaine, and nitrous oxide in oxygen. During surgery, the propofol infusion rate was adjusted to try to keep BIS at 40 + or - 3 for 10 min and then decreased to keep the BIS at 60 + or - 3 for 10 min.

RESULTS

The BIS had a larger value for the time between switching on the apparatus and starting to measure at a signal quality index >75%. The recovery time from disturbance by an electric cautery event was 41 + or - 14 s for the BIS and 3 + or - 1 s for the CSI (P < 0.05). The absolute values of the BIS and CSI were not significantly different and they showed a good correlation. The bias (mean of the differences, BIS - CSI) was negative at all measurement points, but the limits of agreement and percentage error were small.

CONCLUSIONS

The absolute values of the BIS and CSI were not significantly different during propofol-fentanyl-nitrous oxide anesthesia. The start of the measurement was faster with the CSI than with the BIS after switch-on, and measurement was less disturbed by electric cautery with the CSI.

Depth of anaesthesia and post-operative cognitive dysfunction

BACKGROUND

A deep level of anaesthesia measured by the bispectral index has been found to improve processing speed as one aspect of cognitive function after surgery. The purpose of the present study was to assess the possible effect of the level of anaesthesia on post-operative cognitive dysfunction (POCD) 1 week after surgery, as assessed by a neuropsychological test battery.

METHODS

We included 70 patients >60 years of age scheduled for elective non-cardiac surgery with general anaesthesia. The depth of anaesthesia was monitored using the cerebral state monitor, which provided a cerebral state index (CSI) value. Cognitive function was assessed by the ISPOCD neuropsychological test battery before and at 1 week (or hospital discharge) after surgery and POCD was defined as a Z score above 1.96.

RESULTS

Five patients were not assessed after surgery. The mean CSI was 40 and 43 in patients with (N=9) and without POCD (N=56), respectively (P=0.41). The cumulated time of both deep anaesthesia (CSI<40) and light anaesthesia (CSI>60) did not differ significantly, and no significant correlation was found between the mean CSI and the Z score.

CONCLUSION

We were unable to detect a significant association between the depth of anaesthesia and the presence of POCD 1 week after the surgery.