Monitoring the brain in cardiac surgery – an evolving area for research

Grocott, Hilary P.

doi:10.1111/j.1365-2044.2012.07076.x

Cited by 14 publications

(13 citation statements)

References 35 publications

(32 reference statements)

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“…It could be argued that the BIS index target range of 55–60 is too near the ‘margins of consciousness’ . Yet, current BIS guidance indicates that 45–60 is acceptable and there is therefore no justification for such criticism.…”

Section: Discussionmentioning

confidence: 99%

The ability of bispectral index to detect intra‐operative wakefulness during total intravenous anaesthesia compared with the isolated forearm technique

Russell

2013

Anaesthesia

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SummaryIt has been suggested that monitoring during total intravenous anaesthesia should include aspects of brain function. The current study used a manually adjusted target-controlled infusion of propofol for anaesthesia, guided to a bispectral index range of 55-60. Intra-operative responsiveness, as assessed by the isolated forearm technique, was compared with whether the bispectral index predicted/identified a patient's appropriate hand movements in responses to commands. Twenty-two women underwent major gynaecological surgery with total intravenous anaesthesia, propofol, remifentanil and atracurium. Sixteen women responded, on 80 occasions, with appropriate hand movements to commands during surgery, of which the bispectral index detected 47 (sensitivity 59%). The bispectral index suggested consciousness 220 times in the absence of movement responses (specificity 85%). The positive predictive value of a bispectral index response was 18%. While two women had vague recall about squeezing fingers, none had recall of surgery. For patients who responded more than once during surgery the bispectral index value associated with a response was not constant. Although there was no difference in the median (IQR [range]) effect site propofol concentration between intra-operative responses (2.0 (1.5-2.3 [1.2-4.0]) lg.ml À1) and eye opening after surgery (2.1 (1.7-2.8 [1.5-3.9]) lg.ml À1 ), the median (IQR [range]) bispectral index value at eye opening after surgery was significantly higher than that associated with responses during surgery: 75 (70-78 [51-93]) vs 61 (52-67 [37-80]) respectively, (p < 0.001). The manual control of propofol intravenous anaesthesia to target a bispectral index range of 55-60 may result in an unacceptable number of patients who are conscious during surgery (albeit without recall).

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Section: Discussionmentioning

confidence: 99%

The ability of bispectral index to detect intra‐operative wakefulness during total intravenous anaesthesia compared with the isolated forearm technique

Russell

2013

Anaesthesia

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“…A bolus of atracurium in these circumstances resulted in the EMG and BIS declining back to their baseline. It is known that the EEG and EMG frequencies overlap in the [35][36][37][38][39][40][41][42][43][44][45][46][47] Hz range and this EMG activity is interpreted by the BIS monitor as high-frequency, lowamplitude waves, falsely elevating the BIS [36,37]. Figures 2 and 3 demonstrate how such 'contamination' from the EMG signal can result in high BIS values and when the EMG signal disappears, either spontaneously or after atracurium, the high BIS index values return to their previous values.…”

Section: Discussionmentioning

confidence: 99%

The ability of bispectral index to detect intra‐operative wakefulness during isoflurane/air anaesthesia, compared with the isolated forearm technique

Russell

2013

Anaesthesia

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SummaryClinical signs are unreliable for guiding anaesthetic administration and it is suggested that using the bispectral index can improve anaesthetic delivery. In the current study, isoflurane administration was guided to a bispectral index range of 55-60. Intra-operative responsiveness, as assessed by the isolated forearm technique, was compared with whether the bispectral index predicted/identified a patient's appropriate hand movements in response to commands. Thirty-four women underwent major gynaecological surgery with isoflurane/air and atracurium. Eleven women responded on 32 occasions with appropriate hand movements to commands given during surgery, of which the bispectral index detected 17 (sensitivity 53%). The bispectral index suggested consciousness 660 times in the absence of any movement responses (specificity 69%). The positive predictive value of the bispectral index was 3%. The median (IQR [range]) bispectral index value associated with an intra-operative response was significantly lower than that associated with eye opening after surgery: 60 (50-68 [36-83]) vs 77 (75-84 [59-90]), respectively (p = 2.25 9 10 À8 ).Conversely, end-tidal isoflurane concentration was significantly higher at intra-

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“…12 Perhaps patients with mild cognitive impairment, dementia, and/or others who appear sick remain at high risk of delirium even when treated with appropriate ageadjusted anesthetic dosages. 13,14 Where are we now? 13,14 Where are we now?…”

mentioning

confidence: 99%

Preventing Delirium After Cardiothoracic Surgery

Berger

Nadler²,

Mathew³

2014

Anesthesia &Amp; Analgesia

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E ver since Bedford's seminal 1955 case series in the Lancet titled "Adverse Cerebral Effects of Anesthesia on Old People," we have known that some patients have cognitive problems after anesthesia and surgery. 1 Today, the term postoperative delirium is often used to describe the mental state of many of these patients. Delirium is a syndrome of waxing and waning mental status changes and alterations in the level of consciousness. It is a common (and likely underrecognized) complication correlated with adverse outcomes including decreased quality of life and increased hospital and 6-month mortality. 2 More recently, postoperative delirium has also been associated with cognitive decline during the first year after cardiac surgery. 3 Is there anything that we as anesthesiologists can do to decrease the incidence of delirium? Processed electroencephalography (EEG) (e.g., Bispectral Index, BIS) is a controversial tool in anesthesiology but may be a useful instrument for preventing postoperative delirium. In this issue of Anesthesia & Analgesia, Whitlock et al. 4 examine whether using a BIS monitor decreases the incidence of delirium in cardiothoracic surgery patients. They report a trend toward less delirium in the BIS-guided anesthetic group versus the end-tidal anesthetic concentration (ETAC)-guided group (18.8% vs 28%), although this difference was not statistically significant (P = 0.058) despite adequate statistical power. Nevertheless, this finding is consistent with the results of similar studies in noncardiac surgical patients, which have shown that BIS-guided anesthetic titration (as opposed to typical titration to hemodynamic end points) lowers the incidence of delirium. 5,6 Even when spinal anesthesia was the primary anesthetic technique, titrating sedation depth to a BIS ≥80 vs approximately 50 decreased the incidence of delirium. 7 In each of these studies, BIS usage (or a higher BIS target range) was associated with lower average anesthetic dosage 6,7 or a decreased incidence of deep anesthesia (e.g., BIS values <20). 5 Although Whitlock et al. 4 also found a trend toward lower delirium incidence in patients enrolled in the BIS arm, neither the average ETAC, nor cumulative anesthetic exposure (e.g., MAC-hours), 8 nor the occurrence of deep anesthesia (BIS <20) is given for the BIS versus ETAC titration arms. Thus, it is unclear whether the trend toward less delirium in the BIS group was also associated with less anesthetic delivery. The authors did compare delirious and nondelirious patients and found no differences in the time spent under deep anesthesia in these 2 groups (as measured by duration of BIS <45, proportion of time with a BIS <20, or the percentage of patients in each group whose BIS was ever <20). In a multivariable analysis employing elegant statistical methodology, comorbidity scores, transfusion, and average ETAC were associated with delirium, but BIS usage (i.e., BIS group) was not. 4 If that is the case, can we really posit that BIS offers more value than ETAC for preventing delirium?...

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Monitoring the brain in cardiac surgery – an evolving area for research

Cited by 14 publications

References 35 publications

The ability of bispectral index to detect intra‐operative wakefulness during total intravenous anaesthesia compared with the isolated forearm technique

The ability of bispectral index to detect intra‐operative wakefulness during total intravenous anaesthesia compared with the isolated forearm technique

The ability of bispectral index to detect intra‐operative wakefulness during isoflurane/air anaesthesia, compared with the isolated forearm technique

Preventing Delirium After Cardiothoracic Surgery

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