Depth of Anesthesia Monitoring in Cardiac Surgery Adam Dryden MD, FRCPC University of Ottawa Heart Institute
Depth of Anesthesia Monitoring in Cardiac Surgery Because it s not all about the heart. The anesthetist and surgeon could have before them on tape or screen a continuous record of the electric activity of both heart and brain.
None Disclosures
Objectives Review the general principles of monitoring Highlight the commercially available monitors Determine whether depth of anesthesia monitoring can allow us to prevent awareness Evaluate whether titrating anesthesia to a processed EEG value can promote positive outcomes Share our experience with processed EEG at the Ottawa Heart Institute
GENERAL PRINCIPLES OF MONITORING
Barash, 2013 Are you asleep?
Purdon et al, 2015 Are you asleep?
General Principles of Monitoring Awake? Aware?
Are you asleep? Awake? Aware?
Power analysis
Power analysis d q a b g
Power analysis in 3D!!! Or 4D? Ok Density Spectral Analysis
Purdon et al, 2015 Anesthetic Signatures on DSA
Limitations of (Processed) EEG Muscular activity Medical devices Pacemakers, electrocautery, surgical navigation systems, forced air warmers Changes in cerebral metabolism Cardiac arrest, hypovolemia, hypotension, hypoglycemia, hypothermia Seizures (or other abnormal EEG states) Medication limitations Ketamine, nitrous oxide, etomidate, ephedrine
Whitlock et al, 2011 BIS = Depth of Anesthesia?
Barash, 2013 MAC!= Effect Site!= Anesthetic Depth
COMMERCIALLY AVAILABLE MONITORS
Commercially Available Monitors Bispectal Index Covidien (Boulder, CO) Sedline Masimo (Irvine, CA) State Entropy GE Healthcare (Helsinki, Finland) Narcotrend Narcotrend-Gruppe (Hannover, Germany)
Bispectral Index
Sedline
State Entropy
Narcotrend
First Do No Harm. PREVENTING AWARENESS
Sebel et al, 2004 Pollard et al, 2007 Awareness Incidence is likely 1-2/1000 Cardiac surgical procedures Obstetrical surgical procedures ASA III or IV Use of neuromuscular blocking agents? Older? Longer case
B Aware Awareness: BIS 0.17% vs Routine 0.91% NNT of 138 Anesthetic technique differences Less midazolam in the BIS group (2mg vs 2.5mg) Lower target plasma propofol concentration (2mg/L vs 2.4mg/L) No significant differences in nearly all post operative parameters and complications Myles et al, 2004
BAG - RECALL Goal was to determine whether BIS guided anesthetic management was superior to end tidal anesthetic concentration (ETAC) for awareness prevention Alarms used to guide therapy BIS was not superior to ETAC for preventing awareness BIS 0.24% compared to ETAC 0.07% No difference in median BIS No difference in median ETAC Avidan et al, 2011
MACS Patients with no particular risk for awareness were included Very large (n=21,601) effectiveness study Planned for 30,000 patients terminated for futility at interim endpoint Based on randomization, practitioners received alerts MAC < 0.5 (age adjusted) BIS > 60 Mashour et al, 2012
MACS Significant differences when analyzed by intention to treat vs post hoc grouping Technical malfunction Mashour et al, 2012
The Holy Grail of Cochrane Decreases the risk of awareness in high risk patients But ETAC may be as effective No clinically relevant difference in discharge readiness Less anesthetic use Especially consistent and relevant for TIVA Impact of BIS on outcome was not evaluated Punjasawadwong et al, 2014
PROMOTING OUTCOMES
The Holy Grail of Cochrane, Round 2 Non Cardiac Surgery Probably reduces risk of postoperative delirium in first 7 days NNT 17 Moderate quality evidence No support for other outcomes All cause mortality Length of stay Punjasawadwong et al, 2018
B Aware Long term follow-up was done with included patients Median follow-up time of 4.1 years No difference in post-30 day death rates in the BIS monitored compared to routine care Patients who had BIS < 40 for more than 5 minutes were less likely to be alive at follow-up (HR=0.66, p=0.003) Leslie et al, 2010
Kertai et al, 2010 B Unaware Duration of BIS < 45
Burst Suppression and Delirium A single centre prospective observational study 81 patients enrolled with identical anesthetic management Divided into delirious and non-delirous groups No difference in mean BIS values No other statistically significant risk factors identified Burst suppression duration was associated Burst suppression ratio was associated Soehle et al, 2015
High BIS vs Low BIS Possible? Anesthetic management at discretion of provider Except no nitrous oxide Short et al, 2014
BIS AND THE OTTAWA HEART INSTITUTE
Our Experience Use of Processed EEG 1800 1600 1400 1200 1000 800 600 400 200 0 Number of BIS Cases 43.3 Number of Sedline Cases 42.5 42.0 42.1 Yearly Average BIS 41.8 41.2 41.3 Yearly Average PSI 39.8 39.1 37.5 37.3 37.8 946 29.88 239 28.2 344 408 639 1014 958 1133 1148 1260 1322 1633 1510 758 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 45 43 41 39 37 35 33 31 29 27 25
Our Experience Average BIS 600 600000 500 400 Average BIS All BIS Values 500000 400000 300 300000 200 200000 100 100000 0 0 0 10 20 30 40 50 60 70 80 90 100
Summary Depth of anesthesia is not a number The use of depth of anesthesia monitors, in high risk patients, can prevent awareness Preventing excessive anesthetic depth is an area of very active investigation
My Conclusions, Predictions and Bias The threshold value for deep anesthesia is suspect Burst suppression/suppression ratio may prove to be useful signal Low numerical depth of anesthesia indicates frailty The expected low BIS in a critically ill patient The unexpected low BIS in a well appearing patient Excessive anesthetic depth is harmful Neurologic specific outcomes Outcomes related to vasoactive agent use Will be easier to demonstrate in vulnerable patients Sedation and anesthetic depth perioperatively is as, or more important than intraoperatively
Questions
References 1. Avidan MS, Jacobsohn E, Glick D, Burnside BA, Zhang L, Villafranca A, et al. Prevention of intraoperative awareness in a high-risk surgical population. N Engl J Med. 2011;365(7):591-600. 2. Barash PG. Clinical anesthesia. Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins; 2013. 3. Kertai MD, Pal N, Palanca BJ, Lin N, Searleman SA, Zhang L, et al. Association of perioperative risk factors and cumulative duration of low bispectral index with intermediate-term mortality after cardiac surgery in the B-Unaware Trial. Anesthesiology. 2010;112(5):1116-27. 4. Leslie K, Myles PS, Forbes A, Chan MT. The effect of bispectral index monitoring on long-term survival in the B-aware trial. Anesth Analg. 2010;110(3):816-22. 5. Mashour GA, Shanks A, Tremper KK, Kheterpal S, Turner CR, Ramachandran SK, et al. Prevention of intraoperative awareness with explicit recall in an unselected surgical population: a randomized comparative effectiveness trial. Anesthesiology. 2012;117(4):717-25. 6. Maheshwari A, McCormick PJ, Sessler DI, et al. Prolonged concurrent hypotension and low bispectral index ('double low') are associated with mortality, serious complications, and prolonged hospitalization after cardiac surgery. Br J Anaesth. 2017;119(1):40-49 7. Myles PS, Leslie K, McNeil J, Forbes A, Chan MT. Bispectral index monitoring to prevent awareness during anaesthesia: the B-Aware randomised controlled trial. Lancet. 2004;363(9423):1757-63. 8. Nitzschke R, Wilgusch J, Kersten JF, Trepte CJ, Haas SA, Reuter DA, et al. Bispectral index guided titration of sevoflurane in on-pump cardiac surgery reduces plasma sevoflurane concentration and vasopressor requirements: a prospective, controlled, sequential two-arm clinical study. Eur J Anaesthesiol. 2014;31(9):482-90. 9. Pollard RJ, Coyle JP, Gilbert RL, Beck JE. Intraoperative awareness in a regional medical system: a review of 3 years' data. Anesthesiology. 2007;106(2):269-74. 10. Punjasawadwong Y, Phongchiewboon A, Bunchungmongkol N. Bispectral index for improving anaesthetic delivery and postoperative recovery. Cochrane Database Syst Rev. 2014;6:CD003843. 11. Punjasawadwong Y, Chau-In W, Laopaiboon M, Punjasawadwong S, Pin-On P. Processed electroencephalogram and evoked potential techniques for amelioration of postoperative delirium and cognitive dysfunction following non-cardiac and non-neurosurgical procedures in adults. Cochrane Database Syst Rev. 2018;5:CD011283. 12. Purdon PL, Sampson A, Pavone KJ, Brown EN. Clinical Electroencephalography for Anesthesiologists: Part I: Background and Basic Signatures. Anesthesiology. 2015;123(4):937-60. 13. Sebel PS, Bowdle TA, Ghoneim MM, Rampil IJ, Padilla RE, Gan TJ, et al. The incidence of awareness during anesthesia: a multicenter United States study. Anesth Analg. 2004;99(3):833-9. 14. Short TG, Leslie K, Campbell D, Chan MT, Corcoran T, O'Loughlin E, et al. A pilot study for a prospective, randomized, double-blind trial of the influence of anesthetic depth on long-term outcome. Anesth Analg. 2014;118(5):981-6. 15. Sigl JC, Chamoun NG. An introduction to bispectral analysis for the electroencephalogram. J Clin Monit. 1994;10(6):392-404. 16. Soehle M, Dittmann A, Ellerkmann RK, Baumgarten G, Putensen C, Guenther U. Intraoperative burst suppression is associated with postoperative delirium following cardiac surgery: a prospective, observational study. BMC Anesthesiol. 2015;15:61. 17. Whitlock EL, Torres BA, Lin N, Helsten DL, Nadelson MR, Mashour GA, et al. Postoperative delirium in a substudy of cardiothoracic surgical patients in the BAG-RECALL clinical trial. Anesth Analg. 2014;118(4):809-17. 18. Whitlock EL, Villafranca AJ, Lin N, Palanca BJ, Jacobsohn E, Finkel KJ, et al. Relationship between bispectral index values and volatile anesthetic concentrations during the maintenance phase of anesthesia in the B-Unaware trial. Anesthesiology. 2011;115(6):1209-18.
Selected References Short TG, Leslie K, Campbell D, Chan MT, Corcoran T, O'Loughlin E, et al. A pilot study for a prospective, randomized, double-blind trial of the influence of anesthetic depth on longterm outcome. Anesth Analg. 2014;118(5):981-6. Whitlock EL, Torres BA, Lin N, Helsten DL, Nadelson MR, Mashour GA, et al. Postoperative delirium in a substudy of cardiothoracic surgical patients in the BAG-RECALL clinical trial. Anesth Analg. 2014;118(4):809-17. Kertai MD, Pal N, Palanca BJ, Lin N, Searleman SA, Zhang L, et al. Association of perioperative risk factors and cumulative duration of low bispectral index with intermediate-term mortality after cardiac surgery in the B-Unaware Trial. Anesthesiology. 2010;112(5):1116-27 Purdon PL, Sampson A, Pavone KJ, Brown EN. Clinical Electroencephalography for Anesthesiologists: Part I: Background and Basic Signatures. Anesthesiology. 2015;123(4):937-60.