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ORIGINAL ARTICLE Table of Contents   
Year : 2008  |  Volume : 11  |  Issue : 2  |  Page : 105-110
Bispectral index-guided anaesthesia for off-pump coronary artery bypass grafting

Department of Anaesthesia, Narayana Hrudayalaya, Bangalore, India

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Bispectral index (BIS) monitoring may assist reduction in utilisation of anaesthetic agents during general surgical procedures. This study was designed to test whether the use of BIS monitoring reduces the anaesthetic requirements during off-pump coronary artery bypass grafting (CABG). This prospective - clinical trial was conducted on 40 adult patients undergoing elective off-pump CABG. Patients received either isoflurane or propofol anaesthesia. BIS monitoring, which guided the dose of anaesthetic, was carried out in 50 percent of the patients. The amount of anaesthetic agent (isoflurane or propofol) administered from the start of anaesthesia to the end of surgical procedure was calculated and were compared in four groups of patients - namely Group A (I-no BIS) received isoflurane; end tidal concentration was maintained at 1-1.2% in a low flow technique throughout the procedure, Group B (I-BIS) received isoflurane in a low flow technique; inspired concentration was dictated by BIS value maintained at 50; Group C (P-no BIS) received propofol at a dose range of 4-8 mg/kg/hr and in Group D(P-BIS) the propofol infusion rate was dictated by BIS value maintained at 50. The quantity of isoflurane was significantly less for Group B (I-BIS) as compared with Group A (I-no BIS) (37 ± 4 vs. 24 ± 4 ml; p<0.05) and similarly the amount of propofol infused was significantly less in Group D (P-BIS) as compared with Group C (P-no BIS) (176 ± 9 vs. 120 ± 6 ml; p<0.05). BIS guided anaesthesia reduces the anaesthetic agent required for the performance of off-pump CABG. This can be extrapolated in terms of saving agent and reduced cardiac depression during off-pump CABG.

Keywords: Cardiac anaesthesia, coronary artery bypass grafting, depth of anaesthesia, monitoring

How to cite this article:
Muralidhar K, Banakal S, Murthy K, Garg R, Rani G R, Dinesh R. Bispectral index-guided anaesthesia for off-pump coronary artery bypass grafting. Ann Card Anaesth 2008;11:105-10

How to cite this URL:
Muralidhar K, Banakal S, Murthy K, Garg R, Rani G R, Dinesh R. Bispectral index-guided anaesthesia for off-pump coronary artery bypass grafting. Ann Card Anaesth [serial online] 2008 [cited 2022 Dec 8];11:105-10. Available from:

The technique of fast track cardiac anaesthesia may facilitate early tracheal extubation after cardiac surgery. [1],[2] The safety of this early extubation practice in cardiac surgical patients has been extensively reported in the last 20 years. [3] Fast-track protocols depend on a low-dose-opioid anaesthetic to expedite recovery of spontaneous respiration, extubation and ambulation. [4] Fast tracking is fuelled in part by market forces demanding more cost effective quality care and to this end has achieved decreased hospital costs through reduced intensive care unit and hospital stay. [5] Titrating propofol with BIS monitoring during balanced anaesthesia decreases propofol use and significantly improves recovery with no difference in intraoperative conditions. [6] Similarly, titrating desflurane and sevoflurane with the use of BIS monitoring decreased utilisation of drugs and contributed to faster emergence from anaesthesia. [7]

The measurement of depth of anaesthesia is of clinical interest for titrating anaesthetic drugs and for avoiding patient awareness during anaesthesia. However, defining "anaesthetic depth" is difficult as unresponsiveness cannot be measured directly [8] and there is no clear definition of what "depth of anaesthesia" means exactly. In the last two decades, there have been several variables, such as response to skin incision, loss of consciousness, or drug concentrations, which have been represented by different parameters, such as heamodynamics, [9] oesophageal contractility [10] pupillary reflex, and skin conductivity [11] to assess the depth of anaesthesia. The most reliable variables were derived from the electroencephalogram (EEG). The bispectral index (BIS), a modern variable derived from the phase coupling of the spontaneous EEG, [12] has been investigated in many different studies. High correlation coefficients between BIS and propofol plasma concentrations and clinical criteria of sedation have been observed. It has been shown that BIS-monitored anaesthesia reduced risk of awareness in 'at-risk' adult surgical patients. [13] Incidence of intra-operative awareness is high in cardiac surgical patients. BIS monitoring reduces the incidence of awareness during general anaesthesia requiring endotracheal intubation and neuromuscular blocking agents. [14]

The current study was aimed to test the feasibility of BIS during the conduct of off-pump coronary artery bypass grafting (CABG) to find out if BIS monitoring altered the doses of anaesthetic agents needed for off-pump CABG.

   Materials and Methods Top

After obtaining approval of the institutional review board, this prospective randomised control study was conducted on 40 patients (estimated power for two-sample comparison of means = 1.0000) undergoing elective CABG. The following patients were excluded from the study; patients requiring extra corporeal circulation either electively or during the course of the operation; patient with poor left ventricular (LV) function (left ventricular ejection fraction <40%), LV aneurysms, renal/hepatic dysfunction, patients requiring preoperative or intraoperative intra-aortic balloon pump (IABP). Presence of unstable angina, carotid stenosis, cerebrovascular accident (CVA), excessive alcohol intake and drug abuse were also reasons for exclusion from the study.

Anti-hypertensive and anti-anginal medications were continued until the morning of surgery. Pre-anaesthesia medication consisted of oral 10 mg of diazepam at bed time on the night prior to surgery and approximately 2 hours prior to anaesthesia and surgery. After arrival to the anaesthetic room, patients were administered oxygen (O 2 ) by facemask and monitoring of ECG (5 lead) with automated ST segment analysis (Marquette Solar 5000, GE Medical System, Milwaukee, USA) and pulse oximetry was initiated. A 14-G intravenous cannula was inserted in the dorsum of right hand and an 18-G; 9 cm intra-arterial cannula was introduced into the right femoral artery for monitoring of the arterial pressure and obtaining arterial blood for analysis. General anaesthesia was induced, while patients breathed 100% O 2 by facemask, using a combination of fentanyl 2 µg/kg, midazolam 100 µg/kg and sleep dose of thiopentone. Endotracheal intubation was performed after administration of pancuronium bromide 0.15 mg/kg and mechanical ventilation was initiated. Low-flow technique (fresh gas flow of 1 L/min) using anaesthesia machine (Excel 210 SE, Datex Ohmeda, Madison, MI, USA) to achieve end-tidal carbon-dioxide tensions of 35 ± 3 mm Hg was used. Inspired and expired gas concentration of O 2 , carbon dioxide (CO 2 ) and isoflurane were measured using smart anaesthetic gas monitoring system (Smart anaesthesia multi gas module, Solar 5000, GE Medical Systems, Milwaukee, USA). Haemodynamic parameters were maintained within 20% of the basal values with dopamine, phenylephrine, and glyceryltrinitrate, as required. Intraoperative hypothermia was prevented by the use of warm airflow at 40 o (Bear Hugger warming unit, model 505, Augustine Medical Inc, Eden Prairie, MN, USA), warming blanket (Hemotherm, Cincinnati Sub Zero, Cincinnato, Ohio, USA), warm intravenous fluids. Filling pressures and fluid balance was maintained using lactated Ringers solution and 6% hydroxy-ethyl starch (HAES-steril, Fresenius Kabi). Total amount of fentanyl and midazolam administered during entire procedure was restricted to 10 µg/kg and 10mg respectively. Perioperative analgesia was supplemented with the use of rectal diclofenac sodium administered after anaesthetic induction in the operating room.

Patients were randomly divided into four groups by a sealed envelop technique as follows: Group A (I-no BIS): In this group, anaesthesia was maintained using isoflurane in O 2 ; the end-tidal concentration of isoflurane was adjusted to 1-1.2% during the entire procedure. Group B (I-BIS): In this group, anaesthesia was maintained using isoflurane in O 2 : the isoflurane inspired concentration was adjusted to maintain a BIS value of 50 ± 5. Group C (P-no BIS): In this group, anaesthesia was maintained with propofol infusion (after a 50mg bolus) at 6-8 mg/kg/hr till sternotomy and 4-6-mg/kg/hr thereafter. Group D (P-BIS): In this group, anaesthesia was maintained (after a 50mg bolus) with variable propofol infusion rate titrated to a BIS value of 50 ± 5. In Group B (I-BIS) and Group D (P-BIS) monitoring included BIS: in these patients prior to induction of general anaesthesia, non-invasive monitoring device the BIS monitor (Model A-2000, Aspect Medical systems, Inc, Natick, MA, USA) was applied. The 2-channel electroencephalographic signal for the BIS was captured using cutaneous electrodes (Zipprep, Aspect Medical Systems, Natick, MA, USA) positioned as recommended by the manufacturer. A smoothing window of 15-second duration, which updates every 2 seconds was used, the impedance was maintained less than 5 k?. To minimise artifactual error, the BIS score was recorded only in the absence of possible confounding signals; the BIS values during use of the electrocautery were not taken into consideration during the study.

Isoflurane was administered in groups A (I-no BIS) and B (I-BIS) through a calibrated Isotec 5 vaporiser (Ohmeda BOC Health care, west Yorkshire, UK;). Propofol was infused (in groups C (P-no BIS) and D (P-BIS) using a syringe pump (perfusor Compact, B Braun, Melsurgen AG) and a 50 ml syringe (Becton Dickinson, Singapore). In groups A (I-no BIS) and B (I-BIS) the amount of isoflurane administered during the procedure was calculated by using the formula: consumption of anaesthetic agent in ml/hr = 3 x set concentration % x fresh gas flow L/min. [ 15]

All patients underwent off-pump CABG done after a median sternotomy under normothermic conditions. Traditional cardiopulmonary bypass circuit was kept ready as a rescue measure. Patients received heparin in a dose of 300 units/kg prior to anastomosis so as to maintain an activated coagulation time of greater than 300 seconds. Proximal anastomosis was performed with partial clamping of the ascending aorta and the distal grafting was performed using tissue stabiliser (Octopus-3, 28400-O, Medtronic, Inc710, Medtronic Parkway, Minneapolis, MN 55432-5604, USA). Off-pump CABG was converted to conventional CABG with CPB at any point should the patient not tolerate the period of ischaemia required to complete the graft or for surgical reasons. ST segment analysis was carried out during the entire procedure and leads I, II and V5 were continuously monitored. ST segment depression or elevation of >1.0mm was considered clinically significant. All patients were ventilated postoperatively for 2-4 hours and tracheal extubation performed after satisfying the criteria for extubation, (namely patient being heamodynamically stable, good spontaneous respiratory efforts, neurological recovery, conscious, warm, not bleeding excessively and fully recovered from the effects of neuromuscular blocking agents).

An intensive care unit research fellow interviewed all patients at 18 h after extubation. After an initial introduction, the interview, which was very structured, was begun. Each patient was asked the following standard set of questions. 1.What was the last thing you remember before surgery? 2. What was the very next thing you remember? 3. Can you remember anything in between these two periods? 4.Did you have any dreams during your operation? If the patient indicated that he or she did not have explicit memory of intraoperative events while answering these questions, no further questions were asked. If the patient indicated that he or she had explicit memory of intraoperative events while answering the questions, the following sub-questions were asked: 1. What did you notice; sounds, touch, pain, paralysis? 2. How long did it last? 3. Did you try to alert anything? 4. Have these been any consequences for you? No supplemental questions were asked. Awareness was defined by the presence of explicit memory of any event from induction of anaesthesia to recovery of consciousness in the cardiac surgical intensive therapy unit (ITU). If patient suggested that he suffered from awareness under anaesthesia he/she was visited by the senior author and the attending anaesthesiologist to discuss, explain the peri-operative events, answer patient's questions sympathetically and refer the patient for psychological counseling, if necessary. The data are presented as mean ± SD and statistically analysed using students 't' test. A P value of less than 0.05 was considered significant.

   Results Top

Forty patients were included in the study. The four groups were comparable with regard to the demographic and preoperative data [Table 1].

The quantity of isoflurane required for the performance (formula used to derive the amount is mentioned under methods) of off-pump CABG was 37 ± 4 ml in Group A (I-no BIS) and 24 ± 4 ml in-Group B (I-BIS): this is a 35.2% reduction in isoflurane usage. This reduction in isoflurane requirements with BIS monitoring was statistically significant. The quantity of propofol required for the conduct of off-pump CABG was 176 ± 9 ml in-group C (P-no BIS) and 120 ± 6 ml in-group D (P-BIS): this is a 32% reduction in propofol usage. The reduction in propofol requirements with BIS monitoring was statistically significant [Table 2].

All patients tolerated the off-pump CABG well and none was converted to an on-pump procedure. Time to tracheal extubation was significantly reduced in group B (I-BIS), C (P-no BIS) and D (P-BIS) as compared with group A (I-no BIS). There were no significant differences between the duration of surgery, intensive therapy unit (ITU) stay and length of hospital stay in the four groups. No patient had explicit memory of any event from the induction of anaesthesia to recovery of consciousness in the cardiac surgical ITU.

   Discussion Top

In the present study BIS was used to maintain a constant, moderate depth of anaesthesia and the anaesthesia dose was adjusted to obtain a BIS value of 50 ± 5. During continuous infusion of fentanyl and midazolam anaesthesia for cardiac surgery, a BIS of less than 50 was effective in preventing intra operative awareness. [16] Our study has demonstrated a reduction in the anaesthetic drug requirements (by 36% with isoflurane and 32% with propofol) with the use of BIS monitoring during the performance of off-pump CABG.

Depth of anaesthesia is the interaction of two drug effects to clinical anaesthesia, one drug effect involves hypnotic component and the second effect involves the analgesic component. The hypnotic component can be induced by intravenous and inhaled anaesthetics whereas analgesia component can be induced by opioids and local anaesthetics. Several new monitors have been studied to assess the depth of anaesthesia; amongst them, the BIS monitor (Bi-spectral Index, Aspect Medical System, Natick, MA) has undergone extensive investigation. BIS is a processed EEG with advanced algorithms that report a number from 0 to 100; 100 represents an awake state and 0 represents complete EEG inactivity. BIS index is presently the most extensively validated measure of depth of anaesthesia. Titration of anaesthetic agents by BIS index appears to decrease the incidence of intraoperative awareness, currently estimated at 0.2% in healthy patients undergoing general anaesthesia and 1.14% in patients undergoing cardiac surgery. [8],[17] Although midlatency auditory evoked potentials (MLAEP) show best correlation with plasma drug concentrations, MLAEPs have inconveniences that have limited its clinical use. [18],[19] A new method for extracting MLAEP from EEG signal that involves as autoregressive model with exogenous input to allow extraction of auditory evoked potential signal; BIS index provides a better discrimination from unconscious states than the A-line ABI index. [20]

Many authors have demonstrated a good correlation of BIS index and level of awareness. [21],[22],[23] BIS correlates well with the level of responsiveness and provides an excellent prediction of the loss of consciousness and is a valuable monitor of the level of sedation and loss of consciousness for propofol, midazolam, and isoflurane. [24] While comparing the abilities of narcotrend (NT) and BIS to monitor the depth of anaesthesia, NT and BIS were found be more reliable indicators for assessment of anaesthetic states than the classical electroencephalographic (EEG) variables and haemodynamics. [25] Song et al , have shown that titrating desflurane and sevoflurane using BIS monitor decreased the utilisation of those volatile agents and contributed to a faster emergence from anaesthesia in outpatients undergoing laparoscopic tubal ligation procedures. [7] Likewise titrating propofol with BIS monitoring decreases anaesthetic drug requirements and significantly improves recovery. [6] The use of BIS monitoring during general anaesthesia requiring endotracheal intubation and/or muscle relaxants was associated with significantly reduced incidence of awareness. [13] In a study evaluating the influence of BIS on decision-making, BIS monitoring was useful in taking corrective measures like titration of anaesthetic drug in 70.5% of patients, titration of vasoactive drugs in 8%, titration of both in 11.6% and other diagnostic or corrective action in 9.8% patients. [26] BIS enables one to titrate anaesthesia to meet individual patient's needs, for example those with haemodynamic instability, cardiovascular disease, obesity, and trauma and elderly subjects.

Gan et al. , have demonstrated a reduced use of propofol and faster recovery compared with standard clinical practice and this may result in potential economic benefits. [6] The length of postoperative intubation, i.e., duration of mechanical ventilation postoperatively was significantly less in group B (I-BIS), C (P-no BIS) and D (P-BIS). The recovery profile of propofol and isoflurane is reported to be similar in several studies. [27],[28],[29] The authors feel that there are factors other than the dose of propofol or isoflurane used in this study, which have influenced the differences in the extubation times.

There were concerns of increased myocardial ischaemia, infarction or death due to early extubation after cardiac surgery; but research into fast-track protocols have not supported these concerns. On the contrary, they have suggested better cardiac and respiratory outcomes with fast-track techniques. This study supports the fast-track protocols and compares two very distinct anaesthetic techniques and analyses the variables with regard to influence of BIS monitoring on the anaesthetic drug requirements. Reduction in the anaesthetic drug requirements by 30-40% with BIS monitoring is a significant finding in this study, but this reduction in the anaesthetic dose in the BIS group did not influence the length of ITU stay and hospital stay in patients undergoing off-pump CABG. BIS monitoring decreased the consumption of propofol and sevoflurane significantly (29% and 40% respectively) in a cost and recovery analysis of out-patient anaesthesia using EEG-BIS monitoring. [30] The reduced anaesthetic drug requirements during off-pump CABG can be extrapolated to less myocardial depression, less decrease in system vascular resistance, reduced arrhythmias, decreased need for inotropic support or vasoconstictor medication. Precision of anaesthetic drug usage in cardiac surgery is of great importance in patients with poor LV function, in elderly population, and in high-risk groups.

Limitation of the study

This study has an important limitation, i.e., the number of patients in the study is quite small (40) to test the hypothesis if BIS prevents awareness: Although none of the patients in each group experienced awareness, to test the hypothesis that BIS monitoring would help to decrease awareness under anaesthetic in would need a large patient population size.

The study raises an important question that it is possible that cardiac patients (who are otherwise healthy) get more anaesthesia than necessary when BIS is not monitored. In this era of fast-track-anaesthesia and an increased reliance of volatile anaesthetics and propofol, it is important to limit the anaesthetic agent concentration/dose within permissible limits. This can be achieved with the use of BIS. Many physicians would prefer to limit the concentration of volatile inhalational anaesthetics because of concern about myocardial depression during off-pump CABG especially during grafting of the distal vessels when haemodynamic instability is common. During that critical period, it would be prudent to provide just enough inhalational agent to keep the patient asleep and amnesic while limiting the concentration to avoid myocardial depression. BIS monitoring aids off-pump CABG in three ways: (1) monitoring depth of anaesthesia and thus prevents likelihood of awareness, (2) reduces the anaesthetic agent required hence reduces the cost of anaesthesia (excluding the cost of electrodes), (3) aids fast-tracking by limiting the dose of anaesthetic agent (although this could not be demonstrated in this study).

In conclusion, BIS monitoring reduces the anaesthetic drug requirements in patients undergoing off-pump CABG without risk of awareness and the author believes and recommends its routine use. Larger prospective studies are needed to extrapolate these finding in patients with poor LV function, elderly and those undergoing high-risk CABG without cardiopulmonary bypass.

   References Top

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2.Myles PS, Bukland MR, Weeks AM, Bujor MA, McRae R, Langley M, et al. Hemodynamic effects, myocardial ischemia, and timing of tracheal extubation with propofol - based anesthesia for cardiac surgery. Anesth Analg 1997;84:12-9.  Back to cited text no. 2    
3.Larson SL, Schimmel CH, Shott S, Myers PB, Foy BK. Influence of fast-track anesthetic technique on cardiovascular infusions and weight gain. J Cardiothorac Vasc Anesth 1999;13:424-30.  Back to cited text no. 3  [PUBMED]  [FULLTEXT]
4.Shapiro B, Licjtenthal P. Inhalation based anesthetics are the keys to early extubation of the cardiac surgery patient. J Cardiothorac Vasc Anesth 1993;7:135-6.  Back to cited text no. 4    
5.Cohn LH, Rosborough D, Fernandez J. Reducing coast and length of stay and improving efficiency and quality of care in cardiac surgery. Ann Thorac Surg 1997;64:S58-60.  Back to cited text no. 5  [PUBMED]  
6.Gan TJ, Glass PS, Windsor A, Payne F, Rosow C, Sebel P, et al. Bispectral index monitoring allows faster emergence and improved recovery from propofol, Alfentanil and nitrous oxide anaesthesia. Anaesthesiology 1997;87:808-15.  Back to cited text no. 6    
7.Song, D, Joshi, Girish P, White, Paul F. Titration of volatile anesthetics using bispectral index facilitates recovery after ambulatory anesthesia. Anesthesiology 1997;87:842-8.  Back to cited text no. 7    
8.Donald R, Stanski, Shafer SL. Measuring depth of anesthesia, Chapter 31. In : Miller RD, editor. Miller's Anesthesia 6 th ed. Philadelphia: Elsevier Churchill Livingstone; 2005. p. 1227-64.  Back to cited text no. 8    
9.White PF, Boyle WA. Relationship between hemodynamic and electroencephalographic changes during general anesthesia. Anesth Analg 1989;68:177-81.  Back to cited text no. 9  [PUBMED]  
10.Thornton C, Konieczko KM, Knight AB, Kaul B, Jones JG, Dore CJ, et al. Effect of propofol on the auditory evoked response and esophageal contractility. Br J Anaesth 1989;63:411-7.  Back to cited text no. 10  [PUBMED]  [FULLTEXT]
11.Goddard GF. A pilot study of the changes of skin electrical conductance in patients undergoing general anesthesia and surgery. Anesthesia 1982;37:408-15.  Back to cited text no. 11    
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13.Myles PS, Leslie K, McNeil J, Forbes A. Bispectral index monitoring to prevent awareness during anaesthesia: The B-Aware randomised controlled trial. Lancet 2004;363:1757-63.  Back to cited text no. 13    
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20.Schmidt GN, Bischoff P, Standl T, Issleib M, Voigt M, Schulte Am Esch J. ARX-derived auditory evoked potential index and bispectral index during the induction of anesthesia with propofol and remifentanil Anesth Analg 2003;97:139-44.  Back to cited text no. 20    
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23.Liu J, Singh H, White PF. Electroencephalogram bispectral index correlates with intraoperative recall and depth of propofol induced sedation. Anesth Analg 1997;84:185-9.  Back to cited text no. 23  [PUBMED]  [FULLTEXT]
24.Glass PS, Bloom M, Kearse L, Rosow C, Sebel P, Manberg P. Bispectral analysis measures sedation and memory effects of propofol, midazolom, isoflurane and alfentanil in healthy volunteers. Anesthesiology 1997;86:836-47.  Back to cited text no. 24  [PUBMED]  [FULLTEXT]
25.Schmidt GM, Bischoff P. Comparative evaluation of narcotrend, bispectral index and classical EEG. Anesth Anal 2004; 98:1346-53.  Back to cited text no. 25    
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27.Robinson BJ, Uhrich TD, Ebert TJ. A review of recovery from sevoflurane anaesthesia: Comparisons with isoflurane and propofol including meta-analysis. Acta Anaesthesiol Scand 1999;43:185-90.  Back to cited text no. 27  [PUBMED]  [FULLTEXT]
28.Myles PS, Hunt JO, Fletcher H, Smart J, Jackson T. Propofol, thiopental, sevoflurane, and isoflurane: A randomized, controlled trial of effectiveness. Anesth Analg 2000;91:1163-9.  Back to cited text no. 28  [PUBMED]  [FULLTEXT]
29.Milligan KR, O'Toole DP, Howe JP, Cooper JC, Dundee JW. Recovery from outpatient anaesthesia: A comparison of incremental propofol and propofol-isoflurane. Br J Anaesth 1987;59:1111-4.  Back to cited text no. 29  [PUBMED]  [FULLTEXT]
30.Kakkuri A, Korttila K, Yli-Hankala A; Anesthesia Research Group. Dept of OB-GYN, Helsinki University Central Hospital, FIN-00029, HYKS, Finland.  Back to cited text no. 30    

Correspondence Address:
Kanchi Muralidhar
Department of Anaesthesia, Narayana Hrudayalaya Institute of Medical Sciences, #258/A Bommasandra Industrial Area, Anekal Taluk, Bangalore - 560 099
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0971-9784.41578

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Andrey I. Lenkin,Viktor I. Zaharov,Pavel I. Lenkin,Alexey A. Smetkin,Lars J. Bjertnaes,Mikhail Y. Kirov
Journal of Cardiothoracic and Vascular Anesthesia. 2013;
[Pubmed] | [DOI]
10 Comparative effectiveness research it is not
Myles, P.S.
Anesthesiology. 2013; 118(5): 1231-1233
11 Sedation with propofol during combined spinal epidural anesthesia: Comparison of dose requirement of propofol with and without BIS monitoring
Verma, R.K. and Paswan, A.K. and Prakash, S. and Gupta, S.K. and Gupta, P.K.
Anaesthesia, Pain and Intensive Care. 2013; 17(1): 14-17
12 Comparative Effectiveness Research It Is Not
Paul S. Myles
Anesthesiology. 2013; 118(5): 1231
[Pubmed] | [DOI]
13 Brain Monitoring with Electroencephalography and the Electroencephalogram-Derived Bispectral Index During Cardiac Surgery
Miklos D. Kertai,Elizabeth L. Whitlock,Michael S. Avidan
Anesthesia & Analgesia. 2012; 114(3): 533
[Pubmed] | [DOI]
14 Brain monitoring with electroencephalography and the electroencephalogram- derived bispectral index during cardiac surgery
Kertai, M.D. and Whitlock, E.L. and Avidan, M.S.
Anesthesia and Analgesia. 2012; 114(3): 533-543
15 Assessment of the Level of Sedation in Children After Cardiac Surgery
Adelaida Lamas,Jesús López-Herce,Luis Sancho,Santiago Mencía,Ángel Carrillo,Maria José Santiago,Vicente Martínez
The Annals of Thoracic Surgery. 2009; 88(1): 144
[Pubmed] | [DOI]
16 Assessment of the Level of Sedation in Children After Cardiac Surgery
Lamas, A. and Lopez-Herce, J. and Sancho, L. and Mencia, S. and Carrillo, A. and Santiago, M.J. and Martinez, V.
The Annals of Thoracic Surgery. 2009; 88(1): 144-150