The Effect of BIS Monitorization to Intraoperative Anesthetic Consumption During Coronary Artery Surgery
Condition: Unconscious State
MeSH terms: Unconsciousness
Study type: Interventional

Summary: 
      213 patients undergoing elective on-pump coronary artery bypass grafting (CABG) were enrolled
      into this prospective-clinical trial.After hundred and sixty three patients were excluded due
      to various reasons, 50 patients were randomized to BIS (bispectral index) and MAC (minimum
      alveolar concentration) groups. In BIS group (Group B, n=25), desflurane was titrated within
      40 to 60 BIS values and in MAC group (Group M, n=25) within 0.7 to 1.3 MAC. Primary end point
      of the study was to investigate the difference of desflurane consumption between groups.
    

Detailed description: 
      This study was approved by Baskent University Institutional Review Board and Ethics Committee
      (Project No: KA13/294) and supported by Baskent University Research Fund. The study was
      conducted in a single university hospital (Başkent University Hospital, Ankara, Turkey).
      Between January 2014 and October 2014, 213 patients undergoing CABG surgery were assessed for
      eligibility. 163 patients were excluded because of not meeting inclusion criteria. 50
      patients were enrolled into this prospective-clinical trial. All patients were informed of
      the nature of the study and gave their written consent during preoperative visit performed by
      the investigators.Diazepam 0.1 mg/kg (Diazem®) and famotidine HCI 40 mg (Famodin®) were given
      by the oral route to all patients, the day before surgery at 11 pm and midazolam 0.1 mg/kg
      (Dormicum®) was given to all patients by oral route 30 min before starting anesthesia. After
      routine 5 lead electrocardiography, pulse oximeter monitoring and peripheric venous and
      arterial cannulations, endotracheal intubation was performed. BIS monitoring (BIS Quatro
      Sensor, Aspect Medical Systems, Inc, Norwood, MA, USA) was applied to BIS group in accordance
      with the manufacturer's instructions. Anesthesia was induced with propofol 1-2 mg/kg and
      fentanyl 5-7 mcg/kg by intravenous route, based on the patient's physical status. Muscle
      relaxation was achieved using iv rocuronium 0.6 mg/kg. Desflurane was administered through a
      calibrated vaporizer (D-Vapor, Drager Medical AG&Co. KG, Lübeck, Germany) in both groups.

      In BIS group (Grup B, n=25) desflurane was titrated to maintain a BIS value of 40 to 60.
      Anesthesia was maintained with remifentanil 0.1-0.4 mcg/kg/min, and desflurane as a volatile
      agent. In MAC group (Grup M, n=25) desflurane was titrated within 0.7 to 1.3 MAC. During
      maintenance, all patients were assessed for hypotension (systolic artery pressure (SAP) < 20%
      from baseline), bradycardia (heart rate (HR) < 45 bpm) or signs of inadequate anesthesia.
      Inadequate anesthesia was defined as hypertension (SAP >20% from baseline), tachycardia (HR >
      100 bpm) or patient movement, eye opening, swallowing, grimacing, lacrimation or sweating. In
      MAC group, if anesthesia was inadequate, the desflurane concentration was increased in steps
      of 0.5 vol % as necessary. In BIS group desflurane was titrated for BIS values between 40 and
      60. If this was judged insufficient, the infusion rate of remifentanil was increased by 0.05
      g/kg/min. Hemodynamic parameters were maintained within 20% of the basal values with dopamine
      and nitroglycerin, as required. Dopamine was administered 2-20 mcg/kg/min by central venous
      route. Calcium and noradrenaline were used as iv boluses if needed. All patients were given
      fluid infusions to maintain central venous pressure between 10-15 mmHg. Hypotension was
      initially treated with 100-250 mL iv fluid boluses; desflurane concentration was then reduced
      in steps of 0.5 vol % and finally, an iv vasopressor (dopamine, adrenaline, dobutamine) was
      given at a dose chosen by the practitioners. Bradycardia was treated with 0.5 mg atropine.
      Practitioners were reminded of this protocol via a visual protocol in the room. Morphine 0.1
      mg/kg was given all of the patients for pain control. The amount of desflurane administered
      from the start of the anesthesia to the end of surgical procedure was calculated in two
      groups. The amount of desflurane administered during the procedure was calculated by using
      the formula below:

      Consumption of anesthetic agent in ml/hr = 3 X set concentration % X fresh gas flow
      L/min.Patient characteristics and surgical variables such as intraoperative blood loss,
      anesthesia and surgery durations, BIS (bispectral index) and MAC (minimum alveolar
      concentration) values, intraoperative hemodynamic parameters and drug requirements of
      patients, amounts of fluid and blood administered, CVP, urine output, features of the surgery
      were documented by research staff. All patients were transferred to the ICU. Applying an a
      priory power analysis, 24 patients at least had to be enrolled in each group to detect a
      reduction of 20% at least in desflurane consumption with a risk of a of 0.05 and a
      statistical power of 0.8. Vanderbilt University power and sample size calculation program had
      been used for power analysis.

      Data are presented as medians (interquantile ranges), percentages, or number of cases.
      Continuous data were compared by Mann-Whitney tests. Categorical data were compared with
      ki-square test. Significance was defined by P values less than 0.05 using a two-tailed test.
      Data analysis was performed using IBM-SPSS version 20.0 (IBM-SPSS Science Inc., Chicago, IL).
      Demographic features, intraoperative use of propofol, intraoperative hourly and total amounts
      of remifentanil, fentanyl, muscle relaxant and morphine, hourly desflurane consumption,
      hemodynamic parameters, duration of surgery, aortic cross-clamp and cardiopulmonary bypass
      (CPB) times, defibrillation and pacemaker requirements, maximum positive inotropic and
      vasodilator drug requirements, amount of intraoperative fluids, blood and blood products
      used, urine outputs at the end of the surgery and central venous pressure (CVP) values,
      intraoperative arterial blood gas results were recorded.Durations of intubation, mechanical
      ventilation, lengths of ICU and hospital stay, 28 days mortality and postoperative
      complications were also recorded.
    

Intervention name(s): BIS; Desflurane
Intervention type(s): Device; Drug
Intervention description(s): Bispectral index monitoring; volatile agent for maintenance of anesthesia
Other intervention name(s): processed electroencephalograpy; suprane
Intervention MeSH terms: Desflurane
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Health Services Research
Keywords: desflurane; BIS; coronary artery bypass grafting surgery