Comparison of Low Versus Normal Flow Anesthesia on Cerebral Oxygenation and Bispectral Index in Morbidly Obese Patients Undergoing Sleeve Gastrectomy: Prospective, Randomized Clinical Trial
Phase: NA
Conditions: Morbid Obesity, Anesthesia Awareness, Anesthesia Complication
Sponsor: Inonu University

17.02.2018 
Does Low Flow Anesthesia Affect Cerebral Oxygenization in Bariatric Surgery? 
Prospective Randomized Clinical Study 
 
Sedat Akbas, Asst. Prof. Department of Anesthesiology and Reanimation, Inonu University 
Medical Faculty, Malatya, Turkey 
Ahmet Selim Ozkan, Asst. Prof. Department of Anesthesiology and Reanimation, Inonu 
University Medical Faculty, Malatya, Turkey 
 
Address all correspondence to: 
Sedat Akbas, Asst. Prof. Department of Anesthesiology and Reanimation, Inonu University 
Medical Faculty, Malatya, Turkey 
Mail: sedat.akbas@inonu.edu.tr 
Phone Number: +905058263912 
 
Keywords: Bariatric surgery, low flow anesthesia, bispectral index, regional cerebral 
oxymetry 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

17.02.2018 
Does Low Flow Anesthesia Affect Cerebral Oxygenization in Bariatric Surgery? 
Prospective Randomized Clinical Study 
Study Protocol 
This study will perform in 60 adult patients who undergoing laparoscopic sleeve gastrectomy or gastric bypass 
surgery. Morbidly obese patients with ASA (American Society of Anesthesiology) score I-III, aged 18-65 years, 
BMI> 35 will include in the study. Patients with ASA IV, under 18 years, over 65 years, obstetric patients, 
uncontrolled diabetes mellitus, cardiovascular and pulmonary disease, cerebrovascular disease and patients who 
refused informed consent forms will exclude from the study. 
Heart rate (HR), noninvasive blood pressure, electrocardiogram (ECG) and peripheral oxygen saturation (SpO2), 
monitoring will perform to all patients in operation room without premedication. In addition, regional cerebral 
oxygen saturation (Near-infrared spectroscopy system, NIRS, INVOS 4100 Cerebral Oximeter, Software 
Version 7.2.5.0, Somanetics Corporation) and BIS (Bispectral Index, VISTATM Monitoring System) monitoring 
will perform to all patients. Two cerebral sensors of NIRS and BIS sensors will glue to the right and left frontal 
areas under the hairline and covered with tape to prevent exposure to light.  
After preoxygenation (100% 4 L/min O2 for 3 minutes), propofol (1-2 mg/kg), rocuronium (0.8 mg/kg) and 
fentanyl (0.1 μg/kg) will administer in anesthesia induction via intravenous route at doses calculated according to 
ideal body weights. Randomly select patients will divide into two groups: Group L: low flow desflurane and 
group N: normal flow desflurane. Initially, anesthesia maintain with desflurane inhalation with a flow of 2 L/min 
in 0.5 O2 oxygen-air mixture in both groups. While target minimum alveolar concentration (MAC) was 1-1.5 and 
BIS values are 40-60 concurrently, the flow rate adjust to 0.75 L/min in Group L and 1.5 L/min in Group N. 
Age-related MAC values will determine and express as a percentage of volume. The ventilation parameters will 
adjust to maintain the end-tidal carbon dioxide (EtCO2) values at 35-45 mmHg. Neuromuscular blocker will 
administer based on Train of Four (TOF, Datex-Ohmeda) values.  
HR, SpO2, EtCO2, mean arterial pressure (MAP), BIS values, left regional cerebral oxygen saturations (LrSO2) 
and right regional cerebral oxygen saturations (RrSO2) will record at before anesthesia (T0), after intubation (T1), 
before insufflation of CO2 (T2), after insufflation of CO2 (T3), after reverse trendelenburg position (T4), after 
supine position (T5), after desufflation of CO2 (T6), after awakening from anesthesia (T7). Also anesthesia and 
surgery times, perioperative and postoperative complications will record. Postoperative analgesia was achieved 
in all patients with appropriate doses of tramadol and paracetamol via intravenous route.  

17.02.2018 
Does Low Flow Anesthesia Affect Cerebral Oxygenization in Bariatric Surgery? 
Prospective Randomized Clinical Study 
Statistical Analysis 
Statistical analysis will carry out by using SPSS program (SPSS for Windows version 22). T-test and Chi-Square 
Test will be used for the comparison between groups. Correlation analysis will be based on the calculation of 
Pearson’s rank correlation coefficients. Value of p below 0.05 will be considered as statistically significant. 
Consent to conduct the study was obtained from Local Ethic Committee of Inonu University.