Comparison of Low Versus Normal Flow Anesthesia on Cerebral Oxygenation and Bispectral Index in Morbidly Obese Patients

Study Overview
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Brief Summary
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Obesity is a chronic disease that affects quality and duration of life negatively. It's not clearly known the effects of low flow anesthesia on cerebral oxygenation with high-risk morbidly obese patients. In this study, it was aimed to compare the effects of general anesthesia with low flow (0,75 L/min) and normal flow (1,5 L/min) on cerebral oxygenation and depth of anesthesia in morbidly obese patients in bariatric surgery.

Detailed Description
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Obesity is a chronic disease that affects quality and duration of life negatively. It is one of the most important health problem in the world along with very common in Turkey. Initially, obesity was considered the problem of developed countries but it has become inevitable with increase income levels, changes in lifestyles, reduction of energy consumption and increase of energy intake in developing countries. Today, the second important cause of preventable deaths after smoking is obesity. The World Health Organization (WHO) has stated that it will be the most important health problem of the 21st century. According to WHO determinations; as of 2008, the prevalence of overweight in the world is 35% and the prevalence of obesity is around 11%. The definition of body mass index (BMI) is used in defining and classifying obesity. WHO is making the definition of overweight and obesity based on body mass index [BMI = Weight (kg) / Height (m2)]. It is called as obesity when the calculated value is over 30 kg/m2, morbid obesity over 40 kg/m2 and super obesity over 50 kg/m2. Morbid obesity operations, with effective results on achieving weight loss continuity once it has been widely applied in Europe and the United States, have been frequently implemented in Turkey as well. With the rising obesity in Turkey, laparoscopic bariatric surgery which has low complication rates is preferred. Low flow general anesthesia is applied to reduce pollution rates and treatment costs in operation rooms. However, the reduction of fresh gas flow should not affect the quality and safety of anesthesia management, especially in high risk operations such as morbid obesity surgery. Insufflation of abdominal cavity with carbon dioxide during laparoscopic surgery is resulted in increased intraabdominal pressure, decreased functional residual capacity and pulmonary compliance, increased hypercapnia and systemic vascular resistance. Especially in the trendelenburg position it may be difficult to detect cerebral hypoxia as a consequence of increased intracranial pressure and decreased cerebral blood flow . During general anesthesia, there are several options for monitoring the cerebral condition. One of them is cerebral oximetry method which estimates regional tissue oxygenation by transcutaneous measurement on the frontal cortex. Near-infrared spectroscopy (NIRS) is a monitor used following the adequacy of cerebral perfusion with noninvasive and continuous measurement and reflects regional saturation. With the development of technology, the safety of anesthesia devices and the advancement of monitoring techniques are positively affecting the anesthesia management. The effects of low flow anesthesia, which has been used for years and whose positive aspects are well practiced, are not clearly known on cerebral oxygenation with high-risk morbidly obese patients. In this prospective randomized study, it was aimed to compare the effects of general anesthesia with low flow (0,75 L/min) and normal flow (1,5 L/min) on cerebral oxygenation and depth of anesthesia in morbidly obese patients in bariatric surgery.

Official Title
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Comparison of Low Versus Normal Flow Anesthesia on Cerebral Oxygenation and Bispectral Index in Morbidly Obese Patients Undergoing Sleeve Gastrectomy: Prospective, Randomized Clinical Trial

Conditions
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Morbid Obesity, Anesthesia Awareness, Anesthesia Complication

Intervention / Treatment
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* Device: Regional cerebral oxygen saturation
* Device: Bispectral Index (BIS)


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: American Society of Anesthesiology score I-III, 18-65 years, BMI> 35 Exclusion Criteria: American Society of Anesthesiology IV, Under 18 years, Over 65 years, Obstetric patients, Uncontrolled diabetes mellitus, cardiovascular and pulmonary disease, Cerebrovascular disease, Patients who refused informed consent forms

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 65 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Screening
Allocation: Randomized
Intervention Model: Crossover Assignment
Interventional Model Description: Prospective Randomized Clinical Study
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Low flow<br>Anesthesia was maintained 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 the flow rate was adjusted to 0.75 L/min. Regional cerebral oxygen saturation is a useful clinical research tool for noninvasive and continuous monitoring of hemodynamic and brain oxygenation. Regional cerebral oxygen saturation (Near-infrared spectroscopy system, NIRS, Cerebral Oximeter) monitoring was performed to all patients. The most effective method for depth of anesthesia and assessment of sedation is bispectral analysis of mean frequency of electroencephalography. The values of Bispectral Index (BIS, Bispectral Index, Monitoring System) decreases with the deepening of anesthesia. | Device: Regional cerebral oxygen saturation<br>* Regional cerebral oxygen saturation is a useful clinical research tool for noninvasive and continuous monitoring of hemodynamic and brain oxygenation. Regional cerebral oxygen saturation (Near-infrared spectroscopy system, NIRS, Cerebral Oximeter) monitoring was performed to all patients.<br>* Other names: NIRS (Near-infrared spectroscopy system);Device: Bispectral Index (BIS)<br>* The most effective method for depth of anesthesia and assessment of sedation is bispectral analysis of mean frequency of electroencephalography. The values of BIS decreases with the deepening of anesthesia.<br>* Other names: BIS;|
| Sham Comparator: Normal flow<br>Anesthesia was maintained 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 the flow rate was adjusted to 1.5 L/min.Regional cerebral oxygen saturation is a useful clinical research tool for noninvasive and continuous monitoring of hemodynamic and brain oxygenation. Regional cerebral oxygen saturation (Near-infrared spectroscopy system, NIRS, Cerebral Oximeter) monitoring was performed to all patients. The most effective method for depth of anesthesia and assessment of sedation is bispectral analysis of mean frequency of electroencephalography. The values of Bispectral Index (BIS, Bispectral Index, Monitoring System) decreases with the deepening of anesthesia. | Device: Regional cerebral oxygen saturation<br>* Regional cerebral oxygen saturation is a useful clinical research tool for noninvasive and continuous monitoring of hemodynamic and brain oxygenation. Regional cerebral oxygen saturation (Near-infrared spectroscopy system, NIRS, Cerebral Oximeter) monitoring was performed to all patients.<br>* Other names: NIRS (Near-infrared spectroscopy system);Device: Bispectral Index (BIS)<br>* The most effective method for depth of anesthesia and assessment of sedation is bispectral analysis of mean frequency of electroencephalography. The values of BIS decreases with the deepening of anesthesia.<br>* Other names: BIS;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Regional Cerebral Oxygen Saturations (Left and Right) | The measurement of Regional Cerebral Oxygen Saturations by cerebral oximetry method which estimates regional tissue oxygenation by transcutaneous measurement on the frontal cortex. Cerebral oximeter (or named as NIRS, Near-infrared spectroscopy) is a monitor used following the adequacy of cerebral perfusion with noninvasive and continuous measurement and reflects regional saturation | From beginning of anesthesia (15 minutes before anesthesia) to end of anesthesia (15 minutes after anesthesia) up to nearly 5 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Heart rate | Heart rate (beat/min) | From beginning of anesthesia (15 minutes before anesthesia) to end of anesthesia (15 minutes after anesthesia) up to nearly 5 hours | 
| Systolic and Diastolic Arterial Pressure (both) | Systolic and Diastolic Arterial Pressure (both) (mmHg) | From beginning of anesthesia (15 minutes before anesthesia) to end of anesthesia (15 minutes after anesthesia) up to nearly 5 hours | 
| End-tidal carbon dioxide (EtCO2) | EtCO2 is the measurement of the exhaled CO2 by capnography. This value is expressed in millimeters of mercury (mmHg) of CO2. | From beginning of anesthesia (15 minutes before anesthesia) to end of anesthesia (15 minutes after anesthesia) up to nearly 5 hours | 
| Bispectral Index (BIS) | Bispectral Index is a method for depth of anesthesia and assessment of sedation. The values of BIS decreases with the deepening of anesthesia. The values of 40-60 characterize the appropriate depth of anesthesia. | From beginning of anesthesia (15 minutes before anesthesia) to end of anesthesia (15 minutes after anesthesia) up to nearly 5 hours | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Bariatric surgery, Low flow anesthesia, Bispectral index, Regional cerebral oximetry