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

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.