the Effect of Different Modes of Mechanical Ventilation on Cerebral Blood Flow During Thoracoscopic Surgeries in Neonates (RCT)

The brain uses aerobic metabolism exclusively for energy production, so the brain is critically dependent on the nearly continuous delivery of oxygen to maintain cellular energy production. Normal cerebral blood flow is approximately 50 ml/100 gram of brain tissue/min. The brain represents 2% of the total body weight but it receives about 15% of the cardiac output. The brain is supplied by the circle of Willis which is formed of anastomosis between the internal carotid artery and the vertebro-basillar system. Monitoring of the CBF depends on either assessing the blood flow itself (e.g, radioactive substance and transcranial duplex) or assessing the oxygen delivery to the brain (e.g, cerebral oximetry and jugular bulb venous O2 saturation). CBF monitoring is an important parameter in both Intensive care unit and operation room in several aspects e.g, traumatic brain injury (TBI), acute stroke, carotid artery surgeries and cardiopulmonary bypass.

Cerebral oximetry is a continuous noninvasive technique that monitors the cerebral blood flow with several advantages over other CBF monitors including the ease of use and interpretation. It is painless and does not utilize ionizing radiation. The recordings provide real time information rather than single static measurements. Using the cerebral oximetry has few limitations including representing local rather than global CBF and absence of normal and cutoff values.

Thoracoscopic surgery was first introduced in 1910 and allowed a major advance in the field of thoracic surgery. Then with the improvement of the Instrumentation, thoracoscopic surgery started in the pediatric field in 1976 for simple procedures and now it is used predominantly in the pediatric thoracic surgery. The use of thoracoscope has many advantages over the open approach including using a smaller incision and reducing blood loss, postoperative pain, hospital stay and musculoskeletal deformities. Thoracoscope utilizes either one lung ventilation (OLV) or CO2 insufflation technique. In neonates the OLV technique is not suitable, so CO2 insufflation ( capnothorax ) is usually used.

Several studies were done and revealed the effect of thoracoscopy in neonate on CBF due to the effect of capnothorax which increases the intrathoracic pressure leading to decreased venous return and cardiac output, subsequently the CBF decreases, and with the increase of the insufflation pressure the decease in the CBF becomes more significant. Also the capnothorax may lead to hypercapnia which leads to changes in the CBF.

The incidence of newborn with congenital anomalies that require surgical procedure during the neonatal period is not low. With the increase of the survival rate, several studies proved that exposure of the neonates to surgery and anesthesia is associated with a higher risk of neuro-developmental delay in different aspects (sensory, motor, language, behavioral, cognitive, etc.) and thoracoscopic surgery is associated with higher risk due to the nature of the disease and the surgery. Using cerebral oximetry in addition to other routine monitors is of added value to maintain CBF within normal range to decrease the incidence of neurological injuries.