Chnages in Cerebral Oxygenation State and Blood Volume During Tracheal Intubation: Comparison Between Thiamylal and Propofol

Tracheal intubation may affect the cerebral oxygenation state and the cerebral blood volume because cerebral blood flow has been reported to increase during this procedure. In this study, we evaluated these changes by using near-infrared spectroscopy during tracheal intubation after induction of anesthesia by propofol and thiamylal. We studied 30 females (ASA 1 or 2) undergoing elective obstetric laparoscopy. The patients were randomly allocated into thiamylal (5 mg.kg-1) and propofol (2.5 mg.kg-1) induction groups (n = 15 each). Changes in brain tissue concentrations of oxy- and deoxygenated hemoglobin were measured. We also evaluated changes in the sum of the concentrations of oxy- and deoxygenated hemoglobin, which reflects the changes in cerebral blood volume. Systemic hemodynamics was also monitored. During tracheal intubation, the concentrations of oxygenated hemoglobin was increased by more than 3 μmol.L-1 in both groups. This increase was significantly higher compared to the preanesthetic values. Changes in the sum of the concentrations of oxy- and deoxygenated hemoglobin were insignificant and small (presumably within 3 % of the whole cerebral hemoglobin concentration) during the procedure. Although an increase in blood pressure and heart rate was better suppressed in the propofol group, changes in the cerebral oxygenation state were similar between the groups. During the tracheal intubation, cerebral oxygenation increased presumably due to an increase in cerebral blood flow. However, the changes in cerebral blood volume by the procedure were small and the effect of thiamylal and propofol on the changes were similar.