The effect of pneumoperitoneum and Trendelenburg position on acute cerebral blood flow-carbon dioxide reactivity under sevoflurane anaesthesia

This study compared cerebral blood flow-carbon dioxide (CBF-CO₂) reactivities in the supine and modest Trendelenburg position under pnemoperitoneum during sevoflurane anaesthesia. After induction of anaesthesia in 25 patients, mechanical ventilation was adjusted to increase PaCO₂ from 4.7 (T₁) to 6.0 kPa (T₂) in the supine position, and the change in jugular bulb oxygen saturation was measured as an index of CBF. Then, after establishment of pneumoperitoneum and 30°Trendelenburg position, the CO₂ step and measurement of CBF were repeated. The CBF-CO ₂reactivity was 7.5 (3.3) %.kPa^-1(% change in jugular bulb oxygen saturation per unit change in PaCO₂) in the supine position and 6.8 (2.3) %.kPa^-1 in the 30° Trendelenburg-pneumoperitoneum condition (p = 0.086). We conclude that CBF-CO₂ reactivity is unchanged by the modest Trendelenburg position under pneumoperitoneum during sevoflurane anaesthesia.