Newly identified precipitating factors in mechanical ventilation-induced brain damage: implications for treating ICU delirium.

Delirium is 1.5 to 4.1 times as likely in intensive care unit patients when they are mechanically ventilated. While progress in treatment has occurred, delirium is still a major problem in mechanically ventilated patients. Based on studies of a murine mechanical ventilation model, we summarize evidence here for a novel mechanism by which such ventilation can quickly initiate brain damage likely to cause cognitive deficits expressed as delirium. That mechanism consists of aberrant vagal sensory input driving sustained dopamine D2 receptor (D2R) signaling in the hippocampal formation, which induces apoptosis in that brain area within 90 min without causing hypoxia, oxidative stress, or inflammatory responses. This argues for minimizing the duration and tidal volumes of mechanical ventilation and for more effectively reducing sustained D2R signaling than achieved with haloperidol alone. The latter might be accomplished by reducing D2R cell surface expression and D2R-mediated Akt inhibition by elevating protein expression of dysbindin-1C.