Transient loss of consciousness during hypercapnia and hypoxia: Involvement of pathways associated with general anesthesia.

Transient loss of consciousness (TLOC), frequently triggered by perturbation in essential physiological parameters such as pCO or O, is considered a passive consequence of generalized degradation in high-level cerebral functioning. However, the fact that it is almost always accompanied by atonia and loss of spinal nocifensive reflexes suggests that it might actually be part of a "syndrome" mediated by neural circuitry, and ultimately be adaptive. Widespread suppression by molecules distributed in the vasculature is also the classical explanation of general anesthesia.