Postoperative delirium and plasma melatonin.

The molecular mechanisms of postoperative delirium are not understood in detail yet. This condition is similar to cases of mental symptoms in interferon therapy or hemodialysis. We propose that postoperative delirium is caused by a deficiency of serotonin, an important neurotransmitter, and review the evidence supporting our hypothesis. The serotonin deficiency results from a decrease in tryptophan, the serotonin precursor, and from an increase in melatonin, a serotonin metabolite. Our hypothesis may be applicable to the mechanisms of mental symptoms in interferon therapy and hemodialysis. In addition, we discuss to the relationship between homeostasis and biorhythms because postoperative delirium may be a dysrhythmia.