Is delirium after cardiac surgery related to plasma amino acids and physical condition?

The authors studied interrelationships between plasma levels of amino acids , physical condition (as apparent from cortisol, albumin, and thyroid hormo ne concentrations), and postoperative delirium in 296 patients undergoing e lective cardiac surgery. Both plasma tryptophan (Trp) and ratio of Tup to t he other large neutral amino acids (oLNAA) were reduced in delirious patien ts compared with control patients. The lower availability of Tup far the br ain in delirious patients may lead to decreased serotonergic function. Besi des, the ratio of phenylalanine (Phe) to the oLNAA was increased in deliriu m, which may result in a higher synthesis of cerebral dopamine and norepine phrine. Delirious patients were also in poorer physi- cal condition than no ndelirious patients, having decreased albumin level and increased untie of inactive reverse triiodothyronine (T-3) to active T-3. Decreased Trp and in creased Phe availability may give rise to an imbalance in cerebral neurotra nsmitters and thus contribute to delirium.