Low tryptophan levels are associated with postoperative delirium in the elderly.
BACKGROUND
Postoperative delirium is a common complication in geriatric patients. Tryptophan is an amino acid precursor to the mood-stabilizing neurotransmitters serotonin and melatonin. We hypothesized that tryptophan levels are lower in elderly subjects who develop postoperative delirium.


METHODS
A prospective observational study was performed. Subjects older than 50 years undergoing surgery with an anticipated postoperative intensive care unit admission were recruited. Postoperative delirium assessment occurred daily using the Confusion Assessment Method-intensive care unit. Peripheral serum tryptophan levels were measured 2 days after surgery.


RESULTS
Forty-nine subjects (46 men) were enrolled, with an average age of 64 +/- 7 years. The incidence of delirium was 43% (21 of 49). The average duration of delirium was 2.9 +/- 3.0 days. Tryptophan levels were lower in the subjects who developed delirium (29.9 +/- 13.3 vs 48.5 +/- 19.8 microg/mL; P = .001).


CONCLUSIONS
Lower levels of tryptophan postoperatively were associated with the development of delirium in the elderly.
Robinson
Thomas N
TN
Department of Surgery, University of Colorado at Denver, Health Sciences Center, 12631 East 17th Ave., Mail Stop C313, PO Box 6511, Aurora, CO 80045, USA. thomas.robinson@uchsc.edu
Raeburn
Christopher D
CD
Angles
Erik M
EM
Moss
Marc
M
D000368:Aged; D016009:Chi-Square Distribution; D003693:Delirium / Q000097:blood* / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000097:blood* / Q000453:epidemiology; D011446:Prospective Studies; D012307:Risk Factors; D012680:Sensitivity and Specificity; D014364:Tryptophan / Q000097:blood*
D014364:Tryptophan
Psychol Med. 1986 May;16(2):297-305
3726005
JAMA. 1994 Jan 12;271(2):134-9
8264068
Med Hypotheses. 1999 Aug;53(2):103-6
10532699
J Chronic Dis. 1987;40(5):373-83
3558716
Lancet. 1991 Oct 5;338(8771):851-2
1681217
Crit Care Med. 2001 Jul;29(7):1370-9
11445689
Psychopharmacology (Berl). 2006 Jul;187(1):121-30
16767422
J Neuropsychiatry Clin Neurosci. 2000 Winter;12(1):57-63
10678514
Md State Med J. 1965 Feb;14:61-5
14258950
Crit Care. 2006;10(4):R121
16919169
J Gerontol A Biol Sci Med Sci. 2006 Dec;61(12):1281-6
17234821
J Gerontol A Biol Sci Med Sci. 2000 May;55(5):B249-52; discussion B253-4
10819312
J Chromatogr B Analyt Technol Biomed Life Sci. 2002 Nov 25;780(2):381-7
12401365
Am J Clin Nutr. 2000 Jun;71(6):1536-44
10837296
Curr Opin Crit Care. 2005 Aug;11(4):360-8
16015117
J Am Geriatr Soc. 2003 Oct;51(10):1451-4
14511167