title: Insulin-like growth factor-1 and delirium in critically ill mechanically ventilated patients: a preliminary investigation.
abstract: BACKGROUND
  Delirium occurs frequently in the intensive care unit (ICU), but its pathophysiology is still unclear. Low levels of insulin-like growth factor 1 (IGF-1), a hormone with neuroprotective properties, have been associated with delirium in some non-ICU studies, but this relationship has not been examined in the ICU. We sought to test the hypothesis that low IGF-1 concentrations are associated with delirium during critical illness.
  
  
  METHODS
  Mechanically ventilated medical ICU patients were prospectively enrolled, and blood was collected after enrollment for measurement of IGF-1 using radioimmunometric assay. Delirium and coma were identified daily using the Confusion Assessment Method for the ICU and the Richmond Agitation-Sedation Scale, respectively. The association between IGF-1 and delirium was evaluated with logistic regression. In addition, the association between IGF-1 and duration of normal mental state, measured as days alive without delirium or coma, was assessed using multiple linear regression.
  
  
  RESULTS
  Among 110 patients, the median age was 65 years (IQR, 52-75) and APACHE II was 27 (IQR, 22 -32). IGF-1 levels were not a risk factor for delirium on the day after IGF-1 measurement (p = 0.97), at which time 65% of the assessable patients were delirious. No significant association was found between IGF-1 levels and duration of normal mental state (p = 0.23).
  
  
  CONCLUSIONS
  This pilot study, the first to investigate IGF-1 and delirium in critically ill patients, found no association between IGF-1 and delirium. Future studies including serial measurements of IGF-1 and IGF-1 binding proteins are needed to determine whether this hormone has a role in delirium during critical illness.
authors.affiliation: Center for Quality of Aging, Vanderbilt University School of Medicine, Nashville, Tennessee, USA. alessandro.morandi@vanderbilt.edu
authors.forename: A
authors.initials: A
authors.lastname: Morandi
authors.forename: M L
authors.initials: ML
authors.lastname: Gunther
authors.forename: P P
authors.initials: PP
authors.lastname: Pandharipande
authors.forename: J C
authors.initials: JC
authors.lastname: Jackson
authors.forename: J L
authors.initials: JL
authors.lastname: Thompson
authors.forename: A K
authors.initials: AK
authors.lastname: Shintani
authors.forename: E W
authors.initials: EW
authors.lastname: Ely
authors.forename: T D
authors.initials: TD
authors.lastname: Girard
mesh_terms: D018806:APACHE; D000368:Aged; D003422:Critical Care / Q000379:methods; D016638:Critical Illness / Q000523:psychology / Q000628:therapy; D003693:Delirium / Q000175:diagnosis / Q000209:etiology / Q000378:metabolism*; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011569:Psychiatric Status Rating Scales; D012121:Respiration, Artificial / Q000009:adverse effects* / Q000523:psychology; D012307:Risk Factors
chemical_list: D007334:Insulin-Like Growth Factor I