Research Article

Insulin-like growth factor-1 and delirium in critically ill mechanically ventilated patients: a preliminary investigation

A. Morandi^a1a2a3 c1, M. L. Gunther^a1a2a4a5, P. P. Pandharipande^a6a8, J. C. Jackson^a1a5a9, J. L. Thompson^a7, A. K. Shintani^a7, E. W. Ely^a1a2a3a10 and T. D. Girard^a1a2a3a10

^a1 Center for Quality of Aging, Vanderbilt University School of Medicine, Nashville, Tennessee, USA

^a2 Center for Health Services Research, Vanderbilt University School of Medicine, Nashville, Tennessee, USA

^a3 Division of Allergy, Pulmonary and Critical Care Medicine in the Department of Medicine at the Vanderbilt University School of Medicine, Nashville, Tennessee, USA

^a4 Vanderbilt University Institute of Imaging Sciences (VUIIS), Nashville, Tennessee, USA

^a5 Department of Psychiatry, Vanderbilt University School of Medicine, Nashville, Tennessee, USA

^a6 Department of Anesthesiology, Division of Critical Care Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee, USA

^a7 Department of Biostatistics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA

^a8 Anesthesia Service, Department of Veterans Affairs Medical Center, Tennessee Valley Healthcare System, Nashville, Tennessee, USA

^a9 Research Service, Department of Veterans Affairs Medical Center, Tennessee Valley Healthcare System, Nashville, Tennessee, USA

^a10 Geriatric Research, Education and Clinical Center (GRECC) Service, Department of Veterans Affairs Medical Center, Tennessee Valley Healthcare System, Nashville, Tennessee, USA

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.

(Received October 02 2010)

(Revised November 16 2010)

(Revised December 21 2010)

(Accepted December 22 2010)

(Online publication February 04 2011)

Key words:

• insulin-like growth factor-1;
• delirium;
• acute brain dysfunction;
• coma;
• critical illness;
• intensive care unit;
• elderly

Correspondence:

^c1 Correspondence should be addressed to: Alessandro Morandi, MD, 1211 21^st Avenue South Suite 6100, Nashville, TN 37212, USA Phone: +1 (615) 936–5068; Fax: +1 (615) 936–1269. Email: alessandro.morandi@vanderbilt.edu.