Delirium in the intensive care unit: searching for causes and sources.

INTRODUCTION: Currently, diagnosis of delirium in theintensive care unit requires the use of one of a range of screening scales. Publications on delirium in the ICU are increasing, but most focus on psychological markers, with only limited data on physiological indicators of delirium. AIM: To assess the relationship between a range of physiological and treatment markers and the presence of delirium in an ICU cohort. METHODS: Patients admitted to the ICU of a metropolitan tertiary hospital between 1 August 2002 and 31 January 2003 were prospectively screened for delirium using the Intensive Care Delirium Screening Checklist (ICDSC). A retrospective chart review was undertaken to identify potential markers: raised white cell count, neutrophil count, and serum C-reactive protein concentration, lactic acidosis, low haemoglobin concentration, use of inotropic support, corticosteroids, or continuous venovenous haemodiafiltration (CVVHDF), and presence of systemic inflammatory response syndrome. Association of these markers with delirium was assessed using chi2 statistics. RESULTS: Of 56 ICU patients who were screened for delirium, charts could be retrieved for 44 (80%): 21 had delirium during the ICU admission, and 23 did not. CVVHDF was the only variable associated with an increased risk of delirium (P=0.03). CONCLUSIONS: Treatment with CVVHDF was the only factor associated with the presence of delirium. Further research is warranted into physiological indicators as adjuncts to psychological assessment scales for delirium. The quest to find a simple biomarker for delirium continues.