Predisposing factors for delirium in the surgical intensive care unit

Delirium is a sign of deterioration in the homeostasis and physical status of the patient. The objective of our study was to investigate the predisposing factors for delirium in a surgical intensive care unit (ICU) setting.

Between January 1996 and 1997, we screened prospectively 818 patients who were consecutive applicants to the general surgery service of Dicle-University Hospital and had been kept in the ICU for delirium. All patients were hospitalized either for elective or emergency services and were treated either with medication and/or surgery. Suspected cases of delirium were identified during daily interviews. The patients who had changes in the status of consciousness (n = 150) were consulted with an experienced consultation-liaison psychiatrist. The diagnosis of delirium was based on Diagnostic and Statistical Manual of Mental Disorders (revised third edition) criteria and established through psychiatric interviews. Patients were divided into two groups: the 'delirious group' (DG) (n = 90) and the 'non-delirious group' (NDG) (n = 728). During delirium, all abnormal findings related to physical conditions, laboratory features, and additional diseases were evaluated as probable risk factors of delirium.

Of 818 patients, 386 (47.2%) were male and 432 (52.8%) were female. Delirium developed in 90 of 818 patients (11%). The cases of delirium in the DG were more frequent among male patients (63.3%) than female patients (36.7%) (χ² = 10.5, P = 0.001). The mean age was 48.9 ± 18.1 and 38.5 ± 13.8 years in the DG and NDG, respectively (t = 6.4, P = 0.000). Frequency of delirium is higher in the patients admitted to the Emergency Department (χ² = 43.6, P = 0.000). The rate of postoperative delirium was 10.9%, but there was no statistical difference related to operations between the DG and NDG (χ² = 0.13, P = 0.71). The length of stay in the ICU was 10.7 ± 13.9 and 5.6 ± 2.9 days in the DG and NDG, respectively (t = 0.11, P = 0.000). The length of stay in hospital was 15.6 ± 16.5 and 8.1 ± 2.7 days in the DG and NDG, respectively (t = 11.08, P = 0.000). Logistic regression was used to explore the associations between probable risk factors and delirium. Delirium was not correlated with conditions such as hypertension, hypo/hyperpotassemia, hypernatremia, hypoalbuminemia, hypo/hyperglycemia, cardiac disease, emergency admission, age, length of stay in the ICU, length of stay in hospital, and gender. It was determined that conditions such as respiratory diseases (odds ratio [OR] = 30.6, 95% confidence interval [CI] = 9.5–98.4), infections (OR = 18.0, 95% CI = 3.5–90.8), fever (OR = 14.3, 95% CI = 4.1–49.3), anemia (OR = 5.4, 95% CI = 1.6–17.8), hypotension (OR = 19.8, 95% CI = 5.3–74.3), hypocalcemia (OR = 30.9, 95% CI = 5.8–163.2), hyponatremia (OR = 8.2, 95% CI = 2.5–26.4), azotemia (OR = 4.6, 95% CI = 1.4–15.6), elevated liver enzymes (OR = 6.3, 95% CI = 1.2–32.2), hyperamylasemia (OR = 43.4, 95% CI = 4.2–442.7), hyperbilirubinemia (OR = 8.7, 95% CI = 2.0–37.7) and metabolic acidosis (OR = 4.5, 95% CI = 1.1–17.7) were predicting factors for delirium.

We determined that conditions such as respiratory diseases, infections, fever, anemia, hypotension, hypocalcemia, hyponatremia, azotemia, elevated liver enzymes, hyperamylasemia, hyperbilirubinemia and metabolic acidosis were predicting factors for delirium.