Original article
Hypoactive Delirium After Cardiac Surgery as an Independent Risk Factor for Prolonged Mechanical Ventilation

https://doi.org/10.1053/j.jvca.2011.05.004Get rights and content

Objective

The authors' intention was to evaluate the incidence of the three subtypes of delirium, the risk factors of the subtypes in cardiac surgery, and the impact of the subtypes on clinical outcomes.

Design

A prospective study.

Setting

A university hospital.

Participants

A total population of 506 patients undergoing cardiac surgery was screened for delirium.

Interventions

None.

Measurement and Main Results

Patients undergoing cardiac surgery were screened by using the Intensive Care Delirium Screening Checklist (ICDSC) and the Richmond Agitation and Sedation Scale (RASS). Patients with hypoactive delirium were compared with nondelirious patients. Outcomes measured were the duration of mechanical ventilation and the length of stay in the intensive care unit. The overall delirium incidence was 11.6%, whereas the incidence of the hypoactive subtype was 9%. Age (odds ratio [OR] 1.04; 95% confidence interval [CI], 1.01-1.09, p = 0.02), a history of depression (OR = 3.57; 95% CI, 1.04-10.74; p = 0.03), preoperative therapy with diuretics (OR = 2.85; 95% CI, 1.36-6.35; p < 0.01), aortic clamping times (OR = 1.01; 95% CI, 1.00-1.02; p < 0.01) and blood transfusions (OR = 1.18; 95% CI, 1.05-1.34; p < 0.01) were predictors for the development of hypoactive delirium. Preoperative therapy with β-blockers (OR = 0.32; 95% CI, 0.16-0.65; p < 0.01) and higher hemoglobin before surgery (OR = 0.73; 95% CI, 0.60-0.91; p < 0.01) were associated with a lower prevalence of hypoactive delirium. Hypoactive delirium is an independent predictor for prolonged mechanical ventilation time (OR = 1.56; 95% CI, 1.25-1.92; p < 0.01) and the length of stay in the ICU (OR = 1.42; 95% CI, 1.22-1.65, p < 0.01).

Conclusion

Hypoactive delirium itself is a strong predictor for a longer ICU stay and a prolonged period of mechanical ventilation. Some of the risk factors related to the intraoperative and postoperative setting are suitable for preventive action.

Section snippets

Materials and Methods

After approval by the local Ethics Committee, all patients undergoing cardiac surgery in the authors' clinic were screened after admission to the ICU between May 2008 and November 2008. The requirement for informed consent was waived by the Ethics Committee. Patients who were readmitted to the ICU, patients who were comatose during the first 3 postoperative days, and patients who were deeply sedated and could not be examined neurologically were excluded. The definitions of comatose patients and

Results

A total of 506 patients were screened. Because 39 patients were excluded because of coma or deep sedation, 467 patients ultimately were included; 42 patients were classified as hypoactive delirium, 6 as hyperactive delirium, and 6 as mixed delirium. Because the incidence of hyperactive delirium and the mixed form was too low for statistical analysis, the patients were divided into 2 groups depending on whether they developed hypoactive delirium (42 patients) or no delirium (413 patients).

Discussion

The overall incidence of delirium was 11.6% in the present study. This figure falls well within the previously established range of 5% to 30% reported by previous cardiac surgery studies.4, 22 The incidence of the hypoactive subtype was 8.99%. In the present study, nearly 80% of all delirious patients were assigned to the hypoactive subtype, whereas previous studies in geriatric units have found hyperactive or mixed forms of delirium in most cases.14 One reason for the high incidence of

Conclusion

This research outlined the risk factors, which were divided into pre-, intra- and postoperative factors, for hypoactive delirium after cardiac surgery. Multiple risk factors included patients' age, history of depression, preoperative diuretics, duration of aortic clamping, and the number of blood transfusions. However, higher hemoglobin levels before surgery and preoperative therapy with β-blockers were associated with a significantly lower prevalence of hypoactive delirium. Some of these

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