Hypoactive delirium after cardiac surgery as an independent risk factor for prolonged mechanical ventilation

Abstract

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.