title: Intra-operative events during cardiac surgery are risk factors for the development of delirium in the ICU.
abstract: BACKGROUND
  Risk factors for delirium following cardiac surgery are incompletely understood. The aim of this study was to investigate whether intra-operative pathophysiological alterations and therapeutic interventions influence the risk of post-operative delirium.
  
  
  METHODS
  This retrospective cohort study was performed in a 12-bed cardiosurgical intensive care unit (ICU) of a university hospital and included patients consecutively admitted after cardiac surgery during a 2-month period. The diagnosis of delirium was made clinically using validated scores. Comparisons between patients with and without delirium were performed with non-parametric tests. Logistic regression was applied to identify independent risk factors. Results are given as number (percent) or median (range).
  
  
  RESULTS
  Of the 194 consecutive post-cardiac surgery patients, 50 (26 %) developed delirium during their ICU stay. Univariate analysis revealed that significant differences between patients with and without delirium occurred in the following intra-operative variables: duration of cardiopulmonary bypass (184 [72-299] vs 113 (37-717) minutes, p < 0.001), lowest mean arterial pressure (50 [30-70] vs 55 [30-75] mmHg, p = 0.004), lowest haemoglobin level (85 [56-133] vs 98 [53-150] g/L, p = 0.005), lowest body temperature (34.5 [24.4-37.2] vs 35.1 [23.9-37.2] °C, p = 0.035), highest noradrenaline support (0.11 [0.00-0.69] vs 0.07 [0.00-0.42] μg/kg/minute, p = 0.001), and frequency of red blood cell transfusions (18 [36 %] vs 26 [18 %], p = 0.018) and platelet transfusions (23 [46 %] vs 24 [17 %], p < 0.001). Only platelet transfusions remained an independent risk factor in the multivariate analysis (p < 0.001).
  
  
  CONCLUSIONS
  In patients undergoing cardiac surgery, various intra-operative events, such as transfusion of platelets, were risk factors for the development of a post-operative delirium in the ICU. Further research is needed to unravel the underlying mechanisms.
authors.affiliation: Cardio-Surgical Intensive Care Unit, Institute of Anesthesiology, University Hospital Zurich and University of Zurich, Rämistrasse 100, CH-8091, Zurich, Switzerland. alain.rudiger@usz.ch.
authors.forename: Alain
authors.identifier: http://orcid.org/0000-0001-7943-7624
authors.initials: A
authors.lastname: Rudiger
authors.affiliation: Cardio-Surgical Intensive Care Unit, Institute of Anesthesiology, University Hospital Zurich and University of Zurich, Rämistrasse 100, CH-8091, Zurich, Switzerland.
authors.forename: Hülya
authors.initials: H
authors.lastname: Begdeda
authors.affiliation: Cardio-Surgical Intensive Care Unit, Institute of Anesthesiology, University Hospital Zurich and University of Zurich, Rämistrasse 100, CH-8091, Zurich, Switzerland.
authors.forename: Daniela
authors.initials: D
authors.lastname: Babic
authors.affiliation: Cardio-Surgical Intensive Care Unit, Institute of Anesthesiology, University Hospital Zurich and University of Zurich, Rämistrasse 100, CH-8091, Zurich, Switzerland.
authors.forename: Bernard
authors.initials: B
authors.lastname: Krüger
authors.affiliation: Epidemiology, Biostatistics and Prevention Institute (EBPI), Department of Biostatistics, University of Zurich, Hirschengraben 84, CH-8001, Zurich, Switzerland.
authors.forename: Burkhardt
authors.initials: B
authors.lastname: Seifert
authors.affiliation: Centre of Clinical Nursing Science, University Hospital Zurich, Rämistrasse 100, CH-8091, Zurich, Switzerland.|Directorate of Nursing/MTT, Inselspital, University Hospital, Freiburgstrasse, 3010, Bern, Switzerland.
authors.forename: Maria
authors.initials: M
authors.lastname: Schubert
authors.affiliation: Institute of Anesthesiology, University Hospital Zurich and University of Zurich, Rämistrasse 100, CH-8091, Zurich, Switzerland.
authors.forename: Donat R
authors.initials: DR
authors.lastname: Spahn
authors.affiliation: Cardio-Surgical Intensive Care Unit, Institute of Anesthesiology, University Hospital Zurich and University of Zurich, Rämistrasse 100, CH-8091, Zurich, Switzerland.
authors.forename: Dominique
authors.initials: D
authors.lastname: Bettex
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D062186:Arterial Pressure / Q000502:physiology; D001803:Blood Transfusion; D001831:Body Temperature / Q000502:physiology; D006348:Cardiac Surgical Procedures / Q000009:adverse effects* / Q000592:standards; D002315:Cardiopulmonary Bypass / Q000009:adverse effects; D015331:Cohort Studies; D003693:Delirium / Q000209:etiology*; D005260:Female; D006454:Hemoglobins / Q000032:analysis; D006801:Humans; D007362:Intensive Care Units / Q000458:organization & administration; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D017713:Platelet Transfusion / Q000009:adverse effects; D011183:Postoperative Complications / Q000503:physiopathology*; D012189:Retrospective Studies; D012307:Risk Factors; D013557:Switzerland
chemical_list: D006454:Hemoglobins
keywords: Cardiac surgery; Cardiopulmonary bypass; Delirium; Intensive care unit; Platelets; Risk factors; Transfusion