Background and Objective: ­ ­Delirium is a kind of fluctuating cognitive­ destruction , disorientation and ­a common problem for inpatients, which leads to increased mortality, prolonged hospital stay, increased cost and decreased rehabilitation.­ This study evaluates the incidence of delirium and its associated risk factors in open heart surgery.

  Material and Methods: This descriptive-analytical study was conducted ­­in six month (2011), via convenience sampling, on 404 patients undergoing elective cardiac surgery in the heart center of Fatemeh Zahra in Sari, Iran. Using Neecham questionnaire and demographic checklist, delirium was evaluated from the first till the fifth day of surgical operation. We used survival analysis (Kaplan-Meier and Cox regression) to­ analyze the findings, using SPSS software version18.
Results: The incidence of delirium is reported 28.5%. There is a significant relation between the incidence of delirium and variables such as age , lower education, rural, history of kidney failure, heart failure, stroke, hearing disorder, atrial fibrillation, increased serum potassium and increased serum urea.

  Conclusion: ­ According to the results, screening for d elirium is a matter of the utmost importance . With attention to individual profile and preoperative factors related to delirium, it is necessary to train elder and lower education patients, to maintain electrolyte balance before operation and to eliminate sensory deprivation in order to lessen the incidence of delirium.