title: Impact of intraoperative hypotension and blood pressure fluctuations on early postoperative delirium after non-cardiac surgery.
abstract: BACKGROUND
  Postoperative delirium is common in older patients. Despite its prognostic significance, the pathophysiology is incompletely understood. Although many risk factors have been identified, no reversible factors, particularly ones potentially modifiable by anaesthetic management, have been identified. The goal of this prospective cohort study was to investigate whether intraoperative hypotension was associated with postoperative delirium in older patients undergoing major non-cardiac surgery.
  
  
  METHODS
  Study subjects were patients >65 years of age, undergoing major non-cardiac surgery, who were enrolled in an ongoing prospective observational study of the pathophysiology of postoperative delirium. Intraoperative blood pressure was measured and predefined criteria were used to define hypotension. Delirium was measured by the Confusion Assessment Method on the first two postoperative days. Data were analysed using t-tests, two-sample proportion tests and ordered logistic regression multivariable models, including correction for multiple comparisons.
  
  
  RESULTS
  Data from 594 patients with a mean age of 73.6 years (sd 6.2) were studied. Of these 178 (30%) developed delirium on day 1 and 176 (30%) on day 2. Patients developing delirium were older, more often female, had lower preoperative cognitive scores, and underwent longer operations. Relative hypotension (decreases by 20, 30, or 40%) or absolute hypotension [mean arterial pressure (MAP)<50 mm Hg] were not significantly associated with postoperative delirium, nor was the duration of hypotension (MAP<50 mm Hg). Conversely, intraoperative blood pressure variance was significantly associated with postoperative delirium.
  
  
  CONCLUSIONS
  These results showed that increased blood pressure fluctuation, not absolute or relative hypotension, was predictive of postoperative delirium.
authors.affiliation: Department of Anesthesia and Perioperative Care, University of California, San Francisco 94143-0648, USA jan.hirsch@ucsf.edu.
authors.forename: J
authors.initials: J
authors.lastname: Hirsch
authors.affiliation: Department of Statistics, Purdue University, West Lafayette, IN 47907-2069, USA.
authors.forename: G
authors.initials: G
authors.lastname: DePalma
authors.affiliation: Department of Anesthesia and Perioperative Care, University of California, San Francisco 94143-0648, USA.
authors.forename: T T
authors.initials: TT
authors.lastname: Tsai
authors.affiliation: Department of Statistics, Purdue University, West Lafayette, IN 47907-2069, USA.
authors.forename: L P
authors.initials: LP
authors.lastname: Sands
authors.affiliation: Department of Anesthesia and Perioperative Care, University of California, San Francisco 94143-0648, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Leung
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001794:Blood Pressure; D015331:Cohort Studies; D015897:Comorbidity; D003693:Delirium / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007022:Hypotension / Q000453:epidemiology*; D007431:Intraoperative Complications / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications; D011446:Prospective Studies; D012307:Risk Factors; D013514:Surgical Procedures, Operative
keywords: arterial blood pressure; delirium; hypotension