A systematic review and meta-analysis of factors for delirium in vascular surgical patients

Background: Delirium is a common syndrome responsible for a large burden of morbidity and mortality. In surgical settings, research into risk factors for postoperative delirium has largely focused on elective orthopedic patients. We performed a systematic review and meta-analysis to evaluate the evidence surrounding risk factors for delirium in vascular surgical populations. Methods: Two independent reviewers searched five databases (MEDLINE, Web of Science, Embase, Cumulative Index to Nursing and Allied Health Literature, and PsycINFO) from January 1987 to December 2015. We included primary research studies for incident delirium that used validated delirium assessment tools in exclusively vascular surgical populations. Results: We identified 16 studies (3817 patients) that met the inclusion criteria. There was substantial clinical heterogeneity in the populations included under a heading of vascular surgery. Studies were high quality, with an average Newcastle-Ottawa Scale score of 6.9. Summary incidence of delirium was 23.4% (range, 4.8%-39%). Across all studies, 157 separate risk factors were examined. Ten of the included studies used multivariable models in their analysis of risk factors. Meta-analysis of risk factors with data from more than three studies identified the following factors as conferring an increased risk of delirium: American Society of Anesthesiologists score >2 (odds ratio [OR], 3.44), renal failure (OR, 2.09), previous stroke (OR, 1.87), history of neurologic comorbidity (OR, 1.57), and male sex (OR, 1.30). Delirious patients were older (mean difference [MD], +4.99 years), had lower preoperative hemoglobin levels (MD, -0.66 g/dL), and stayed longer in intensive care units (MD, +1.06 days). Conclusions: Delirium is common in vascular surgery settings. Meta-analysis has identified significant risk factors relating to the patient, the presentation, and the pathway of care. Better understanding of these risk factors may help in prediction, prevention, and early identification of delirium.