Association Between Preoperative Anemia and Cognitive Function in a Large Cohort Study of Older Patients Undergoing Elective Surgery

Abstract

Background: The etiology of anemia has tremendous overlap with the disease states responsible for cognitive decline. We used data from a perioperative database of older adults undergoing elective surgery with anesthesia to (1) examine relationships among preoperative anemia blood markers, preoperative screeners of cognitive function, and chronic disease status; and (2) examine the relationship of these factors with operative outcomes. The primary goal of this study was to investigate the association between preoperative anemia blood markers and cognition measured by a preoperative cognitive screener. Secondary goals were to (1) examine the relationship between preoperative anemia blood markers and chronic disease states (ie, American Society of Anesthesiologists [ASA] and frailty), and (2) investigate the relationship of preoperative anemia blood markers and cognition with operative outcomes (ie, discharge disposition, 1-year mortality, number of surgical complications, length of hospital stay, and length of intensive care unit [ICU] stay).

Methods: Data were collected at the University of Florida Health Shands Presurgical Center and the Perioperative Cognitive Anesthesia Network clinic within the electronic medical record. Patients 65 years of age or older were included if they had a preoperative hemoglobin (Hgb) value and a preoperative screening. Nonparametric methods were used for bivariate analysis. Logistic regression was used for the simultaneous examination of variables associated with nonhome discharge and 1-year mortality. Primary outcomes were discharge disposition and 1-year mortality. Secondary outcomes were number of surgical complications and length of hospital and ICU stay.

Results: Of 14,795 patients cognitively assessed, 8643 met the inclusion criteria. Of these, 26.7% were anemic, with 16.8%, 9.5%, and 0.4% having mild, moderate, and severe anemia, respectively. The Spearman correlation coefficient [95% confidence interval, CI] between the Hgb level and the clock drawing time (CDT) was -.15 [-.17 to -.13] ( P < .0001) indicating that a lower Hgb level was associated with cognitive vulnerability. Hgb was also negatively correlated with the ASA physical status classification, patient Fried Frailty Index, and hospital and ICU length of stay. In the multivariable model, age, surgical service, ASA and Fried Frailty Index significantly predicted nonhome discharge. Furthermore, age, surgical service, ASA, Fried Frailty Index, and Hgb independently predicted death within 1 year of surgery. The odds of death, adjusted for ASA, Fried Frailty, and covariates, were 2.7 times higher for those in the mild anemic group compared to those who were not anemic (odds ratio [OR], 2.7, 95% CI, [2.1-3.5]). The odds of death, adjusted for ASA, Fried Frailty, and covariates, were 3.6 times higher for those in the moderate/severe anemic group compared to those who were not anemic (OR, 3.6, 95% CI, [2.7-4.9]).

Conclusions: In this first medicine study, we established relationships among anemia, preoperative markers of frailty and cognition, and chronic disease states in a large cohort of older patients undergoing elective surgery in a large tertiary medical center. We found that anemia, cognitive vulnerability, and chronic health disease states predicted death within 1 year of surgery, and that these preoperative factors negatively contribute to surgical outcomes such as time in the ICU, length of hospital stay, nonhome discharge, and 1-year mortality. The World Health Organization (WHO) and many academic medical societies have urged the adoption of patient blood management (PBM) disciplines, yet anemia is not routinely optimized as a preoperative risk factor. Given the well-defined association between preoperative anemia and postoperative morbidity and mortality, performing elective surgery on an untreated anemic patient should be considered substandard care. With established safe and effective treatment regimens, iron deficiency anemia is a modifiable preoperative risk factor that should be addressed before elective surgery.