Postoperative anaemia might be a risk factor for postoperative delirium and prolonged hospital stay: A secondary analysis of a prospective cohort study.

Kunz JV, Spies CD, Bichmann A, Sieg M, Mueller A
PLoS One 2020;15:e0229325.
NATA Rating :
Review by : M. T. Prochaska
NATA Review

This study examines the association between postoperative anaemia and postoperative delirium. Given the high prevalence of postoperative anaemia, the authors were interested in understanding whether the lower oxygen delivery associated with anaemia would result in higher rates of postoperative delirium.

This study was a secondary analysis of a previously done retrospective study. The study population included adults 18 years and older undergoing any elective surgery. The primary outcome was a diagnosis of delirium postoperatively assessed by using the Nursing Delirium Screening Scale (NU-DESC). The study included 183 patients. Among those patients with anaemia, 38.4% had postoperative delirium. In patients without anaemia, only 10.9% had postoperative delirium. In a logistic regression model, patients with postoperative anaemia were nearly 4 times as likely to develop postoperative delirium compared to patients without anaemia. In addition, patients with postoperative anaemia were found to have longer length of stays than patients without postoperative anaemia. The longer length of stay in patients with postoperative anaemia was likely in some part due to patients developing postoperative delirium.

The authors suggest that these findings raise concerns for the association between postoperative anaemia and postoperative delirium, and suggest that the link should be studied more in the future. This article adds to the robust literature describing the adverse effects of anaemia, in this case postoperative anaemia, although the study design does limit the authors in defining the relationship between postoperative anaemia and postoperative delirium as causal.

– Micah T. Prochaska (SABM reviewer)

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