The temporal relationship between early postoperative delirium and postoperative cognitive dysfunction in older patients: a prospective cohort study

Abstract

Background: Postoperative delirium and cognitive dysfunction are frequent phenomena in older patients; however, few studies have examined the temporal relationship between these two conditions in the early postoperative period. Therefore, this study aimed to determine if postoperative delirium and postoperative cognitive dysfunction (POCD) coexist after major noncardiac surgery.

Methods: This was a prospective cohort study of patients who were ≥ 65 yr of age undergoing noncardiac surgery. Patients were evaluated preoperatively and for two days postoperatively for delirium and POCD. Delirium was determined using the Confusion Assessment Method, and POCD was measured by three cognitive tests addressing changes in executive function, memory, attention, and concentration. For each postoperative day, patients' neurologic status was categorized into three mutually exclusive categories: delirium, POCD, or neither condition.

Results: Four hundred sixty-one patients aged ≥ 65 yr of age were studied, and 421 patients with complete postoperative cognitive testing were reported. Eighty percent of patients experienced either delirium or POCD on the first day after surgery. Seventy percent of patients who had delirium on the first postoperative day also had delirium on the second postoperative day. Sixty-three percent of patients who had POCD on postoperative day one continued to have POCD on the next day. Sixteen percent of patients with delirium on day one were non-delirious on day two but met criteria for POCD on day two. Conversely, 15% of patients with POCD on day one became delirious on day two. Only 13% of patients did not experience delirium or POCD on either day after surgery.

Conclusions: Eighty percent of surgical patients experienced some form of cognitive dysfunction the day after surgery, and few recovered by the second day after surgery.

Conflict of interest statement

Declaration of interests None of the authors has a conflict of interest to declare.

Figures

Fig. 1

The study flow chart is shown in Fig. 1. Overall, 461 patients were recruited, but 421 patients were included in this study. The reasons for excluding 40 patients included eight who were discharged early, 22 who refused testing, one was too sedated, and nine were physically incapable of performing the cognitive tests. The patients’ cognitive status for postoperative days one and two is shown here, stratified by the presence of delirium, no delirium but presented signs of POCD, or neither. POCD = postoperative cognitive dysfunction

Fig. 2

For hospital length of stay, post hoc analysis after Tukey adjustment (alpha = 0.05) showed that the hospital length of stay was significantly longer in patients with delirium than in those with POCD or with neither condition. Nevertheless, the hospital length of stay in patients with POCD was not significantly different from those with neither condition. The red line indicates the mean for each group. Specifically, the mean (SD) length of stay in patients with delirium was 8.2 (7.5) days, 5.9 (4.8) days in those with POCD, and 4.7 (3.6) days in those with neither condition. POCD = postoperative cognitive dysfunction