Predictors of Cognitive Dysfunction after Major Noncardiac Surgery

This article and its accompanying editorial have been selected for the ANESTHESIOLOGYCME Program. After reading both articles, go to http://www.asahq.org/journal-cme to take the test and apply for Category 1 credit. Complete instructions may be found in the CME section at the back of this issue. Background: The authors designed a prospective longitudinal study to investigate the hypothesis that advancing age is a risk factor for postoperative cognitive dysfunction (POCD) after major noncardiac surgery and the impact of POCD on mortality in the first year after surgery. Methods: One thousand sixty-four patients aged 18 yr or older completed neuropsychological tests before surgery, at hospital discharge, and 3 months after surgery. Patients were categorized as young (18‐39 yr), middle-aged (40‐59 yr), or elderly (60 yr or older). At 1 yr after surgery, patients were contacted to determine their survival status. Results: At hospital discharge, POCD was present in 117 (36.6%) young, 112 (30.4%) middle-aged, and 138 (41.4%) elderly patients. There was a significant difference between all age groups and the age-matched control subjects (P < 0.001). At 3 months after surgery, POCD was present in 16 (5.7%) young, 19 (5.6%) middle-aged, and 39 (12.7%) elderly patients. At this time point, the prevalence of cognitive dysfunction was similar between age-matched controls and young and middle-aged patients but significantly higher in elderly patients compared to elderly control subjects (P < 0.001). The independent risk factors for POCD at 3 months after surgery were increasing age, lower educational level, a history of previous cerebral vascular accident with no residual impairment, and POCD at hospital discharge. Patients with POCD at hospital discharge were more likely to die in the first 3 months after surgery (P 0.02). Likewise, patients who had POCD at both hospital discharge and 3 months after surgery were more likely to die in the first year after surgery (P 0.02). Conclusions: Cognitive dysfunction is common in adult patients of all ages at hospital discharge after major noncardiac surgery, but only the elderly (aged 60 yr or older) are at significant risk for long-term cognitive problems. Patients with POCD are at an increased risk of death in the first year after surgery. POSTOPERATIVE cognitive dysfunction (POCD) is often associated with cardiac surgery, but less is known about the prevalence of this problem after other types of surgery. 1,2 In 1998, the International Study of Postoperative Cognitive Dysfunction (ISPOCD1) evaluated cognitive decline in 1,218 elderly patients, aged 60 yr or older, who had undergone major noncardiac surgery, and found that cognitive dysfunction was present in 26% of older patients 1 week after surgery and in 10% 3 months after surgery. 3 However, this study had significant differences in the incidence of early POCD at the 13 participating hospitals, placing this finding in question. Research evaluating cognitive decline after cardiac and noncardiac surgery has primarily focused on older patients, who might have an increased vulnerability to neurologic deterioration. 1,3,4 However, the cognitive effects of surgery and anesthesia in younger adults are poorly understood, making it difficult to determine whether advancing age is the primary risk factor for this complication. Studies on normal aging have shown that abrupt declines in cognitive function in older adults are associated with early death. 5,6 The relation between POCD and mortality has not been reported. To investigate the hypothesis that advancing age is a risk factor for POCD, we designed a prospective cohort study evaluating the incidence of early (hospital discharge) and late (3 months after surgery) cognitive dysfunction in adults of all ages undergoing elective, major noncardiac surgery. This study used the same neuropsychological methodology as the ISPOCD1 study in an attempt to replicate its results at a single institution. 3 Patients were also followed to determine the impact of POCD on survival in the first year after major surgery. A companion article analyzes the type and severity of cognitive impairment in the elderly patients in this study. 7