Anesthesia, Surgery Affect Postoperative Neurological Outcomes

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Although the average plasma tau levels returned close to baseline 6 hours after surgery, they continued to remain elevated 48 hours later.
Although the average plasma tau levels returned close to baseline 6 hours after surgery, they continued to remain elevated 48 hours later.

Anesthesia and surgery may affect neurologic outcomes following surgery by exerting neurotoxicity on the central nervous system, according to an analysis published in JAMA Neurology.

In this analysis, investigators examined blood samples from patients enrolled in the Cerebrospinal Fluid and Preclinical Alzheimer Cognitive Trajectory (CAPACITY; n=13) and Assessment and Review of Cognition, Alzheimer Disease, and Inflammation in Elderly Patients After Hospital Intervention (ARCADIAN; n=17) observational studies who received general anesthesia for surgery. Investigators compared blood samples taken prior to anesthesia administration and at 30 minutes, 6 hours, 24 hours, and 48 hours after surgery. Investigators also measured plasma tau concentrations in each blood sample. The average age (standard deviation [SD]) across both cohorts was 69.1 (7.0) years, and the majority of patients were women (59%).

There was a maximal 67% increase (95% CI, 45%-89%; P <.001) in postoperative mean neurofilament light at 48 hours from the combined baseline mean (SD) to the maximal combined mean (SD) level (22.3 pg/mL [20.4] and 35.1 pg/mL [28.7], respectively). In addition, investigators observed significant increases in tau at each measurement from baseline (combined baseline mean [SD] 3.1 [1.3] pg/mL, maximal combined mean [SD] 10.8 [9.5] pg/mL), with a significant peak increase of 257% (95% CI, 154%-361%; P <.001) at 6 hours following surgery. Although the average level returned close to baseline 6 hours after surgery, levels continued to remain elevated at 48 hours following operation.

Considering surgery is often accompanied by anesthesia administration, the study is limited in that it did not attempt to differentiate brain injury from anesthesia or other surgery outcomes such as inflammation or stress. In addition, this study was limited to older adults, and it is unclear whether these findings extrapolate to other age groups.

The findings indicate that “measurement of an increase in neurological biomarkers after anesthesia and surgery suggests a neuronal injury has taken place” in adults, and future studies should determine whether identifying these postoperative biomarkers may help in the early identification and management of potential neurologic decline.

Reference

Evered L, Silbert B, Scott DA, Zetterberg H, Blennow K. Association of changes in plasma neurofilament light and tau levels with anesthesia and surgery: results from the CAPACITY and ARCADIAN studies [published online February 19, 2018]. JAMA Neurol. doi:10.1001/jamaneurol.2017.4913

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