# Comparison of Cerebral Blood Flow During General Anesthesia in Elderly Patients with and Without Dementia: A Prospective Controlled Clinical Trial

## TL;DR

This study shows that cerebral blood flow drops significantly in elderly dementia patients during general anesthesia, even when vital signs are kept stable.

## Contribution

The study provides new evidence that dementia patients experience a larger decrease in cerebral blood flow during anesthesia despite maintained physiological parameters.

## Key findings

- Cerebral blood flow, measured by nTHI, decreased by 40% in dementia patients during anesthesia.
- Dementia patients had significantly lower nTHI values compared to non-dementia patients under similar conditions.
- Physiological parameters like MAP, BIS, SpO2, and etCO2 remained within target ranges in both groups.

## Abstract

Background/Objectives: The maintenance of cerebral blood flow (CBF) by managing blood pressure and brain cell activity and avoiding hypocapnia is important when administering anesthesia to patients with dementia. This study aimed to evaluate CBF during general anesthesia in elderly patients with severe dementia while maintaining their physiological parameters within an adequate range. Methods: The patients were anesthetized within a set range of parameters without affecting CBF (mean arterial pressure [MAP] > 50 mmHg; bispectral index [BIS] > 20; percutaneous arterial oxygen saturation [SpO2] > 95%; end-tidal CO2 [etCO2] 35–40 mmHg). The normalized tissue hemoglobin index (nTHI), which reflects CBF, was measured using near-infrared spectroscopy. The parameters were compared between patients with severe dementia (n = 13) and those without cognitive impairment (n = 13). Results: There were no differences in patient background. A similar decline in MAP and BIS values was observed in both groups, but the values remained within the set range. The nTHI decreased significantly to 0.60 in the dementia group and to 0.79 in the non-dementia group after the start of the treatment (p ≤ 0.049). Even when the MAP, BIS, SpO2, and etCO2 values were maintained in their adequate ranges during general anesthesia, the nTHI decreased by 40% in the dementia group. Conclusions: These findings indicate that CBF greatly decreases in elderly patients with severe dementia during general anesthesia.