2632 Determining the feasibility of a TCD-NIRS protocol to measure cerebral haemodynamics in dementia, delirium, and depression

Abstract

Introduction Transcranial Doppler ultrasonography (TCD) and Near-Infrared spectroscopy (NIRS) are indirect measures of neurovascular coupling (NVC). NVC is the relationship between cerebral blood flow and neuronal activity to meet the metabolic demands of the brain. No studies have integrated TCD-NIRS to investigate the feasibility of measuring NVC in those with dementia, delirium, and depression. Methods 32 participants (median [IQR] age 73.0 [70.0,78.5], 50% female, healthy (HC, n = 10), depression (n = 11), dementia (n = 6), delirium (n = 5)), underwent continuous cerebral blood velocity measurements in the middle (dominant MCAv) and posterior (non-dominant PCAv) cerebral arteries using TCD at rest and in response to four tasks. Heart rate (3-lead ECG), end-tidal CO (nasal capnography), blood pressure (Finometer), and prefrontal oxygenated (HbO2) and deoxygenated (HbR) haemoglobin (NIRS) were also measured. NVC was determined as absolute change in MCAv (cm/s) or concentration change for an attention task (serial subtraction), passive motor (arm movement) and passive sensory task (cotton wool), or PCAv for a visuospatial task (dot counting). We determined differences in NVC by a mixed two-way repeated measures analysis of variance, with post-hoc testing via Tukey. Results Resting CBv (cm/s) was significantly different between groups in MCAv (HC: 53.9 (SD = 8.09), depression: 41.9 (9.31), dementia: 42.5 (13.7), delirium: 32.6 (7.48), p = 0.002) and PCAv (p = 0.045), after correction for age and BP (p = 0.011). TCD: initial NVC responses increased for all three groups (delirium excluded) for all tasks (20–30s), (p = 0.026), but with no main effect of diagnosis. NIRS: There was a significant difference between tasks for the HbO2 and HbR responses (p = 0.046, p = 0.033). Diagnosis had a significant effect on the HbR response only (p = 0.034). Conclusion An integrated TCD-NIRS protocol was feasible in these patient groups to measure NVC, but less-so in delirium. Further work is needed to investigate NVC using integrated TCD-NIRS in larger sample sizes.