68 Autonomic Impairment and its Manifestations in Patients with Delirium (Age and Ageing)

AbstractBackgroundDelirium is common among unwell older adults. Despite this the pathophysiology remains poorly understood. We hypothesised that autonomic dysfunction may be associated with the development of delirium.Methods35 participants completed a case-control study. Delirium was assessed using DSM-IV and DRS-R98. Autonomic function was assessed with Head-Up Tilt testing (HUT), baroreflex sensitivity (BRS) testing using Baroreflex Effectiveness Index (BEI), 24-hour blood pressure variability (BPV), nocturnal blood pressure dipping status and 24-hour heart rate variability (HRV). A subgroup analysis of those without pre-existing cognitive impairment (CI) was completed.ResultsDuring tilting the delirium group (DG) had a median decrease of 1mmHg (IQR 38.5) in systolic blood pressure (SBP) compared to a median decrease of 17.5mmHg (IQR 20.75) in the control group (CG) (p=0.04). Increased delirium severity correlated with a reduction in the decrease in SBP (rs= -0.42, p=0.03).In those without CI, BRS testing during HUT showed that increases in blood pressure were not followed by an appropriate reduction in heart rate with a mean BEI of 36.87% (SD 22.26) in the DG and 56.03% (SD 23.04) in the CG (p=0.05).Nocturnal dipping differed during subgroup analysis. 58.3% (7) of DG were reverse dippers, 33.3% (4) were non-dippers and 8.3% (1) had a normal dipping pattern. In CG 57.1% (4) were non-dippers, 14.3% (1) had a normal dipping pattern and 28.6% (2) were extreme dippers (p=0.01).BPV was measured by average real variability (ARV). In those without CI mean ARV was 13.81 (SD 5.98) in the CG and 9.69 (SD 2.75) in the DG (p=0.05).No difference was detected in HRV.ConclusionWe identified differences in autonomic function between the DG and CG. This is the first study to look at several components of autonomic function in delirium and thus can provide insights into physiological abnormalities present during, or contributing to delirium.