Home-based monitoring of cerebral oxygenation in response to postural changes using near-infrared spectroscopy.

Orthostatic hypotension (OH) is prevalent in older adults and can cause falls and hospitalization. Diagnostic intermittent blood pressure (BP) measurements are only a proxy for cerebral perfusion and do not reflect daily-life BP fluctuations. Near-infrared spectroscopy (NIRS)-measured cerebral oxygenation potentially overcomes these drawbacks. This study aimed to determine feasibility, face validity, and reliability of NIRS in the home environment. Ten participants with OH (2 female, mean age 77, SD 3.7) and 11 without OH (5 female, mean age 78, SD 6.7) wore a NIRS sensor at home on two different days for 10-11 h per day. Preceded by a laboratory-situated test, cerebral oxygenation was measured during three standardized supine-stand tests per day and during unsupervised daily life activities. Data availability, quality, and user experience were assessed (feasibility), as well as differences in posture-related oxygenation responses between participants with and without OH and between symptomatic (dizziness, light-headedness, blurred vision) and asymptomatic postural changes (face validity). Reliability was assessed through repetitive supine-stand tests. Up to 80% of the standardized home-based supine-stand tests could be analyzed. Oxygenation recovery values were lower for participants with OH (p = 0 .03-0.15); in those with OH, oxygenation showed a deeper maximum drop for symptomatic than asymptomatic postural changes (p = 0.04). Intra-class correlation coefficients varied from 0.07 to 0.40, with no consistent differences over measurements. This proof-of-concept study shows feasibility and face validity of at-home oxygenation monitoring using NIRS, confirming its potential value for diagnosis and monitoring in OH and OH-related symptoms. Further data are needed for conclusions about reliability.

The effect of a change in antihypertensive treatment on orthostatic hypotension in older adults: A systematic review and meta-analysis.

BACKGROUND: Orthostatic hypotension (OH) is common in older adults with hypertension. Antihypertensive treatment (AHT) prevents cardio- and cerebrovascular events. However, physicians are concerned to cause OH, making them hesitant to initiate or augment AHT in older adults with hypertension. METHODS: We systematically researched electronic databases for trials with older participants (≥65 years) with hypertension and OH assessment after initiating, discontinuing, or augmenting AHT. Study quality was assessed using the ROBINS-I tool. Meta-analyses on OH prevalence and postural blood pressure (BP) drop were performed. RESULTS: Twenty-five studies (26,695 participants) met inclusion criteria, of which fifteen could be included in the meta-analyses. OH prevalence decreased after AHT initiation or augmentation (risk ratio 0.39 (95 % CI = 0.21-0.72; I2 = 47 %; p < 0.01), n = 6 studies), but also after AHT discontinuation (risk ratio 0.39 (95 % CI = 0.28-0.55; I2 = 0 %; p < 0.01), n = 2 studies). Postural BP drop did not change after initiation or augmentation of AHT (mean difference 1.07 (95 % CI = -0.49-2.64; I2 = 92 %; p = 0.18), n = 11 studies). The main reason for ten studies not to be included in the meta-analyses was absence of baseline OH data. Most of these studies reported OH incidences between 0 and 2 %. Studies were heterogeneous in OH assessment methods (postural change, timing of BP measurements, and OH definition). Risk of bias was moderate to serious in twenty studies. CONCLUSION: Results suggest that AHT initiation or augmentation decreases OH prevalence, implying that the risk of inducing OH may be overestimated in current AHT decision-making in older adults. However, the overall low level of evidence and the finding that AHT discontinuation reduces OH prevalence limit firm conclusions at present and highlight an important research gap. Future AHT trials in older adults should measure OH in a standardized protocol, adhering to consensus guidelines to overcome these limitations.

Capturing postural blood pressure dynamics with near-infrared spectroscopy-measured cerebral oxygenation.

Orthostatic hypotension (OH) is highly prevalent in older adults and associated with dizziness, falls, lower physical and cognitive function, cardiovascular disease, and mortality. OH is currently diagnosed in a clinical setting with single-time point cuff measurements. Continuous blood pressure (BP) devices can measure OH dynamics but cannot be used for daily life monitoring. Near-infrared spectroscopy (NIRS) has potential diagnostic value in measuring cerebral oxygenation continuously over a longer time period, but this needs further validation. This study aimed to compare NIRS-measured (cerebral) oxygenation with continuous BP and transcranial Doppler-measured cerebral blood velocity (CBv) during postural changes. This cross-sectional study included 41 participants between 20 and 88 years old. BP, CBv, and cerebral (long channels) and superficial (short channels) oxygenated hemoglobin (O2Hb) were measured continuously during various postural changes. Pearson correlations between BP, CBv, and O2Hb were calculated over curves and specific characteristics (maximum drop amplitude and recovery). BP and O2Hb only showed good curve-based correlations (0.58-0.75) in the initial 30 s after standing up. Early (30-40 s) and 1-min BP recovery associated significantly with O2Hb, but no consistent associations were found for maximum drop amplitude and late (60-175 s) recovery values. Associations between CBv and O2Hb were poor, but stronger for long-channel than short-channel measurements. BP associated well with NIRS-measured O2Hb in the first 30 s after postural change. Stronger associations for CBv with long-channel O2Hb suggest that long-channel NIRS specifically reflects cerebral blood flow during postural transitions, necessary to better understand the consequences of OH such as intolerance symptoms.

Applying systems thinking to unravel the mechanisms underlying orthostatic hypotension related fall risk.

Orthostatic hypotension (OH) is an established and common cardiovascular risk factor for falls. An in-depth understanding of the various interacting pathophysiological pathways contributing to OH-related falls is essential to guide improvements in diagnostic and treatment opportunities. We applied systems thinking to multidisciplinary map out causal mechanisms and risk factors. For this, we used group model building (GMB) to develop a causal loop diagram (CLD). The GMB was based on the input of experts from multiple domains related to OH and falls and all proposed mechanisms were supported by scientific literature. Our CLD is a conceptual representation of factors involved in OH-related falls, and their interrelatedness. Network analysis and feedback loops were applied to analyze and interpret the CLD, and quantitatively summarize the function and relative importance of the variables. Our CLD contains 50 variables distributed over three intrinsic domains (cerebral, cardiovascular, and musculoskeletal), and an extrinsic domain (e.g., medications). Between the variables, 181 connections and 65 feedback loops were identified. Decreased cerebral blood flow, low blood pressure, impaired baroreflex activity, and physical inactivity were identified as key factors involved in OH-related falls, based on their high centralities. Our CLD reflects the multifactorial pathophysiology of OH-related falls. It enables us to identify key elements, suggesting their potential for new diagnostic and treatment approaches in fall prevention. The interactive online CLD renders it suitable for both research and educational purposes and this CLD is the first step in the development of a computational model for simulating the effects of risk factors on falls.

Delirium after cardiac arrest: Phenotype, prediction, and outcome.

AIM: To establish incidence, phenotype, long-term functional outcome, and early EEG predictors of delirium after cardiac arrest. METHODS: This is an ad hoc analysis of a prospective cohort study on outcome prediction of comatose patients after cardiac arrest. Patients with recovery of consciousness, who survived until hospital discharge, were subdivided in groups with and without delirium based on psychiatric consultation. Delirium phenotype and medical treatment were retrieved from patient files. All other data were prospectively collected. We used univariate analyses of baseline and early EEG characteristics for identification of possible delirium predictors. Association of delirium with neurological recovery at six months was analyzed with multinomial logistic regression analysis. RESULTS: Of 233 patients, 141 survived until hospital discharge, of whom 47 (33%) were diagnosed with delirium. There were no differences in baseline characteristics between patients with and without delirium. All delirious patients were treated with relatively high dosages of psychopharmaceuticals, mostly haloperidol and benzodiazepine agonists. Prevalent characteristics were disturbed cognition, perception and psychomotor functioning (98%). Half of the patients had language disorders or shouting. Delirium was associated with longer ICU and hospital admission, and more frequent discharge to rehabilitation centre or nursing home. There was a trend towards poorer neurological recovery. EEG measurements within 12 h after cardiac arrest could predict delirium with 91% specificity and 40% sensitivity. DISCUSSION: Delirium is common after cardiac arrest, and probably leads to longer hospitalization and poorer outcome. Optimal treatment is unclear. Early EEG holds potential to identify patients at risk.