The effect of formal training on the clinical utility of transcranial Doppler ultrasound monitoring in patients with aneurysmal subarachnoid haemorrhage

Transcranial Doppler Ultrasound and Concussion-Supplemental Symptoms with Physiology: A Systematic Review

Sport-related concussion (SRC) can impair the cerebrovasculature both acutely and chronically. Transcranial Doppler (TCD) ultrasound assessment has the potential to illuminate the mechanisms of impairment and provide an objective evaluation of SRC. The current systematic review investigated studies employing TCD ultrasound assessment of intracranial arteries across three broad categories of cerebrovascular regulation: neurovascular coupling (NVC), cerebrovascular reactivity (CVR), and dynamic cerebral autoregulation (dCA). The current review was registered in the International Prospective Register of Systematic Reviews (PROSPERO) database (CRD42021275627). The search strategy was applied to PubMed, as this database indexes all biomedical journals. Original articles on TCD for athletes with medically diagnosed SRC were included. Title/abstract and full-text screening were completed by three authors. Two authors completed data extraction and risk of bias using the Methodological Index for Non-Randomized Studies and Scottish Intercollegiate Guideline Network checklists. Of the 141 articles identified, 14 met the eligibility criteria. One article used an NVC challenge, eight assessed CVR, and six investigated dCA. Methodologies varied widely among studies, and results were heterogeneous. There was evidence of cerebrovascular impairment in all three domains roughly 2 days post-SRC, but the magnitude and recovery of these impairments were not clear. There was evidence that clinical symptom resolution occurred before cerebrovascular function, indicating that physiological deficits may persist despite clinical recovery and return to play. Collectively, this emphasizes an opportunity for the use of TCD to illuminate the cerebrovascular deficits caused by SRC. It also highlights that there is need for consistent methodological rigor when employing TCD in a SRC population.

Transcranial sonographic assessment of the third ventricle in neuro-ICU patients to detect hydrocephalus: a diagnostic reliability pilot study

Background

Transcranial sonography is a point-of-care tool recommended in intensive care units (ICU) to monitor brain injured patients. Objectives of the study was to assess feasibility and reliability of the third ventricle (V3) diameter measurement using transcranial sonography (TCS) compared to brain computed-tomography (CT), the gold standard measurement, and to measure the TCS learning curve. Design: prospective study, in a 16-bed neurological ICU in an academic hospital. Every consecutive brain injured adult patient, who required a brain CT and TCS monitoring were included. The V3 diameter was blindly measured by TCS and CT. Intraclass correlation coefficient (ICC) and Bland–Altman plot were used to assess the reliability and agreement between TCS and CT V3 measurements. Diagnosis performance of the V3 diameter using TCS to detect hydrocephalus was measured. Absolute difference between V3 measurement by residents and experts was measured consecutively to assess the learning curve.

Results

Among the 100 patients included in the study, V3 diameter could be assessed in 87 patients (87%) from at least one side of the skull. Both temporal windows were available in 70 patients (70%). The ICC between V3 diameter measured by TCS and CT was 0.90 [95% CI 0.84–0.93] on the right side, and 0.92 [0.88–0.95] on the left side. In Bland–Altman analysis, mean difference, standard deviation, 95% limits of agreement were 0.36, 1.52, − 2.7 to 3.3 mm, respectively, on the right side; 0.25, 1.47, − 2.7 to 3.1 mm, respectively, on the left side. Among the 35 patients with hydrocephalus, V3 diameters could be measured by TCS in 31 patients (89%) from at least one side. Hydrocephalus was, respectively, excluded, confirmed, or inconclusive using TCS in 35 (40%), 25 (29%) and 27 (31%) of the 87 assessable patients. After 5 measurements, every resident reached a satisfactory measurement compared to the expert operator.

Conclusion

TCS allows rapid, simple and reliable V3 diameter measurement compared with the gold standard in neuro-ICU patients. Aside from sparing irradiating procedures and transfers to the radiology department, it may especially increase close patient monitoring to detect clinically occult hydrocephalus earlier. Further studies are needed to measure the potential clinical benefit of this method.

Trial registration: ClinicalTrials.gov ID: NCT02830269.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00857-x.

Relationships Among Cognitive Function and Cerebral Blood Flow, Oxidative Stress, and Inflammation in Older Heart Failure Patients

BACKGROUND

The mechanisms for cognitive impairment in heart failure (HF) are unclear. We investigated the relative contributions of cerebral blood flow velocity (BFV), oxidative stress, and inflammation to HF-associated cognitive impairment.

METHODS AND RESULTS

Thirty-six HF patients (≥60 years) and 40 healthy controls (68 ± 7 vs 67 ± 5 years, P > .05; 69% vs 50% male, P > .05) completed the Cognitive Drug Research computerized assessment battery and Stroop tasks. Common carotid (CCA) and middle cerebral arterial BFV were obtained by transcranial Doppler. Blood samples were collected for oxidant (diacron-reactive oxygen metabolites; F2-isoprostanes), antioxidant (coenzyme Q10; CoQ10), and inflammatory markers (high-sensitivity C-reactive protein). Compared with controls, patients exhibited impaired attention (Cognitive Drug Research's Power of Attention domain, congruent Stroop) and executive function (incongruent Stroop). Multiple regression modeling showed that CCA-BFV and CoQ10 but not group predicted performance on attention and executive function. Additionally, in HF patients, CCA-BFV and CoQ10 (β = -0.34 vs β = -0.35) were significant predictors of attention, and CCA-BFV (β = -0.34) was a predictor of executive function.

CONCLUSIONS

Power of Attention and executive function is impaired in older HF patients, and reduced CCA-BFV and CoQ10 are associated with worse cognition. Interventions addressing these mechanisms may improve cognition in older HF patients.

The Presto 1000: A novel automated transcranial Doppler ultrasound system

We examined the reliability and ease of use of a novel automated transcranial Doppler (TCD) system in comparison to a conventional TCD system. TCD ultrasound allows non-invasive monitoring of cerebral blood flow, and can predict arterial vasospasm after a subarachnoid hemorrhage (SAH). The Presto 1000 TCD system (PhysioSonics, Bellevue, WA, USA) is designed for monitoring flow through the M1 segment of the middle cerebral artery (MCA) via temporal windows. The Presto 1000 system was tested across multiple preclinical and clinical settings in parallel with a control predicate TCD system. In a phantom flow generating device, both the Presto 1000 and Spencer system (Spencer Technologies, Redmond, WA, USA) were able to detect velocities with high accuracy. In nine volunteer patients, the Presto system was able to locate the MCA in 14 out of 18 temporal windows, in an average of 12.5s. In the SAH cohort of five patients with a total of 25 paired measurements, the mean absolute difference in flow velocities of the M1 segment, as measured by the two systems, was 17.5 cm/s. These data suggest that the Presto system offers an automated TCD that can reliably localize and detect flow of the MCA, with relative ease of use. The system carries the additional benefit of requiring minimal training for the operator, and can be used by many providers across multiple bedside settings. The mean velocities that were generated warrant further validation across an extended group of patients, and the predictive value for vasospasm should be checked against the current standard of angiography.

A continuous correlation between intracranial pressure and cerebral blood flow velocity reflects cerebral autoregulation impairment during intracranial pressure plateau waves

BACKGROUND

In the healthy brain, small oscillations in intracranial pressure (ICP) occur synchronously with those in cerebral blood volume (CBV), cerebrovascular resistance, and consequently cerebral blood flow velocity (CBFV). Previous work has shown that the usual synchrony between ICP and CBFV is lost during intracranial hypertension. Moreover, a continuously computed measure of the ICP/CBFV association (Fix index) was a more sensitive predictor of outcome after traumatic brain injury (TBI) than a measure of autoregulation (Mx index). In the current study we computed Fix during ICP plateau waves, to observe its behavior during a defined period of cerebrovascular vasodilatation.

METHODS

Twenty-nine recordings of arterial blood pressure (ABP), ICP, and CBFV taken during ICP plateau waves were obtained from the Addenbrooke's hospital TBI database. Raw data was filtered prior to computing Mx and Fix according to previously published methods. Analyzed data was segmented into three phases (pre, peak, and post), and a median value of each parameter was stored for analysis.

RESULTS

ICP increased from a median of 22-44 mmHg before falling to 19 mmHg. Both Mx and Fix responded to the increase in ICP, with Mx trending toward +1, while Fix trended toward -1. Mx and Fix correlated significantly (Spearman's R = -0.89, p < 0.000001), however, Fix spanned a greater range than Mx. A plot of Mx and Fix against CPP showed a plateau (Mx) or trough (Fix) consistent with a zone of "optimal CPP".

CONCLUSIONS

The Fix index can identify complete loss of cerebral autoregulation as the point at which the normally positive CBF/CBV correlation is reversed. Both CBF and CBV can be monitored noninvasively using near-infrared spectroscopy (NIRS), suggesting that a noninvasive method of monitoring autoregulation using only NIRS may be possible.