Cerebral autoregulation derived blood pressure targets in elective neurosurgery.

Poor postoperative outcomes may be associated with cerebral ischaemia or hyperaemia, caused by episodes of arterial blood pressure (ABP) being outside the range of cerebral autoregulation (CA). Monitoring CA using COx (correlation between slow changes in mean ABP and regional cerebral O2 saturation-rSO2) could allow to individualise the management of ABP to preserve CA. We aimed to explore a continuous automated assessment of ABPOPT (ABP where CA is best preserved) and ABP at the lower limit of autoregulation (LLA) in elective neurosurgery patients. Retrospective analysis of prospectively collected data of 85 patients [median age 60 (IQR 51-68)] undergoing elective neurosurgery. ABPBASELINE was the mean of 3 pre-operative non-invasive measurements. ABP and rSO2 waveforms were processed to estimate COx-derived ABPOPT and LLA trend-lines. We assessed: availability (number of patients where ABPOPT/LLA were available); time required to achieve first values; differences between ABPOPT/LLA and ABP. ABPOPT and LLA availability was 86 and 89%. Median (IQR) time to achieve the first value was 97 (80-155) and 93 (78-122) min for ABPOPT and LLA respectively. Median ABPOPT [75 (69-84)] was lower than ABPBASELINE [90 (84-95)] (p < 0.001, Mann-U test). Patients spent 72 (56-86) % of recorded time with ABP above or below ABPOPT ± 5 mmHg. ABPOPT and ABP time trends and variability were not related to each other within patients. 37.6% of patients had at least 1 hypotensive insult (ABP < LLA) during the monitoring time. It seems possible to assess individualised automated ABP targets during elective neurosurgery.

Sedatives in neurocritical care: an update on pharmacological agents and modes of sedation.

PURPOSE OF REVIEW: In this article, the specific and general indications for sedatives in the neurocritical care unit are discussed, together with an overview on current insights in sedative protocols for these patients. In addition, physiological effects of sedative agents on the central nervous system are reviewed. RECENT FINDINGS: In the general ICU population, a large body of evidence supports light protocolized sedation over indiscriminate deep sedation. Unfortunately, in patients with severe acute brain injury, the evidence from randomized controlled trials is scarce to nonexistent, and practice is supported by expert opinion, physiological studies and observational or small interventional trials. The different sedatives each have different beneficial effects and side-effects. SUMMARY: Extrapolating the findings from studies in the general ICU population suggests to reserve deep continuous sedation in the neuro-ICU for specific indications. Although an improved understanding of cerebral physiological changes in patients with brain injury may be helpful to guide individualized sedation, we still lack the evidence base to make broad recommendations for specific patient groups.

Anesthesia for embolization of cerebral aneurysms.

PURPOSE OF REVIEW: In the last decade, there has been a rapid development in new endovascular treatment options for cerebral aneurysms. These techniques have their own inherent risk and can be challenging for the attending anesthetist. RECENT FINDINGS: The recent developments of stent-assisted aneurysm coiling, flow-diverting stents and gel embolization, have implications for the attending anesthesiologist and the patient. These developments allow embolization of more complex aneurysms, but require anticoagulation with its inherent risks. SUMMARY: The different endovascular techniques relevant to the anesthetist, the anesthetic options and complications that can occur during endovascular treatment of these patients will be discussed. This article can be a guidance to the anesthesiologist attending endovascular procedures for cerebral aneurysms.

The Pressure Reactivity Index as a Measure for Cerebrovascular Autoregulation: Validation in a Porcine Cranial Window Model.

BACKGROUND AND OBJECTIVES: Pressure reactivity index (PRx) has been proposed as a metric associated with cerebrovascular autoregulatory (CA) function and has been thoroughly investigated in clinical research. In this study, PRx is validated in a porcine cranial window model, developed to visualize pial arteriolar autoregulation and its limits. METHODS: We measured arterial blood pressure, intracranial pressure, pial arteriolar diameter, and red blood cell (RBC) velocity in a closed cranial window piglet model during gradual balloon catheter-induced arterial hypotension (n = 10) or hypertension (n = 10). CA limits were derived through piecewise linear regression of calculated RBC flux vs cerebral perfusion pressure (CPP), leading for each arteriole to 1 lower limit of autoregulation (LLA) and 2 upper limits of autoregulation (ULA1 and ULA2). Autoregulation limits were compared with PRx thresholds, and receiver operating curve analysis was performed with and without CPP binning. A linear mixed effects model of PRx was performed. RESULTS: Receiver operating curve analysis indicated an area under the curve (AUC) for LLA prediction by a PRx of 0.65 (95% CI: 0.64-0.67) and 0.77 (95% CI: 0.69-0.86) without and with CPP binning, respectively. The AUC for ULA1 prediction by PRx was 0.69 (95% CI: 0.68-0.69) without and 0.75 (95% CI: 0.68-0.82) with binning. The AUC for ULA2 prediction was 0.55 (95% CI: 0.55-0.58) without and 0.63 (95% CI 0.53-0.72) with binning. The sensitivity and specificity of binned PRx were 65%/90% for LLA, 69%/71% for ULA1, and 59%/74% for ULA2, showing wide interindividual variability. In the linear mixed effects model, pial arteriolar diameter changes were significantly associated with PRx changes (P = .002), whereas RBC velocity (P = .28) and RBC flux (P = .24) were not. CONCLUSION: We conclude that PRx is predominantly determined by pial arteriolar diameter changes and moderately predicts CA limits. Performance to detect the CA limits varied highly on an individual level. Active therapeutic strategies based on PRx and the associated correlation metrics should incorporate these limitations.

Assessing Practice Variation of Anesthetic Management for Endovascular Thrombectomy in Acute Ischemic Stroke: A Comprehensive Multicenter Survey.

OBJECTIVE: This study explored the current global landscape of periprocedural care of acute ischemic stroke patients undergoing endovascular thrombectomy (EVT). METHODS: An anonymous, 54-question electronic survey was sent to 354 recipients in hospitals worldwide. The responses were stratified by World Bank country income level into high-income (HICs) and low/middle-income (LMICs) countries. RESULTS: A total of 354 survey invitations were issued. Two hundred twenty-three respondents started the survey, and 87 fully completed surveys were obtained from centers in which anesthesiologists were routinely involved in EVT care (38 in HICs; 49 in LMICs). Respondents from 35 (92.1%) HICs and 14 (28.6%) LMICs reported that their centers performed >50 EVTs annually. Respondents from both HICs and LMICs reported low rates of anesthesiologist involvement in pre-EVT care, though a communication system was in place in 100% of HIC centers and 85.7% of LMIC centers to inform anesthesiologists about potential EVTs. Respondents from 71.1% of HIC centers and 51% of LMIC centers reported following a published guideline during EVT management, though the use of cognitive aids was low in both (28.9% and 24.5% in HICs and LMICs, respectively). Variability in multiple areas of practice, including choice of anesthetic techniques, monitoring and management of physiological variables during EVT, and monitoring during intrahospital transport, were reported. Quality metrics were rarely tracked or reported to the anesthesiology teams. CONCLUSIONS: This study demonstrated variability in anesthesiology involvement and in clinical care during and after EVT. Centers may consider routinely involving anesthesiologists in pre-EVT care, using evidence-based recommendations for EVT management, and tracking adherence to published guidelines and other quality metrics.

Differential Hemodynamic Response of Pial Arterioles Contributes to a Quadriphasic Cerebral Autoregulation Physiology.

Background Cerebrovascular autoregulation (CA) regulates cerebral vascular tone to maintain near-constant cerebral blood flow during fluctuations in cerebral perfusion pressure (CPP). Preclinical and clinical research has challenged the classic triphasic pressure-flow relationship, leaving the normal pressure-flow relationship unclear. Methods and Results We used in vivo imaging of the hemodynamic response in pial arterioles to study CA in a porcine closed cranial window model during nonpharmacological blood pressure manipulation. Red blood cell flux was determined in 52 pial arterioles during 10 hypotension and 10 hypertension experiments to describe the pressure-flow relationship. We found a quadriphasic pressure-flow relationship with 4 distinct physiological phases. Smaller arterioles demonstrated greater vasodilation during low CPP when compared with large arterioles (P<0.01), whereas vasoconstrictive capacity during high CPP was not significantly different between arterioles (P>0.9). The upper limit of CA was defined by 2 breakpoints. Increases in CPP lead to a point of maximal vasoconstriction of the smallest pial arterioles (upper limit of autoregulation [ULA] 1). Beyond ULA1, only larger arterioles maintain a limited additional vasoconstrictive capacity, extending the buffer for high CPP. Beyond ULA2, vasoconstrictive capacity is exhausted, and all pial arterioles passively dilate. There was substantial intersubject variability, with ranges of 29.2, 47.3, and 50.9 mm Hg for the lower limit, ULA1, and ULA2, respectively. Conclusions We provide new insights into the quadriphasic physiology of CA, differentiating between truly active CA and an extended capacity to buffer increased CPP with progressive failure of CA. In this experimental model, the limits of CA widely varied between subjects.

Neuroanesthesia Practice During the COVID-19 Pandemic: Recommendations From Society for Neuroscience in Anesthesiology and Critical Care (SNACC).

The pandemic of coronavirus disease 2019 (COVID-19) has several implications relevant to neuroanesthesiologists, including neurological manifestations of the disease, impact of anesthesia provision for specific neurosurgical procedures and electroconvulsive therapy, and health care provider wellness. The Society for Neuroscience in Anesthesiology and Critical Care appointed a task force to provide timely, consensus-based expert guidance for neuroanesthesiologists during the COVID-19 pandemic. The aim of this document is to provide a focused overview of COVID-19 disease relevant to neuroanesthesia practice. This consensus statement provides information on the neurological manifestations of COVID-19, advice for neuroanesthesia clinical practice during emergent neurosurgery, interventional radiology (excluding endovascular treatment of acute ischemic stroke), transnasal neurosurgery, awake craniotomy and electroconvulsive therapy, as well as information about health care provider wellness. Institutions and health care providers are encouraged to adapt these recommendations to best suit local needs, considering existing practice standards and resource availability to ensure safety of patients and providers.