Monitoring of the Effect of Cerebral Autoregulation on Delayed Cerebral Ischemia in Patients with Aneurysmal Subarachnoid Hemorrhage

The Diagnostic Value of Near-Infrared Spectroscopy to Predict Delayed Cerebral Ischemia and Unfavorable Outcome After Subarachnoid Hemorrhage

OBJECTIVE

Near-infrared spectroscopy (NIRS) is a noninvasive tool to monitor cerebral regional oxygen saturation. Impairment of microvascular circulation with subsequent cerebral hypoxia during delayed cerebral ischemia (DCI) is associated with poor functional outcome after subarachnoid hemorrhage (SAH). Therefore, NIRS could be useful to predict the risk for DCI and functional outcome. However, only limited data are available on NIRS regional cerebral tissue oxygen saturation (rSO2) distribution in SAH. The aim of this study was to compare the distribution of NIRS rSO2 values in patients with nontraumatic SAH with the occurrence of DCI and functional outcome at 2 months. In addition, the predictive value of NIRS rSO2 was compared with the previously validated SAFIRE grade (derived from Size of the aneurysm, Age, FIsher grade, World Federation of Neurosurgical Societies after REsuscitation).

METHODS

In this study, the rSO2 distribution of patients with and without DCI after SAH was compared. The optimal cutoff points to predict DCI and outcome were assessed, and its predictive value was compared with the SAFIRE grade.

RESULTS

Of 41 patients, 12 developed DCI, and 9 had unfavorable outcome at 60 days. Prediction of DCI with NIRS had an area under the curve of 0.77 (95% confidence interval 0.62-0.92; P = 0.0028) with an optimal cutoff point of 65% (sensitivity 1.00; specificity 0.45). Prediction of favorable outcome with NIRS had an area under the curve of 0.86 (95% confidence interval 0.74-0.98; P = 0.0003) with an optimal cutoff point of 63% (sensitivity 1.00; specificity 0.63). Regression analysis showed that NIRS rSO2 score is complementary to the SAFIRE grade.

CONCLUSIONS

NIRS rSO2 monitoring in patients with SAH may improve prediction of DCI and clinical outcome after SAH.

ED BP Management for Subarachnoid Hemorrhage

PURPOSE OF REVIEW

To review most recent literature on management of blood pressure in acute aneurysmal subarachnoid hemorrhage (SAH) and provide practice recommendations for the emergency clinician.

RECENT FINDINGS

There is increased risk of aneurysmal rebleeding with systolic blood pressure (SBP) greater than 160 mmHg in the acute setting. Avoiding large degrees of blood pressure variability improves clinical outcomes in aneurysmal SAH. Acute lowering of SBP to a range of 140-160 mmHg decreases risk of rebleeding while also maintaining cerebral perfusion pressure (CPP) after aneurysmal rupture. Treatment with a short acting antihypertensive agent allows for rapid titration of blood pressure (BP) and reduces BP variability. Elevations in intracranial pressure occur commonly after SAH due to increased intracranial blood volume, cerebral edema, or development of hydrocephalus. Clinicians should be familiar with changes in cerebral autoregulation and effects on CPP when treating elevated BP, in order to mitigate the risk of secondary neurological injury.

Near Infrared Spectroscopy for Poor Grade Aneurysmal Subarachnoid Hemorrhage-A Concise Review

Delayed cerebral ischemia (DCI) disproportionately affects poor grade aneurysmal subarachnoid hemorrhage (aSAH) patients. An unreliable neurological exam and the lack of appropriate monitoring leads to unrecognized DCI, which in turn is associated with severe long-term deficits and higher mortality. Near Infrared Spectroscopy (NIRS) offers simple, continuous, real time, non-invasive cerebral monitoring. It provides regional cerebral oxygen saturation (c-rSO2), which reflects the balance between cerebral oxygen consumption and supply. Reports have demonstrated a good correlation with other cerebral oxygen and blood flow monitoring, and credible cerebrovascular reactivity indices were also derived from NIRS signals. Multiple critical c-rSO2 values have been reported in aSAH patients, based on various thresholds, duration, variation from baseline or cerebrovascular reactivity indices. Some were associated with vasospasm, some with DCI and others with clinical outcomes. However, the poor grade aSAH population has not been specifically studied and no randomized clinical trial has been published. The available literature does not support a specific NIRS-based intervention threshold to guide diagnostic or treatment in aSAH patients. We review herein the fundamental basic concepts behind NIRS technology, relationship of c-rSO2 to other brain monitoring values and their potential clinical interpretation. We follow with a critical evaluation of the use of NIRS in the aSAH population, more specifically its ability to diagnose vasospasm, to predict DCI and its association to outcome. In summary, NIRS might offer significant potential for poor grade aSAH in the future. However, current evidence does not support its use in clinical decision-making, and proper technology evaluation is required.

Impact of Cerebral Autoregulation Monitoring in Cerebrovascular Disease: A Systematic Review

Cerebral autoregulation (CA) prevents brain injury by maintaining a relatively constant cerebral blood flow despite fluctuations in cerebral perfusion pressure. This process is disrupted consequent to various neurologic pathologic processes, which may result in worsening neurologic outcomes. Herein, we aim to highlight evidence describing CA changes and the impact of CA monitoring in patients with cerebrovascular disease, including ischemic stroke, intracerebral hemorrhage (ICH), and aneurysmal subarachnoid hemorrhage (aSAH). The study was preformed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. English language publications were identified through a systematic literature conducted in Ovid Medline, PubMed, and Embase databases. The search spanned the dates of each database's inception through January 2021. We selected case-control studies, cohort observational studies, and randomized clinical trials for adult patients (≥ 18 years) who were monitored with continuous metrics using transcranial Doppler, near-infrared spectroscopy, and intracranial pressure monitors. Of 2799 records screened, 48 studies met the inclusion criteria. There were 23 studies on ischemic stroke, 18 studies on aSAH, 5 studies on ICH, and 2 studies on systemic hypertension. CA impairment was reported after ischemic stroke but generally improved after tissue plasminogen activator administration and successful mechanical thrombectomy. Persistent impairment in CA was associated with hemorrhagic transformation, malignant cerebral edema, and need for hemicraniectomy. Studies that investigated large ICHs described bilateral CA impairment up to 12 days from the ictus, especially in the presence of small vessel disease. In aSAH, impairment of CA was associated with angiographic vasospasm, delayed cerebral ischemia, and poor functional outcomes at 6 months. This systematic review highlights the available evidence for CA disruption during cerebrovascular diseases and its possible association with long-term neurological outcome. CA may be disrupted even before acute stroke in patients with untreated chronic hypertension. Monitoring CA may help in establishing individualized management targets in patients with cerebrovascular disease.

Cerebral Autoregulation in Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) is a devastating stroke subtype with a high rate of mortality and morbidity. The poor clinical outcome can be attributed to the biphasic course of the disease: even if the patient survives the initial bleeding emergency, delayed cerebral ischemia (DCI) frequently follows within 2 weeks time and levies additional serious brain injury. Current therapeutic interventions do not specifically target the microvascular dysfunction underlying the ischemic event and as a consequence, provide only modest improvement in clinical outcome. SAH perturbs an extensive number of microvascular processes, including the “automated” control of cerebral perfusion, termed “cerebral autoregulation.” Recent evidence suggests that disrupted cerebral autoregulation is an important aspect of SAH-induced brain injury. This review presents the key clinical aspects of cerebral autoregulation and its disruption in SAH: it provides a mechanistic overview of cerebral autoregulation, describes current clinical methods for measuring autoregulation in SAH patients and reviews current and emerging therapeutic options for SAH patients. Recent advancements should fuel optimism that microvascular dysfunction and cerebral autoregulation can be rectified in SAH patients.

Near-Infrared Spectroscopy in Neurocritical Care: A Review of Recent Updates

Neurocritical diseases and conditions are common causes of long-term disability and mortality. Early recognition and management of neurocritically ill patients is a significant challenge for neurosurgeons, neurologists, and neurointensivists. Although cerebral angiography, magnetic resonance imaging, computed tomography, and radionuclide imaging are useful in neuromonitoring and neuroimaging, they have several important limitations: they are not readily available, cannot be used for a continuous assessment of cerebral function, and frequently require patient transport to the radiological department. Near-infrared spectroscopy (NIRS) is an inexpensive, portable, noninvasive method that does not require advanced expertise and can be used at the bedside for critically ill patients without moving them to the radiology department. NIRS can detect and monitor multiple critical parameters, including cerebral oximetry, intracranial pressure, temperature, and cerebral blood flow. NIRS can be valuable for a wide variety of neurocritical diseases and conditions, such as ischemic and hemorrhagic strokes, severe traumatic brain injury, brain tumors, and perioperative neurosurgery. Although NIRS has been studied extensively in multiple neurocritical conditions, more evidence on its application is needed.

Predictive Value of Cerebral Autoregulation Impairment for Delayed Cerebral Ischemia in Aneurysmal Subarachnoid Hemorrhage: A Meta-Analysis

OBJECTIVE

Delayed cerebral ischemia (DCI) happens in about 30% of patients with aneurysmal subarachnoid hemorrhage (SAH) and is related to higher mortality and disability. Some studies have shown cerebral autoregulation impairment can be a predictor of DCI in aneurysmal SAH. We conducted this meta-analysis to evaluate the predictive value of cerebral autoregulation impairment for DCI based on the current literature.

METHODS

A systematic literature search was performed in PubMed and Embase. According to inclusion and exclusion criteria, 2 authors screened the records and extracted data from the included studies. Pooled sensitivity, specificity, and their 95% confidence intervals (CIs) were obtained. To investigate the overall accuracy, a summary receiver operating characteristic (SROC) curve was built and the area under SROC curve was calculated. Deeks' linear regression was used to assess the publication bias. All statistical analyses were performed with Stata 14.0.

RESULTS

A total of 7 studies were finally included in this meta-analysis. The pooled sensitivity and specificity values of impaired cerebral autoregulation for DCI prediction were 0.79 (95% CI, 0.65-0.88) and 0.85 (95% CI, 0.615-0.96). Moreover, the area under the SROC curve of cerebral autoregulation impairment for DCI prediction was 0.87 (95% CI, 0.835-0.89). No obvious publication bias was found in Deeks' linear regression (P = 0.99).

CONCLUSIONS

Cerebral autoregulation impairment can be a helpful predictor of DCI in aneurysmal SAH. Its accuracy for DCI prediction should be verified by more studies in the future.