Impact of Therapeutic Interventions on Cerebral Autoregulatory Function Following Severe Traumatic Brain Injury: A Secondary Analysis of the BOOST-II Study

BACKGROUND

The Brain Oxygen Optimization in Severe Traumatic Brain Injury Phase II randomized controlled trial used a tier-based management protocol based on brain tissue oxygen (PbtO2) and intracranial pressure (ICP) monitoring to reduce brain tissue hypoxia after severe traumatic brain injury. We performed a secondary analysis to explore the relationship between brain tissue hypoxia, blood pressure (BP), and interventions to improve cerebral perfusion pressure (CPP). We hypothesized that BP management below the lower limit of autoregulation would lead to cerebral hypoperfusion and brain tissue hypoxia that could be improved with hemodynamic augmentation.

METHODS

Of the 119 patients enrolled in the Brain Oxygen Optimization in Severe Traumatic Brain Injury Phase II trial, 55 patients had simultaneous recordings of arterial BP, ICP, and PbtO2. Autoregulatory function was measured by interrogating changes in ICP and PbtO2 in response to fluctuations in CPP using time-correlation analysis. The resulting autoregulatory indices (pressure reactivity index and oxygen reactivity index) were used to identify the "optimal" CPP and limits of autoregulation for each patient. Autoregulatory function and percent time with CPP outside personalized limits of autoregulation were calculated before, during, and after all interventions directed to optimize CPP.

RESULTS

Individualized limits of autoregulation were computed in 55 patients (mean age 38 years, mean monitoring time 92 h). We identified 35 episodes of brain tissue hypoxia (PbtO2 < 20 mm Hg) treated with CPP augmentation. Following each intervention, mean CPP increased from 73 ± 14 mm Hg to 79 ± 17 mm Hg (p = 0.15), and mean PbtO2 improved from 18.4 ± 5.6 mm Hg to 21.9 ± 5.6 mm Hg (p = 0.01), whereas autoregulatory function trended toward improvement (oxygen reactivity index 0.42 vs. 0.37, p = 0.14; pressure reactivity index 0.25 vs. 0.21, p = 0.2). Although optimal CPP and limits remained relatively unchanged, there was a significant decrease in the percent time with CPP below the lower limit of autoregulation in the 60 min after compared with before an intervention (11% vs. 23%, p = 0.05).

CONCLUSIONS

Our analysis suggests that brain tissue hypoxia is associated with cerebral hypoperfusion characterized by increased time with CPP below the lower limit of autoregulation. Interventions to increase CPP appear to improve autoregulation. Further studies are needed to validate the importance of autoregulation as a modifiable variable with the potential to improve outcomes.

Imaging biomarkers of cerebral edema automatically extracted from routine CT scans of large vessel occlusion strokes

BACKGROUND AND PURPOSE

Volumetric and densitometric biomarkers have been proposed to better quantify cerebral edema after stroke, but their relative performance has not been rigorously evaluated.

METHODS

Patients with large vessel occlusion stroke from three institutions were analyzed. An automated pipeline extracted brain, cerebrospinal fluid (CSF), and infarct volumes from serial CTs. Several biomarkers were measured: change in global CSF volume from baseline (ΔCSF); ratio of CSF volumes between hemispheres (CSF ratio); and relative density of infarct region compared with mirrored contralateral region (net water uptake [NWU]). These were compared to radiographic standards, midline shift and relative hemispheric volume (RHV) and malignant edema, defined as deterioration resulting in need for osmotic therapy, decompressive surgery, or death.

RESULTS

We analyzed 255 patients with 210 baseline CTs, 255 24-hour CTs, and 81 72-hour CTs. Of these, 35 (14%) developed malignant edema and 63 (27%) midline shift. CSF metrics could be calculated for 310 (92%), while NWU could only be obtained from 193 (57%). Peak midline shift was correlated with baseline CSF ratio (ρ = -.22) and with CSF ratio and ΔCSF at 24 hours (ρ = -.55/.63) and 72 hours (ρ = -.66/.69), but not with NWU (ρ = .15/.25). Similarly, CSF ratio was correlated with RHV (ρ = -.69/-.78), while NWU was not. Adjusting for age, National Institutes of Health Stroke Scale, tissue plasminogen activator treatment, and Alberta Stroke Program Early CT Score, CSF ratio (odds ratio [OR]: 1.95 per 0.1, 95% confidence interval [CI]: 1.52-2.59) and ΔCSF at 24 hours (OR: 1.87 per 10%, 95% CI: 1.47-2.49) were associated with malignant edema.

CONCLUSION

CSF volumetric biomarkers can be automatically measured from almost all routine CTs and correlate better with standard edema endpoints than net water uptake.

Mechanisms and treatments of neuropathic itch in a mouse model of lymphoma

Our understanding of neuropathic itch is limited due to a lack of relevant animal models. Patients with cutaneous T cell lymphoma (CTCL) experience severe itching. Here, we characterize a mouse model of chronic itch with remarkable lymphoma growth, immune cell accumulation, and persistent pruritus. Intradermal CTCL inoculation produced time-dependent changes in nerve innervations in lymphoma-bearing skin. In the early phase (20 days), CTCL caused hyperinnervations in the epidermis. However, chronic itch was associated with loss of epidermal nerve fibers in the late phases (40 and 60 days). CTCL was also characterized by marked nerve innervations in mouse lymphoma. Blockade of C-fibers reduced pruritus at early and late phases, whereas blockade of A-fibers only suppressed late-phase itch. Intrathecal (i.t.) gabapentin injection reduced late-phase, but not early-phase, pruritus. IL-31 was upregulated in mouse lymphoma, whereas its receptor Il31ra was persistently upregulated in Trpv1-expressing sensory neurons in mice with CTCL. Intratumoral anti-IL-31 treatment effectively suppressed CTCL-induced scratching and alloknesis (mechanical itch). Finally, i.t. administration of a TLR4 antagonist attenuated pruritus in early and late phases and in both sexes. Collectively, we have established a mouse model of neuropathic and cancer itch with relevance to human disease. Our findings also suggest distinct mechanisms underlying acute, chronic, and neuropathic itch.

Abstract 11: Identifiable Patterns Of Noninvasive Cerebral Oximetry During Endovascular Therapy For Acute Ischemic Stroke Are Associated With Neurological Deterioration

Background: Cerebral near-infrared spectroscopy (NIRS) is a useful tool to monitor real-time cerebral oxygenation levels. However, the mechanisms through which varying oxygenation levels during endovascular thrombectomy (EVT) affect functional outcomes remain to be determined. In this study, we categorized NIRS trends into descriptive “fingerprints” and examined the relationship between these fingerprints and neurological worsening.

Methods: We enrolled patients that presented to Yale New Haven Hospital with large vessel occlusion acute ischemic stroke and underwent EVT. NIRS was implemented into the standard operating procedure. Time stamps of defined events (medication administration, recanalization, etc.) were synchronized with corresponding NIRS values. We inspected NIRS curves from arrival to angio-suite to time of recanalization. Neurological deterioration was defined as an increase of 4 points or more on the National Institutes of Health Stroke Scale (NIHSS).

Results: Forty-eight patients (mean age 72 ± 13, mean NIHSS 14) were analyzed. Five “fingerprints” were observed in the affected hemisphere: sustained decreases, downward rSO2 peaks, no change, upward rSO2 peaks, and sustained increases (Fig. 1), which were assigned nominal values of -2, -1, 0, 1, and 2, respectively. After adjusting for age and admission NIHSS, sustained decreases and downward rSO2 peaks were independently associated with neurological deterioration (P = 0.0076, Fig. 2).

Conclusions: Identifiable NIRS “fingerprints” of downward rSO2 peaks and sustained decreases in the affected hemisphere during EVT are associated with neurological deterioration. Further distillation of identifiable intraprocedural NIRS trends in real time could provide guidance for anesthesia and hemodynamic management during EVT to optimize patient outcomes after stroke.

Abstract 9: Autoregulation-based Blood Pressure Targets After Endovascular Thrombectomy

Background: Optimal level blood pressure (BP) targets in acute stroke remain elusive. Tailored hemodynamic management after endovascular thrombectomy (EVT) may reduce the risk of reperfusion injury and promote penumbral recovery. Our study aimed to evaluate the relationship between personalized autoregulation-based BP targets, secondary brain injury, and functional outcomes.

Methods: We prospectively enrolled 200 patients with acute ischemic stroke who underwent EVT. Autoregulatory function was continuously measured for >=24 hours using simultaneous recordings of near-infrared spectroscopy and mean arterial pressure (MAP). The resulting autoregulatory index was used to calculate and trend the BP range at which autoregulation was most preserved. Percent time and “dose” that MAP exceeded the upper limit or dropped below the lower limit of autoregulation (ULA, LLA) were calculated for each patient. Hemodynamic parameters were correlated with short-term clinical endpoints (symptomatic ICH), biomarkers of secondary brain injury (net water uptake, hemorrhagic transformation (HT), infarct progression), and 90-day functional outcomes.

Results: Personalized BP targets were successfully computed in 195 patients (mean age 70 ± 16, 45% female, mean NIHSS 14, mean monitoring time 31 ± 28 hours). Time above the ULA was associated with worse functional outcomes at 90-days after adjusting for age, sex, NIHSS, ASPECTS and TICI (adjusted OR per 10% increase 1.4, 95% CI 1.1-1.6, P=0.004). The burden of hyperperfusion was significantly greater among patients with HT (median 2.7 vs. 3.2 mmHg*min, p=0.01) and sICH (median 2.8 vs. 4.8 mmHg*min, p=0.05) than in those without it. Furthermore, time spent above the ULA was significantly correlated with net water uptake at 72 hours (r=0.37, p=0.03). Among patients with unsuccessful reperfusion, there was a non-significant correlation between time below the LLA and infarct progression (r=0.35, p=0.064).

Conclusions: In the largest study conducted to date, deviations from personalized BP targets were associated with an increased risk of secondary brain injury and worse functional outcomes. Autoregulation-oriented BP management represents a promising strategy for maximizing recovery after ischemic stroke.

Abstract 12: Higher Blood Pressure Trajectories After Endovascular Thrombectomy Are Associated With Cerebral Edema Development

Introduction: High blood pressure after endovascular thrombectomy (EVT) can cause cerebral hyperemia and disrupt the blood-brain barrier. However, its role in cerebral edema development is incompletely understood. In this study, we examined the relationship between post-EVT systolic blood pressure (SBP) trajectories and cerebral edema.

Methods: We prospectively enrolled patients with large-vessel occlusion stroke who underwent EVT. Cerebrospinal fluid (CSF) volume was measured using a deep-learning algorithm on CT images at baseline, 24 hours, and 72 hours after stroke. The ratio of CSF volumes between hemispheres was calculated. Automated segmentation of infarct regions on follow-up scans was used to measure net water uptake (NWU), the ratio of density within infarcted tissue relative to the mirrored contralateral region. Latent variable mixture modeling (LVMM) divided patients into SBP trajectory groups during the first 72 hours post-EVT (Fig. 1A). Measures of edema (change in CSF ratio, NWU) were compared between groups.

Results: One hundred patients (mean age 70 ± 16, mean NIHSS 15) were analyzed. Edema was assessed by a gradual increase in NWU (20.5, 27.0) at 24 and 72 hours, respectively, and by a reduction in CSF ratio (0.95, 0.78, 0.68) in the affected hemisphere at baseline, 24 hours, and 72 hours, respectively. LVMM identified five SBP trajectories. Higher SBP trajectories were associated with higher NWU (Fig. 1B) but not lower CSF ratio at 24 hours (p<0.001 and p=0.343, respectively). After adjusting for age, admission NIHSS, and TICI score, the moderate-to-high and high-to-moderate trajectory groups were independently associated with higher NWU (aOR 11.40, 95% CI 2.14-20.66) and (aOR 10.97, 95% CI 0.12-21.82), relative to the low and moderate groups.

Conclusions: Higher SBP trajectories are associated with an increase in NWU post-EVT. NWU is a promising radiographic biomarker for measuring cerebral edema during the early phase after stroke.

Abstract WP154: Low-field Portable Mri For Routine Post-thrombectomy Assessment Of Ongoing Brain Injury

Introduction: Conventional MRI (cMRI) is not routinely available post-mechanical thrombectomy (MT), which can preclude accurate infarction assessment. Our objective was to evaluate the use of low-field portable MRI (pMRI) for bedside evaluation post-MT, including its use as a post-procedural baseline monitor.

Methods: Low-field pMRI was used to obtain bedside imaging in post-MT patients between December 2021 to August 2022 at Yale-New Haven Hospital. All pMRI exams were conducted in the standard ferromagnetic environment of the IR suite. Volumetric analyses were performed by a neuroradiologist using 3D Slicer software. If cMRI was not available for comparison, a CT was used. Patients’ charts were reviewed for pre-revascularization MAP and occurrences of MAP dropping by 10% and 20% from individual baselines between the time of pMRI and delayed imaging.

Results: A total of 25 patients (64% females, median age 77 years-old [IQR 69.5-84.5]) underwent bedside pMRIs in the IR suite post-MT. The median time from last known normal to access was 6 hours [IQR 4-17]. The median pMRI examination time was 30 minutes [IQR 17-32]. Of the 24 patients with available delayed imaging, 7 (29.2%) had infarct progression compared to immediate post-MT pMRI, while 15 patients (62.5%) had stable/decreased stroke volume. Two patients (8.3%) had parenchymal hemorrhage type 2 and were excluded from further analysis. There was no statistically significant difference between the proportions of favorable TICI scores (85.7% in the infarct progression group vs. 92.3% in the stable/decreased infarct group, p=1.00). Patients with infarct progression had comparable pre-revascularization MAP compared to those with stable/decreased delayed infarct volume (mean of 100.3±4.6 vs. 101.9±15.9 respectively, p=0.727) but had more occurrences of MAP dropping by 10% and 20% of their baseline between the time of pMRI and delayed imaging (mean of 35.0±23.3 vs. 14.7±11.3 occurrences, p=0.011; and mean of 21.7±16.5 vs. 8.5±9.5 occurrences, p=0.026, respectively).

Conclusions: The use of low-field MRI in the post-MT setting can facilitate benchmark brain monitoring and serial examinations to evaluate the impact of potential physiological perturbations that may impact ongoing brain injury.

Open revascularization in a patient with chronic mesenteric ischemia and a history of aorto-bifemoral bypass - a case report

INTRODUCTION

This case report describes surgical treatment of chronic mesenteric ischemia in a polymorbid patient with the history of an aorto-bifemoral bypass implant.

CASE REPORT

The patient suffered from chronic occlusions of the mesenteric arteries. He experienced postprandial pain and significant weight loss. Endovascular repair of the occlusions failed. Open single retrograde bypass from the left branch of the aorto-bifemoral graft to the superior mesenteric artery was implanted successfully.

CONCLUSION

The discussion briefly mentions current trends in the treatment of chronic mesenteric ischemia. Despite the development of interventional radiology, surgical treatment remains a relevant alternative for the management of chronic mesenteric ischemia.