Acute intracranial hemorrhage during the installation of the LICOX microdialysis system: A case report

Neuro-monitoring is widely employed for the evaluation of intubated patients in the intensive care unit with stroke, severe head trauma, subarachnoid hemorrhage and/or hepatic encephalopathy. The present study reports the case of a patient with acute intracranial hemorrhage following the insertion of neuromonitoring catheters, which required surgical management. The patient was a 14-year-old male who sustained a severe traumatic brain injury and underwent a right-sided hemicraniectomy. During the installation of the neuromonitoring catheters, an acute hemorrhage was noted with a rapidly elevating intracranial pressure. A craniotomy was performed to identify and coagulate the injured cortical vessel. As demonstrated herein, the thorough evaluation of the clotting profile of the patient, a meticulous surgical technique and obtaining a post-insertion computed tomography scan may minimize the risk of any neuromonitoring-associated hemorrhagic complications.

The Role of Brain Tissue Oxygenation Monitoring in the Management of Subarachnoid Hemorrhage: A Scoping Review

Monitoring of brain tissue oxygenation (PbtO2) is an important component of multimodal monitoring in traumatic brain injury. Over recent years, use of PbtO2 monitoring has also increased in patients with poor-grade subarachnoid hemorrhage (SAH), particularly in those with delayed cerebral ischemia. The aim of this scoping review was to summarize the current state of the art regarding the use of this invasive neuromonitoring tool in patients with SAH. Our results showed that PbtO2 monitoring is a safe and reliable method to assess regional cerebral tissue oxygenation and that PbtO2 represents the oxygen available in the brain interstitial space for aerobic energy production (i.e., the product of cerebral blood flow and the arterio-venous oxygen tension difference). The PbtO2 probe should be placed in the area at risk of ischemia (i.e., in the vascular territory in which cerebral vasospasm is expected to occur). The most widely used PbtO2 threshold to define brain tissue hypoxia and initiate specific treatment is between 15 and 20 mm Hg. PbtO2 values can help identify the need for or the effects of various therapies, such as hyperventilation, hyperoxia, induced hypothermia, induced hypertension, red blood cell transfusion, osmotic therapy, and decompressive craniectomy. Finally, a low PbtO2 value is associated with a worse prognosis, and an increase of the PbtO2 value in response to treatment is a marker of good outcome.

Invasive Neuromonitoring Modalities in the Pediatric Population

Invasive neuromonitoring has become an important part of pediatric neurocritical care, as neuromonitoring devices provide objective data that can guide patient management in real time. New modalities continue to emerge, allowing clinicians to integrate data that reflect different aspects of cerebral function to optimize patient management. Currently, available common invasive neuromonitoring devices that have been studied in the pediatric population include the intracranial pressure monitor, brain tissue oxygenation monitor, jugular venous oximetry, cerebral microdialysis, and thermal diffusion flowmetry. In this review, we describe these neuromonitoring technologies, including their mechanisms of function, indications for use, advantages and disadvantages, and efficacy, in pediatric neurocritical care settings with respect to patient outcomes.

Brain tissue oxygenation monitoring in subarachnoid hemorrhage for the detection of delayed ischemia: a systematic review and meta-analysis

INTRODUCTION

Subarachnoid hemorrhage (SAH) is a severe subtype of stroke which can be caused by the rupture of an intracranial aneurysm. Following SAH, about 30% of patients develop a late neurologic deterioration due to a delayed cerebral ischemia (DCI). This is a metanalysis and systematic review on the association between values of brain tissue oxygenation (PbtO2) and DCI in patients with SAH.

EVIDENCE ACQUISITION

The protocol was written according to the PRISMA-P (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and approved by the International Prospective Register of Systematic Reviews (PROSPERO registration number CRD42021229338). Relevant literature published up to August 1, 2022 was systematically searched throughout the databases MEDLINE, WEB OF SCIENCE, SCOPUS. A systematic review and metanalysis was carried out. The studies considered eligible were those published in English; that enrolled adult patients (≥18years) admitted to neurointensive care units with aneurysmal SAH (aSAH); that reported presence of multimodality monitoring including PbtO2 and detection of DCI during the period of monitoring.

EVIDENCE SYNTHESIS

We founded 286 studies, of which six considered eligible. The cumulative mean of PbtO2 was 19.5 mmHg in the ischemic group and 24.1mmHg in the non ischemic group. The overall mean difference of the values of PbtO2 between the patients with or without DCI resulted significantly different (-4.32 mmHg [IC 95%: -5.70, -2.94], without heterogeneity, I² = 0%, and a test for overall effect with P<0.00001).

CONCLUSIONS

PbtO2 values were significantly lower in patients with DCI. Waiting for definitive results, monitoring of PbtO2 should be considered as a complementary parameter for multimodal monitoring of the risk of DCI in patients with SAH.

The effect of hypoxia on photodynamic therapy with 5-aminolevulinic acid in malignant gliomas

BACKGROUND

Glioblastoma (GBM) is a high-grade, poor prognosis tumor that is resistant to standard treatment. The presence of a small number of glioma stem cells (GSCs) surviving in the harsh microenvironment is responsible for their refractoriness. This study aimed to investigate the effect of a hypoxic environment on the sensitivity of GSCs to photodynamic therapy with 5-aminolevulinic acid (ALA-PDT).

MATERIALS AND METHODS

Six human GSC lines, Mesenchymal types HGG13, HGG30, HGG1123, and Proneural types HGG146, HGG157, HGG528, were divided into two groups: normoxia (O₂ 21%)-cultured cells (Normoxia-GSCs), and hypoxia (O₂ 5%)-cultured cells (Hypoxia-GSCs). To compare the effects of different oxygen partial pressures on photoporphyrin Ⅸ (PpⅨ) biosynthetic activity, PpⅨ biosynthetic enzyme and transporter expression levels were examined by qRT-PCR; the intracellular PpⅨ concentration was determined using flow cytometry. Additionally, the sensitivity of these two groups of cells to ALA-PDT was evaluated in vitro.

RESULTS

Hypoxia-GSCs showed higher mRNA levels of FECH (ferrochelatase), which is required for iron synthesis to convert PpⅨ to heme, compared with Normoxia-GSCs. Flow cytometry revealed that the accumulation of PpⅨ in Hypoxia-GSCs reduced upon incubation with ALA. However, Hypoxia-GSCs showed less reduction in sensitivity to ALA-PDT than Normoxia-GSCs.

CONCLUSION

Hypoxia-GSCs had lower intracellular PpⅨ accumulation than Normoxia-GSCs due to increased gene expression of FECH, and that their sensitivity to ALA-PDT was reduced less, despite accumulating lower concentrations of PpⅨ. ALA-PDT is a potentially effective therapy for hypoxia-tolerant GSCs that exist in hypoxia at 5% oxygen concentration.

Brain Oxygen-Directed Management of Aneurysmal Subarachnoid Hemorrhage. Temporal Patterns of Cerebral Ischemia During Acute Brain Attack, Early Brain Injury, and Territorial Sonographic Vasospasm

BACKGROUND

Neurocritical management of aneurysmal subarachnoid hemorrhage focuses on delayed cerebral ischemia (DCI) after aneurysm repair.

METHODS

This study conceptualizes the pathophysiology of cerebral ischemia and its management using a brain oxygen-directed protocol (intracranial pressure [ICP] control, eubaric hyperoxia, hemodynamic therapy, arterial vasodilation, and neuroprotection) in patients with subarachnoid hemorrhage, undergoing aneurysm clipping (n = 40).

RESULTS

The brain oxygen-directed protocol reduced Lbo₂ (Pbto₂ [partial pressure of brain tissue oxygen] <20 mm Hg) from 67% to 15% during acute brain attack (<24 hours of ictus), by increasing Pbto₂ from 11.31 ± 9.34 to 27.85 ± 6.76 (P < 0.0001) and then to 29.09 ± 17.88 within 72 hours. Day-after-bleed, Fio₂ change, ICP, hemoglobin, and oxygen saturation were predictors for Pbto₂ during early brain injury. Transcranial Doppler ultrasonography velocities (>20 cm/second) increased at day 2. During DCI caused by territorial sonographic vasospasm (TSV), middle cerebral artery mean velocity (V_m) increased from 45.00 ± 15.12 to 80.37 ± 38.33/second by day 4 with concomitant Pbto₂ reduction from 29.09 ± 17.88 to 22.66 ± 8.19. Peak TSV (days 7-12) coincided with decline in Pbto₂. Nicardipine mitigated Lbo₂ during peak TSV, in contrast to nimodipine, with survival benefit (P < 0.01). Intravenous and cisternal nicardipine combination had survival benefit (Cramer Φ = 0.43 and 0.327; G² = 28.32; P < 0.001). This study identifies 4 zones of Lbo₂ during survival benefit (Cramer Φ = 0.43 and 0.3) TSV, uncompensated; global cerebral ischemia, compensated, and normal Pbto₂. Admission Glasgow Coma Scale score (not increased ICP) was predictive of low Pbto₂ (β = 0.812, R² = 0.661, F_1,30 = 58.41; P < 0.0001) during early brain injury. Coma was the only credible predictor for mortality (odds ratio, 7.33/>4.8∗; χ² = 7.556; confidence interval, 1.70-31.54; P < 0.01) followed by basilar aneurysm, poor grade, high ICP and Lbo₂ during TSV. Global cerebral ischemia occurs immediately after the ictus, persisting in 30% of patients despite the high therapeutic intensity level, superimposed by DCI during TSV.

CONCLUSIONS

We propose implications for clinical practice and patient management to minimize cerebral ischemia.

Correlation between brain tissue oxygen tension and regional cerebral oximetry in uninjured human brain under conditions of changing ventilation strategy

Controversy surrounds regional cerebral oximetry (rSO₂) because extracranial contamination and unmeasured changes in cerebral arterial:venous ratio confound readings. Correlation of rSO₂ with brain tissue oxygen (PbrO₂), a “gold standard” for cerebral oxygenation, could help resolve this controversy but PbrO₂ measurement is highly invasive. This was a prospective cohort study. The primary aim was to evaluate correlation between PbrO₂ and rSO₂ and the secondary aim was to investigate the relationship between changing ventilation regimens and measurement of PbrO₂ and rSO₂. Patients scheduled for elective removal of cerebral metastases were anesthetized with propofol and remifentanil, targeted to a BIS range 40–60. rSO₂ was measured using the INVOS 5100B monitor and PbrO₂ using the Licox brain monitoring system. The Licox probe was placed into an area of normal brain within the tumor excision corridor. FiO₂ and minute ventilation were sequentially adjusted to achieve two set points: (1) FiO₂ 0.3 and paCO₂ 30 mmHg, (2) FiO₂ 1.0 and paCO₂ 40 mmHg. PbrO₂ and rSO₂ were recorded at each. Nine participants were included in the final analysis, which showed a positive Spearman’s correlation (r = 0.50, p = 0.036) between PbrO₂ and rSO₂. From set point 1 to set point 2, PbrO₂ increased from median 6.0, IQR 4.0–11.3 to median 22.5, IQR 9.8–43.6, p = 0.015; rSO₂ increased from median 68.0, IQR 62.5–80.5 to median 83.0, IQR 74.0–90.0, p = 0.047. Correlation between PbrO₂ and rSO₂ is evident. Increasing FiO₂ and PaCO₂ results in significant increases in cerebral oxygenation measured by both monitors.

Effects of Temporary Clipping as an Expression of Circulatory Individuality: Online Measurement of Temporal Lobe Oxygen Levels During Surgery for Middle Cerebral Artery Aneurysms

OBJECTIVE

Despite its widespread use, much is left to understand about the repercussions of parent artery temporary clipping in neurosurgery. This study seeks a better comprehension of the subject by aiming at the online measurement of brain tissue oxygen pressure (P_btO₂) during such events.

METHODS

This was a prospective observational study. Patients submitted to surgery for middle cerebral artery aneurysms (both ruptured and unruptured) were continuously monitored under Intensive Care Monitoring+ software, in order to obtain temporal (downstream) P_btO₂ levels while temporary clips were applied. Separate P_btO₂ curve events were identified, extracted, and processed. These were studied for assessing intraindividual and interindividual variability and the potential impact of repeated clipping and previous aneurysmal rupture.

RESULTS

Eighty-six temporary clippings (from 20 patients) were recorded with a mean duration of 140.8 (41 - 238) seconds. Temporary arterial occlusion at the M1 segment of the middle cerebral artery produced specifically shaped trajectories, characterized by a preclipping P_btO₂ level, rapid downward sigmoid-shaped curve, succession of progressively angled slopes, and lower plateau. The steepest slope of the curve correlated strongly with P_btO₂ range (P < 0.001, r = 0.944). These features were highly reproducible only intraindividually and did not vary significantly with repeated clippings.

CONCLUSIONS

The effects of temporary arterial occlusion on temporal lobe oxygenation demonstrate a high degree of singularity, highlighting the potential benefits of assessing individual available collateral circulation intraoperatively. The "P_btO₂ steepest slope" predicted the severity of P_btO₂ decrease and was available within the first minute.

Relationship between Brain Tissue Oxygen Tension and Transcranial Doppler Ultrasonography

BACKGROUND

Multimodal monitoring of intracranial pressure and brain tissue oxygen tension (PbtO₂) have been increasingly used to detect delayed cerebral ischemia (DCI) after subarachnoid hemorrhage. At our center, patients who cannot be easily assessed clinically will undergo intracranial pressure and PbtO₂ monitoring via a NEUROVENT-PTO bolt. We aimed to determine whether the Lindegaard ratios (LRs) computed from transcranial Doppler ultrasonography (TCDU) would correlate with, or can predict, the simultaneously recorded PbtO₂ value.

METHODS

Patients with aneurysmal subarachnoid hemorrhage, PbtO₂ recordings from the middle cerebral artery territory, and simultaneous TCDU scans available from the ipsilateral middle cerebral artery and internal carotid artery from August 2018 to 2019 were included in the present study. The index test result was vasospasm (LR of ≥3) found on TCDU. The reference standard was the presence of regional hypoxia (PbtO₂ <20 mm Hg). The PbtO₂ results were compared with those from computed tomography angiography as a radiological standard. The predictive values were calculated using a contingency table and receiver operating characteristic curve.

RESULTS

A total of 28 patients (6 men and 22 women; age, 59.04 ± 13.75 years) were identified with simultaneous brain tissue oxygen and TCDU recordings available. Of the 28 patients, 7 had cerebral hypoxia (PbtO₂ <20 mm Hg). We found no correlation between the PbtO₂ measurements and simultaneously recorded LRs (r² = 0.048; P = 0.26). A LR of ≥3 had high specificity (95.24%) for hypoxia but relatively low sensitivity (42.86%; P = 0.037).

CONCLUSION

We find TCDU to be specific for predicting cerebral hypoxia (measured via an intraparenchymal probe). Therefore, it could be a useful and noninvasive tool in the context of preventative DCI monitoring. However, given the low sensitivity, the lack of vasospasm on TCDU should not preclude the possibility of the presence of evolving DCI.

Monitoring of brain and systemic oxygenation in neurocritical care patients

Maintenance of adequate oxygenation is a mainstay of intensive care, however, recommendations on the safety, accuracy, and the potential clinical utility of invasive and non-invasive tools to monitor brain and systemic oxygenation in neurocritical care are lacking. A literature search was conducted for English language articles describing bedside brain and systemic oxygen monitoring in neurocritical care patients from 1980 to August 2013. Imaging techniques e.g., PET are not considered. A total of 281 studies were included, the majority described patients with traumatic brain injury (TBI). All tools for oxygen monitoring are safe. Parenchymal brain oxygen (PbtO2) monitoring is accurate to detect brain hypoxia, and it is recommended to titrate individual targets of cerebral perfusion pressure (CPP), ventilator parameters (PaCO2, PaO2), and transfusion, and to manage intracranial hypertension, in combination with ICP monitoring. SjvO2 is less accurate than PbtO2. Given limited data, NIRS is not recommended at present for adult patients who require neurocritical care. Systemic monitoring of oxygen (PaO2, SaO2, SpO2) and CO2 (PaCO2, end-tidal CO2) is recommended in patients who require neurocritical care.

Impact of percutaneous dilatational tracheostomy in brain injured patients

OBJECTIVE

Tracheostomy is an established method in the airway management of critically ill patients with traumatic and non-traumatic brain injuries. High priority in the treatment of those patients is to protect vulnerable brain tissue. While bedside percutaneously dilatative tracheostomy (PDT) technique is increasingly used, there is disagreement about the harms of this intervention for the damaged brain. Therefore, discussions about the safety of tracheostomy in those patients must consider direct and indirect cerebral parameters.

METHODS

We examined a series of 289 tracheostomies regarding vital signs, respiratory and intracranial parameters in a retrospective study. Complications were recorded and risk factors for a complicated scenario statistically determined.

RESULTS

Severe complications were rare (1/289). Arterial hypotension occurred in 3 of 289 cases with a systolic blood pressure below 90mmHg. We had two patients (0.5%) with transient hypoxia, but 43 cases (15%) of severe hypercapnia during PDT. Invasive measurement of brain tissue oxygen tension (PBrO2) ruled out any cerebral hypoxia during the procedure in 39 available cases. Intracranial pressure (ICP) rose temporarily in 24% of the cases. Cerebral perfusion pressure (CPP) however remained unaffected. Surgery time and hypercapnia are capable risk factors for intraoperative ICP elevation. There is no significant difference in intraoperative ICP rises between disease entities.

CONCLUSION

PDT is a safe procedure for the most common neurosurgical diseases, even for patients with respiratory insufficiency. Shortening surgical time seems to be the most important factor to avoid ICP increase.

Advances in neuro-monitoring

Neuromonitoring aims to detect harmful physiologic events, early enough to guide the treatment instituted. Evidences encourage us to implement multimodal monitoring, as no single monitor is capable of providing a complete picture of dynamic cerebral state. This review highlights the role of intracranial pressure monitoring, cerebral oxygenation (jugular venous oximetry, brain tissue oxygenation, near infrared oximetry, cerebral microdialysis) and cerebral blood flow monitoring (direct and indirect methods) in the management of neurologically injured patients. In this context, the recent developments of these monitors along with the relevant clinical implications have been discussed. Nevertheless, the diverse range of data obtained from these monitors needs to be integrated and simplified for the clinician. Hence, the future research should focus on identification of a most useful monitor for integration into multimodal system.

Delayed cerebral ischemia in aneurysmal subarachnoid hemorrhage: proposal of an evidence-based combined clinical and imaging reference standard

SUMMARY

Aneurysmal subarachnoid hemorrhage is associated with high morbidity and mortality, with delayed neurologic deficits from delayed cerebral ischemia contributing to a large portion of the adverse outcomes in this patient population. There is currently no consensus reference standard for establishing the diagnosis of delayed cerebral ischemia either in the research or clinical settings, ultimately limiting strategies for preventing delayed infarction and permanent neurologic deficits. There are currently both clinical and imaging-based criteria for the diagnosis of delayed neurologic deficits and vasospasm, respectively, however, neither clinical nor angiographic assessment alone has been shown to identify patients who develop adverse outcomes from delayed infarction. Thus, the purpose of this work is to propose a 3-tiered combined imaging and clinical reference standard based on evidence from the literature to standardize the diagnosis of delayed cerebral ischemia, both to allow consistency across research studies and to ultimately improve outcomes in the clinical setting.

Physiological oxygen concentration alters glioma cell malignancy and responsiveness to photodynamic therapy in vitro

OBJECTIVES

The partial pressure of oxygen (pO2) in brain tumors ranges from 5 to 15%. Nevertheless, the majority of in vitro experiments with glioblastoma multiforme (GBM) cell lines are carried out under an atmospheric pO2 of 19 to 21%. Recently, 5-aminolevulinic acid (5-ALA), a precursor of protoporphyrin IX (PpIX), has been introduced to neurosurgery to allow for photodynamic diagnosis and photodynamic therapy (PDT) in high-grade gliomas. Here, we investigate whether low pO2 affects GBM cell physiology, PpIX accumulation, or PDT efficacy.

METHODS

GBM cell lines (U-87 MG and U-251 MG) were cultured under atmospheric (pO2  =  19%) and physiological (pO2  =  9%) oxygen concentrations. PpIX accumulation and localization were investigated, and cell survival and cell death were observed following in vitro PDT.

RESULTS

A physiological pO2 of 9% stimulated GBM cell migration, increased hypoxia-inducible factor (HIF)-1 alpha levels, and elevated resistance to camptothecin in U-87 MG cells compared to cultivation at a pO2 of 19%. This oxygen reduction did not alter 5-ALA-induced intracellular PpIX accumulation. However, physiological pO2 changed the responsiveness of U-87 MG but not of U-251 MG cells to in vitro PDT. Around 20% more irradiation light was required to kill U-87 MG cells at physiological pO2, resulting in reduced lactate dehydrogenase (LDH) release (one- to two-fold) and inhibition of caspase 3 activation.

DISCUSSION

Reduction of oxygen concentration from atmospheric to a more physiological level can influence the malignant behavior and survival of GBM cell lines after in vitro PDT. Therefore, precise oxygen concentration control should be considered when designing and performing experiments with GBM cells.

Invasive and noninvasive multimodal bedside monitoring in subarachnoid hemorrhage: a review of techniques and available data

Delayed-cerebral ischemia is a major cause of morbidity and mortality in the setting of aneurysmal subarachnoid hemorrhage. Despite extensive research efforts and a breadth of collective clinical experience, accurate diagnosis of vasospasm remains difficult, and effective treatment options are limited. Classically, diagnosis has focused on imaging assessment of the cerebral vasculature. Recently, invasive and noninvasive bedside techniques designed to characterize relevant hemodynamic and metabolic alterations have gained substantial attention. Such modalities include microdialysis, brain tissue oxygenation, jugular bulb oximetry, thermal diffusion cerebral blood flow, and near-infrared spectroscopy. This paper reviews these modalities and examines data pertinent to the diagnosis and management of cerebral vasospasm.