In vitro comparison of two generations of Licox and Neurotrend catheters

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.

Mismatch between Tissue Partial Oxygen Pressure and Near-Infrared Spectroscopy Neuromonitoring of Tissue Respiration in Acute Brain Trauma: The Rationale for Implementing a Multimodal Monitoring Strategy

The brain tissue partial oxygen pressure (PbtO₂) and near-infrared spectroscopy (NIRS) neuromonitoring are frequently compared in the management of acute moderate and severe traumatic brain injury patients; however, the relationship between their respective output parameters flows from the complex pathogenesis of tissue respiration after brain trauma. NIRS neuromonitoring overcomes certain limitations related to the heterogeneity of the pathology across the brain that cannot be adequately addressed by local-sample invasive neuromonitoring (e.g., PbtO₂ neuromonitoring, microdialysis), and it allows clinicians to assess parameters that cannot otherwise be scanned. The anatomical co-registration of an NIRS signal with axial imaging (e.g., computerized tomography scan) enhances the optical signal, which can be changed by the anatomy of the lesions and the significance of the radiological assessment. These arguments led us to conclude that rather than aiming to substitute PbtO₂ with tissue saturation, multiple types of NIRS should be included via multimodal systemic- and neuro-monitoring, whose values then are incorporated into biosignatures linked to patient status and prognosis. Discussion on the abnormalities in tissue respiration due to brain trauma and how they affect the PbtO₂ and NIRS neuromonitoring is given.

Brain tissue oxygen tension and its response to physiological manipulations: influence of distance from injury site in a swine model of traumatic brain injury

OBJECTIVE The optimal site for placement of tissue oxygen probes following traumatic brain injury (TBI) remains unresolved. The authors used a previously described swine model of focal TBI and studied brain tissue oxygen tension (P_btO₂) at the sites of contusion, proximal and distal to contusion, and in the contralateral hemisphere to determine the effect of probe location on P_btO₂ and to assess the effects of physiological interventions on P_btO₂ at these different sites. METHODS A controlled cortical impact device was used to generate a focal lesion in the right frontal lobe in 12 anesthetized swine. P_btO₂ was measured using Licox brain tissue oxygen probes placed at the site of contusion, in pericontusional tissue (proximal probe), in the right parietal region (distal probe), and in the contralateral hemisphere. P_btO₂ was measured during normoxia, hyperoxia, hypoventilation, and hyperventilation. RESULTS Physiological interventions led to expected changes, including a large increase in partial pressure of oxygen in arterial blood with hyperoxia, increased intracranial pressure (ICP) with hypoventilation, and decreased ICP with hyperventilation. Importantly, P_btO₂ decreased substantially with proximity to the focal injury (contusion and proximal probes), and this difference was maintained at different levels of fraction of inspired oxygen and partial pressure of carbon dioxide in arterial blood. In the distal and contralateral probes, hypoventilation and hyperventilation were associated with expected increased and decreased P_btO₂ values, respectively. However, in the contusion and proximal probes, these effects were diminished, consistent with loss of cerebrovascular CO₂ reactivity at and near the injury site. Similarly, hyperoxia led to the expected rise in P_btO₂ only in the distal and contralateral probes, with little or no effect in the proximal and contusion probes, respectively. CONCLUSIONS P_btO₂ measurements are strongly influenced by the distance from the site of focal injury. Physiological alterations, including hyperoxia, hyperventilation, and hypoventilation substantially affect P_btO₂ values distal to the site of injury but have little effect in and around the site of contusion. Clinical interpretations of brain tissue oxygen measurements should take into account the spatial relation of probe position to the site of injury. The decision of where to place a brain tissue oxygen probe in TBI patients should also take these factors into consideration.

Rapid resolution of brain ischemic hypoxia after cerebral revascularization in moyamoya disease

BACKGROUND

In moyamoya disease (MMD), cerebral revascularization is recommended in patients with recurrent or progressive ischemic events and associated reduced cerebral perfusion reserve. Low-flow bypass with or without indirect revascularization is generally the standard surgical treatment. Intraoperative monitoring of cerebral partial pressure of oxygen (PtiO2) with polarographic Clark-type probes in cerebral artery bypass surgery for MMD-induced chronic cerebral ischemia has not yet been described.

OBJECTIVE

To describe basal brain tissue oxygenation in MMD patients before revascularization as well as the immediate changes produced by the surgical procedure using intraoperative PtiO2 monitoring.

METHODS

Between October 2011 and January 2013, all patients with a diagnosis of MMD were intraoperatively monitored. Cerebral oxygenation status was analyzed based on the Ptio2/PaO2 ratio. Reference thresholds of PtiO2/PaO2 had been previously defined as below 0.1 for the lower reference threshold (hypoxia) and above 0.35 for the upper reference threshold (hyperoxia).

RESULTS

Before STA-MCA bypass, all patients presented a situation of severe tissue hypoxia confirmed by a PtiO2/PaO2 ratio <0.1. After bypass, all patients showed a rapid and sustained increase in PtiO2, which reached normal values (PtiO2/PaO2 ratio between 0.1 and 0.35). One patient showed an initial PtiO2 improvement followed by a decrease due to bypass occlusion. After repeat anastomosis, the patient's PtiO2 increased again and stabilized.

CONCLUSION

Direct anastomosis quickly improves cerebral oxygenation, immediately reducing the risk of ischemic stroke in both pediatric and adult patients. Intraoperative PtiO2 monitoring is a very reliable tool to verify the effectiveness of this revascularization procedure.

The oxygen reactivity index and its relation to sensor technology in patients with severe brain lesions

BACKGROUND

The oxygen reactivity index (ORx) has been introduced to assess the status of cerebral autoregulation after traumatic brain injury (TBI) or subarachnoid hemorrhage (SAH). Currently, there is some controversy about whether the ORx depends on the type of PbrO2-sensor technology used for its calculation. To examine if the probe technology does matter, we compared the ORx and the resulting optimal cerebral perfusion pressures (CPPopt) of simultaneously implanted Licox (CC1.SB, Integra Neuroscience, France) and Neurovent-PTO (Raumedic, Germany) probes in patients after aneurysmal SAH or severe TBI.

METHODS

Licox and Raumedic probes were implanted side by side in 11 patients after TBI or SAH. ORx and CPPopt were recorded continuously. The equivalence of both probes was examined using Bland-Altman analyses.

RESULTS

The mean difference in ORx was 0.1, with Licox producing higher values. The limits of agreement regarding ORx ranged from -0.6 to +0.7. When both probes' ORx values were compared in each patient, no specific pattern in their relationship was seen. The mean difference in CPPopt was 0 mmHg with limits of agreement between -16.5 and +16.4 mmHg.

CONCLUSIONS

Owing to the rather limited number of patients, we view the results of this study as preliminary. The main result is that Licox and Raumedic showed consistent differences in ORx and CPPopt. Therefore, ORx values of both probes cannot be interchanged and should not be viewed as equivalent. This should be taken into consideration when discussing ORx data generated by different PbrO2 probe types.

Multi frequency phase fluorimetry (MFPF) for oxygen partial pressure measurement: ex vivo validation by polarographic clark-type electrode

Background

Measurement of partial pressure of oxygen (P_O2) at high temporal resolution remains a technological challenge. This study introduces a novel P_O2 sensing technology based on Multi-Frequency Phase Fluorimetry (MFPF). The aim was to validate MFPF against polarographic Clark-type electrode (CTE) P_O2 measurements.

Methodology/Principal Findings

MFPF technology was first investigated in N = 8 anaesthetised pigs at F_IO2 of 0.21, 0.4, 0.6, 0.8 and 1.0. At each F_IO2 level, blood samples were withdrawn and P_O2 was measured in vitro with MFPF using two FOXY-AL300 probes immediately followed by CTE measurement. Secondly, MFPF-P_O2 readings were compared to CTE in an artificial circulatory setup (human packed red blood cells, haematocrit of 30%). The impacts of temperature (20, 30, 40°C) and blood flow (0.8, 1.6, 2.4, 3.2, 4.0 L min⁻¹) on MFPF-P_O2 measurements were assessed. MFPF response time in the gas- and blood-phase was determined. Porcine MFPF-P_O2 ranged from 63 to 749 mmHg; the corresponding CTE samples from 43 to 712 mmHg. Linear regression: CTE = 15.59+1.18*MFPF (R² = 0.93; P<0.0001). Bland Altman analysis: mean_diff 69.2 mmHg, range_diff -50.1/215.6 mmHg, 1.96-SD limits -56.3/194.8 mmHg. In artificial circulatory setup, MFPF-P_O2 ranged from 20 to 567 mmHg and CTE samples from 11 to 575 mmHg. Linear regression: CTE = −8.73+1.05*MFPF (R² = 0.99; P<0.0001). Bland-Altman analysis: mean_diff 6.6 mmHg, range_diff -9.7/20.5 mmHg, 1.96-SD limits -12.7/25.8 mmHg. Differences between MFPF and CTE-P_O2 due to variations of temperature were less than 6 mmHg (range 0–140 mmHg) and less than 35 mmHg (range 140–750 mmHg); differences due to variations in blood flow were less than 15 mmHg (all P-values>0.05). MFPF response-time (monoexponential) was 1.48±0.26 s for the gas-phase and 1.51±0.20 s for the blood-phase.

Conclusions/Significance

MFPF-derived P_O2 readings were reproducible and showed excellent correlation and good agreement with Clark-type electrode-based P_O2 measurements. There was no relevant impact of temperature and blood flow upon MFPF-P_O2 measurements. The response time of the MFPF FOXY-AL300 probe was adequate for real-time sensing in the blood phase.

Position of probe determines prognostic information of brain tissue PO2 in severe traumatic brain injury

BACKGROUND

Monitoring brain tissue PO2 (PbtO2) is part of multimodality monitoring of patients with traumatic brain injury (TBI). However, PbtO2 measurement is a sampling of only a small area of tissue surrounding the sensor tip.

OBJECTIVE

To examine the effect of catheter location on the relationship between PbtO2 and neurological outcome.

METHODS

A total of 405 patients who had PbtO2 monitoring as part of standard management of severe traumatic brain injury were studied. The relationships between probe location and resulting PbtO2 and outcome were examined.

RESULTS

When the probe was located in normal brain, PbtO2 averaged 30.8 ± 18.2 compared with 25.6 ± 14.8 mm Hg when placed in abnormal brain (P < .001). Factors related to neurological outcome in the best-fit logistic regression model were age, PbtO2 probe position, postresuscitation motor Glasgow Coma Scale score, and PbtO2 trend pattern. Although average PbtO2 was significantly related to outcome in univariate analyses, it was not significant in the final logistic model. However, the interaction between PbtO2 and probe position was statistically significant. When the PbtO2 probe was placed in abnormal brain, the average PbtO2 was higher in those with a favorable outcome, 28.8 ± 12.0 mm Hg, compared with those with an unfavorable outcome, 19.5 ± 13.7 mm Hg (P = .01). PbtO2 and outcome were not related when the probe was placed in normal-appearing brain.

CONCLUSION

These results suggest that the location of the PbtO2 probe determines the PbtO2 values and the relationship of PbtO2 to neurological outcome.

Brain tissue oxygen monitoring to assess reperfusion after intra-arterial treatment of aneurysmal subarachnoid hemorrhage-induced cerebral vasospasm: a retrospective study

BACKGROUND AND PURPOSE

Cerebral vasospasm resistant to medical management frequently requires intra-arterial spasmolysis. Angiographic resolution of vasospasm does not provide physiologic data on the adequacy of reperfusion. We recorded pre- and postspasmolysis PbO(2) data in the endovascular suite to determine whether this physiologic parameter could be used to determine when successful reperfusion was established.

MATERIALS AND METHODS

Eight patients with 10 Licox monitors and cerebral vasospasm underwent intra-arterial spasmolysis. Pre- and postspasmolytic PbO(2) was recorded for comparison. Other physiologic parameters, such as CPP, ICP, SaO(2), and Fio(2), were also recorded.

RESULTS

Mean prespasmolysis PbO(2) recordings were 35.2 and 27.3 for the mild-to-moderate and moderate-to-severe vasospasm group, respectively. Mean postspasmolysis PbO(2) increased to 40.3 and 38.4, respectively, which was statistically significant (P < .05) for both groups. In 100% of instances in the moderate-to-severe group and 83% of instances in mild-to-moderate group, the mean PbO(2) increased after spasmolysis and correlated with improvement in angiographic vasospasm. Other physiologic parameters, such as CPP, ICP, SaO(2), and Fio(2), did not show any statistically significant difference before and after spasmolysis.

CONCLUSIONS

PbO(2) monitoring provides the interventionalist with an objective physiologic parameter to determine adequate spasmolysis. Further investigation is needed to establish target PbO(2) rates indicative of adequate reperfusion, which can be used in the endovascular suite.

Brain tissue oxygen monitoring and hyperoxic treatment in patients with traumatic brain injury

Cerebral ischemia is a well-recognized contributor to high morbidity and mortality after traumatic brain injury (TBI). Standard of care treatment aims to maintain a sufficient oxygen supply to the brain by avoiding increased intracranial pressure (ICP) and ensuring a sufficient cerebral perfusion pressure (CPP). Devices allowing direct assessment of brain tissue oxygenation have showed promising results in clinical studies, and their use was implemented in the Brain Trauma Foundation Guidelines for the treatment of TBI patients in 2007. Results of several studies suggest that a brain tissue oxygen-directed therapy guided by these monitors may contribute to reduced mortality and improved outcome of TBI patients. Whether increasing the oxygen supply to supraphysiological levels has beneficial or detrimental effects on TBI patients has been a matter of debate for decades. The results of trials of hyperbaric oxygenation (HBO) have failed to show a benefit, but renewed interest in normobaric hyperoxia (NBO) in the treatment of TBI patients has emerged in recent years. With the increased availability of advanced neuromonitoring devices such as brain tissue oxygen monitors, it was shown that some patients might benefit from this therapeutic approach. In this article, we review the pathophysiological rationale and technical modalities of brain tissue oxygen monitors, as well as its use in studies of brain tissue oxygen-directed therapy. Furthermore, we analyze hyperoxia as a treatment option in TBI patients, summarize the results of clinical trials, and give insights into the recent findings of hyperoxic effects on cerebral metabolism after TBI.