Normobaric hyperoxia--induced improvement in cerebral metabolism and reduction in intracranial pressure in patients with severe head injury: a prospective historical cohort-matched study

Post-traumatic hyperoxia after pediatric TBI

OBJECTIVE

Hyperoxia has been suggested as a mechanism for secondary injury following adult traumatic brain injury (TBI), but its effects have not been well described in pediatric patients.

METHODS

Pediatric (≤18yo) TBI patients were identified in a prospective institutional registry from October 2008 to April 2022. The first, highest, and the Area Under the Curve (AUC) PaO2 in the first 24 hours were collected and calculated for each patient from arterial blood gas reports after admission to the ICU. Neurological outcome after 6 months was measured using dichotomized modified Rankin Scale (mRS) and Glasgow Outcome Scale - Extended (GOS-E). Multivariable logistic regression models were used to determine if the three measurements for hyperoxia predicted an unfavorable outcome after controlling for well-established clinical and imaging predictors of outcome.

RESULTS

We identified 98 pediatric patients with severe accidental TBI during the study period. Hyperoxia (PaO2 > 300 mmHg) occurred in 33% of the patients. The presence of elevated PaO2 values, determined by all three evaluations of hyperoxia, was not associated with unfavorable outcome after 6 months.

CONCLUSION

Utilizing multiple methods to assess exposure, hyperoxia was present in a substantial number of patients with severe TBI but was not associated with an unfavorable outcome.

Review of evidence for treatments of acute non arteritic anterior ischemic optic neuropathy

OBJECTIVE

To review treatment modalities that have been studied in acute non arteritic anterior ischemic optic neuropathy (NAION).

METHODS

We performed a comprehensive literature search of English language publications in the last 5 years, with human species and NAION. Articles were reviewed to identify those that described original research on treatment of acute NAION. Study type, setting, duration, interventions, and results were extracted and articles were reviewed for biases and limitations.

RESULTS

We identified 22 kinds of treatment varying by compound and modality. These include topical, intravitreal, and systemic drugs as well as surgical approaches. Evidence for efficacy ranges from expert opinion to randomized control trials.

CONCLUSIONS

Although several treatments are utilized in practice, none of these have high quality evidence of efficacy to improve visual outcomes.  Continued collaborative research is necessary to complete high quality studies in order identify effective therapies for this rare and blinding disease.

Brain tissue oxygen combined with intracranial pressure monitoring versus isolated intracranial pressure monitoring in patients with traumatic brain injury: an updated systematic review and meta-analysis

Monitoring intracranial pressure (ICP) is pivotal in the management of severe traumatic brain injury (TBI), but secondary brain injuries can arise despite normal ICP levels. Cerebral tissue oxygenation monitoring (PbtO2) may detect neuronal tissue infarction thresholds, enhancing neuroprotection. We performed a systematic review and meta-analysis to evaluate the effects of combined cerebral tissue oxygenation (PbtO2) and ICP compared to isolated ICP monitoring in patients with TBI. PubMed, Embase, Cochrane, and Web of Sciences databases were searched for trials published up to June 2023. A total of 16 studies comprising 37,820 patients were included. ICP monitoring was universal, with additional placement of PbtO2 in 2222 individuals (5.8%). The meta-analysis revealed a reduction in mortality (OR 0.57, 95% CI 0.37-0.89, p = 0.01), a greater likelihood of favorable outcomes (OR 2.28, 95% CI 1.66-3.14, p < 0.01), and a lower chance of poor outcomes (OR 0.51, 95% CI 0.34-0.79, p < 0.01) at 6 months for the PbtO2 plus ICP group. However, these patients experienced a longer length of hospital stay (MD 2.35, 95% CI 0.50-4.20, p = 0.01). No significant difference was found in hospital mortality rates (OR 0.81, 95% CI 0.61-1.08, p = 0.16) or intensive care unit length of stay (MD 2.46, 95% CI - 0.11-5.04, p = 0.06). The integration of PbtO2 to ICP monitoring improved mortality outcomes and functional recovery at 6 months in patients with TBI. PROSPERO (International Prospective Register of Systematic Reviews) CRD42022383937; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=383937.

The Effect of Early Severe Hyperoxia in Adults Intubated in the Prehosptial Setting or Emergency Department: A Scoping Review

BACKGROUND

The detrimental effects of hyperoxia exposure have been well-described in patients admitted to intensive care units. However, data evaluating the effects of short-term, early hyperoxia exposure in patients intubated in the prehospital setting or emergency department (ED) have not been systematically reviewed.

OBJECTIVE

Our aim was to quantify and describe the existing literature examining the clinical outcomes in ED patients exposed to hyperoxia within the first 24 h of mechanical ventilation.

METHODS

This review was performed in concordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for scoping reviews. Two rounds of review using Rayyan QCRI software were performed for title and abstract screening and full-text search. Of the 2739 articles, 27 articles were retrieved after initial screening, of which 5 articles were excluded during the full-text screening, leaving 22 articles for final review and data extraction.

RESULTS

Of 22 selected publications, 9 described patients with traumatic brain injury, 6 with cardiac arrest, 3 with multisystem trauma, 1 with stroke, 2 with septic shock, and 1 was heterogeneous. Three studies were randomized controlled trials. The available data have widely heterogeneous definitions of hyperoxia exposure, outcomes, and included populations, limiting conclusions.

CONCLUSIONS

There is a paucity of data that examined the effects of severe hyperoxia exposure in the acute, post-intubation phase of the prehospital and ED settings. Further research with standardized definitions is needed to provide more detailed guidance regarding early oxygen titration in intubated patients.

The Impact of Invasive Brain Oxygen Pressure Guided Therapy on the Outcome of Patients with Traumatic Brain Injury: A Systematic Review and Meta-Analysis

Traumatic brain injury (TBI) is a major public health burden, causing death and disability worldwide. Intracranial hypertension and brain hypoxia are the main mechanisms of secondary brain injury. As such, management strategies guided by intracranial pressure (ICP) and brain oxygen (PbtO₂) monitoring could improve the prognosis of these patients. Our objective was to summarize the current evidence regarding the impact of PbtO₂-guided therapy on the outcome of patients with TBI. We performed a systematic search of PubMed, Scopus, and the Cochrane library databases, following the protocol registered in PROSPERO. Only studies comparing PbtO₂/ICP-guided therapy with ICP-guided therapy were selected. Primary outcome was neurological outcome at 3 and 6 months assessed by using the Glasgow Outcome Scale; secondary outcomes included hospital and long-term mortality, burden of intracranial hypertension, and brain tissue hypoxia. Out of 6254 retrieved studies, 15 studies (n = 37,245 patients, of who 2184 received PbtO₂-guided therapy) were included in the final analysis. When compared with ICP-guided therapy, the use of combined PbO₂/ICP-guided therapy was associated with a higher probability of favorable neurological outcome (odds ratio 2.21 [95% confidence interval 1.72-2.84]) and of hospital survival (odds ratio 1.15 [95% confidence interval 1.04-1.28]). The heterogeneity (I²) of the studies in each analysis was below 40%. However, the quality of evidence was overall low to moderate. In this meta-analysis, PbtO₂-guided therapy was associated with reduced mortality and more favorable neurological outcome in patients with TBI. The low-quality evidence underlines the need for the results from ongoing phase III randomized trials.

The Impact of Short-Term Hyperoxia on Cerebral Metabolism: A Systematic Review and Meta-Analysis

BACKGROUND

Cerebral ischemia due to hypoxia is a major cause of secondary brain injury and is associated with higher morbidity and mortality in patients with acute brain injury. Hyperoxia could improve energetic dysfunction in the brain in this setting. Our objectives were to perform a systematic review and meta-analysis of the current literature and to assess the impact of normobaric hyperoxia on brain metabolism by using cerebral microdialysis.

METHODS

We searched Medline and Scopus, following the recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement; we searched for retrospective and prospective observational studies, interventional studies, and randomized clinical trials that performed a hyperoxia challenge in patients with acute brain injury who were concomitantly monitored with cerebral microdialysis. This study was registered in PROSPERO (CRD420211295223).

RESULTS

We included a total of 17 studies, with a total of 311 patients. A statistically significant reduction in cerebral lactate values (pooled standardized mean difference [SMD] - 0.38 [- 0.53 to - 0.23]) and lactate to pyruvate ratio values (pooled SMD - 0.20 [- 0.35 to - 0.05]) was observed after hyperoxia. However, glucose levels (pooled SMD - 0.08 [- 0.23 to 0.08]) remained unchanged after hyperoxia.

CONCLUSIONS

Normobaric hyperoxia may improve cerebral metabolic disturbances in patients with acute brain injury. The clinical impact of such effects needs to be further elucidated.

Monitoring Neurochemistry in Traumatic Brain Injury Patients Using Microdialysis Integrated with Biosensors: A Review

In a traumatically injured brain, the cerebral microdialysis technique allows continuous sampling of fluid from the brain’s extracellular space. The retrieved brain fluid contains useful metabolites that indicate the brain’s energy state. Assessment of these metabolites along with other parameters, such as intracranial pressure, brain tissue oxygenation, and cerebral perfusion pressure, may help inform clinical decision making, guide medical treatments, and aid in the prognostication of patient outcomes. Currently, brain metabolites are assayed on bedside analysers and results can only be achieved hourly. This is a major drawback because critical information within each hour is lost. To address this, recent advances have focussed on developing biosensing techniques for integration with microdialysis to achieve continuous online monitoring. In this review, we discuss progress in this field, focusing on various types of sensing devices and their ability to quantify specific cerebral metabolites at clinically relevant concentrations. Important points that require further investigation are highlighted, and comments on future perspectives are provided.

Monitoring Spinal Cord Tissue Oxygen in Patients With Acute, Severe Traumatic Spinal Cord Injuries

Objectives

To determine the feasibility of monitoring tissue oxygen tension from the injury site (psctO2) in patients with acute, severe traumatic spinal cord injuries.

Design

We inserted at the injury site a pressure probe, a microdialysis catheter, and an oxygen electrode to monitor for up to a week intraspinal pressure (ISP), spinal cord perfusion pressure (SCPP), tissue glucose, lactate/pyruvate ratio (LPR), and psctO2. We analyzed 2,213 hours of such data. Follow-up was 6-28 months postinjury.

Setting

Single-center neurosurgical and neurocritical care units.

Subjects

Twenty-six patients with traumatic spinal cord injuries, American spinal injury association Impairment Scale A-C. Probes were inserted within 72 hours of injury.

Interventions

Insertion of subarachnoid oxygen electrode (Licox; Integra LifeSciences, Sophia-Antipolis, France), pressure probe, and microdialysis catheter.

Measurements and Main Results

psctO2 was significantly influenced by ISP (psctO2 26.7 +/- 0.3 mm Hg at ISP > 10 mmHg vs psctO2 22.7 +/- 0.8 mm Hg at ISP <= 10 mm Hg), SCPP (psctO2 26.8 +/- 0.3 mm Hg at SCPP < 90 mm Hg vs psctO2 32.1 +/- 0.7 mm Hg at SCPP >= 90 mm Hg), tissue glucose (psctO2 26.8 +/- 0.4 mm Hg at glucose < 6 mM vs 32.9 +/- 0.5 mm Hg at glucose >= 6 mM), tissue LPR (psctO2 25.3 +/- 0.4 mm Hg at LPR > 30 vs psctO2 31.3 +/- 0.3 mm Hg at LPR <= 30), and fever (psctO2 28.8 +/- 0.5 mm Hg at cord temperature 37-38[degrees]C vs psctO2 28.7 +/- 0.8 mm Hg at cord temperature >= 39[degrees]C). Tissue hypoxia also occurred independent of these factors. Increasing the FIO2 by 0.48 increases psctO2 by 71.8% above baseline within 8.4 minutes. In patients with motor-incomplete injuries, fluctuations in psctO2 correlated with fluctuations in limb motor score. The injured cord spent 11% (39%) hours at psctO2 less than 5 mm Hg (< 20 mm Hg) in patients with motor-complete outcomes, compared with 1% (30%) hours at psctO2 less than 5 mm Hg (< 20 mm Hg) in patients with motor-incomplete outcomes. Complications were cerebrospinal fluid leak (5/26) and wound infection (1/26).

Conclusions

This study lays the foundation for measuring and altering spinal cord oxygen at the injury site. Future studies are required to investigate whether this is an effective new therapy.

Blood-Brain Barrier Mechanisms in Stroke and Trauma

The brain microenvironment is tightly regulated. The blood-brain barrier (BBB), which is composed of cerebral endothelial cells, astrocytes, and pericytes, plays an important role in maintaining the brain homeostasis by regulating the transport of both beneficial and detrimental substances between circulating blood and brain parenchyma. After brain injury and disease, BBB tightness becomes dysregulated, thus leading to inflammation and secondary brain damage. In this chapter, we overview the fundamental mechanisms of BBB damage and repair after stroke and traumatic brain injury (TBI). Understanding these mechanisms may lead to therapeutic opportunities for brain injury.

The Impact of Hyperoxia Treatment on Neurological Outcomes and Mortality in Moderate to Severe Traumatic Brain Injured Patients

Background

Traumatic brain injury is a leading cause of morbidity and mortality worldwide. The relationship between hyperoxia and outcomes in patients with TBI remains controversial. We assessed the effect of persistent hyperoxia on the neurological outcomes and survival of critically ill patients with moderate-severe TBI.

Method

This was a retrospective cohort study of all adults with moderate-severe TBI admitted to the ICU between 1st January 2016 and 31st December 2019 and who required invasive mechanical ventilation. Arterial blood gas data was recorded within the first 3 hours of intubation and then after 6-12 hours and 24-48 hours. The patients were divided into two categories: Group I had a PaO2 < 120mmHg on at least two ABGs undertaken in the first twelve hours post intubation and Group II had a PaO2 ≥ 120mmHg on at least two ABGs in the same period. Multivariable logistic regression was performed to assess predictors of hospital mortality and good neurologic outcome (Glasgow outcome score ≥ 4).

Results

The study included 309 patients: 54.7% (n=169) in Group I and 45.3% (n=140) in Group II. Hyperoxia was not associated with increased mortality in the ICU (20.1% vs. 17.9%, p=0.62) or hospital (20.7% vs. 17.9%, p=0.53), moreover, the hospital discharge mean (SD) Glasgow Coma Scale (11.0(5.1) vs. 11.2(4.9), p=0.70) and mean (SD) Glasgow Outcome Score (3.1(1.3) vs. 3.1(1.2), p=0.47) were similar. In multivariable logistic regression analysis, persistent hyperoxia was not associated with increased mortality (adjusted odds ratio [aOR] 0.71, 95% CI 0.34-1.35, p=0.29). PaO2 within the first 3 hours was also not associated with mortality: 121-200mmHg: aOR 0.58, 95% CI 0.23-1.49, p=0.26; 201-300mmHg: aOR 0.66, 95% CI 0.27-1.59, p=0.35; 301-400mmHg: aOR 0.85, 95% CI 0.31-2.35, p=0.75 and >400mmHg: aOR 0.51, 95% CI 0.18-1.44, p=0.20; reference: PaO2 60-120mmHg within 3 hours. However, hyperoxia >400mmHg was associated with being less likely to have good neurological (GOS ≥4) outcome on hospital discharge (aOR 0.36, 95% CI 0.13-0.98, p=0.046; reference: PaO2 60-120mmHg within 3 hours.

Conclusion

In intubated patients with moderate-severe TBI, hyperoxia in the first 48 hours was not independently associated with hospital mortality. However, PaO2 >400mmHg may be associated with a worse neurological outcome on hospital discharge.

Inhalational Gases for Neuroprotection in Traumatic Brain Injury

Despite multiple prior pharmacological trials in traumatic brain injury (TBI), the search for an effective, safe, and practical treatment of these patients remains ongoing. Given the ease of delivery and rapid absorption into the systemic circulation, inhalational gases that have neuroprotective properties will be an invaluable resource in the clinical management of TBI patients. In this review, we perform a systematic review of both pre-clinical and clinical reports describing inhalational gas therapy in the setting of TBI. Hyperbaric oxygen, which has been investigated for many years, and some of the newest developments are reviewed. Also, promising new therapies such as hydrogen gas, hydrogen sulfide gas, and nitric oxide are discussed. Moreover, novel therapies such as xenon and argon gases and delivery methods using microbubbles are explored.

Association of Flow Rate of Prehospital Oxygen Administration and Clinical Outcomes in Severe Traumatic Brain Injury

The goal of this study was to investigate the association of prehospital oxygen administration flow with clinical outcome in severe traumatic brain injury (TBI) patients. This was a cross-sectional observational study using an emergency medical services-assessed severe trauma database in South Korea. The sample included adult patients with severe blunt TBI without hypoxia who were treated by EMS providers in 2013 and 2015. Main exposure was prehospital oxygen administration flow rate (no oxygen, low-flow 1~5, mid-flow 6~14, high-flow 15 L/min). Primary outcome was in-hospital mortality. A total of 1842 patients with severe TBI were included. The number of patients with no oxygen, low-flow oxygen, mid-flow oxygen, high-flow oxygen was 244, 573, 607, and 418, respectively. Mortality of each group was 34.8%, 32.3%, 39.9%, and 41.1%, respectively. Compared with the no-oxygen group, adjusted odds (95% CI) for mortality in the low-, mid-, and high-flow oxygen groups were 0.86 (0.62-1.20), 1.15 (0.83-1.60), and 1.21 (0.83-1.73), respectively. In the interaction analysis, low-flow oxygen showed lower mortality when prehospital saturation was 94-98% (adjusted odds ratio (AOR): 0.80 (0.67-0.95)) and ≥99% (AOR: 0.69 (0.53-0.91)). High-flow oxygen showed higher mortality when prehospital oxygen saturation was ≥99% (AOR: 1.33 (1.01~1.74)). Prehospital low-flow oxygen administration was associated with lower in-hospital mortality compared with the no-oxygen group. High-flow administration showed higher mortality.

Association Between Hyperoxia, Supplemental Oxygen, and Mortality in Critically Injured Patients

Supplemental Digital Content is available in the text.

OBJECTIVES:

Hyperoxia is common among critically ill patients and may increase morbidity and mortality. However, limited evidence exists for critically injured patients. The objective of this study was to determine the association between hyperoxia and in-hospital mortality in adult trauma patients requiring ICU admission.

DESIGN, SETTING, AND PARTICIPANTS:

This multicenter, retrospective cohort study was conducted at two level I trauma centers and one level II trauma center in CO between October 2015 and June 2018. All adult trauma patients requiring ICU admission within 24 hours of emergency department arrival were eligible. The primary exposure was oxygenation during the first 7 days of hospitalization.

INTERVENTIONS:

None.

MEASUREMENTS AND MAIN RESULTS:

Primary outcome was in-hospital mortality. Secondary outcomes were hospital-free days and ventilator-free days. We included 3,464 critically injured patients with a mean age of 52.6 years. Sixty-five percent were male, and 66% had blunt trauma mechanism of injury. The primary outcome of in-hospital mortality occurred in 264 patients (7.6%). Of 226,057 patient-hours, 46% were spent in hyperoxia (oxygen saturation > 96%) and 52% in normoxia (oxygen saturation 90–96%). During periods of hyperoxia, the adjusted risk for mortality was higher with greater oxygen administration. At oxygen saturation of 100%, the adjusted risk scores for mortality (95% CI) at Fio₂ of 100%, 80%, 60%, and 50% were 6.4 (3.5–11.8), 5.4 (3.4–8.6), 2.7 (1.7–4.1), and 1.5 (1.1–2.2), respectively. At oxygen saturation of 98%, the adjusted risk scores for mortality (95% CI) at Fio₂ of 100%, 80%, 60%, and 50% were 7.7 (4.3–13.5), 6.3 (4.1–9.7), 3.2 (2.2–4.8), and 1.9 (1.4–2.7), respectively.

CONCLUSIONS:

During hyperoxia, higher oxygen administration was independently associated with a greater risk of mortality among critically injured patients. Level of evidence: Cohort study, level III.

Hyperoxemia during resuscitation of trauma patients and increased intensive care unit length of stay: inverse probability of treatment weighting analysis

Background

Information on hyperoxemia among patients with trauma has been limited, other than traumatic brain injuries. This study aimed to elucidate whether hyperoxemia during resuscitation of patients with trauma was associated with unfavorable outcomes.

Methods

A post hoc analysis of a prospective observational study was carried out at 39 tertiary hospitals in 2016–2018 in adult patients with trauma and injury severity score (ISS) of > 15. Hyperoxemia during resuscitation was defined as PaO₂ of ≥ 300 mmHg on hospital arrival and/or 3 h after arrival. Intensive care unit (ICU)-free days were compared between patients with and without hyperoxemia. An inverse probability of treatment weighting (IPW) analysis was conducted to adjust patient characteristics including age, injury mechanism, comorbidities, vital signs on presentation, chest injury severity, and ISS. Analyses were stratified with intubation status at the emergency department (ED). The association between biomarkers and ICU length of stay were then analyzed with multivariate models.

Results

Among 295 severely injured trauma patients registered, 240 were eligible for analysis. Patients in the hyperoxemia group (n = 58) had shorter ICU-free days than those in the non-hyperoxemia group [17 (10–21) vs 23 (16–26), p < 0.001]. IPW analysis revealed the association between hyperoxemia and prolonged ICU stay among patients not intubated at the ED [ICU-free days = 16 (12–22) vs 23 (19–26), p = 0.004], but not among those intubated at the ED [18 (9–20) vs 15 (8–23), p = 0.777]. In the hyperoxemia group, high inflammatory markers such as soluble RAGE and HMGB-1, as well as low lung-protective proteins such as surfactant protein D and Clara cell secretory protein, were associated with prolonged ICU stay.

Conclusions

Hyperoxemia until 3 h after hospital arrival was associated with prolonged ICU stay among severely injured trauma patients not intubated at the ED.

Trial registration

UMIN-CTR, UMIN000019588. Registered on November 15, 2015.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13017-021-00363-2.

How much oxygen for the injured brain - can invasive parenchymal catheters help?

PURPOSE OF REVIEW

Each year in the United States there are over 2.5 million visits to emergency departments for traumatic brain injury (TBI), 300,000 hospitalizations, and 50,000 deaths. TBI initiates a complex cascade of events which can lead to significant secondary brain damage. Great interest exists in directly measuring cerebral oxygen delivery and demand after TBI to prevent this secondary injury. Several invasive, catheter-based devices are now available which directly monitor the partial pressure of oxygen in brain tissue (PbtO2), yet significant equipoise exists regarding their clinical use in severe TBI.

RECENT FINDINGS

There are currently three ongoing multicenter randomized controlled trials studying the use of PbtO2 monitoring in severe TBI: BOOST-3, OXY-TC, and BONANZA. All three have similar inclusion/exclusion criteria, treatment protocols, and outcome measures. Despite mixed existing evidence, use of PbtO2 is already making its way into new TBI guidelines such as the recent Seattle International Brain Injury Consensus Conference. Analysis of high-fidelity data from multimodal monitoring, however, suggests that PbtO2 may only be one piece of the puzzle in severe TBI.

SUMMARY

While current evidence regarding the use of PbtO2 remains mixed, three ongoing clinical trials are expected to definitively answer the question of what role PbtO2 monitoring plays in severe TBI.

Fine Tuning of Traumatic Brain Injury Management in Neurointensive Care-Indicative Observations and Future Perspectives

Neurointensive care (NIC) has contributed to great improvements in clinical outcomes for patients with severe traumatic brain injury (TBI) by preventing, detecting, and treating secondary insults and thereby reducing secondary brain injury. Traditional NIC management has mainly focused on generally applicable escalated treatment protocols to avoid high intracranial pressure (ICP) and to keep the cerebral perfusion pressure (CPP) at sufficiently high levels. However, TBI is a very heterogeneous disease regarding the type of injury, age, comorbidity, secondary injury mechanisms, etc. In recent years, the introduction of multimodality monitoring, including, e.g., pressure autoregulation, brain tissue oxygenation, and cerebral energy metabolism, in addition to ICP and CPP, has increased the understanding of the complex pathophysiology and the physiological effects of treatments in this condition. In this article, we will present some potential future approaches for more individualized patient management and fine-tuning of NIC, taking advantage of multimodal monitoring to further improve outcome after severe TBI.

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.

The Association Between Arterial Oxygen Level and Outcome in Neurocritically Ill Patients is not Affected by Blood Pressure

Background

In neurocritically ill patients, one early mechanism behind secondary brain injury is low systemic blood pressure resulting in inadequate cerebral perfusion and consequent hypoxia. Intuitively, higher partial pressures of arterial oxygen (PaO₂) could be protective in case of inadequate cerebral circulation related to hemodynamic instability.

Study purpose

We examined whether the association between PaO₂ and mortality is different in patients with low compared to normal and high mean arterial pressure (MAP) in patients after various types of brain injury.

Methods

We screened the Finnish Intensive Care Consortium database for mechanically ventilated adult (≥ 18) brain injury patients treated in several tertiary intensive care units (ICUs) between 2003 and 2013. Admission diagnoses included traumatic brain injury, cardiac arrest, subarachnoid and intracranial hemorrhage, and acute ischemic stroke. The primary exposures of interest were PaO₂ (recorded in connection with the lowest measured PaO₂/fraction of inspired oxygen ratio) and the lowest MAP, recorded during the first 24 h in the ICU. PaO₂ was grouped as follows: hypoxemia (< 8.2 kPa, the lowest 10th percentile), normoxemia (8.2–18.3 kPa), and hyperoxemia (> 18.3 kPa, the highest 10th percentile), and MAP was divided into equally sized tertiles (< 60, 60–68, and > 68 mmHg). The primary outcome was 1-year mortality. We tested the association between hyperoxemia, MAP, and mortality with a multivariable logistic regression model, including the PaO₂, MAP, and interaction of PaO₂*MAP, adjusting for age, admission diagnosis, premorbid physical performance, vasoactive use, intracranial pressure monitoring use, and disease severity. The relationship between predicted 1-year mortality and PaO₂ was visualized with locally weighted scatterplot smoothing curves (Loess) for different MAP levels.

Results

From a total of 8290 patients, 3912 (47%) were dead at 1 year. PaO₂ was not an independent predictor of mortality: the odds ratio (OR) for hyperoxemia was 1.16 (95% CI 0.85–1.59) and for hypoxemia 1.24 (95% CI 0.96–1.61) compared to normoxemia. Higher MAP predicted lower mortality: OR for MAP 60–68 mmHg was 0.73 (95% CI 0.64–0.84) and for MAP > 68 mmHg 0.80 (95% CI 0.69–0.92) compared to MAP < 60 mmHg. The interaction term PaO₂*MAP was nonsignificant. In Loess visualization, the relationship between PaO₂ and predicted mortality appeared similar in all MAP tertiles.

Conclusions

During the first 24 h of ICU treatment in mechanically ventilated brain injured patients, the association between PaO₂ and mortality was not different in patients with low compared to normal MAP.

Supplementary Information

The online version of this article (10.1007/s12028-020-01178-w) contains supplementary material, which is available to authorized users.

Early hyperoxemia is associated with lower adjusted mortality after severe trauma: results from a French registry

BACKGROUND

Hyperoxemia has been associated with increased mortality in critically ill patients, but little is known about its effect in trauma patients. The objective of this study was to assess the association between early hyperoxemia and in-hospital mortality after severe trauma. We hypothesized that a PaO2 ≥ 150 mmHg on admission was associated with increased in-hospital mortality.

METHODS

Using data issued from a multicenter prospective trauma registry in France, we included trauma patients managed by the emergency medical services between May 2016 and March 2019 and admitted to a level I trauma center. Early hyperoxemia was defined as an arterial oxygen tension (PaO2) above 150 mmHg measured on hospital admission. In-hospital mortality was compared between normoxemic (150 > PaO2 ≥ 60 mmHg) and hyperoxemic patients using a propensity-score model with predetermined variables (gender, age, prehospital heart rate and systolic blood pressure, temperature, hemoglobin and arterial lactate, use of mechanical ventilation, presence of traumatic brain injury (TBI), initial Glasgow Coma Scale score, Injury Severity Score (ISS), American Society of Anesthesiologists physical health class > I, and presence of hemorrhagic shock).

RESULTS

A total of 5912 patients were analyzed. The median age was 39 [26-55] years and 78% were male. More than half (53%) of the patients had an ISS above 15, and 32% had traumatic brain injury. On univariate analysis, the in-hospital mortality was higher in hyperoxemic patients compared to normoxemic patients (12% versus 9%, p < 0.0001). However, after propensity score matching, we found a significantly lower in-hospital mortality in hyperoxemic patients compared to normoxemic patients (OR 0.59 [0.50-0.70], p < 0.0001).

CONCLUSION

In this large observational study, early hyperoxemia in trauma patients was associated with reduced adjusted in-hospital mortality. This result contrasts the unadjusted in-hospital mortality as well as numerous other findings reported in acutely and critically ill patients. The study calls for a randomized clinical trial to further investigate this association.

Arterial Oxygenation in Traumatic Brain Injury-Relation to Cerebral Energy Metabolism, Autoregulation, and Clinical Outcome

Background:

Ischemic and hypoxic secondary brain insults are common and detrimental in traumatic brain injury (TBI). Treatment aims to maintain an adequate cerebral blood flow with sufficient arterial oxygen content. It has been suggested that arterial hyperoxia may be beneficial to the injured brain to compensate for cerebral ischemia, overcome diffusion barriers, and improve mitochondrial function. In this study, we investigated the relation between arterial oxygen levels and cerebral energy metabolism, pressure autoregulation, and clinical outcome.

Methods:

This retrospective study was based on 115 patients with severe TBI treated in the neurointensive care unit, Uppsala university hospital, Sweden, 2008 to 2018. Data from cerebral microdialysis (MD), arterial blood gases, hemodynamics, and intracranial pressure were analyzed the first 10 days post-injury. The first day post-injury was studied in particular.

Results:

Arterial oxygen levels were higher and with greater variability on the first day post-injury, whereas it was more stable the following 9 days. Normal-to-high mean pO₂ was significantly associated with better pressure autoregulation/lower pressure reactivity index (P = .02) and lower cerebral MD-lactate (P = .04) on day 1. Patients with limited cerebral energy metabolic substrate supply (MD-pyruvate below 120 µM) and metabolic disturbances with MD-lactate-/pyruvate ratio (LPR) above 25 had significantly lower arterial oxygen levels than those with limited MD-pyruvate supply and normal MD-LPR (P = .001) this day. Arterial oxygenation was not associated with clinical outcome.

Conclusions:

Maintaining a pO₂ above 12 kPa and higher may improve oxidative cerebral energy metabolism and pressure autoregulation, particularly in cases of limited energy substrate supply in the early phase of TBI. Evaluating the cerebral energy metabolic profile could yield a better patient selection for hyperoxic treatment in future trials.

Brain Tissue Oxygen Response as Indicator for Cerebral Lactate Levels in Aneurysmal Subarachnoid Hemorrhage Patients

BACKGROUND

Early detection of cerebral ischemia and metabolic crisis is crucial in critically ill subarachnoid hemorrhage (SAH) patients. Variable increases in brain tissue oxygen tension (PbtO2) are observed when the fraction of inspired oxygen (FiO2) is increased to 1.0. The aim of this prospective study was to evaluate whether a 3-minute hyperoxic challenge can identify patients at risk for cerebral ischemia detected by cerebral microdialysis.

METHODS

Twenty consecutive severe SAH patients undergoing continuous cerebral PbtO2 and microdialysis monitoring were included. FiO2 was increased to 1.0 for 3 minutes (the FiO2 challenge) twice a day and PbtO2 responses during the FiO2 challenges were related to cerebral microdialysis-measures, ie, lactate, the lactate-pyruvate ratio, and glycerol. Multivariable linear and logistic regression models were created for each outcome parameter.

RESULTS

After predefined exclusions, 274 of 400 FiO2 challenges were included in the analysis. Lower absolute increases in PbtO2 ([INCREMENT]PbtO2) during FiO2 challenges were significantly associated with higher cerebral lactate concentration (P<0.001), and patients were at higher risk for ischemic lactate levels >4 mmol/L (odds ratio 0.947; P=0.04). Median (interquartile range) [INCREMENT]PbtO2 was 7.1 (4.6 to 12.17) mm Hg when cerebral lactate was >4 mmol/L and 10.2 (15.76 to 14.24) mm Hg at normal lactate values (≤4 mmol/L). Median [INCREMENT]PbtO2 was significantly lower during hypoxic than during hyperglycolytic lactate elevations (4.6 vs. 10.6 mm Hg, respectively; P<0.001). Lactate-pyruvate ratio and glycerol levels were mainly determined by baseline characteristics.

CONCLUSIONS

A 3-minute FiO2 challenge is an easy to perform and feasible bedside diagnostic tool in SAH patients. The absolute increase in PbtO2 during the FiO2 challenge might be a useful surrogate marker to estimate cerebral lactate concentrations and might be used to identify patients at risk for impending ischemia.

Systematic review of oxygenation and clinical outcomes to inform oxygen targets in critically ill trauma patients

BACKGROUND

Oxygen therapy is frequently administered to critically ill trauma patients to avoid hypoxia, but optimal oxygenation strategies are not clear.

METHODS

We conducted a systematic review of oxygen targets and clinical outcomes in trauma and critically ill patients. We searched Ovid MEDLINE, Cochrane Library, Embase, and Web of Science Core Collection from 1946 through 2017. Our initial search yielded 14,774 articles with 209 remaining after abstract review. We reviewed full text articles of human subjects with conditions of interest, an oxygen exposure or measurement, and clinical outcomes, narrowing the review to 43 articles. We assessed article quality using Grading of Recommendation, Assessment, Development, and Evaluation (GRADE) criteria.

RESULTS

Of the 43 final studies meeting inclusions criteria, 17 focused on trauma and 26 studies focused on medical and/or surgical critical illness without trauma specifically. Four trauma studies supported lower oxygenation/normoxia, two supported higher oxygenation, and 11 supported neither normoxia nor higher oxygenation (five neutral and six supported avoidance of hypoxia). Fifteen critical illness studies supported lower oxygenation/normoxia, one supported higher oxygenation, and 10 supported neither normoxia nor higher oxygenation (nine neutral and one supported avoidance of hypoxia). We identified seven randomized controlled trials (four high quality, three moderate quality). Of the high-quality randomized controlled trials (none trauma-related), one supported lower oxygenation/normoxia and three were neutral. Of the moderate-quality randomized controlled trials (one trauma-related), one supported higher oxygenation, one was neutral, and one supported avoidance of hypoxia.

CONCLUSION

We identified few trauma-specific studies beyond traumatic brain injury; none were high quality. Extrapolating primarily from nontrauma critical illness, reduced oxygen administration targeting normoxia in critically ill trauma patients may result in better or equivalent clinical outcomes. Additional trauma-specific trials are needed to determine the optimal oxygen strategy in critically injured patients.

LEVEL OF EVIDENCE

Systematic review, level IV.

Matching early arterial oxygenation to long-term outcome in severe traumatic brain injury: target values

OBJECTIVE

The aim of this study was to examine the relationship between early arterial oxygenation thresholds and long-term outcome after severe traumatic brain injury (TBI).

METHODS

In a post hoc analysis of a randomized trial, adults with severe TBI were classified based on exposure to different levels of arterial oxygenation as measured using the average of arterial partial pressure of oxygen (PaO2) values obtained within 24 hours of admission. Potentially important PaO2 thresholds were defined a priori. The primary outcome was Glasgow Outcome Scale-Extended (GOSE) score at 6 months. Secondary outcomes were cognitive outcomes measured using a battery of 9 neuropsychological tests administered at 6 months, and 6-month mortality.

RESULTS

In adjusted analyses, oxygenation thresholds of 150 and 200 mm Hg were associated with better functional outcome at 6 months (adjusted OR for better functional outcome on GOSE 1.82 [95% CI 1.12-2.94] and 1.59 [95% CI 1.06-2.37], respectively) and improved cognitive outcome at 6 months (adjusted beta coefficients for better cognitive percentile across 9 neuropsychological tests: 6.9 [95% CI 1.3-12.5] and 6.8 [95% CI 2.4-11.3], respectively). There was no significant association between oxygenation level and 6-month mortality except at a PaO2 threshold of 200 mm Hg (OR for death 0.36, 95% CI 0.18-0.71). Higher or lower oxygenation thresholds were not associated with functional or cognitive outcome.

CONCLUSIONS

In this observational study, the relationship between early arterial oxygenation and long-term functional and cognitive TBI outcomes appears to be U-shaped. Mild levels of hyperoxemia within the first 24 hours after injury were associated with better long-term functional and cognitive outcomes. These findings highlight the importance of examining balanced oxygen supplementation as a potential strategy to improve TBI outcomes in future research.

Minimal PaO2 threshold after traumatic brain injury and clinical utility of a novel brain oxygenation ratio

OBJECTIVE

Avoiding decreases in brain tissue oxygenation (PbtO2) after traumatic brain injury (TBI) is important. How best to adjust PbtO2 remains unclear. The authors investigated the association between partial pressure of oxygen (PaO2) and PbtO2 to determine the minimal PaO2 required to maintain PbtO2 above the hypoxic threshold (> 20 mm Hg), accounting for other determinants of PbtO2 and repeated measurements in the same patient. They also explored the clinical utility of a novel concept, the brain oxygenation ratio (BOx ratio = PbtO2/PaO2) to detect overtreatment with the fraction of inspired oxygen (FiO2).

METHODS

A retrospective cohort study at an academic level 1 trauma center included 38 TBI patients who required the insertion of a monitor to measure PbtO2. Various determinants of PbtO2 were collected simultaneously whenever a routine arterial blood gas was drawn. A PbtO2/PaO2 ratio was calculated for each blood gas and plotted over time for each patient. All patients were managed according to a standardized clinical protocol. A mixed effects model was used to account for repeated measurements in the same patient.

RESULTS

A total of 1006 data points were collected. The lowest mean PaO2 observed to maintain PbtO2 above the ischemic threshold was 94 mm Hg. Only PaO2 and cerebral perfusion pressure were predictive of PbtO2 in multivariate analysis. The PbtO2/PaO2 ratio was below 0.15 in 41.7% of all measures and normal PbtO2 values present despite an abnormal ratio in 27.1% of measurements.

CONCLUSIONS

The authors' results suggest that the minimal PaO2 target to ensure adequate cerebral oxygenation during the first few days after TBI should be higher than that suggested in the Brain Trauma Foundation guidelines. The use of a PbtO2/PaO2 ratio (BOx ratio) may be clinically useful and identifies abnormal O2 delivery mechanisms (cerebral blood flow, diffusion, and cerebral metabolic rate of oxygen) despite normal PbtO2.

The effect of hyperoxia on mortality in critically ill patients: a systematic review and meta analysis

Background

Studies investigating the role of hyperoxia in critically ill patients have reported conflicting results. We did this analysis to reveal the effect of hyperoxia in the patients admitted to the intensive care unit (ICU).

Methods

Electronic databases were searched for all the studies exploring the role of hyperoxia in adult patients admitted to ICU. The primary outcome was mortality. Random-effect model was used for quantitative synthesis of the adjusted odds ratio (aOR).

Results

We identified 24 trials in our final analysis. Statistical heterogeneity was found between hyperoxia and normoxia groups in patients with mechanical ventilation (I² = 92%, P < 0.01), cardiac arrest(I² = 63%, P = 0.01), traumatic brain injury (I² = 85%, P < 0.01) and post cardiac surgery (I² = 80%, P = 0.03). Compared with normoxia, hyperoxia was associated with higher mortality in overall patients (OR 1.22, 95% CI 1.12~1.33), as well as in the subgroups of cardiac arrest (OR 1.30, 95% CI 1.08~1.57) and extracorporeal life support (ELS) (OR 1.44, 95% CI 1.03~2.02).

Conclusions

Hyperoxia would lead to higher mortality in critically ill patients especially in the patients with cardiac arrest and ELS.

Electronic supplementary material

The online version of this article (10.1186/s12890-019-0810-1) contains supplementary material, which is available to authorized users.

A hypothetical method for controlling highly glycolytic cancers and metastases

Most proliferating cancer cells and cancer-associated tumor stroma have an upregulated glucose energy demand in relation to normal cells. Cancer cells are further less metabolically flexible than normal cells. They can therefore not survive metabolic stress as well as normal cells can. Metabolic deprivation thus provides a potential therapeutic window. Unfortunately, current glucose blockers have toxicity problems. An alternative way to reduce a cancer patient's blood glucose (BG), for a short-term period to very low levels, without the concomitant toxicity, is hypothesized in this paper. In vitro tests have shown that short-term BG deprivation to 2 mmol/L for 180 min is an effective cancer treatment. This level of hypoglycaemia can be maintained in vivo with a combination of very low-dose insulin and the suppression of the glucose counter-regulation system. Such suppression can be safely achieved by the infusion of somatostatin and a combination of both α and β-blockers. The proposed short-term in vivo method, was shown to be non-toxic and safe for non-cancer patients. The next step is to test the effect of the proposed method on cancer patients. It is also suggested to incorporate well-known, long-term BG deprivation treatments to achieve maximum effect.

The effect of normobaric oxygen in patients with acute stroke: a systematic review and meta-analysis

Background Normobaric oxygen (NBO) has received considerable attention due to controversial data in brain protection in patients with acute stroke. This study aims to analyze current data of NBO on brain protection as used in the clinic. Methods We searched for and reviewed relevant articles and references from Pubmed, Medline, Embase, Cochrane, and Clincialtrials.gov that were published prior to October 2017. Data from prospective studies were processed using RevMan5.0 software, provided by Cochrane collaboration and transformed using relevant formulas. Results A total of 11 prospective RCT studies including 6366 patients with acute stroke (NBO group, 3207; control group, 3159) were enrolled in this analysis. △NIHSS represented the values of NIHSS at 4, 24 h, or 7 days post-stroke minus baseline NIHSS. Compared to controls, there was a minor trend toward NBO benefits in short-term prognostic indices, as indicated by decreased ΔNIHSS at our defined time points. By contrast, NBO decreased Barthel Index scores between 3 and 7 months, and increased death rates at 3, 6 months, and 1 year, whereas, modified Rankin Scale scores between 3 and 6 months were unchanged. Conclusions The existing trends toward benefits revealed in this meta-analysis help us appreciate the promising value of NBO, although current evidence of NBO on improving clinical outcomes of stroke is insufficient. Well-designed multi-center clinical trials are encouraged and urgently needed to further explore the efficacy of NBO on brain protection.

Highs and lows of hyperoxia: physiological, performance, and clinical aspects

Molecular oxygen (O₂) is a vital element in human survival and plays a major role in a diverse range of biological and physiological processes. Although normobaric hyperoxia can increase arterial oxygen content ([Formula: see text]), it also causes vasoconstriction and hence reduces O₂ delivery in various vascular beds, including the heart, skeletal muscle, and brain. Thus, a seemingly paradoxical situation exists in which the administration of oxygen may place tissues at increased risk of hypoxic stress. Nevertheless, with various degrees of effectiveness, and not without consequences, supplemental oxygen is used clinically in an attempt to correct tissue hypoxia (e.g., brain ischemia, traumatic brain injury, carbon monoxide poisoning, etc.) and chronic hypoxemia (e.g., severe COPD, etc.) and to help with wound healing, necrosis, or reperfusion injuries (e.g., compromised grafts). Hyperoxia has also been used liberally by athletes in a belief that it offers performance-enhancing benefits; such benefits also extend to hypoxemic patients both at rest and during rehabilitation. This review aims to provide a comprehensive overview of the effects of hyperoxia in humans from the "bench to bedside." The first section will focus on the basic physiological principles of partial pressure of arterial O₂, [Formula: see text], and barometric pressure and how these changes lead to variation in regional O₂ delivery. This review provides an overview of the evidence for and against the use of hyperoxia as an aid to enhance physical performance. The final section addresses pathophysiological concepts, clinical studies, and implications for therapy. The potential of O₂ toxicity and future research directions are also considered.

Cerebral Microdialysis Monitoring to Improve Individualized Neurointensive Care Therapy: An Update of Recent Clinical Data

Cerebral microdialysis (CMD) allows bedside semicontinuous monitoring of patient brain extracellular fluid. Clinical indications of CMD monitoring are focused on the management of secondary cerebral and systemic insults in acute brain injury (ABI) patients [mainly, traumatic brain injury (TBI), subarachnoid hemorrhage, and intracerebral hemorrhage (ICH)], specifically to tailor several routine interventions—such as optimization of cerebral perfusion pressure, blood transfusion, glycemic control and oxygen therapy—in the individual patient. Using CMD as clinical research tool has greatly contributed to identify and better understand important post-injury mechanisms—such as energy dysfunction, posttraumatic glycolysis, post-aneurysmal early brain injury, cortical spreading depressions, and subclinical seizures. Main CMD metabolites (namely, lactate/pyruvate ratio, and glucose) can be used to monitor the brain response to specific interventions, to assess the extent of injury, and to inform about prognosis. Recent consensus statements have provided guidelines and recommendations for CMD monitoring in neurocritical care. Here, we summarize recent clinical investigation conducted in ABI patients, specifically focusing on the role of CMD to guide individualized intensive care therapy and to improve our understanding of the complex disease mechanisms occurring in the immediate phase following ABI. Promising brain biomarkers will also be described.

Normobaric hyperoxia does not improve derangements in diffusion tensor imaging found distant from visible contusions following acute traumatic brain injury

We have previously shown that normobaric hyperoxia may benefit peri-lesional brain and white matter following traumatic brain injury (TBI). This study examined the impact of brief exposure to hyperoxia using diffusion tensor imaging (DTI) to identify axonal injury distant from contusions. Fourteen patients with acute moderate/severe TBI underwent baseline DTI and following one hour of 80% oxygen. Thirty-two controls underwent DTI, with 6 undergoing imaging following graded exposure to oxygen. Visible lesions were excluded and data compared with controls. We used the 99% prediction interval (PI) for zero change from historical control reproducibility measurements to demonstrate significant change following hyperoxia. Following hyperoxia DTI was unchanged in controls. In patients following hyperoxia, mean diffusivity (MD) was unchanged despite baseline values lower than controls (p < 0.05), and fractional anisotropy (FA) was lower within the left uncinate fasciculus, right caudate and occipital regions (p < 0.05). 16% of white and 14% of mixed cortical and grey matter patient regions showed FA decreases greater than the 99% PI for zero change. The mechanistic basis for some findings are unclear, but suggest that a short period of normobaric hyperoxia is not beneficial in this context. Confirmation following a longer period of hyperoxia is required.

Does Normobaric Hyperoxia Cause Oxidative Stress in the Injured Brain? A Microdialysis Study Using 8-Iso-Prostaglandin F2α as a Biomarker

Significant controversy exists regarding the potential clinical benefit of normobaric hyperoxia (NBO) in patients with traumatic brain injury (TBI). This study consisted of two aims: 1) to assess whether NBO improves brain oxygenation and metabolism and 2) to determine whether this therapy may increase the risk of oxidative stress (OxS), using 8-iso-Prostaglandin F2α (PGF2α) as a biomarker. Thirty-one patients with a median admission Glasgow Coma Scale score of 4 (min: 3, max: 12) were monitored with cerebral microdialysis and brain tissue oxygen sensors and treated with fraction of inspired oxygen (FiO₂) of 1.0 for 4 h. Patients were divided into two groups according to the area monitored by the probes: normal injured brain and traumatic penumbra/traumatic core. NBO maintained for 4 h did not induce OxS in patients without preOxS at baseline, except in one case. However, for patients in whom OxS was detected at baseline, NBO induced a significant increase in 8-iso-PGF2α. The results of our study showed that NBO did not change energy metabolism in the whole group of patients. In the five patients with brain lactate concentration ([Lac]_brain) > 3.5 mmol/L at baseline, NBO induced a marked reduction in both [Lac]_brain and lactate-to-pyruvate ratio. Although these differences were not statistically significant, together with the results of our previous study, they suggest that TBI patients would benefit from receiving NBO when they show indications of disturbed brain metabolism. These findings, in combination with increasing evidence that TBI metabolic crises are common without brain ischemia, open new possibilities for the use of this accessible therapeutic strategy in TBI patients.

Early exposure to hyperoxia and mortality in critically ill patients with severe traumatic injuries

BACKGROUND

Hyperoxia is common early in the course of resuscitation of critically ill patients. It has been associated with mortality in some, but not all, studies of cardiac arrest patients and other critically ill cohorts. Reasons for the inconsistency are unclear and may depend on unmeasured patient confounders, the timing and duration of hyperoxia, population characteristics, or the way that hyperoxia is defined and measured. We sought to determine whether, in a prospectively collected cohort of mechanically ventilated patients with traumatic injuries with and without head trauma, higher maximum partial pressure of arterial oxygen (PaO2) within 24 hours of admission would be associated with increased risk of in-hospital mortality.

METHODS

Critically ill patients with traumatic injuries undergoing invasive mechanical ventilation enrolled in the Validating Acute Lung Injury biomarkers for Diagnosis (VALID) study were included in this study. All arterial blood gases (ABGs) from the first 24 hours of admission were recorded. Primary analysis was comparison of the highest PaO2 between hospital survivors and non-survivors.

RESULTS

A total of 653 patients were evaluated for inclusion. Of these, 182 were not mechanically ventilated or did not have an ABG measured in the first 24 hours, leaving 471 patients in the primary analysis. In survivors, the maximum PaO2 was 141 mmHg (median, interquartile range 103 - 212) compared to 148 mmHg (IQR 105 - 209) in non-survivors (p = 0.82). In the subgroup with head trauma (n = 266), the maximum PaO2 was 133 mmHg (IQR 97 - 187) among survivors and 152 mmHg (108 - 229) among nonsurvivors (p = 0.19). After controlling for age, injury severity score, number of arterial blood gases, and fraction of inspired oxygen, maximum PaO2 was not associated with increased mortality (OR 1.27 for every fold increase of PaO2 (95% CI 0.72 - 2.25).

CONCLUSIONS

In mechanically ventilated patients with severe traumatic injuries, hyperoxia in the first 24 hours of admission was not associated with increased risk of death or worsened neurological outcomes in a setting without brain tissue oxygenation monitoring.

Stereotactic radiosurgery for intradural spine tumors using cone-beam CT image guidance

OBJECTIVE

Cone-beam CT (CBCT) image guidance technology has been widely adopted for spine radiosurgery delivery. There is relatively little experience with spine radiosurgery for intradural tumors using CBCT image guidance. This study prospectively evaluated a series of intradural spine tumors treated with radiosurgery. Patient setup accuracy for spine radiosurgery delivery using CBCT image guidance for intradural spine tumors was determined.

METHODS

Eighty-two patients with intradural tumors were treated and prospectively evaluated. The positioning deviations of the spine radiosurgery treatments in patients were recorded. Radiosurgery was delivered using a linear accelerator with a beam modulator and CBCT image guidance combined with a robotic couch that allows positioning correction in 3 translational and 3 rotational directions. To measure patient movement, 3 quality assurance CBCTs were performed and recorded in 30 patients: before, halfway, and after the radiosurgery treatment. The positioning data and fused images of planning CT and CBCT from the treatments were analyzed to determine intrafraction patient movements. From each of 3 CBCTs, 3 translational and 3 rotational coordinates were obtained.

RESULTS

The radiosurgery procedure was successfully completed for all patients. Lesion locations included cervical (22), thoracic (17), lumbar (38), and sacral (5). Tumor histologies included schwannoma (27), neurofibromas (18), meningioma (16), hemangioblastoma (8), and ependymoma (5). The mean prescription dose was 17 Gy (range 12–27 Gy) delivered in 1–3 fractions. At the halfway point of the radiation, the translational variations and standard deviations were 0.4 ± 0.5, 0.5 ± 0.8, and 0.4 ± 0.5 mm in the lateral (x), longitudinal (y), and anteroposterior (z) directions, respectively. Similarly, the variations immediately after treatment were 0.5 ± 0.4, 0.5 ± 0.6, and 0.6 ± 0.5 mm along x, y, and z directions, respectively. The mean rotational angles were 0.3° ± 0.4°, 0.3° ± 0.4°, and 0.3° ± 0.4° along yaw, roll, and pitch, respectively, at the halfway point and 0.5° ± 0.5°, 0.4° ± 0.5°, and 0.2° ± 0.3° immediately after treatment.

CONCLUSIONS

Radiosurgery offers an alternative treatment option for intradural spine tumors in patients who may not be optimal candidates for open surgery. CBCT image guidance for patient setup for spine radiosurgery is accurate and successful in patients with intradural tumors.

The effect of high-dose steroids, and normobaric oxygen therapy, on recent onset non-arteritic anterior ischemic optic neuropathy: a randomized clinical trial

BACKGROUND

To evaluate the effect of high-dose intravenous steroids, as well as normobaric oxygen therapy, in the management of recent onset non-arteritic anterior ischemic optic neuropathy (NAION).

METHOD

Ninety eyes of 90 patients diagnosed with NAION within 14 days of onset were included in this single masked randomized clinical trial. Thirty patients were randomized into each set as group 1 (control), group 2 (steroids), and group 3 (oxygen). Controls received placebo; group 2 received methylprednisolone 500 mg twice a day for 3 days followed by 2 weeks of oral prednisolone 1 mg/kg/day; group 3 received 100 % normobaric oxygen with mask, at a flow rate of 5 liters per minute for 1 hour twice a day for two weeks. Functional and structural outcomes were analyzed at 1 and 6 months following treatment. Best corrected visual acuity (BCVA) was the main outcome measure, and mean deviation (MD) of visual field (VF) test and peripaillary retinal nerve fiber layer thickness (PRNFLT) were secondary outcome measures.

RESULTS

The mean BCVA at the time of presentation was 1.02 ± 0.63, 1.05 ± 0.7, and 0.76 ± 0.5 LogMAR in groups 1, 2, and 3, respectively (p = 0.293); corresponding values were 0.8 ± 0.45, 0.84 ± 0.45, and 0.58 ± 0.4 at month 1 (p = 0.127, 0.19, and 0.168, respectively). BCVA improved to 0.71 ± 0.46, 0.73 ± 0.36, and 0.59 ± 0.41 LogMAR at the 6-month follow-up point (p = 0.039, 0.048, and 0.195, respectively). The mean deviation (MD) at the time of presentation was 19.26 ± 7.02, 20.51 ± 4.68, and 19.3 ± 7.17 in the control, steroid, and oxygen groups, respectively (p = 0.65). Corresponding values at month 1 were 20.26 ± 8.52, 19.52 ± 7.08, and 18.3 ± 7.45, (p = 0.656); and at month 6 were 18.42 ± 8.17, 17.66 ± 6.44 and 16.53 ± 6.32, respectively (p = 0.635). PRNFLT at presentation was 166 ± 57, 184 ± 57, and 193 ± 65 micrometer in the control, steroid, and oxygen groups, respectively (p = 0.265); which decreased to 73 ± 11, 87 ± 26, and 79 ± 19 at the final foll-w up (all p < 0.001). There were no statistically significant differences between the three groups in terms of final visual function and structure.

CONCLUSION

The lack of demonstrable improvement in the structural and functional outcomes of NAION with high-dose IV steroids, or normobaric oxygen, in this randomized controlled trial calls into question the administering of systemic steroid or normobaric oxygen in this condition.

Multimodal brain monitoring in fulminant hepatic failure

Acute liver failure, also known as fulminant hepatic failure (FHF), embraces a spectrum of clinical entities characterized by acute liver injury, severe hepatocellular dysfunction, and hepatic encephalopathy. Cerebral edema and intracranial hypertension are common causes of mortality in patients with FHF. The management of patients who present acute liver failure starts with determining the cause and an initial evaluation of prognosis. Regardless of whether or not patients are listed for liver transplantation, they should still be monitored for recovery, death, or transplantation. In the past, neuromonitoring was restricted to serial clinical neurologic examination and, in some cases, intracranial pressure monitoring. Over the years, this monitoring has proven insufficient, as brain abnormalities were detected at late and irreversible stages. The need for real-time monitoring of brain functions to favor prompt treatment and avert irreversible brain injuries led to the concepts of multimodal monitoring and neurophysiological decision support. New monitoring techniques, such as brain tissue oxygen tension, continuous electroencephalogram, transcranial Doppler, and cerebral microdialysis, have been developed. These techniques enable early diagnosis of brain hemodynamic, electrical, and biochemical changes, allow brain anatomical and physiological monitoring-guided therapy, and have improved patient survival rates. The purpose of this review is to discuss the multimodality methods available for monitoring patients with FHF in the neurocritical care setting.

Sanguinate's effect on pial arterioles in healthy rats and cerebral oxygen tension after controlled cortical impact

Sanguinate, a polyethylene glycol-conjugated carboxyhemoglobin, was investigated for cerebral vasoactivity in healthy male Sprague-Dawley rats (Study 1) and for its ability to increase brain tissue oxygen pressure (PbtO2) after controlled cortical impact (CCI) - traumatic brain injury (TBI) (Study 2). In both studies ketamine-acepromazine anesthetized rats were ventilated with 40% O2. In Study 1, a cranial window was used to measure the diameters of medium - (50-100μm) and small-sized (<50μm) pial arterioles before and after four serial infusions of Sanguinate (8mL/kg/h, cumulative 16mL/kg IV), volume-matched Hextend, or normal saline. In Study 2, PbtO2 was measured using a phosphorescence quenching method before TBI, 15min after TBI (T15) and then every 10min thereafter for 155min. At T15, rats received either 8mL/kg IV Sanguinate (40mL/kg/h) or no treatment (saline, 4mL/kg/h). Results showed: 1) in healthy rats, percentage changes in pial arteriole diameter were the same among the groups, 2) in TBI rats, PbtO2 decreased from 36.5±3.9mmHg to 19.8±3.0mmHg at T15 in both groups after TBI and did not recover in either group for the rest of the study, and 3) MAP increased 16±4mmHg and 36±5mmHg after Sanguinate in healthy and TBI rats, respectively, while MAP was unchanged in control groups. In conclusion, Sanguinate did not cause vasoconstriction in the cerebral pial arterioles of healthy rats but it also did not acutely increase PbtO2 when administered after TBI. Sanguinate was associated with an increase in MAP in both studies.

Perfluorocarbon NVX-108 increased cerebral oxygen tension after traumatic brain injury in rats

BACKGROUND

Hypoxia is a critical secondary injury mechanism in traumatic brain injury (TBI), and early intervention to alleviate post-TBI hypoxia may be beneficial. NVX-108, a dodecafluoropentane perfluorocarbon, was screened for its ability to increase brain tissue oxygen tension (PbtO2) when administered soon after TBI.

METHODS

Ketamine-acepromazine anesthetized rats ventilated with 40% oxygen underwent moderate controlled cortical impact (CCI)-TBI at time 0 (T0). Rats received either no treatment (NON, n=8) or 0.5 ml/kg intravenous (IV) NVX-108 (NVX, n=9) at T15 (15 min after TBI) and T75.

RESULTS

Baseline cortical PbtO2 was 28±3 mm Hg and CCI-TBI resulted in a 46±6% reduction in PbtO2 at T15 (P<0.001). Significant differences in time-group interactions (P=0.013) were found when comparing either absolute or percentage change of PbtO2 to post-injury (mixed-model ANOVA) suggesting that administration of NVX-108 increased PbtO2 above injury levels while it remained depressed in the NON group. Specifically in the NVX group, PbtO2 increased to a peak 143% of T15 (P=0.02) 60 min after completion of NVX-108 injection (T135). Systemic blood pressure was not different between the groups.

CONCLUSION

NVX-108 caused an increase in PbtO2 following CCI-TBI in rats and should be evaluated further as a possible immediate treatment for TBI.

Normobaric hyperoxia is associated with increased cerebral excitotoxicity after severe traumatic brain injury

BACKGROUND

Normobaric oxygen therapy is frequently applied in neurocritical care, however, whether supplemental FiO2 has beneficial cerebral effects is still controversial. We examined in patients with severe traumatic brain injury (TBI) the effect of incremental FiO2 on cerebral excitotoxicity, quantified by cerebral microdialysis (CMD) glutamate.

METHODS

This was a retrospective analysis of a database of severe TBI patients monitored with CMD and brain tissue oxygen (PbtO2). The relationship of FiO2--categorized into four separate ranges (<40, 41-60, 61-80, and >80 %)--with CMD glutamate was examined using ANOVA with Tukey's post hoc test.

RESULTS

A total of 1,130 CMD samples from 36 patients--monitored for a median of 4 days--were examined. After adjusting for brain (PbtO2, intracranial pressure, cerebral perfusion pressure, lactate/pyruvate ratio, Marshall CT score) and systemic (PaCO2, PaO2, hemoglobin, APACHE score) covariates, high FiO2 was associated with a progressive increase in CMD glutamate [8.8 (95 % confidence interval 7.4-10.2) µmol/L at FiO2 < 40 % vs. 12.8 (10.9-14.7) µmol/L at 41-60 % FiO2, 19.3 (15.6-23) µmol/L at 61-80 % FiO2, and 22.6 (16.7-28.5) µmol/L at FiO2 > 80 %; multivariate-adjusted p < 0.05]. The threshold of FiO2-related increase in CMD glutamate was lower for samples with normal versus low PbtO2 < 20 mmHg (FiO2 > 40 % vs. FiO2 > 60 %). Hyperoxia (PaO2 > 150 mmHg) was also associated with increased CMD glutamate (adjusted p < 0.001).

CONCLUSIONS

Incremental normobaric FiO2 levels were associated with increased cerebral excitotoxicity in patients with severe TBI, independent from PbtO2 and other important cerebral and systemic determinants. These data suggest that supra-normal oxygen may aggravate secondary brain damage after severe TBI.

Hyperoxic resuscitation improves survival but worsens neurologic outcome in a rat polytrauma model of traumatic brain injury plus hemorrhagic shock

BACKGROUND

Many traumatic brain injury (TBI) patients experience additional injuries, including those that result in hemorrhagic shock (HS). Interactions between HS and TBI can include reduced brain O2 delivery, resulting in partial cerebral ischemia and worse neurologic outcome. This study tested the hypothesis that inspiration of 100% O2 during resuscitation following TBI and HS improves survival, reduces brain lesion volume, and improves neurologic outcome compared with resuscitation in the absence of supplemental O2.

METHODS

The adult male rat polytrauma model consisted of controlled cortical impact-induced TBI followed by 30 minutes of HS (mean arterial pressure, 35-40 mm Hg) induced by blood withdrawal. The HS phase was followed by a 1-hour "prehospital" Hextend fluid resuscitation phase and then a 1-hour "hospital phase" when shed blood was reinfused. Rats were randomized on the day of surgery to three groups with 10 per group: sham, polytrauma normoxic, and polytrauma hyperoxic. Normoxic animals inspired room air, and hyperoxic animals inspired 100% O2 during both resuscitation phases. Neurobehavioral tests were conducted weekly until the rats were perfused with fixative at 30 days after injury. Brain sections were stained with Fluoro Jade B and used for quantification of contusion, penumbral, and healthy cortical volumes.

RESULTS

Survival was greater following hyperoxic compared with normoxic resuscitation. Composite neuroscores obtained at 2 weeks to 4 weeks following hyperoxic resuscitation were lower than those of shams. Balance beam foot faults measured at 2 weeks after injury were greater following hyperoxic resuscitation compared with normoxic resuscitation and those of shams. There was no significant difference in cerebrocortical pathology between the normoxic and hyperoxic polytrauma groups.

CONCLUSION

The survival of rats following controlled cortical impact plus HS was greater following hyperoxic resuscitation. In contrast, neurologic outcomes were better following normoxic resuscitation.

Hyperoxia in intensive care, emergency, and peri-operative medicine: Dr. Jekyll or Mr. Hyde? A 2015 update

This review summarizes the (patho)-physiological effects of ventilation with high FiO₂ (0.8–1.0), with a special focus on the most recent clinical evidence on its use for the management of circulatory shock and during medical emergencies. Hyperoxia is a cornerstone of the acute management of circulatory shock, a concept which is based on compelling experimental evidence that compensating the imbalance between O₂ supply and requirements (i.e., the oxygen dept) is crucial for survival, at least after trauma. On the other hand, “oxygen toxicity” due to the increased formation of reactive oxygen species limits its use, because it may cause serious deleterious side effects, especially in conditions of ischemia/reperfusion. While these effects are particularly pronounced during long-term administration, i.e., beyond 12–24 h, several retrospective studies suggest that even hyperoxemia of shorter duration is also associated with increased mortality and morbidity. In fact, albeit the clinical evidence from prospective studies is surprisingly scarce, a recent meta-analysis suggests that hyperoxia is associated with increased mortality at least in patients after cardiac arrest, stroke, and traumatic brain injury. Most of these data, however, originate from heterogenous, observational studies with inconsistent results, and therefore, there is a need for the results from the large scale, randomized, controlled clinical trials on the use of hyperoxia, which can be anticipated within the next 2–3 years. Consequently, until then, “conservative” O₂ therapy, i.e., targeting an arterial hemoglobin O₂ saturation of 88–95 % as suggested by the guidelines of the ARDS Network and the Surviving Sepsis Campaign, represents the treatment of choice to avoid exposure to both hypoxemia and excess hyperoxemia.

International multidisciplinary consensus conference on multimodality monitoring: cerebral metabolism

Microdialysis is a powerful technique, which enables the chemistry of the extracellular space to be measured directly. Applying this technique to patients in neurointensive care has increased our understanding of the pathophysiology of traumatic brain injury and spontaneous hemorrhage. In parallel, it is important to determine the place of microdialysis in assisting in the management of patients on an individual intention to treat basis. This is made possible by the availability of analyzers which can measure the concentration of glucose, pyruvate, lactate, and glutamate at the bedside. Samples can then be stored for later analysis of other substrate and metabolites e.g., other amino acids and cytokines. The objective of this paper is to review the fundamental literature pertinent to the clinical application of microdialysis in neurointensive care and to give recommendations on how the technique can be applied to assist in patient management and contribute to outcome. A literature search detected 1,933 publications of which 55 were used for data abstraction and analysis. The role of microdialysis was evaluated in three conditions (traumatic brain injury, subarachnoid hemorrhage, and intracerebral hemorrhage) and recommendations focused on three fundamental areas (relationship to outcome, application of microdialysis to guide therapy, and the ability of microdialysis to predict secondary deterioration).

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.

Single versus multiple session stereotactic body radiotherapy for spinal metastasis: the risk-benefit ratio

Spine stereotactic body radiation therapy represents an important advancement in the management of spinal metastases that allows precise delivery of ablative doses of radiation therapy with excellent local control. Although the technique is being increasingly used in clinical practice, the optimal fractionation schedule remains uncertain. In this perspective paper, we review radiobiologic principles that support the use of multiple- versus single-fraction spine stereotactic body radiation therapy schedules and clinical data supporting the multiple-fraction approach. Specifically, we suggest that there may be a local control benefit of fractionation, while helping to limit the risk of toxicities such as vertebral body fracture, pain flare and radiation myelopathy. We conclude with future directions and the need for future study on this important topic.