The Considerations and Controversies in Using High-Flow Nasal Oxygen with Self-Prone Positioning in SARS-CoV-2 COVID-19 Disease.

Evidence exists for the use of high-flow nasal oxygen (HFNO) in the general critical care population for acute hypoxemic respiratory failure. There is discord between guidelines for hypoxemia management in COVID-19. Both noninvasive management and intubation present risk to patients and staff and potentially overwhelm hospital mechanical ventilator capacity. The use of HFNO has been particularly controversial in the UK, with oxygen infrastructure failure. We discuss our experience of managing COVID-19 with HFNO and awake self-prone positioning. We focus upon the less-usual case of an eighteen-year-old female to illustrate the type of patient where HFNO may be used when perhaps earlier intubation once was. It is important to consider the wider implications of intubation. We have used HFNO as a bridge to intubation or as definitive management. As we await clinical trial evidence, HFNO with self-prone positioning has a role in COVID-19 for certain patients. Response parameters must be set and reviewed, oxygen infrastructure considered, and potential staff droplet exposure minimised.

A Systematic Review and Meta-Analysis of Hypothermia in Experimental Traumatic Brain Injury: Why Have Promising Animal Studies Not Been Replicated in Pragmatic Clinical Trials?

Therapeutic hypothermia was a mainstay of severe traumatic brain injury (TBI) management for half a century. Recent trials have suggested that its effect on long-term functional outcome is neutral or negative, despite apparently promising pre-clinical data. Systematic review and meta-analysis is a useful tool to collate experimental data and investigate the basis of its conclusions. We searched three online databases to identify studies testing systemic hypothermia as monotherapy for treatment of animals subjected to a TBI. Data pertaining to TBI paradigm, animal subjects, and hypothermia management were extracted as well as those relating to risk of bias. We pooled outcome data where sufficient numbers allowed and investigated heterogeneity in neurobehavioral outcomes using multi-variate meta-regression. We identified 90 publications reporting 272 experiments testing hypothermia in animals subject to TBI. The subjects were mostly small animals, with well-established models predominating. Target temperature was comparable to clinical trial data but treatment was initiated very early. Study quality was low and there was some evidence of publication bias. Delay to treatment, comorbidity, and blinded outcome assessment appeared to predict neurobehavioral outcome on multi-variate meta-regression. Therapeutic hypothermia appears to be an efficacious treatment in experimental TBI, which differs from the clinical evidence. The pre-clinical literature showed limitations in quality and design and these both appeared to affect neurobehavioral experiment outcome. These should be acknowledged when designing and interpreting pre-clinical TBI studies in the future.

Substantial Metabolic Activity of Human Brown Adipose Tissue during Warm Conditions and Cold-Induced Lipolysis of Local Triglycerides.

Current understanding of in vivo human brown adipose tissue (BAT) physiology is limited by a reliance on positron emission tomography (PET)/computed tomography (CT) scanning, which has measured exogenous glucose and fatty acid uptake but not quantified endogenous substrate utilization by BAT. Six lean, healthy men underwent 18fluorodeoxyglucose-PET/CT scanning to localize BAT so microdialysis catheters could be inserted in supraclavicular BAT under CT guidance and in abdominal subcutaneous white adipose tissue (WAT). Arterial and dialysate samples were collected during warm (∼25°C) and cold exposure (∼17°C), and blood flow was measured by 133xenon washout. During warm conditions, there was increased glucose uptake and lactate release and decreased glycerol release by BAT compared with WAT. Cold exposure increased blood flow, glycerol release, and glucose and glutamate uptake only by BAT. This novel use of microdialysis reveals that human BAT is metabolically active during warm conditions. BAT activation substantially increases local lipolysis but also utilization of other substrates such as glutamate.

Revisited: A Systematic Review of Therapeutic Hypothermia for Adult Patients Following Traumatic Brain Injury.

OBJECTIVES: Therapeutic hypothermia has been of topical interest for many years and with the publication of two international, multicenter randomized controlled trials, the evidence base now needs updating. The aim of this systematic review of randomized controlled trials is to assess the efficacy of therapeutic hypothermia in adult traumatic brain injury focusing on mortality, poor outcomes, and new pneumonia. DATA SOURCES: The following databases were searched from January 1, 2011, to January 26, 2018: Cochrane Central Register of Controlled Trial, MEDLINE, PubMed, and EMBASE. STUDY SELECTION: Only foreign articles published in the English language were included. Only articles that were randomized controlled trials investigating adult traumatic brain injury sustained following an acute, closed head injury were included. Two authors independently assessed at each stage. DATA EXTRACTION: Quality was assessed using the Cochrane Collaboration's tool for assessing the risk of bias. All extracted data were combined using the Mantel-Haenszel estimator for pooled risk ratio with 95% CIs. p value of less than 0.05 was considered statistically significant. All statistical analyses were conducted using RevMan 5 (Cochrane Collaboration, Version 5.3, Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration, 2014). DATA SYNTHESIS: Twenty-two studies with 2,346 patients are included. Randomized controlled trials with a low risk of bias show significantly more mortality in the therapeutic hypothermia group (risk ratio, 1.37; 95% CI, 1.04-1.79; p = 0.02), whereas randomized controlled trials with a high risk of bias show the opposite with a higher mortality in the control group (risk ratio, 0.70; 95% CI, 0.60-0.82; p < 0.00001). CONCLUSIONS: Overall, this review is in-keeping with the conclusions published by the most recent randomized controlled trials. High-quality studies show no significant difference in mortality, poor outcomes, or new pneumonia. In addition, this review shows a place for fever control in the management of traumatic brain injury.

Mortality Risk Stratification After Traumatic Brain Injury and Hazard of Death With Titrated Hypothermia in the Eurotherm3235Trial.

OBJECTIVES: Hypothermia reduces intracranial hypertension in patients with traumatic brain injury but was associated with harm in the Eurotherm3235Trial. We stratified trial patients by International Mission for Prognosis and Analysis of Clinical Trials in [Traumatic Brain Injury] (IMPACT) extended model sum scores to determine where the balance of risks lay with the intervention. DESIGN: The Eurotherm3235Trial was a randomized controlled trial, with standardized and blinded outcome assessment. Patients in the trial were split into risk tertiles by IMPACT extended model sum scores. A proportional hazard analysis for death between randomization and 6 months was performed by intervention and IMPACT extended model sum scores tertiles in both the intention-to-treat and the per-protocol populations of the Eurotherm3235Trial. SETTING: Forty-seven neurologic critical care units in 18 countries. PATIENTS: Adult traumatic brain injury patients admitted to intensive care who had suffered a primary, closed traumatic brain injury; increased intracranial pressure; an initial head injury less than 10 days earlier; a core temperature at least 36°C; and an abnormal brain CT. INTERVENTION: Titrated Hypothermia in the range 32-35°C as the primary intervention to reduce raised intracranial pressure. MEASUREMENTS AND MAIN RESULTS: Three hundred eighty-six patients were available for analysis in the intention-to-treat and 257 in the per-protocol population. The proportional hazard analysis (intention-to-treat and per-protocol populations) showed that the treatment effect behaves similarly across all risk stratums. However, there is a trend that indicates that patients in the low-risk group could be at greater risk of suffering harm due to hypothermia. CONCLUSIONS: Hypothermia as a first line measure to reduce intracranial pressure to less than 20 mm Hg is harmful in patients with a lower severity of injury and no clear benefit exists in patients with more severe injuries.

Study protocol - A systematic review and meta-analysis of hypothermia in experimental traumatic brain injury: Why have promising animal studies not been replicated in pragmatic clinical trials?

Traumatic brain injury (TBI) is a major cause of death and permanent disability. Systemic hypothermia, a treatment used in TBI for many decades, has recently been found to be associated with neutral or unfavourable clinical outcomes despite apparently promising preclinical research. Systematic review and meta-analysis is a tool to summarize literature and observe trends in experimental design and quality that underpin its general conclusions. Here we aim to use these techniques to describe the use of hypothermia in animal TBI models, collating data relating to outcome and both study design and quality. From here we intend to observe correlations between features and attempt to explain any discrepancies found between animal and clinical data. This protocol describes the relevant methodology in detail.

Hypothermia for Intracranial Hypertension after Traumatic Brain Injury.

BACKGROUND: In patients with traumatic brain injury, hypothermia can reduce intracranial hypertension. The benefit of hypothermia on functional outcome is unclear. METHODS: We randomly assigned adults with an intracranial pressure of more than 20 mm Hg despite stage 1 treatments (including mechanical ventilation and sedation management) to standard care (control group) or hypothermia (32 to 35°C) plus standard care. In the control group, stage 2 treatments (e.g., osmotherapy) were added as needed to control intracranial pressure. In the hypothermia group, stage 2 treatments were added only if hypothermia failed to control intracranial pressure. In both groups, stage 3 treatments (barbiturates and decompressive craniectomy) were used if all stage 2 treatments failed to control intracranial pressure. The primary outcome was the score on the Extended Glasgow Outcome Scale (GOS-E; range, 1 to 8, with lower scores indicating a worse functional outcome) at 6 months. The treatment effect was estimated with ordinal logistic regression adjusted for prespecified prognostic factors and expressed as a common odds ratio (with an odds ratio <1.0 favoring hypothermia). RESULTS: We enrolled 387 patients at 47 centers in 18 countries from November 2009 through October 2014, at which time recruitment was suspended owing to safety concerns. Stage 3 treatments were required to control intracranial pressure in 54% of the patients in the control group and in 44% of the patients in the hypothermia group. The adjusted common odds ratio for the GOS-E score was 1.53 (95% confidence interval, 1.02 to 2.30; P=0.04), indicating a worse outcome in the hypothermia group than in the control group. A favorable outcome (GOS-E score of 5 to 8, indicating moderate disability or good recovery) occurred in 26% of the patients in the hypothermia group and in 37% of the patients in the control group (P=0.03). CONCLUSIONS: In patients with an intracranial pressure of more than 20 mm Hg after traumatic brain injury, therapeutic hypothermia plus standard care to reduce intracranial pressure did not result in outcomes better than those with standard care alone. (Funded by the National Institute for Health Research Health Technology Assessment program; Current Controlled Trials number, ISRCTN34555414.).

Study of therapeutic hypothermia (32 to 35°C) for intracranial pressure reduction after traumatic brain injury (the Eurotherm3235Trial): outcome of the pilot phase of the trial.

BACKGROUND: Clinical trials in traumatic brain injury (TBI) are challenging. Previous trials of complex interventions were conducted in high-income countries, reported long lead times for site setup and low screened-to-recruitment rates.In this report we evaluate the internal pilot phase of an international, multicentre TBI trial of a complex intervention to assess: design and implementation of an online case report form; feasibility of recruitment (sites and patients); feasibility and effectiveness of delivery of the protocol. METHODS: All aspects of the pilot phase of the trial were conducted as for the main trial. The pilot phase had oversight by independent Steering and Data Monitoring committees. RESULTS: Forty sites across 12 countries gained ethical approval. Thirty seven of 40 sites were initiated for recruitment. Of these, 29 had screened patients and 21 randomized at least one patient. Lead times to ethics approval (6.8 weeks), hospital approval (18 weeks), interest to set up (61 weeks), set up to screening (11 weeks), and set up to randomization (31.6 weeks) are comparable with other international trials. Sixteen per cent of screened patients were eligible. We found 88% compliance rate with trial protocol. CONCLUSION: The pilot data demonstrated good feasibility for this large international multicentre randomized controlled trial of hypothermia to control intracranial pressure. The sample size was reduced to 600 patients because of homogeneity of the patient group and we showed an optimized cooling intervention could be delivered. TRIAL REGISTRATION: Current Controlled Trials: ISRCTN34555414.

Ventilatory strategies for patients with acute brain injury.

PURPOSE OF REVIEW: The ventilation of patients with acute brain injuries can present significant challenges. Frequently, guidelines recommending management strategies for patients with traumatic brain injuries come into conflict with what is now considered best ventilatory practice. In this review, we will explore many of these areas of conflict. RECENT FINDINGS: The use of ventilatory strategies to control partial pressure of carbon dioxide in patients with traumatic brain injury is associated with the development of acute lung injury. Analysis of the International Mission for Prognosis And Clinical Trial (IMPACT) database has confirmed the association between hypoxia and poor neurological outcome. Although a recent meta-analysis has suggested a survival benefit for steroids in acute lung injury, the use of steroids has been associated with a worsening of outcome in patients with traumatic brain injuries and their effects on the brain have not been fully elucidated. SUMMARY: There are unlikely to be randomized controlled trials advising how best to ventilate patients with acute brain injuries because of the heterogeneous nature of such injuries. Hypoxia should be avoided. The more widespread use of multimodal brain monitoring, including brain tissue oxygen and cerebral blood flow monitoring, may allow clinicians to tolerate a higher arterial partial pressure of carbon dioxide than has been traditional, allowing a less injurious ventilatory strategy. Modest positive end-expiratory pressure can be used. In severe respiratory failure, most 'rescue' strategies have been attempted in patients with acute brain injuries. Choice of rescue therapy at present is best decided on a case-by-case basis in conjunction with local expertise.

The temporal expression, cellular localization, and inhibition of the chemokines MIP-2 and MCP-1 after traumatic brain injury in the rat.

The expression of the neutrophil chemokine macrophage inflammatory protein-2 (MIP-2/CXCL2) and the monocyte chemokine monocyte chemotactic protein-1 (MCP-1/CCL2) have been described in glial cells in vitro but their origin following TBI has not been established. Furthermore, little is known of the modulation of these chemokines. Chemokine expression was investigated in male Sprague-Dawley rats following moderate lateral fluid percussion injury (LFPI). At 0, 4, 8, 12, and 24 h after injury, brains were harvested and MIP-2/CXCL2 and MCP-1/CCL2 levels measured by ELISA. To investigate the inhibition of chemokine expression a second cohort of animals received dexamethasone (1-15mg/kg), FK506 (1mg/kg), or vehicle, systemically, immediately after injury. These animals were sacrificed at the time of peak chemokine expression. A third cohort of animals was also sacrificed at the time of peak chemokine expression and immunohistochemistry performed for MIP-2/CXCL2 and MCP-1/CCL2. Following LFPI, chemokines were increased in the ipsilateral hemisphere, MIP-2/CXCL2 peaking at 4 h and MCP-1/CCL2 peaking at 8-12 h post-injury. Dexamethasone significantly reduced cortical MCP-1/CCL2, but not MIP-2/CXCL2 concentrations. FK506 did not inhibit chemokine expression. In undamaged brain, chemokine expression was localized to cells with a neuronal morphology. For MIP-2/CXCL2 this was supported by double staining for the neuronal antigen NeuN. In contused tissue, increased MIP-2/CXCL2 and MCP-1/CCL2 staining was visible in cells with the morphology of degenerating neurons. MIP-2/CXCL2 and MCP-1/CCL2 are increased after injury, and neurons appear to be the source of this expression. Chemokine expression was selectively inhibited by dexamethasone. The implications of this are discussed.

Characterization of the pharmacokinetics of human recombinant erythropoietin in blood and brain when administered immediately after lateral fluid percussion brain injury and its pharmacodynamic effects on IL-1beta and MIP-2 in rats.

This study sought to determine the bio-availability of recombinant human erythropoietin (EPO) in the brain and blood and its effects on the cerebral concentrations of the inflammatory mediators interleukin-1beta (IL-1beta) and macrophage-inflammation protein-2 (MIP-2) following lateral fluid percussion brain injury (FPI) in the rat. After induction of moderate FPI (1.6-1.8 atm), EPO was injected intraperitoneally (IP) or intravenously (IV) at doses of 1000-5000 U/kg in a randomized and blinded manner. Animals were then sacrificed at time points (4, 8, 12, 24 h) post-trauma, and the brain concentrations of EPO, IL-1beta, and MIP-2 were determined. EPO administration leads to a dose-dependent increase in the brain concentration of the drug; however, this could only be detected at doses of 3000 and 5000 U/kg. The cerebral concentration peaked in the first 4 h following trauma. EPO concentrations were significantly higher and decreased more slowly in the traumatized cortex compared to the contralateral side (p<0.0125). IV EPO (5000 U/kg) produced slightly higher concentrations of EPO than same doses injected IP; however, this was not significant. At a dose of 5000 U/kg, EPO significantly reduced the increase in IL-1beta at 8 and 12 h in both cortical sides. It also reduced the increase in MIP-2 but only after 8 h, on the contralateral side and after 12 h on the ipsilateral side. Our results suggest that EPO crosses the blood-brain barrier (BBB) by 4 h after trauma and is localized primarily in the traumatized cortex. Further, it has biological efficacy at 8 h on several inflammatory proteins, yet must be employed at high doses to cross the BBB.

Actions of glucocorticoids and related molecules after traumatic brain injury.

PURPOSE OF REVIEW: Despite 25 years of randomized, controlled trials, the benefit of steroid administration to patients with traumatic brain injury is unproved. Traditionally, glucocorticoids have been used empirically to reduce inflammation and edema. However, it is becoming apparent that the mechanisms by which steroid molecules might act to improve recovery after traumatic brain injury are numerous. RECENT FINDINGS: The effects of steroid administration on the central nervous system are not uniform but depend on the population of neurons studied. Definite deleterious effects of steroid administration on neuronal survival have been described. SUMMARY: This review discusses why glucocorticoids might be effective, the considerable laboratory evidence supporting the use of 21-aminosteroids, and the potentially harmful effects of steroid molecules on the brain.

Expression of interleukin-6 messenger RNA in a rat model of diffuse axonal injury.

Having demonstrated a transcranial gradient of the cytokine interleukin-6 (IL-6) in patients with either traumatic brain injury or spontaneous subarachnoid haemorrhage we have employed in situ hybridisation for IL-6 messenger RNA (mRNA) to determine the site of this IL-6 production within the central nervous system (CNS). A rodent weight drop model of traumatic brain injury was used. IL-6 mRNA levels in brains were determined 6 h after injury. Sham animals had normal constitutive expression for IL6 mRNA. In traumatised animals an intense area of IL-6 mRNA labelling was found below the hippocampus. Cells strongly expressing IL-6 mRNA were also seen in the dentate gyrus. This inflammatory cytokine is clearly implicated in the response to CNS injury, but whether this response is neuroprotective or pathological is uncertain.