The use of hyperventilation therapy after traumatic brain injury in Europe: an analysis of the BrainIT database

Evidence-based management of adult traumatic brain injury with raised intracranial pressure in intensive critical care unit at resource-limited settings: a literature review

Background

In underdeveloped countries, there is a greater incidence of mortality and morbidity arising from trauma, with traumatic brain injury (TBI) accounting for 50% of all trauma-related deaths. The occurrence of elevated intracranial pressure (ICP), which is a common pathophysiological phenomenon in cases of TBI, acts as a contributing factor to unfavorable outcomes. The aim of this systematic review is to analyze the existing literature regarding the management of adult TBI with raised ICP in an intensive critical care unit, despite limited resources.

Methods

This systematic review was performed in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis protocol. Search engines such as PubMed, the Cochrane database, and Google Scholar were utilized to locate high-level evidence that would facilitate the formation of sound conclusions.

Result

A total of 11 715 articles were identified and individually assessed to determine their eligibility for inclusion or exclusion based on predetermined criteria and outcome variables. The methodological quality of each study was evaluated using recommended criteria. Ultimately, the review consisted of 51 articles.

Conclusion

Physical examination results and noninvasive assessments of the optic nerve sheath diameter (ONSD) via sonography are positively associated with elevated ICP, and are employed as diagnostic and monitoring tools for elevated ICP in resource-limited settings. Management of elevated ICP necessitates an algorithmic approach that utilizes prophylactic measures and acute intervention treatments to mitigate the risk of secondary brain injury.

Association between the first 24 hours PaCO2 and all-cause mortality of patients suffering from sepsis-associated encephalopathy after ICU admission: A retrospective study

OBJECTIVE

The relationship between the levels of the first 24-h PaCO2 and the prognosis of sepsis-associated encephalopathy (SAE) remains unclear, and the first 24-h optimal target for PaCO2 is currently inconclusive. This study was performed to investigate the correlation between PaCO2 and all-cause mortality for SAE patients, establish a reference range of the initial 24-hour PaCO2 for clinicians in critical care, and explain the possible pathophysiological mechanisms of abnormal PaCO2 levels as a higher mortality risk factor for SAE.

METHODS

The baseline information and clinical data of patients were extracted from the fourth edition Medical Information Mart for Intensive Care database (MIMIC-IV 2.0). Multivariate logistic regressions were performed to assess the relationship between PaCO2 and all-cause mortality of SAE. Additionally, restricted cubic splines, Kaplan-Meier Survival analyses, propensity score matching (PSM) analyses, and subgroup analyses were conducted.

RESULTS

A total of 5471 patients were included in our cohort. In the original and matched cohort, multivariate logistic regression analysis showed that normocapnia and mild hypercapnia may be associated with a more favorable prognosis of SAE patients, and survival analysis supported the findings. In addition, a U-shaped association emerged when examining the initial 24-hour PaCO2 levels in relation to 30-day, 60-day, and 90-day mortality using restricted cubic splines, with an average cut-off value of 36.3mmHg (P for nonlinearity<0.05). Below the cut-off value, higher PaCO2 was associated with lower all-cause mortality, while above the cut-off value, higher PaCO2 was associated with higher all-cause mortality. Subsequent subgroup analyses revealed similar results for the subcohort of GCS≤8 compared to the original cohort. Additionally, when examining the subcohort of GCS>8, a L-shaped relationship between PaCO2 and the three clinical endpoints emerged, in contrast to the previously observed U-shaped pattern. The findings from the subcohort of GCS>8 suggested that patients experiencing hypocapnia had a more unfavorable prognosis, which aligns with the results obtained from corresponding multivariate logistic regression analyses.

CONCLUSION

The retrospective study revealed the association between the first 24-h PaCO2 and all-cause mortality risk (30-day, 60-day, and 90-day) for patients with SAE in ICU. The range (35mmHg-50mmHg) of PaCO2 may be the optimal target for patients with SAE in clinical practice.

Spontaneous Hyperventilation Is Common in Patients with Spontaneous Cerebellar Hemorrhage, and Its Severity Is Associated with Outcome

BACKGROUND

The spontaneous hyperventilation (SHV) accompanying spontaneous cerebellar hemorrhage has yet to attract a sufficient amount of attention. This study aimed to analyze the incidence of SHV in spontaneous cerebellar hemorrhage patients and its risk factors as well as its association with the outcome.

METHODS

We retrospectively reviewed the medical records of all spontaneous cerebellar hemorrhage patients who underwent surgical treatment at Tongji Hospital from July 2018 to December 2020. Arterial blood gas (ABG) test results and clinical characteristics, including demographics, comorbidities, imaging features, laboratory tests, and therapy choices, were collected. The Glasgow Outcome Scale was used to assess the outcome at two weeks and six months after admission.

RESULTS

A total of 147 patients were included, and of these patients 44.9% had spontaneous hyperventilation. Hypertension (OR, 3.175; CI, 1.332-7.569), usage of sedation drugs (OR, 3.693; CI, 1.0563-8.724), and hypernatremia (OR, 2.803; CI, 1.070-7.340) seemed to positively correlate to SHV occurrence. Hematoma removal had an inverse association with SHV (OR, 0.176; CI, 0.068-0.460). Patients with poor and good outcomes had significant differences in pH, PaCO2, and HCO3- values, and the severity of SHV was associated with the PaCO2 level.

CONCLUSIONS

Spontaneous hyperventilation is common in patients with spontaneous cerebellar hemorrhage, and its severity is associated with the outcome.

Optimal Targets of the First 24-h Partial Pressure of Carbon Dioxide in Patients with Cerebral Injury: Data from the MIMIC-III and IV Database

BACKGROUND

It is generally believed that hypercapnia and hypocapnia will cause secondary injury to patients with craniocerebral diseases, but a small number of studies have shown that they may have potential benefits. We assessed the impact of partial pressure of arterial carbon dioxide (PaCO₂) on in-hospital mortality of patients with craniocerebral diseases. The hypothesis of this research was that there is a nonlinear correlation between PaCO₂ and in-hospital mortality in patients with craniocerebral diseases and that mortality rate is the lowest when PaCO₂ is in a normal range.

METHODS

We identified patients with craniocerebral diseases from Medical Information Mart for Intensive Care third and fourth edition databases. Cox regression analysis and restricted cubic splines were used to examine the association between PaCO₂ and in-hospital mortality.

RESULTS

Nine thousand six hundred and sixty patients were identified. A U-shaped association was found between the first 24-h PaCO₂ and in-hospital mortality in all participants. The nadir for in-hospital mortality risk was estimated to be at 39.5 mm Hg (p for nonlinearity < 0.001). In the subsequent subgroup analysis, similar results were found in patients with traumatic brain injury, metabolic or toxic encephalopathy, subarachnoid hemorrhage, cerebral infarction, and other encephalopathies. Besides, the mortality risk reached a nadir at PaCO₂ in the range of 35-45 mm Hg. The restricted cubic splines showed a U-shaped association between the first 24-h PaCO₂ and in-hospital mortality in patients with other intracerebral hemorrhage and cerebral tumor. Nonetheless, nonlinearity tests were not statistically significant. In addition, Cox regression analysis showed that PaCO₂ ranging 35-45 mm Hg had the lowest death risk in most patients. For patients with hypoxic-ischemic encephalopathy and intracranial infections, the first 24-h PaCO₂ and in-hospital mortality did not seem to be correlated.

CONCLUSIONS

Both hypercapnia and hypocapnia are harmful to most patients with craniocerebral diseases. Keeping the first 24-h PaCO₂ in the normal range (35-45 mm Hg) is associated with lower death risk.

Management of arterial partial pressure of carbon dioxide in the first week after traumatic brain injury: results from the CENTER-TBI study

Purpose

To describe the management of arterial partial pressure of carbon dioxide (PaCO₂) in severe traumatic brain-injured (TBI) patients, and the optimal target of PaCO₂ in patients with high intracranial pressure (ICP).

Methods

Secondary analysis of CENTER-TBI, a multicentre, prospective, observational, cohort study. The primary aim was to describe current practice in PaCO₂ management during the first week of intensive care unit (ICU) after TBI, focusing on the lowest PaCO₂ values. We also assessed PaCO₂ management in patients with and without ICP monitoring (ICP_m), and with and without intracranial hypertension. We evaluated the effect of profound hyperventilation (defined as PaCO₂ < 30 mmHg) on long-term outcome.

Results

We included 1100 patients, with a total of 11,791 measurements of PaCO₂ (5931 lowest and 5860 highest daily values). The mean (± SD) PaCO₂ was 38.9 (± 5.2) mmHg, and the mean minimum PaCO₂ was 35.2 (± 5.3) mmHg. Mean daily minimum PaCO₂ values were significantly lower in the ICP_m group (34.5 vs 36.7 mmHg, p < 0.001). Daily PaCO₂ nadir was lower in patients with intracranial hypertension (33.8 vs 35.7 mmHg, p < 0.001). Considerable heterogeneity was observed between centers. Management in a centre using profound hyperventilation (HV) more frequently was not associated with increased 6 months mortality (OR = 1.06, 95% CI = 0.77–1.45, p value = 0.7166), or unfavourable neurological outcome (OR 1.12, 95% CI = 0.90–1.38, p value = 0.3138).

Conclusions

Ventilation is manipulated differently among centers and in response to intracranial dynamics. PaCO₂ tends to be lower in patients with ICP monitoring, especially if ICP is increased. Being in a centre which more frequently uses profound hyperventilation does not affect patient outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00134-021-06470-7.

Use and impact of high intensity treatments in patients with traumatic brain injury across Europe: a CENTER-TBI analysis

PURPOSE

To study variation in, and clinical impact of high Therapy Intensity Level (TIL) treatments for elevated intracranial pressure (ICP) in patients with traumatic brain injury (TBI) across European Intensive Care Units (ICUs).

METHODS

We studied high TIL treatments (metabolic suppression, hypothermia (< 35 °C), intensive hyperventilation (PaCO2 < 4 kPa), and secondary decompressive craniectomy) in patients receiving ICP monitoring in the ICU stratum of the CENTER-TBI study. A random effect logistic regression model was used to determine between-centre variation in their use. A propensity score-matched model was used to study the impact on outcome (6-months Glasgow Outcome Score-extended (GOSE)), whilst adjusting for case-mix severity, signs of brain herniation on imaging, and ICP.

RESULTS

313 of 758 patients from 52 European centres (41%) received at least one high TIL treatment with significant variation between centres (median odds ratio = 2.26). Patients often transiently received high TIL therapies without escalation from lower tier treatments. 38% of patients with high TIL treatment had favourable outcomes (GOSE ≥ 5). The use of high TIL treatment was not significantly associated with worse outcome (285 matched pairs, OR 1.4, 95% CI [1.0-2.0]). However, a sensitivity analysis excluding high TIL treatments at day 1 or use of metabolic suppression at any day did reveal a statistically significant association with worse outcome.

CONCLUSION

Substantial between-centre variation in use of high TIL treatments for TBI was found and treatment escalation to higher TIL treatments were often not preceded by more conventional lower TIL treatments. The significant association between high TIL treatments after day 1 and worse outcomes may reflect aggressive use or unmeasured confounders or inappropriate escalation strategies.

TAKE HOME MESSAGE

Substantial variation was found in the use of highly intensive ICP-lowering treatments across European ICUs and a stepwise escalation strategy from lower to higher intensity level therapy is often lacking. Further research is necessary to study the impact of high therapy intensity treatments.

TRIAL REGISTRATION

The core study was registered with ClinicalTrials.gov, number NCT02210221, registered 08/06/2014, https://clinicaltrials.gov/ct2/show/NCT02210221?id=NCT02210221&draw=1&rank=1 and with Resource Identification Portal (RRID: SCR_015582).

Hyperventilation in Adult TBI Patients: How to Approach It?

Hyperventilation is a commonly used therapy to treat intracranial hypertension (ICTH) in traumatic brain injury patients (TBI). Hyperventilation promotes hypocapnia, which causes vasoconstriction in the cerebral arterioles and thus reduces cerebral blood flow and, to a lesser extent, cerebral blood volume effectively, decreasing temporarily intracranial pressure. However, hyperventilation can have serious systemic and cerebral deleterious effects, such as ventilator-induced lung injury or cerebral ischemia. The routine use of this therapy is therefore not recommended. Conversely, in specific conditions, such as refractory ICHT and imminent brain herniation, it can be an effective life-saving rescue therapy. The aim of this review is to describe the impact of hyperventilation on extra-cerebral organs and cerebral hemodynamics or metabolism, as well as to discuss the side effects and how to implement it to manage TBI patients.

The effects of arterial CO2 on the injured brain: Two faces of the same coin

Serum levels of carbon dioxide (CO₂) closely regulate cerebral blood flow (CBF) and actively participate in different aspects of brain physiology such as hemodynamics, oxygenation, and metabolism. Fluctuations in the partial pressure of arterial CO₂ (PaCO₂) modify the aforementioned variables, and at the same time influence physiologic parameters in organs such as the lungs, heart, kidneys, and the gastrointestinal tract. In general, during acute brain injury (ABI), maintaining normal PaCO₂ is the target to be achieved. Both hypercapnia and hypocapnia may comprise secondary insults and should be avoided during ABI. The risks of hypocapnia mostly outweigh the potential benefits. Therefore, its therapeutic applicability is limited to transient and second-stage control of intracranial hypertension. On the other hand, inducing hypercapnia could be beneficial when certain specific situations require increasing CBF. The evidence supporting this claim is very weak. This review attempts providing an update on the physiology of CO₂, its risks, benefits, and potential utility in the neurocritical care setting.

Hypocapnia, ischemic lesions, and outcomes after intracerebral hemorrhage

BACKGROUND

An association between spontaneous hyperventilation, delayed cerebral ischemia, and poor clinical outcomes has been reported in subarachnoid hemorrhage. We evaluated the relationship between early pCO₂ changes, ischemic lesions and outcomes in patients with intracerebral hemorrhage (ICH).

METHODS

Consecutive patients with spontaneous ICH were enrolled in an observational cohort study conducted between 2006 and 2019. Patient characteristics and discharge outcome were prospectively recorded. Arterial blood gas (ABG) measurements and mechanical ventilation settings in the first 72 h of admission were retrospectively collected. MRI images were adjudicated for diffusion-restricted lesions consistent with ischemia and distant from the hematoma. We examined the associations between pCO₂ changes, ischemic lesions, and discharge outcomes by univariate and adjusted analyses.

RESULTS

ABG data were available for 220 patients. Hyperventilation occurred in 52 (28%) cases and was not associated with clinical severity. Lower initial pCO₂ was associated with greater risk of in-hospital death (OR 0.94 per mmHg, 95%CI [0.89, 0.996], p = 0.042) after adjustment for ICH Score, pneumonia and mechanical ventilation requirements. MRI data were available for 33 patients. Lower pCO₂ was associated with a higher risk of ischemic lesions, except in patients with low initial systolic blood pressure (p < 0.05 for main and blood pressure interaction effects), after adjustment for other predictors.

CONCLUSIONS

In ICH patients with spontaneous ventilation, lower pCO₂ was independently associated with greater risk of in-hospital death. In patients with elevated initial blood pressure, who undergo blood pressure reduction per guideline recommendations, lower pCO₂ was associated with increased risk to develop ischemic lesions.

Hyperventilation in neurological patients: from physiology to outcome evidence

Hyperventilation is commonly used in neurological patients to decrease elevated intracranial pressure (ICP) or relax a tense brain. However, the potentially deleterious effects of hyperventilation may limit its clinical application. The aim of this review is to summarize the physiological and outcome evidence related to hyperventilation in neurological patients.

High-normal PaCO2 values might be associated with worse outcome in patients with subarachnoid hemorrhage - a retrospective cohort study

BACKGROUND

While both hypercapnia and hypocapnia are harmful in patients with subarachnoid hemorrhage (SAH), it is unknown whether high-normal P_aCO₂ values are better than low-normal values. We hypothesized that high-normal P_aCO₂ values have more detrimental than beneficial effects on outcome.

METHODS

Consecutive patients with aneurysmal subarachnoid hemorrhage (aSAH) requiring mechanical ventilation treated in a tertiary care university hospital were retrospectively analyzed regarding the influence of P_aCO₂ on favorable outcome, defined as modified Rankin scale score < 3 at discharge. Primary endpoint was the difference in the proportion of P_aCO₂ values above 40 mmHg in relation to all measured P_aCO₂ values between patients with favorable and unfavorable outcome.

RESULTS

150 patients were included. Median age was 57 years (p25:50, p75:64), median Hunt-Hess score was 4 (p25:3, p75:5). P_aCO₂ values were mainly within normal range (median 39.0, p25:37.5, p75:41.4). Patients with favorable outcome had a lower proportion of high-normal P_aCO₂ values above 40 mmHg compared to patients with unfavorable outcome (0.21 (p25:0.13, p75:0.50) vs. 0.4 (p25:0.29, p75:0.59)) resulting in a lower chance for favorable outcome (OR 0.04, 95% CI 0.00-0.55, p = 0.017). In multivariable analysis adjusted for Hunt-Hess score, pneumonia and length of stay, elevated P_aCO₂ remained an independent predictor of outcome (OR 0.05, 95% CI 0.00-0.81, p = 0.035).

CONCLUSIONS

A higher proportion of P_aCO₂ values above 40 mmHg was an independent predictor of outcome in patients with aSAH in our study. The results need to be confirmed in a prospective trial.

Feasibility of improving cerebral autoregulation in acute intracerebral hemorrhage (BREATHE-ICH) study: Results from an experimental interventional study

Background

Cerebral autoregulation is impaired in a multitude of neurological conditions. Increasingly, clinical studies are correlating the nature of this impairment with prognostic markers. In acute intracerebral hemorrhage, impairment of cerebral autoregulation has been associated with worsening clinical outcomes including poorer Glasgow Coma Score and larger hematoma volume. Hypocapnia has been shown to improve cerebral autoregulation despite concerns over hypoperfusion and consequent ischemic risks, and it is therefore hypothesized that hypocapnia (via hyperventilation) in acute intracerebral hemorrhage may improve cerebral autoregulation and consequently clinical outcome.

Aims

To assess the feasibility and acceptability of the first cerebral autoregulation-targeted intervention in acute intracerebral hemorrhage utilizing a simple bed-side hyperventilatory maneuver.

Methods

Twelve patients with acute intracerebral hemorrhage within 48 h of onset were enrolled. The experimental setup measured cerebral blood flow velocity (transcranial Doppler), blood pressure (Finometer), and end-tidal CO2 (EtCO2, capnography) at baseline, and in response to hypocapnia (−5 mmHg below baseline) achieved via a 90-s hyperventilatory maneuver. Cerebral autoregulation was evaluated with transfer function analysis and autoregulatory index calculations.

Results

We observed tolerance to the protocol in a cohort of mild (National Institutes of Health Scale 4) supratentorial intracerebral hemorrhage patients with small volume hematomas without intraventricular extension. Importantly, a significant difference was noted between ipsilateral autoregulatory index at baseline 4.8 (1.7) and autoregulatory index during hypocapnic intervention 7.0 (0.8) (p = 0.0004), reflecting improved cerebral autoregulation, though a dose-dependent effect of EtCO2 on autoregulatory index was not observed.

Conclusions

In this small study, there was no observed effect on 14-day death and disability in recruited participants. This is the first report of improvement in cerebral autoregulation in acute intracerebral hemorrhage using a non-invasive interventional maneuver, through induction of hypocapnia via hyperventilation. ClinicalTrials.gov Identifier: NCT03324321 URL: https://clinicaltrials.gov/ct2/show/NCT03324321

Adherence to Brain Trauma Foundation Guidelines for Management of Traumatic Brain Injury Patients and Its Effect on Outcomes: Systematic Review

Traumatic brain injury (TBI) management based on Brain Trauma Foundation (BTF) guidelines is widely accepted and thought to improve outcome. The objectives of this study are to provide an overview of adherence to BTF guidelines and to explore which factors influence adherence. We conducted a search of relevant electronic bibliographic databases. Twenty articles met inclusion/exclusion criteria out of 666 articles screened. All were cohort studies. Wide variation in adherence to BTF guidelines was observed with a median of 66.2% (range 0-100%). The lowest median adherence was observed with surgical management (14%), whereas the highest was observed with oxygenation (100%), steroid (97.8%), and blood pressure recommendation (92.3%). Variability was primarily explained by the variation in the strength of evidence of each recommendation. Treating patients with higher severity of injury as well as treatment in a Level I trauma center positively influenced adherence. Overall, adherence to BTF guidelines varies. Further research is required to strengthen the current evidence and to identify factors related to adherence to guidelines from a professional prospective.

Feasibility of Improving Cerebral Autoregulation in Acute Intracerebral Haemorrhage (BREATHE-ICH) study: a protocol for an experimental interventional study

INTRODUCTION

Cerebral autoregulation (CA) is impaired in a multitude of neurological conditions. Increasingly, clinical studies are correlating the nature of this impairment with prognostic markers. In acute intracerebral haemorrhage (ICH), impairment of CA has been associated with worsening clinical outcomes including poorer Glasgow Coma Score and larger haematoma volume. Hypocapnia has been shown to improve CA despite concerns over hypoperfusion and consequent ischaemic risks, and it is therefore hypothesised that hypocapnia (via hyperventilation) in acute ICH may improve CA and consequently clinical outcome. BREATHE-ICH is a CA-targeted interventional study in acute ICH utilising a simple bedside hyperventilatory manoeuvre.

METHODS AND ANALYSIS

Patients with acute ICH within 48 hours of onset will be included. The experimental set-up measures cerebral blood flow (cerebral blood velocity, transcranial Doppler), blood pressure (Finometer) and end tidal carbon dioxide (capnography) at baseline, and in response to hypocapnia (-5 mm and -10 mm Hg below baseline) achieved via a 90 s hyperventilatory manoeuvre. Autoregulation is evaluated with transfer function analysis and autoregulatory index calculations. Important classical endpoints associated with this before and after interventional study include death and disability at 14 days and the proportion of recruited individuals able to comply with the full measurement protocol.

ETHICS AND DISSEMINATION

A favourable opinion was granted by the East Midlands-Nottingham 1 Research Ethics Committee (17/EM/0283). It is anticipated that the results of this study will be presented at national and international meetings, with reports being published in journals during late 2018.

TRIAL REGISTRATION NUMBER

NCT03324321.

Hyperventilation Therapy for Control of Posttraumatic Intracranial Hypertension

During traumatic brain injury, intracranial hypertension (ICH) can become a life-threatening condition if it is not managed quickly and adequately. Physicians use therapeutic hyperventilation to reduce elevated intracranial pressure (ICP) by manipulating autoregulatory functions connected to cerebrovascular CO₂ reactivity. Inducing hypocapnia via hyperventilation reduces the partial pressure of arterial carbon dioxide (PaCO₂), which incites vasoconstriction in the cerebral resistance arterioles. This constriction decrease cerebral blood flow, which reduces cerebral blood volume and, ultimately, decreases the patient’s ICP. The effects of therapeutic hyperventilation (HV) are transient, but the risks accompanying these changes in cerebral and systemic physiology must be carefully considered before the treatment can be deemed advisable. The most prominent criticism of this approach is the cited possibility of developing cerebral ischemia and tissue hypoxia. While it is true that certain measures, such as cerebral oxygenation monitoring, are needed to mitigate these dangerous conditions, using available evidence of potential poor outcomes associated with HV as justification to dismiss the implementation of therapeutic HV is debatable and remains a controversial subject among physicians. This review highlights various issues surrounding the use of HV as a means of controlling posttraumatic ICH, including indications for treatment, potential risks, and benefits, and a discussion of what techniques can be implemented to avoid adverse complications.

Acute brain trauma, lung injury, and pneumonia: more than just altered mental status and decreased airway protection

Traumatic brain injury (TBI) is a major cause of mortality and morbidity worldwide. Even when patients survive the initial insult, there is significant morbidity and mortality secondary to subsequent pulmonary edema, acute lung injury (ALI), and nosocomial pneumonia. Whereas the relationship between TBI and secondary pulmonary complications is recognized, little is known about the mechanistic interplay of the two phenomena. Changes in mental status secondary to acute brain injury certainly impair airway- and lung-protective mechanisms. However, clinical and translational evidence suggests that more specific neuronal and cellular mechanisms contribute to impaired systemic and lung immunity that increases the risk of TBI-mediated lung injury and infection. To better understand the cellular mechanisms of that immune impairment, we review here the current clinical data that support TBI-induced impairment of systemic and lung immunity. Furthermore, we also review the animal models that attempt to reproduce human TBI. Additionally, we examine the possible role of damage-associated molecular patterns, the chlolinergic anti-inflammatory pathway, and sex dimorphism in post-TBI ALI. In the last part of the review, we discuss current treatments and future pharmacological therapies, including fever control, tracheostomy, and corticosteroids, aimed to prevent and treat pulmonary edema, ALI, and nosocomial pneumonia after TBI.

Association between ventilatory settings and development of acute respiratory distress syndrome in mechanically ventilated patients due to brain injury

PURPOSE

In neurologically critically ill patients with mechanical ventilation (MV), the development of acute respiratory distress syndrome (ARDS) is a major contributor to morbidity and mortality, but the role of ventilatory management has been scarcely evaluated. We evaluate the association of tidal volume, level of PEEP and driving pressure with the development of ARDS in a population of patients with brain injury.

MATERIALS AND METHODS

We performed a secondary analysis of a prospective, observational study on mechanical ventilation.

RESULTS

We included 986 patients mechanically ventilated due to an acute brain injury (hemorrhagic stroke, ischemic stroke or brain trauma). Incidence of ARDS in this cohort was 3%. Multivariate analysis suggested that driving pressure could be associated with the development of ARDS (odds ratio for unit increment of driving pressure 1.12; confidence interval for 95%: 1.01 to 1.23) whereas we did not observe association for tidal volume (in ml per kg of predicted body weight) or level of PEEP. ARDS was associated with an increase in mortality, longer duration of mechanical ventilation, and longer ICU length of stay.

CONCLUSIONS

In a cohort of brain-injured patients the development of ARDS was not common. Driving pressure was associated with the development of this disease.

Contrast-Enhanced Ultrasound Imaging in Detection of Changes in Cerebral Perfusion

Contrast-enhanced ultrasonography (CEU) is a non-invasive imaging technique that provides real-time, bedside information on changes in global and segmental organ perfusion. Currently, there is a lack of data concerning changes in the distribution of segmental brain perfusion in acute ischemic stroke treated by decompressive craniectomy. The aim of our case series was to assess the role of CEU after decompressive craniectomy in patients with acute ischemic stroke. CEU was performed in 12 patients at baseline and after any one of the following interventions was performed as dictated by the patient's clinical condition: vasoactive drug administration (in order to achieve cerebral perfusion pressure ≥70 mm Hg and mean arterial pressure <100 mm Hg for management of arterial blood pressure) and mild hyperventilation (carbon dioxide arterial pressure = 30-35 mm Hg). CEU was able to detect a significant variation in cerebral contrast distribution in both normal and pathologic hemispheres after induced hyperventilation (difference in time to peak [dTTP] = -38.4%), vasodilation (dTTP = -6.6%) and vasoconstriction (dTTP = +31.2%) (p < 0.05). CEU can be useful in assessing real-time cerebral perfusion changes in neurocritical care patients.

Monitoring intracranial pressure utilizing a novel pattern of brain multiparameters in the treatment of severe traumatic brain injury

The aim of the study was to evaluate the clinical value of multiple brain parameters on monitoring intracranial pressure (ICP) procedures in the therapy of severe traumatic brain injury (sTBI) utilizing mild hypothermia treatment (MHT) alone or a combination strategy with other therapeutic techniques. A total of 62 patients with sTBI (Glasgow Coma Scale score <8) were treated using mild hypothermia alone or mild hypothermia combined with conventional ICP procedures such as dehydration using mannitol, hyperventilation, and decompressive craniectomy. The multiple brain parameters, which included ICP, cerebral perfusion pressure, transcranial Doppler, brain tissue partial pressure of oxygen, and jugular venous oxygen saturation, were detected and analyzed. All of these measures can control the ICP of sTBI patients to a certain extent, but multiparameters associated with brain environment and functions have to be critically monitored simultaneously because some procedures of reducing ICP can cause side effects for long-term recovery in sTBI patients. The result suggested that multimodality monitoring must be performed during the process of mild hypothermia combined with conventional ICP procedures in order to safely target different clinical methods to specific patients who may benefit from an individual therapy.

Hypocapnia leads to enhanced expression of pluripotency and meso-endodermal differentiation genes in mouse embryonic stem cells

The efficient utilization of embryonic stem cells for applications like cell based therapy, transplantation and drug discovery largely depends upon the culturing conditions of these cells. In this report, we have analyzed gene, protein expression and morphological changes of embryonic stem cells when subjected to lowered CO2 levels i.e. hypocapnia. We studied the quantitative expression of pluripotent genes, Oct3/4, Nanog and Sox2 and genes involved in the differentiation to the three lineages, under varying CO2 levels. Enhanced expression of these genes was seen at cultures maintained at 1.5% CO2 as compared to those maintained at 5% CO2. The cells exposed to hypocapnic conditions when subjected to immunocytochemical analysis stained positive for Oct-3/4, Nanog and Sox2 transcription factors. Flow cytometry and western blot further showed that the pluripotent proteins in the 1.5% CO2 maintained cultures have higher levels of expression as compared to the ES cells at 5% CO2. In addition, there was enhanced differentiation particularly towards the mesodermal and endodermal lineages at cultures maintained and differentiated at 1.5% CO2 at all the time periods analyzed i.e. day 10 (5+5d), 12 (5+7d) and day 15 (5+10d). These results, which we feel are the first of their kind, indicate that lowered CO2 levels seem to be preferred for the maintenance of pluripotency and the subsequent differentiation.

A survey of routine treatment of patients with intracranial hypertension (ICH) in specialized trauma centers in Sao Paulo, Brazil: a 11 million metropole!

OBJECTIVE

A survey of intensive care units (ICU) in São Paulo that care for patients with TBI and ICH using the hyperventilation technique.

METHODS

A questionnaire was given to the physiotherapist coordinator at 57 hospitals in São Paulo, where 24-h neurosurgery service is provided.

RESULTS

Fifty-one (89.5%) hospitals replied. From this total, thirty-four (66.7% perform the hyperventilation technique, 30 (85%) had the objective to reach values below 35 mmHg, four (11%) levels between 35 mmHg and 40 mmHg and one (3%) values over 40 mmHg.

CONCLUSIONS

We concluded that most hospitals in São Paulo perform hyperventilation in patients with severe brain trauma although there are not any specific Brazilian guidelines on this topic. Widespread controversy on the use of the hyperventilation technique in patients with severe brain trauma highlights the need for a specific Global policy on this topic.

Pro/con debate: should PaCO2 be tightly controlled in all patients with acute brain injuries?

You are the attending intensivist in a neurointensive care unit caring for a woman five days post-rupture of a cerebral aneurysm (World Federation of Neurological Surgeons Grade 4 and Fisher Grade 3). She is intubated for airway protection and mild hypoxemia related to an aspiration event at the time of aneurysm rupture, but is breathing spontaneously on the ventilator. Your patient is spontaneously hyperventilating with high tidal volumes despite minimal support and has developed significant hypocapnia. She has not yet developed the acute respiratory distress syndrome. You debate whether to tightly control her partial pressure of arterial carbon dioxide, weighing the known risks of acute hypocapnia in other forms of brain injury against the potential loss of clinical neuromonitoring associated with deep sedation and neuromuscular blockade in this patient who is at high risk of delayed ischemia from vasospasm. You are also aware of the potential implications of tidal volume control if this patient were to develop the acute respiratory distress syndrome and the effect of permissive hypercapnia on her intracranial pressure. In this paper we provide a detailed and balanced examination of the issues pertaining to this clinical scenario, including suggestions for clinical management of ventilation, sedation and neuromonitoring. Until more definitive clinical trial evidence is available to guide practice, clinicians are forced to carefully weigh the potential benefits of tight carbon dioxide control against the potential risks in each individual patient based on the clinical issues at hand.

Pulmonary complications in patients with severe brain injury

Pulmonary complications are prevalent in the critically ill neurological population. Respiratory failure, pneumonia, acute lung injury and the acute respiratory distress syndrome (ALI/ARDS), pulmonary edema, pulmonary contusions and pneumo/hemothorax, and pulmonary embolism are frequently encountered in the setting of severe brain injury. Direct brain injury, depressed level of consciousness and inability to protect the airway, disruption of natural defense barriers, decreased mobility, and secondary neurological insults inherent to severe brain injury are the main cause of pulmonary complications in critically ill neurological patients. Prevention strategies and current and future therapies need to be implemented to avoid and treat the development of these life-threatening medical complications.

Acute liver failure: current practice and recent advances

ALF is an important cause of liver-related morbidity and mortality. Advances in the management of ICH and SIRS, and cardiorespiratory, metabolic, and renal support have improved the outlook of such patients. Early transfer to a liver transplant center is essential. Routine use of NAC is recommended for patients with early hepatic encephalopathy, irrespective of the etiology. The role of hypothermia remains to be determined. Liver transplantation plays a critical role, particularly for those with advanced encephalopathy. Several detoxification and BAL support systems have been developed to serve as a bridge to transplantation or to spontaneous recovery. However, such systems lack sufficient reliability and efficacy to be applied routinely in clinical practice. Hepatocyte and stem cell transplantation may provide valuable adjunctive therapy in the future.

Acute lung injury in patients with severe brain injury: a double hit model

The presence of pulmonary dysfunction after brain injury is well recognized. Acute lung injury (ALI) occurs in 20% of patients with isolated brain injury and is associated with a poor outcome. The "blast injury" theory, which proposes combined "hydrostatic" and "high permeability" mechanisms for the formation of neurogenic pulmonary edema, has been challenged recently by the observation that a systemic inflammatory response may play an integral role in the development of pulmonary dysfunction associated with brain injury. As a result of the primary cerebral injury, a systemic inflammatory reaction occurs, which induces an alteration in blood-brain barrier permeability and infiltration of activated neutrophils into the lung. This preclinical injury makes the lungs more susceptible to the mechanical stress of an injurious ventilatory strategy. Tight CO2 control is a therapeutic priority in patients with acute brain injury, but the use of high tidal volume ventilation may contribute to the development of ALI. Establishment of a therapeutic regimen that allows the combination of protective ventilation with the prevention of hypercapnia is, therefore, required. Moreover, in patients with brain injury, hypoxemia represents a secondary insult associated with a poor outcome. Optimal oxygenation may be achieved by using an adequate FiO2 and by application of positive end-expiratory pressure (PEEP). PEEP may, however, affect the cerebral circulation by hemodynamic and CO2-mediated mechanisms and the effects of PEEP on cerebral hemodynamics should be monitored in these patients and used to titrate its application.

Traumatic brain injury: review of current management strategies

Head injury is a common condition with a high morbidity and mortality. Serious intracranial haematomas require early recognition and evacuation to maximise chances of independent outcomes. Recent organisational changes have promoted the development of trauma units and major trauma centres where patients can go through triage and be managed in an appropriate environment, and the development of management pathways in intensive treatment units has resulted in improvements in the outcome of traumatic brain injuries. Evidence for the treatment of cerebral perfusion pressure, and management of hyperventilation, osmotherapy, tracheostomy, and leakage of cerebrospinal fluid (CSF) has accumulated during the last decade and is important in the management of patients in all clinical settings. Since head injury is commonly associated with maxillofacial injuries, this review will be relevant to all who deal with this aspect of trauma.

Regulation of gene expression by carbon dioxide

Carbon dioxide (CO(2)) is a physiological gas found at low levels in the atmosphere and produced in cells during the process of aerobic respiration. Consequently, the levels of CO(2) within tissues are usually significantly higher than those found externally. Shifts in tissue levels of CO(2) (leading to either hypercapnia or hypocapnia) are associated with a number of pathophysiological conditions in humans and can occur naturally in niche habitats such as those of burrowing animals. Clinical studies have indicated that such altered CO(2) levels can impact upon disease progression. Recent advances in our understanding of the biology of CO(2) has shown that like other physiological gases such as molecular oxygen (O(2)) and nitric oxide (NO), CO(2) levels can be sensed by cells resulting in the initiation of physiological and pathophysiological responses. Acute CO(2) sensing in neurons and peripheral and central chemoreceptors is important in rapidly activated responses including olfactory signalling, taste sensation and cardiorespiratory control. Furthermore, a role for CO(2) in the regulation of gene transcription has recently been identified with exposure of cells and model organisms to high CO(2) leading to suppression of genes involved in the regulation of innate immunity and inflammation. This latter, transcriptional regulatory role for CO(2), has been largely attributed to altered activity of the NF-B family of transcription factors. Here, we review our evolving understanding of how CO(2) impacts upon gene transcription.

Bench-to-bedside review: carbon dioxide

Carbon dioxide is a waste product of aerobic cellular respiration in all aerobic life forms. PaCO2 represents the balance between the carbon dioxide produced and that eliminated. Hypocapnia remains a common - and generally underappreciated - component of many disease states, including early asthma, high-altitude pulmonary edema, and acute lung injury. Induction of hypocapnia remains a common, if controversial, practice in both adults and children with acute brain injury. In contrast, hypercapnia has traditionally been avoided in order to keep parameters normal. More recently, advances in our understanding of the role of excessive tidal volume has prompted clinicians to use ventilation strategies that result in hypercapnia. Consequently, hypercapnia has become increasingly prevalent in the critically ill patient. Hypercapnia may play a beneficial role in the pathogenesis of inflammation and tissue injury, but may hinder the host response to sepsis and reduce repair. In contrast, hypocapnia may be a pathogenic entity in the setting of critical illness. The present paper reviews the current clinical status of low and high PaCO2 in the critically ill patient, discusses the insights gained to date from studies of carbon dioxide, identifies key concerns regarding hypocapnia and hypercapnia, and considers the potential clinical implications for the management of patients with acute lung injury.

Clinical management and functional neuromonitoring in traumatic brain injury in children

PURPOSE OF REVIEW

Traumatic brain injury is the main cause of childhood disability and death. In this review, we highlight recent original findings and emerging themes from published literature on children with serious traumatic brain injury.

RECENT FINDINGS

We focus this review on lessons learned from our recent randomized clinical trial of hypothermia therapy in severe traumatic brain injury in children and on bedside neuromonitoring. We propose that integrating the measurement of biomarkers into clinical care as surrogate endpoints and as potential prognostic markers would allow us to evaluate earlier the effect of injury and clinical care in children after traumatic brain injury. Several methods are now more readily available to monitor cerebral physiology in children. These methods include indices evaluating the integrity of cerebral autoregulation, such as the pressure reactivity index derived from values obtained from intracranial pressure measurements, flow velocity measurements from transcranial Doppler ultrasonography or from cerebral oximetry. Other methods allow the evaluation of coma with the nonlinear analysis of electroencephalography or the evaluation of cerebral metabolism and cell death pathways with biomarkers from serum, cerebral spinal fluid, and cerebral microdialysis.

SUMMARY

We suggest expanding clinical functional neuromonitoring to help clinicians understand the burden of exposure to physiological variables and response to therapies during intensive care in order to enhance the management of critically ill children with traumatic brain injury.

The pathophysiology and causes of raised intracranial pressure

This article explains the pathophysiology and causes of raised intracranial pressure (ICP), and the significance of assessing and recording vital observations for all patients when admitted to hospital. It discusses the nursing care, treatment and management required in order to minimize the risk of further increases in ICP.

Prehospital endotracheal intubation in patients with severe traumatic brain injury: guidelines versus reality

The international Brain Trauma Foundation guidelines recommend prehospital endotracheal intubation in all patients with traumatic brain injury (TBI) and a Glasgow Coma Scale (GCS)< or =8. Close adherence to these guidelines is associated with improved outcome, but not all severely injured TBI patients receive adequate prehospital airway support. Here we hypothesized that guideline adherence varies when skills are involved that rely on training and expertise, such as endotracheal intubation. We retrospectively studied the medical records of CT-confirmed TBI patients with a GCS< or =8 who were referred to a level 1 trauma centre in Amsterdam (n=127). Records were analyzed for demographic parameters, prehospital treatment modalities, involvement of an emergency medical service (EMS) and respiratory and metabolic parameters upon arrival at the hospital. Patients were mostly male, aged 45+/-21 years with a median injury severity score (ISS) of 26. Of all patients for whom guidelines recommend endotracheal intubation, only 56% were intubated. In 21 out of 106 severe cases an EMS was not called for, suggesting low guideline adherence. Especially those TBI patients treated by paramedics tended to develop higher levels of stress markers like glucose and lactate. We observed a low degree of adherence to intubation guidelines in a Dutch urban area. Main reasons for low adherence were the unavailability of specialized care, scoop and run strategies and absence of a specialist physician in cases where intubation was recommended. The discrepancy between guidelines and reality warrants changing practice to improve guideline compliance and optimize outcome in TBI patients.

Acute lung injury in patients with severe brain injury: a double hit model

The presence of pulmonary dysfunction after brain injury is well recognized. Acute lung injury (ALI) occurs in 20% of patients with isolated brain injury and is associated with a poor outcome. The "blast injury" theory, which proposes combined "hydrostatic" and "high permeability" mechanisms for the formation of neurogenic pulmonary edema, has been challenged recently by the observation that a systemic inflammatory response may play an integral role in the development of pulmonary dysfunction associated with brain injury. As a result of the primary cerebral injury, a systemic inflammatory reaction occurs, which induces an alteration in blood-brain barrier permeability and infiltration of activated neutrophils into the lung. This preclinical injury makes the lungs more susceptible to the mechanical stress of an injurious ventilatory strategy. Tight CO2 control is a therapeutic priority in patients with acute brain injury, but the use of high tidal volume ventilation may contribute to the development of ALI. Establishment of a therapeutic regimen that allows the combination of protective ventilation with the prevention of hypercapnia is, therefore, required. Moreover, in patients with brain injury, hypoxemia represents a secondary insult associated with a poor outcome. Optimal oxygenation may be achieved by using an adequate FiO2 and by application of positive end-expiratory pressure (PEEP). PEEP may, however, affect the cerebral circulation by hemodynamic and CO2-mediated mechanisms and the effects of PEEP on cerebral hemodynamics should be monitored in these patients and used to titrate its application.