Effects of PaCO2 derangements on clinical outcomes after cerebral injury: A systematic review

Partial pressure of carbon dioxide/pH interaction and its association with mortality among patients mechanically ventilated in the emergency department

OBJECTIVES

There is currently conflicting data as to the effects of hypercapnia on clinical outcomes among mechanically ventilated patients in the emergency department (ED). These conflicting results may be explained by the degree of acidosis. We sought to test the hypothesis that hypercapnia is associated with increased in-hospital mortality and decreased ventilator-free days at lower pH, but associated with decreased in-hospital mortality and increased ventilator-free days at higher pH, among patients requiring mechanical ventilation in the emergency department (ED).

METHODS

Secondary analysis of patient level data from prior clinical trials and cohort studies that enrolled adult patients who required mechanical ventilation in the ED. Patients who had a documented blood gas while on mechanical ventilation in the ED were included in these analyses. The primary outcome was in-hospital mortality, and secondary outcome was ventilator-free days. Mixed-effects logistic, linear, and survival-time regression models were used to test if pH modified the association between partial pressure of carbon dioxide (pCO2) and outcome measures.

RESULTS

Of the 2348 subjects included, the median [interquartile range (IQR)] pCO2 was 43 (35-54) and pH was 7.31 (7.22-7.39). Overall, in-hospital mortality was 27%. We found pH modified the association between pCO2 and outcomes, with higher pCO2 associated with increased probability of in-hospital mortality when pH is below 7.00, and decreased probability of in-hospital mortality when pH is above 7.10. These results remained consistent across multiple sensitivity and subgroup analyses. A similar relationship was found with ventilator-free days.

CONCLUSIONS

Higher pCO2 is associated with decreased mortality and greater ventilator-free days when pH is >7.10; however, it is associated with increased mortality and fewer ventilator-free days when the pH is below 7.00. Targeting pCO2 based on pH in the ED may be a potential intervention target for future clinical trials to improve clinical outcomes.

Acute Respiratory Failure in Severe Acute Brain Injury

Acute respiratory failure is commonly encountered in severe acute brain injury due to a multitude of factors related to the sequelae of the primary injury. The interaction between pulmonary and neurologic systems in this population is complex, often with competing priorities. Many treatment modalities for acute respiratory failure can result in deleterious effects on cerebral physiology, and secondary brain injury due to elevations in intracranial pressure or impaired cerebral perfusion. High-quality literature is lacking to guide clinical decision-making in this population, and deliberate considerations of individual patient factors must be considered to optimize each patient's care.

Adult Highlights From the Extracorporeal Life Support Organization Registry: 2017-2022

The Extracorporeal Life Support Organization (ELSO) registry captures clinical data and outcomes on patients receiving extracorporeal membrane oxygenation (ECMO) support across the globe at participating centers. It provides a very unique opportunity to benchmark outcomes and analyze the clinical course to help identify ways of improving patient outcomes. In this review, we summarize select adult ECMO articles published using the ELSO registry over the past 5 years. These articles highlight innovative utilization of the registry data in generating hypotheses for future clinical trials. Members of the ELSO Scientific Oversight Committee can be found here: https://www.elso.org/registry/socmembers.aspx .

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.

Early Changes in Arterial Partial Pressure of Carbon Dioxide and Blood Pressure After Starting Extracorporeal Membrane Oxygenation in Children: Extracorporeal Life Support Organization Database Study of Neurologic Complications

OBJECTIVE

Neurologic complications in pediatric patients supported by extracorporeal membrane oxygenation (ECMO) are common and lead to morbidity and mortality; however, few modifiable factors are known.

DESIGN

Retrospective study of the Extracorporeal Life Support Organization registry (2010-2019).

SETTING

Multicenter international database.

PATIENTS

Pediatric patients receiving ECMO (2010-2019) for all indications and any mode of support.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We investigated if early relative change in Pa co2 or mean arterial blood pressure (MAP) soon after starting ECMO was associated with neurologic complications. The primary outcome of neurologic complications was defined as a report of seizures, central nervous system infarction or hemorrhage, or brain death. All-cause mortality (including brain death) was used as a secondary outcome.Out of 7,270 patients, 15.6% had neurologic complications. Neurologic complications increased when the relative Pa co2 decreased by greater than 50% (18.4%) or 30-50% (16.5%) versus those who had a minimal change (13.9%, p < 0.01 and p = 0.046). When the relative MAP increased greater than 50%, the rate of neurologic complications was 16.9% versus 13.1% those with minimal change ( p = 0.007). In a multivariable model adjusting for confounders, a relative decrease in Pa co2 greater than 30% was independently associated with greater odds of neurologic complication (odds ratio [OR], 1.25; 95% CI, 1.07-1.46; p = 0.005). Within this group, with a relative decrease in Pa co2 greater than 30%, the effects of increased relative MAP increased neurologic complications (0.05% per BP Percentile; 95% CI, 0.001-0.11; p = 0.05).

CONCLUSIONS

In pediatric patients, a large decrease in Pa co2 and increase in MAP following ECMO initiation are both associated with neurologic complications. Future research focusing on managing these issues carefully soon after ECMO deployment can potentially help to reduce neurologic complications.

Dual titration of minute ventilation and sweep gas flow to control carbon dioxide variations in patients on venovenous extracorporeal membrane oxygenation

BACKGROUND

The implantation of venovenous extracorporeal membrane oxygenation (VV-ECMO) support to manage severe acute respiratory distress syndrome generates large variations in carbon dioxide partial pressure (PaCO₂) that are associated with intracranial bleeding. We assessed the feasibility and efficacy of a pragmatic protocol for progressive dual titration of sweep gas flow and minute ventilation after VV-ECMO implantation in order to limit significant PaCO₂ variations.

PATIENTS AND METHODS

A protocol for dual titration of sweep gas flow and minute ventilation following VV-ECMO implantation was implemented in our unit in September 2020. In this single-centre retrospective before-after study, we included patients who required VV-ECMO from March, 2020 to May, 2021, which corresponds to two time periods: from March to August, 2020 (control group) and from September, 2020 to May, 2021 (protocol group). The primary endpoint was the mean absolute change in PaCO₂ in consecutive arterial blood gases samples drawn over the first 12 h following VV-ECMO implantation. Secondary endpoints included large (> 25 mmHg) initial variations in PaCO₂, intracranial bleedings and mortality in both groups.

RESULTS

Fifty-one patients required VV-ECMO in our unit during the study period, including 24 in the control group and 27 in the protocol group. The protocol was proved feasible. The 12-h mean absolute change in PaCO₂ was significantly lower in patients of the protocol group as compared with their counterparts (7 mmHg [6-12] vs. 12 mmHg [6-24], p = 0.007). Patients of the protocol group experienced less large initial variations in PaCO₂ immediately after ECMO implantation (7% vs. 29%, p = 0.04) and less intracranial bleeding (4% vs. 25%, p = 0.04). Mortality was similar in both groups (35% vs. 46%, p = 0.42).

CONCLUSION

Implementation of our protocol for dual titration of minute ventilation and sweep gas flow was feasible and associated with less initial PaCO₂ variation than usual care. It was also associated with less intracranial bleeding.

Association between prehospital end-tidal carbon dioxide levels and mortality in patients with suspected severe traumatic brain injury

PURPOSE

Severe traumatic brain injury is a leading cause of mortality and morbidity, and these patients are frequently intubated in the prehospital setting. Cerebral perfusion and intracranial pressure are influenced by the arterial partial pressure of CO₂ and derangements might induce further brain damage. We investigated which lower and upper limits of prehospital end-tidal CO₂ levels are associated with increased mortality in patients with severe traumatic brain injury.

METHODS

The BRAIN-PROTECT study is an observational multicenter study. Patients with severe traumatic brain injury, treated by Dutch Helicopter Emergency Medical Services between February 2012 and December 2017, were included. Follow-up continued for 1 year after inclusion. End-tidal CO₂ levels were measured during prehospital care and their association with 30-day mortality was analyzed with multivariable logistic regression.

RESULTS

A total of 1776 patients were eligible for analysis. An L-shaped association between end-tidal CO₂ levels and 30-day mortality was observed (p = 0.01), with a sharp increase in mortality with values below 35 mmHg. End-tidal CO₂ values between 35 and 45 mmHg were associated with better survival rates compared to < 35 mmHg. No association between hypercapnia and mortality was observed. The odds ratio for the association between hypocapnia (< 35 mmHg) and mortality was 1.89 (95% CI 1.53-2.34, p < 0.001) and for hypercapnia (≥ 45 mmHg) 0.83 (0.62-1.11, p = 0.212).

CONCLUSION

A safe zone of 35-45 mmHg for end-tidal CO₂ guidance seems reasonable during prehospital care. Particularly, end-tidal partial pressures of less than 35 mmHg were associated with a significantly increased mortality.

Ventilatory targets following brain injury

PURPOSE OF REVIEW

Recent studies have focused on identifying optimal targets and strategies of mechanical ventilation in patients with acute brain injury (ABI). The present review will summarize these findings and provide practical guidance to titrate ventilatory settings at the bedside, with a focus on managing potential brain-lung conflicts.

RECENT FINDINGS

Physiologic studies have elucidated the impact of low tidal volume ventilation and varying levels of positive end expiratory pressure on intracranial pressure and cerebral perfusion. Epidemiologic studies have reported the association of different thresholds of tidal volume, plateau pressure, driving pressure, mechanical power, and arterial oxygen and carbon dioxide concentrations with mortality and neurologic outcomes in patients with ABI. The data collectively make clear that injurious ventilation in this population is associated with worse outcomes; however, optimal ventilatory targets remain poorly defined.

SUMMARY

Although direct data to guide mechanical ventilation in brain-injured patients is accumulating, the current evidence base remains limited. Ventilatory considerations in this population should be extrapolated from high-quality evidence in patients without brain injury - keeping in mind relevant effects on intracranial pressure and cerebral perfusion in patients with ABI and individualizing the chosen strategy to manage brain-lung conflicts where necessary.

Association between rate of change in PaCO2 and functional outcome for patients with hypercapnia after out-of-hospital cardiac arrest: Secondary analysis of a randomized clinical trial

BACKGROUND

Normocapnia is suggested for post resuscitation care. For patients with hypercapnia after cardiac arrest, the relationship between rate of change in partial pressure of carbon dioxide (PaCO₂) and functional outcome was unknown.

METHODS

This was the secondary analysis of Resuscitation Outcomes Consortium (ROC) amiodarone, lidocaine, and placebo (ALPS) trial. Patients with at least 2 PaCO₂ recorded and the first indicating hypercapnia (PaCO₂ > 45 mmHg) after return of spontaneous circulation (ROSC) were included. The rate of change in PaCO₂ was calculated as the ratio of the difference between the second and first PaCO₂ to the time interval. The primary outcome was modified Rankin Score (mRS), dichotomized to good (mRS 0-3) and poor (mRS 4-6) outcomes at hospital discharge. The independent relationship between rate of change in PaCO₂ and outcome was investigated with multivariable logistic regression model.

RESULTS

A total of 746 patients with hypercapnia were included for analysis, of which 264 (35.4%) patients had good functional outcome. The median rate of change in PaCO₂ was 4.7 (interquartile range [IQR] 1.7-12) mmHg per hour. After adjusting for confounders, the rate of change in PaCO₂ (odds ratio [OR] 0.994, confidence interval [CI] 0.985-1.004, p = 0.230) was not associated the functional outcome. However, rate of change in PaCO₂ (OR 1.010, CI 1.001-1.019, p = 0.029) was independently associated with hospital mortality.

CONCLUSIONS

For OHCA patients with hypercapnia on admission, the rate of change in PaCO₂ was not independently associated with functional outcome; however, there was a significant trend that higher decreased rate was associated with increased hospital mortality.

Effect of Different Early Oxygenation Levels on Clinical Outcomes of Patients Presenting in the Emergency Department With Severe Traumatic Brain Injury

STUDY OBJECTIVE

Despite the almost universal administration of supplemental oxygen in patients presenting in the emergency department (ED) with severe traumatic brain injury, optimal early oxygenation levels are unknown. Therefore, we aimed to examine the effect of different early oxygenation levels on the clinical outcomes of patients presenting in the emergency department with severe traumatic brain injury.

METHODS

We performed a secondary analysis of the Resuscitation Outcomes Consortium Traumatic Brain Injury Hypertonic Saline randomized controlled trial by including patients with Glasgow Coma Scale ≤8. Early oxygenation levels were assessed by the worst value of arterial partial pressure of oxygen (PaO₂) during the first 4 hours of presentation in the emergency department. The primary outcome was 6-month neurologic status, as assessed by the Extended Glasgow Outcome Scale. A binary logistic regression was utilized, and an odds ratio (OR) with 95% (95% confidence intervals) was calculated.

RESULTS

A total of 910 patients were included. In unadjusted (crude) analysis, a PaO₂ of 101 to 250 mmHg (OR, 0.59 [0.38 to 0.91]), or 251 to 400 mmHg (OR, 0.53 [0.34 to 0.83]) or ≥401 mmHg (OR, 0.31 [0.20 to 0.49]) was less likely to be associated with poor neurologic status when compared with a PaO₂ of ≤100 mmHg. This was also the case for adjusted analyses (including age, pupillary reactivity, and Revised Trauma Score).

CONCLUSION

High oxygenation levels as early as the first 4 hours of presentation in the emergency department may not be adversely associated with the long-term neurologic status of patients with severe traumatic brain injury. Therefore, during the early phase of trauma, clinicians may focus on stabilizing patients while giving low priority to the titration of oxygenation levels.

Pre-hospital tracheal intubation in severe traumatic brain injury: a systematic review and meta-analysis

BACKGROUND

Severe traumatic brain injury (TBI) continues to be a leading cause of death, particularly in young adults. Severe TBI contributes to significant socioeconomic burden secondary to the long-term disability, impacting the individual and their family, and wider society. The aim of this study was to determine whether establishing a pre-hospital definitive airway was beneficial to mortality and morbidity when compared with no pre-hospital airway.

METHODS

A literature search for all relevant studies was performed in Medline, Embase, Cochrane, EBSCO, and Emcare databases, with studies comparing effects of pre-hospital tracheal intubation vs noninvasive airway management on mortality in non-paediatric patients with severe TBI. There were 1025 studies that had abstracts screened from this search. This study was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

We identified 19 studies that met inclusion criteria. The included studies identified no significant difference in mortality between pre-hospital and no pre-hospital tracheal intubation, with an odds ratio of 1.07 (95% CI, 0.72-1.57; P<0.001). The meta-analysis identified a trend favouring pre-hospital tracheal intubation with respect to long-term morbidity, with an odds ratio of 0.92 (95% CI, 0.51-1.67; P<0.001).

CONCLUSIONS

Management of traumatic brain injuries is a constantly evolving field, with ever-changing target parameters regarding management. There is growing evidence, based on the RCTs and recent studies, that pre-hospital tracheal intubation in patients with severe TBI is beneficial if performed by well-trained, experienced practitioners in accordance with current TBI guidelines.

PROSPERO REGISTRATION

CRD42021234439.

Brain-Lung Crosstalk: Management of Concomitant Severe Acute Brain Injury and Acute Respiratory Distress Syndrome

Purpose of Review

To summarize pathophysiology, key conflicts, and therapeutic approaches in managing concomitant severe acute brain injury (SABI) and acute respiratory distress syndrome (ARDS).

Recent Findings

ARDS is common in SABI and independently associated with worse outcomes in all SABI subtypes. Most landmark ARDS trials excluded patients with SABI, and evidence to guide decisions is limited in this population. Potential areas of conflict in the management of patients with both SABI and ARDS are (1) risk of intracranial pressure (ICP) elevation with high levels of positive end-expiratory pressure (PEEP), permissive hypercapnia due to lung protective ventilation (LPV), or prone ventilation; (2) balancing a conservative fluid management strategy with ensuring adequate cerebral perfusion, particularly in patients with symptomatic vasospasm or impaired cerebrovascular blood flow; and (3) uncertainty about the benefit and harm of corticosteroids in this population, with a mortality benefit in ARDS, increased mortality shown in TBI, and conflicting data in other SABI subtypes. Also, the widely adapted partial pressure of oxygen (P_aO₂) target of > 55 mmHg for ARDS may exacerbate secondary brain injury, and recent guidelines recommend higher goals of 80–120 mmHg in SABI. Distinct pathophysiology and trajectories among different SABI subtypes need to be considered.

Summary

The management of SABI with ARDS is highly complex, and conventional ARDS management strategies may result in increased ICP and decreased cerebral perfusion. A crucial aspect of concurrent management is to recognize the risk of secondary brain injury in the individual patient, monitor with vigilance, and adjust management during critical time windows. The care of these patients requires meticulous attention to oxygenation and ventilation, hemodynamics, temperature management, and the neurological exam. LPV and prone ventilation should be utilized, and supplemented with invasive ICP monitoring if there is concern for cerebral edema and increased ICP. PEEP titration should be deliberate, involving measures of hemodynamic, pulmonary, and brain physiology. Serial volume status assessments should be performed in SABI and ARDS, and fluid management should be individualized based on measures of brain perfusion, the neurological exam, and cardiopulmonary status. More research is needed to define risks and benefits in corticosteroids in this population.

ASNM and ASN joint guidelines for transcranial Doppler ultrasonic monitoring: An update

Today, it seems prudent to reconsider how ultrasound technology can be used for providing intraoperative neurophysiologic monitoring that will result in better patient outcomes and decreased length and cost of hospitalization. An extensive and rapidly growing literature suggests that the essential hemodynamic information provided by transcranial Doppler (TCD) ultrasonography neuromonitoring (TCDNM) would provide effective monitoring modality for improving outcomes after different types of vascular, neurosurgical, orthopedic, cardiovascular, and cardiothoracic surgeries and some endovascular interventional or diagnostic procedures, like cardiac catheterization or cerebral angiography. Understanding, avoiding, and preventing peri- or postoperative complications, including neurological deficits following abovementioned surgeries, endovascular intervention, or diagnostic procedures, represents an area of great public and economic benefit for society, especially considering the aging population. The American Society of Neurophysiologic Monitoring and American Society of Neuroimaging Guidelines Committees formed a joint task force and developed updated guidelines to assist in the use of TCDNM in the surgical and intensive care settings. Specifically, these guidelines define (1) the objectives of TCD monitoring; (2) the responsibilities and behaviors of the neurosonographer during monitoring; (3) instrumentation and acquisition parameters; (4) safety considerations; (5) contemporary rationale for TCDNM; (6) TCDNM perspectives; and (7) major recommendations.

Effects of hyperoxemia on aneurysmal subarachnoid hemorrhage outcomes: a systematic review and meta-analysis

OBJECTIVE

In recent years, hyperoxemia in the intensive care unit has received attention as potentially contributing to negative outcomes in the setting of cardiac arrest, ischemic stroke, and traumatic brain injury. The authors sought to evaluate whether hyperoxemia contributes to worse outcomes in the setting of aneurysmal subarachnoid hemorrhage (aSAH) and to summarize suggested pathophysiological mechanisms.

METHODS

A systematic literature review was conducted without date restrictions on the PubMed and Web of Science databases on September 15, 2021. All studies that assessed the relationship between patients treated for aSAH and hyperoxemia were eligible independent of the criteria used to define hyperoxemia. All nonclinical studies and studies that did not report outcome data specific to patients with aSAH were excluded. A total of 102 records were found and screened, resulting in assessment of 10 full-text studies, of which 7 met eligibility criteria. Risk of bias was assessed using the Downs and Black checklist. A meta-analysis on the pooled 2602 patients was performed, and forest plots were constructed. Additionally, a review of the literature was performed to summarize available data regarding the pathophysiology of hyperoxemia.

RESULTS

The included studies demonstrated an association between hyperoxemia and increased morbidity and mortality following aSAH. The criteria used to determine hyperoxemia varied among studies. Pooling of univariate data showed hyperoxemia to be associated with poor neurological outcome (OR 2.26, 95% CI 1.66-3.07; p < 0.001), delayed cerebral ischemia (DCI) (OR 1.91, 95% CI 1.31-2.78; p < 0.001), and increased incidence of poor neurological outcome or mortality as a combined endpoint (OR 2.36, 95% CI 1.87-2.97; p < 0.001). Pooling of multivariable effect sizes showed the same relationship for poor neurological outcome (OR 1.28, 95% CI 1.07-1.55; p = 0.01) and poor neurological outcome and mortality as a combined endpoint (OR 1.17, 95% CI 1.11-1.23; p < 0.001). Additionally, review of preclinical studies underlined the contribution of oxidative stress due to hyperoxemia to acute secondary brain injury and DCI.

CONCLUSIONS

Reported outcomes from the available studies have indicated that hyperoxemia is associated with worse neurological outcome, mortality, and DCI. These findings provide a general guideline toward avoiding hyperoxemia in the acute setting of aSAH. Further studies are needed to determine the optimal ventilation and oxygenation parameters for acute management of this patient population.

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.

Association Between Arterial Carbon Dioxide Tension and Clinical Outcomes in Venoarterial Extracorporeal Membrane Oxygenation

OBJECTIVES

The manipulation of arterial carbon dioxide tension is associated with differential mortality and neurologic injury in intensive care and cardiac arrest patients; however, few studies have investigated this relationship in patients on venoarterial extracorporeal membrane oxygenation. We investigated the association between the initial arterial carbon dioxide tension and change over 24 hours on mortality and neurologic injury in patients undergoing venoarterial extracorporeal membrane oxygenation for cardiac arrest and refractory cardiogenic shock.

DESIGN

Retrospective cohort analysis of adult patients recorded in the international Extracorporeal Life Support Organization Registry.

SETTING

Data reported to the Extracorporeal Life Support Organization from all international extracorporeal membrane oxygenation centers during 2003-2016.

PATIENTS

Adult patients (≥ 18 yr old) supported with venoarterial extracorporeal membrane oxygenation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 7,168 patients had sufficient data for analysis at the initiation of venoarterial extracorporeal membrane oxygenation, 4,918 of these patients had arterial carbon dioxide tension data available at 24 hours on support. The overall in-hospital mortality rate was 59.9%. A U-shaped relationship between arterial carbon dioxide tension tension at extracorporeal membrane oxygenation initiation and in-hospital mortality was observed. Increased mortality was observed with a arterial carbon dioxide tension less than 30 mm Hg (odds ratio, 1.26; 95% CI, 1.08-1.47; p = 0.003) and greater than 60 mm Hg (odds ratio, 1.28; 95% CI, 1.10-1.50; p = 0.002). Large reductions (> 20 mm Hg) in arterial carbon dioxide tension over 24 hours were associated with important neurologic complications: intracranial hemorrhage, ischemic stroke, and/or brain death, as a composite outcome (odds ratio, 1.63; 95% CI, 1.03-2.59; p = 0.04), independent of the initial arterial carbon dioxide tension.

CONCLUSIONS

Initial arterial carbon dioxide tension tension was independently associated with mortality in this cohort of venoarterial extracorporeal membrane oxygenation patients. Reductions in arterial carbon dioxide tension (> 20 mm Hg) from the initiation of extracorporeal membrane oxygenation were associated with neurologic complications. Further prospective studies testing these associations are warranted.

Effects of hypercapnia in sepsis: A scoping review of clinical and pre-clinical data

BACKGROUND

Perform a scoping review of (1) pre-clinical studies testing the physiological effects of higher PaCO2 levels in the setting of sepsis models and (2) clinical investigations testing the effects of hypercapnia on clinical outcomes in mechanically ventilated patients with sepsis.

METHODS

We performed a search of CENTRAL, PUBMED, CINAHL, and EMBASE. Study inclusion criteria for pre-clinical studies were: (1) bacterial sepsis model (2) measurement of PaCO2 , and (3) comparison of outcome measure between different PaCO2 levels. Inclusion criteria for clinical studies were: (1) diagnosis of sepsis, (2) receiving invasive mechanical ventilation, (3) measurement of PaCO2 , and (4) comparison of outcomes between different PaCO2 levels. We performed a qualitative analysis to collate and summarize the physiological and clinical effects of hypercapnia according to the recommended methodology from the Cochrane Handbook.

RESULTS

Fifteen pre-clinical and nine clinical studies were included. Among pre-clinical studies, the individual studies found higher PaCO2 augments tissue blood flow and oxygenation, and attenuates inflammation and lung injury; however, all pre-clinical studies were found to have some degree of risk of bias. Six of the nine clinical studies were deemed to be good quality. Among clinical studies hypercapnia was associated with increased cerebral perfusion and oxygenation; however, there were conflicting results testing the association between hypercapnia and mortality.

CONCLUSION

While individual pre-clinical studies identified potential mechanisms by which changes in PaCO2 levels could affect pathophysiology in sepsis, there is a paucity of clinical data as to the optimal PaCO2 range, demonstrating a need for future research.

REGISTRATION

PROSPERO number CRD42018086703.

Improper monitoring and deviations from physiologic treatment goals in patients with brain injury in the early phases of emergency care

Severe traumatic brain injury (TBI), out-of-hospital cardiac arrest (OHCA) and intracerebral- and subarachnoid hemorrhage (ICH/SAH) are conditions associated with high mortality and morbidity. The aim of this study was to investigate the feasibility of obtaining continuous physiologic data and to identify possible harmful physiological deviations in these patients, in the early phases of emergency care. Patients with ICH/SAH, OHCA and severe TBI treated by the Physician-staffed Emergency Medical Service (P-EMS) between September and December 2016 were included. Physiological data were obtained from site of injury/illness, during transport, in the emergency department (ED) and until 3 h after admittance to the intensive care unit. Physiological deviations were based on predefined target values within each 5-min interval. 13 patients were included in the study, of which 38% survived. All patients experienced one or more episodes of hypoxia, 38% experienced episodes of hypercapnia and 46% experienced episodes of hypotension. The mean proportion of time without any monitoring in the pre-hospital phase was 29%, 47% and 56% for SpO2, end-tidal CO2 and systolic blood pressure, respectively. For the ED these proportions were 57%, 71% and 56%, respectively. Continuous physiological data was not possible to obtain in this study of critically ill and injured patients with brain injury. The patients had frequent deviations in blood pressure, SpO2 and end tidal CO2-levels, and measurements were frequently missing. There is a potential for improved monitoring as a tool for quality improvement in pre-hospital critical care.

Escalate and De-Escalate Therapies for Intracranial Pressure Control in Traumatic Brain Injury

Severe traumatic brain injury (TBI) is frequently associated with an elevation of intracranial pressure (ICP), followed by cerebral perfusion pressure (CPP) reduction. Invasive monitoring of ICP is recommended to guide a step-by-step “staircase approach” which aims to normalize ICP values and reduce the risks of secondary damage. However, if such monitoring is not available clinical examination and radiological criteria should be used. A major concern is how to taper the therapies employed for ICP control. The aim of this manuscript is to review the criteria for escalating and withdrawing therapies in TBI patients. Each step of the staircase approach carries a risk of adverse effects related to the duration of treatment. Tapering of barbiturates should start once ICP control has been achieved for at least 24 h, although a period of 2–12 days is often required. Administration of hyperosmolar fluids should be avoided if ICP is normal. Sedation should be reduced after at least 24 h of controlled ICP to allow neurological examination. Removal of invasive ICP monitoring is suggested after 72 h of normal ICP. For patients who have undergone surgical decompression, cranioplasty represents the final step, and an earlier cranioplasty (15–90 days after decompression) seems to reduce the rate of infection, seizures, and hydrocephalus.

Mechanical ventilation of patients in helicopter emergency medical service transport: an international survey

BACKGROUND

Mechanical ventilation in helicopter emergency medical service (HEMS) environments is a procedure which carries a significant risk of complications. Limited data on the quality and performance of mechanical ventilation in HEMS are available in the literature.

METHOD

We conducted an international survey to evaluate mechanical ventilation infrastructure in HEMS and collect data of transported ventilated patients. From June 20-22, 2019, the participating HEMS bases were asked to provide data via a web-based platform. Vital parameters and ventilation settings of the patients at first patient contact and at handover were compared using non-parametric statistical tests.

RESULTS

Out of 215 invited HEMS bases, 53 responded. Respondents were from Germany, Denmark, United Kingdom, Luxembourg, Austria and Switzerland. Of the HEMS bases, all teams were physician staffed, mainly anesthesiologists (79%), the majority were board certified (92.5%) and trained in intensive care medicine (89%) and had a median (range) experience in HEMS of 9 (0-25) years. HEMS may provide a high level of expertise in mechanical ventilation whereas the majority of ventilators are able to provide pressure controlled ventilation and continuous positive airway pressure modes (77%). Data of 30 ventilated patients with a median (range) age of 54 (21-100) years and 53% male gender were analyzed. Of these, 24 were primary missions and 6 interfacility transports. At handover, oxygen saturation (p < 0.01) and positive end-expiratory pressure (p = 0.04) of the patients were significantly higher compared to first patient contact.

CONCLUSION

In this survey, the management of ventilated HEMS-patients was not associated with ventilation related serious adverse events. Patient conditions, training of medical crew and different technical and environmental resources are likely to influence management. Further studies are necessary to assess safety and process quality of mechanical ventilation in HEMS.

TRIAL REGISTRATION

The survey was prospectively registered at Research Registry ( researchregistry2925 ).

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.

Management and Challenges of Severe Traumatic Brain Injury

Traumatic brain injury (TBI) is the leading cause of death and disability in trauma patients, and can be classified into mild, moderate, and severe by the Glasgow coma scale (GCS). Prehospital, initial emergency department, and subsequent intensive care unit (ICU) management of severe TBI should focus on avoiding secondary brain injury from hypotension and hypoxia, with appropriate reversal of anticoagulation and surgical evacuation of mass lesions as indicated. Utilizing principles based on the Monro-Kellie doctrine and cerebral perfusion pressure (CPP), a surrogate for cerebral blood flow (CBF) should be maintained by optimizing mean arterial pressure (MAP), through fluids and vasopressors, and/or decreasing intracranial pressure (ICP), through bedside maneuvers, sedation, hyperosmolar therapy, cerebrospinal fluid (CSF) drainage, and, in refractory cases, barbiturate coma or decompressive craniectomy (DC). While controversial, direct ICP monitoring, in conjunction with clinical examination and imaging as indicated, should help guide severe TBI therapy, although new modalities, such as brain tissue oxygen (PbtO₂) monitoring, show great promise in providing strategies to optimize CBF. Optimization of the acute care of severe TBI should include recognition and treatment of paroxysmal sympathetic hyperactivity (PSH), early seizure prophylaxis, venous thromboembolism (VTE) prophylaxis, and nutrition optimization. Despite this, severe TBI remains a devastating injury and palliative care principles should be applied early. To better affect the challenging long-term outcomes of severe TBI, more and continued high quality research is required.

The Early Change in PaCO2 after Extracorporeal Membrane Oxygenation Initiation Is Associated with Neurological Complications

Rationale: Large decreases in Pa_CO2 that occur when initiating extracorporeal membrane oxygenation (ECMO) in patients with respiratory failure may cause cerebral vasoconstriction and compromise brain tissue perfusion.Objectives: To determine if the magnitude of Pa_CO2 correction upon ECMO initiation is associated with an increased incidence of neurological complications in patients with respiratory failure.Methods: We conducted a multicenter, international, retrospective cohort study using the Extracorporeal Life Support Organization Registry, including adults with respiratory failure receiving ECMO via any mode between 2012 and 2017. The relative change in Pa_CO2 in the first 24 hours was calculated as (24-h post-ECMO Pa_CO2 - pre-ECMO Pa_CO2)/pre-ECMO Pa_CO2. The primary outcome was the occurrence of neurological complications, defined as seizures, ischemic stroke, intracranial hemorrhage, or brain death.Measurements and Main Results: We included 11,972 patients, 88% of whom were supported with venovenous ECMO. The median relative change in Pa_CO2 was -31% (interquartile range, -46% to -12%). Neurological complications were uncommon overall (6.9%), with a low incidence of seizures (1.1%), ischemic stroke (1.9%), intracranial hemorrhage (3.5%), and brain death (1.6%). Patients with a large relative decrease in Pa_CO2 (>50%) had an increased incidence of neurological complications compared with those with a smaller decrease (9.8% vs. 6.4%; P < 0.001). A large relative decrease in Pa_CO2 was independently associated with neurological complications after controlling for previously described risk factors (odds ratio, 1.7; 95% confidence interval, 1.3 to 2.3; P < 0.001).Conclusions: In patients receiving ECMO for respiratory failure, a large relative decrease in Pa_CO2 in the first 24 hours after ECMO initiation is independently associated with an increased incidence of neurological complications.

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.

Anesthetic considerations for extracranial injuries in patients with associated brain trauma

Patients with severe traumatic brain injury often presents with extracranial injuries, which may contribute to fatal outcome. Anesthetic management of such polytrauma patients is extremely challenging that includes prioritizing the organ system to be dealt first, reducing on-going injury, and preventing secondary injuries. Neuroprotective and neurorescue measures should be instituted simultaneously during extracranial surgeries. Selection of anesthetic drugs that minimally interferes with cerebral dynamics, maintenance of hemodynamics and cerebral perfusion pressure, optimal utilization of multimodal monitoring techniques, and aggressive rehabilitation approach are the key factors for improving overall patient outcome.

Dutch Prospective Observational Study on Prehospital Treatment of Severe Traumatic Brain Injury: The BRAIN-PROTECT Study Protocol

Background: Severe traumatic brain injury (TBI) is associated with a high mortality rate and those that survive commonly have permanent disability. While there is a broad consensus that appropriate prehospital treatment is crucial for a favorable neurological outcome, evidence to support currently applied treatment strategies is scarce. In particular, the relationship between prehospital treatments and patient outcomes is unclear. The BRAIN-PROTECT study therefore aims to identify prehospital treatment strategies associated with beneficial or detrimental outcomes. Here, we present the study protocol. Study Protocol: BRAIN-PROTECT is the acronym for BRAin INjury: Prehospital Registry of Outcome, Treatments and Epidemiology of Cerebral Trauma. It is a prospective observational study on the prehospital treatment of patients with suspected severe TBI in the Netherlands. Prehospital epidemiology, interventions, medication strategies, and nonmedical factors that may affect outcome are studied. Multivariable regression based modeling will be used to identify confounder-adjusted relationships between these factors and patient outcomes, including mortality at 30 days (primary outcome) or mortality and functional neurological outcome at 1 year (secondary outcomes). Patients in whom severe TBI is suspected during prehospital treatment (Glasgow Coma Scale score ≤ 8 in combination with a trauma mechanism or clinical findings suggestive of head injury) are identified by all four helicopter emergency medical services (HEMS) in the Netherlands. Patients are prospectively followed up in 9 participating trauma centers for up to one year. The manuscript reports in detail the objectives, setting, study design, patient inclusion, and data collection process. Ethical and juridical aspects, statistical considerations, as well as limitations of the study design are discussed. Discussion: Current prehospital treatment of patients with suspected severe TBI is based on marginal evidence, and optimal treatment is basically unknown. The BRAIN-PROTECT study provides an opportunity to evaluate and compare different treatment strategies with respect to patient outcomes. To our knowledge, this study project is the first large-scale prospective prehospital registry of patients with severe TBI that also collects long-term follow-up data and may provide the best available evidence at this time to give useful insights on how prehospital care can be improved.

The acute respiratory distress syndrome after out-of-hospital cardiac arrest: Incidence, risk factors, and outcomes

OBJECTIVE

To define the incidence of the acute respiratory distress syndrome (ARDS) following out-of-hospital cardiac arrest (OHCA) and characterize its impact on outcome.

METHODS

This was a retrospective cohort study conducted at two urban, tertiary, academic hospitals from 2007 to 2014. We included adults with non-traumatic OHCA and survived for ≥48 h. Patients who received mechanical ventilation for ≥24 h, had 2 consecutive arterial blood gases with a ratio of the partial pressure of oxygen to the fraction of inspired oxygen ≤300, and bilateral radiographic opacities within 48 h of hospital admission were defined as having ARDS. We examined the associations between ARDS and outcome using multivariable analyses and performed sensitivity analyses excluding patients with evidence of cardiac dysfunction.

RESULTS

Of 978 OHCA patients transported to the study hospitals, 600 were mechanically ventilated and survived ≥48 h. A total of 287 (48%, 95% CI 44-52%) met criteria for ARDS within 48 h of admission. There were no differences in demographics, OHCA etiology, or cardiac rhythm according to ARDS status. Patients with ARDS had higher hospital mortality, longer ICU stays, more ventilator days, and were less likely to survive with full neurologic recovery. Upon excluding patients with cardiac dysfunction, the incidence of ARDS was unchanged.

CONCLUSION

Nearly half of initial OHCA survivors develop ARDS within 48 h of hospital admission. ARDS was associated with poor outcome and increased resource utilization. OHCA should be considered among the traditional ARDS risk factors.

Association of abnormal carbon dioxide levels with poor neurological outcomes in aneurysmal subarachnoid hemorrhage: a retrospective observational study

Background

In patients with aneurysmal subarachnoid hemorrhage (SAH), an association between hypocapnia and poor clinical outcomes has been reported. However, the optimal arterial carbon dioxide tension (PaCO₂) remains unknown. The present retrospective study aimed to examine the association of abnormal PaCO₂ levels with neurological outcomes and investigate the optimal target PaCO₂ level in patients with SAH.

Methods

We retrospectively selected consecutive adult patients hospitalized in the intensive care unit (ICU) for SAH between January 2009 and April 2017. Univariate and multivariate analyses were performed to identify the independent predictors of unfavorable neurological outcomes (i.e., modified Rankin scale score of 3–6 on hospital discharge).

Results

Among 158 patients with SAH, 73 had unfavorable neurological outcomes. During the first 2 weeks in the ICU, the median number of PaCO₂ measurements per patient was 43. The factors significantly associated with unfavorable neurological outcomes were age, Hunt and Kosnik grade, maximum lactate levels during the first 24 h, and maximum (odds ratio [OR], 1.12; 95% confidence interval [CI], 1.03–1.21; p < 0.01) and minimum PaCO₂ levels (OR, 0.81; 95% CI, 0.72–0.92; p < 0.01). Receiver operating characteristic curve analysis revealed that the cutoff range of PaCO₂ was 30.2–48.3 mmHg. Unfavorable neurological outcomes were noted in 78.8% of patients with PaCO₂ levels outside this range and in 22.8% of patients with PaCO₂ levels within this range.

Conclusions

Both the maximum and minimum PaCO₂ levels during ICU management in patients with SAH were significantly associated with unfavorable neurological outcomes. Further prospective studies are required to validate our findings and explore their clinical implications. Our findings may provide a scientific rationale for these future prospective studies.

Electronic supplementary material

The online version of this article (10.1186/s40560-018-0353-1) contains supplementary material, which is available to authorized users.

Partial pressure of arterial carbon dioxide after resuscitation from cardiac arrest and neurological outcome: A prospective multi-center protocol-directed cohort study

AIMS

Partial pressure of arterial carbon dioxide (PaCO₂) is a regulator of cerebral blood flow after brain injury. We sought to test the association between PaCO₂ after resuscitation from cardiac arrest and neurological outcome.

METHODS

A prospective protocol-directed cohort study across six hospitals.

INCLUSION CRITERIA

age ≥18, non-traumatic cardiac arrest, mechanically ventilated after return of spontaneous circulation (ROSC), and receipt of targeted temperature management. Per protocol, PaCO₂ was measured by arterial blood gas analyses at one and six hours after ROSC. We determined the mean PaCO₂ over this initial six hours after ROSC. The primary outcome was good neurological function at hospital discharge, defined a priori as a modified Rankin Scale ≤3. Multivariable Poisson regression analysis was used to test the association between PaCO₂ and neurological outcome.

RESULTS

Of the 280 patients included, the median (interquartile range) PaCO₂ was 44 (37-52) mmHg and 30% had good neurological function. We found mean PaCO₂ had a quadratic (inverted "U" shaped) association with good neurological outcome, with a mean PaCO₂ of 68 mmHg having the highest predictive probability of good neurological outcome, and worse neurological outcome at higher and lower PaCO₂. Presence of metabolic acidosis attenuated the association between PaCO₂ and good neurological outcome, with a PaCO₂ of 51 mmHg having the highest predictive probability of good neurological outcome among patients with metabolic acidosis.

CONCLUSION

PaCO₂ has a "U" shaped association with neurological outcome, with mild to moderate hypercapnia having the highest probability of good neurological outcome.

Effects of hypercapnia in sepsis: protocol for a systematic review of clinical and preclinical data

BACKGROUND

Respiratory failure requiring mechanical ventilation is a common manifestation of end-organ damage among patients with sepsis and has a high morbidity and mortality rate, as well as substantial associated treatment costs. Considering the burden of this condition, there is great need to identify novel, pragmatic therapies to improve outcomes in this population. Hypercapnia has shown benefits in several different ex vivo and in vivo models of lung injury. However, it is currently unclear if hypercapnia can confer clinical benefit among patients with sepsis. The objective of this systematic review is to collate the biomedical literature of preclinical and clinical studies testing the effects of higher PaCO₂ levels in the setting of sepsis.

METHODS

We will perform a qualitative systematic review of preclinical and clinical studies evaluating the effects of hypercapnia in sepsis. We will search CENTRAL, PubMed, CINAHL, and EMBASE using a comprehensive strategy. We will screen the reference lists of the articles we select for inclusion to identify additional studies for potential inclusion. Two independent reviewers will review all search results. Upon inclusion of articles, we will extract data using a standardized form. We will use tables to describe the study type, population included, exposure and control groups, outcome measures, and effects of exposure on outcome measures compared to controls.

DISCUSSION

This systematic review aims to synthesize the world's literature on the effects of hypercapnia in the setting of sepsis. We expect this systematic review will find that majority of the studies will demonstrate a potential benefit of higher PaCO₂ levels in sepsis. The results of this systematic review will contribute to the understanding of the effects of hypercapnia in the setting of sepsis and promote future research of PaCO₂ management in mechanically ventilated patients with sepsis.

SYSTEMATIC REVIEW REGISTRATION

The systematic review is registered in the PROSPERO international prospective register of systematic review (PROSPERO # CRD42018086703 ).

Association of Hypercapnia and Hypercapnic Acidosis With Clinical Outcomes in Mechanically Ventilated Patients With Cerebral Injury

IMPORTANCE

Clinical studies investigating the effects of hypercapnia and hypercapnic acidosis in acute cerebral injury are limited. The studies performed so far have mainly focused on the outcomes in relation to the changes in partial pressure of carbon dioxide and pH in isolation and have not evaluated the effects of partial pressure of carbon dioxide and pH in conjunction.

OBJECTIVE

To review the association of compensated hypercapnia and hypercapnic acidosis during the first 24 hours of intensive care unit admission on hospital mortality in adult mechanically ventilated patients with cerebral injury.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter, binational retrospective review of patients with cerebral injury (traumatic brain injury, cardiac arrest, and stroke) admitted to 167 intensive care units in Australia and New Zealand between January 2000 and December 2015. Patients were classified into 3 groups based on combination of arterial pH and arterial carbon dioxide (normocapnia and normal pH, compensated hypercapnia, and hypercapnic acidosis) during the first 24 hours of intensive care unit stay.

MAIN OUTCOMES AND MEASURES

Hospital mortality.

RESULTS

A total of 30 742 patients (mean age, 55 years; 21 827 men [71%]) were included. Unadjusted hospital mortality rates were highest in patients with hypercapnic acidosis. Multivariable logistic regression analysis and Cox proportional hazards analysis in 3 diagnostic categories showed increased odds of hospital mortality (cardiac arrest odds ratio [OR], 1.51; 95% CI, 1.34-1.71; stroke OR, 1.43; 95% CI, 1.27-1.6; and traumatic brain injury OR, 1.22; 95% CI, 1.06-1.42; P <.001) and hazard ratios (HR) (cardiac arrest HR, 1.23; 95% CI, 1.14-1.34; stroke HR, 1.3; 95% CI, 1.21-1.4; traumatic brain injury HR, 1.13; 95% CI, 1-1.27), in patients with hypercapnic acidosis compared with normocapnia and normal pH. There was no difference in mortality between patients who had compensated hypercapnia compared with patients who had normocapnia and normal pH. In patients with hypercapnic acidosis, the adjusted OR of hospital mortality increased with increasing partial pressure of carbon dioxide, while no such increase was noted in patients with compensated hypercapnia.

CONCLUSIONS AND RELEVANCE

Hypercapnic acidosis was associated with increased risk of hospital mortality in patients with cerebral injury. Hypercapnia, when compensated to normal pH during the first 24 hours of intensive care unit admission, may not be harmful in mechanically ventilated patients with cerebral injury.

Hyperoxia and Hypocapnia During Pediatric Extracorporeal Membrane Oxygenation: Associations With Complications, Mortality, and Functional Status Among Survivors

OBJECTIVES

To determine the frequency of hyperoxia and hypocapnia during pediatric extracorporeal membrane oxygenation and their relationships to complications, mortality, and functional status among survivors.

DESIGN

Secondary analysis of data collected prospectively by the Collaborative Pediatric Critical Care Research Network.

SETTING

Eight Collaborative Pediatric Critical Care Research Network-affiliated hospitals.

PATIENTS

Age less than 19 years and treated with extracorporeal membrane oxygenation.

INTERVENTIONS

Hyperoxia was defined as highest PaO2 greater than 200 Torr (27 kPa) and hypocapnia as lowest PaCO2 less than 30 Torr (3.9 kPa) during the first 48 hours of extracorporeal membrane oxygenation. Functional status at hospital discharge was evaluated among survivors using the Functional Status Scale.

MEASUREMENTS AND MAIN RESULTS

Of 484 patients, 420 (86.7%) had venoarterial extracorporeal membrane oxygenation and 64 (13.2%) venovenous; 69 (14.2%) had extracorporeal membrane oxygenation initiated during cardiopulmonary resuscitation. Hyperoxia occurred in 331 (68.4%) and hypocapnia in 98 (20.2%). Hyperoxic patients had higher mortality than patients without hyperoxia (167 [50.5%] vs 48 [31.4%]; p < 0.001), but no difference in functional status among survivors. Hypocapnic patients were more likely to have a neurologic event (49 [50.0%] vs 143 (37.0%]; p = 0.021) or hepatic dysfunction (49 [50.0%] vs 121 [31.3%]; p < 0.001) than patients without hypocapnia, but no difference in mortality or functional status among survivors. On multivariable analysis, factors independently associated with increased mortality included highest PaO2 and highest blood lactate concentration in the first 48 hours of extracorporeal membrane oxygenation, congenital diaphragmatic hernia, and being a preterm neonate. Factors independently associated with lower mortality included meconium aspiration syndrome.

CONCLUSIONS

Hyperoxia is common during pediatric extracorporeal membrane oxygenation and associated with mortality. Hypocapnia appears to occur less often and although associated with complications, an association with mortality was not observed.

Italian guidelines on the assessment and management of pediatric head injury in the emergency department

OBJECTIVE

We aim to formulate evidence-based recommendations to assist physicians decision-making in the assessment and management of children younger than 16 years presenting to the emergency department (ED) following a blunt head trauma with no suspicion of non-accidental injury.

METHODS

These guidelines were commissioned by the Italian Society of Pediatric Emergency Medicine and include a systematic review and analysis of the literature published since 2005. Physicians with expertise and experience in the fields of pediatrics, pediatric emergency medicine, pediatric intensive care, neurosurgery and neuroradiology, as well as an experienced pediatric nurse and a parent representative were the components of the guidelines working group. Areas of direct interest included 1) initial assessment and stabilization in the ED, 2) diagnosis of clinically important traumatic brain injury in the ED, 3) management and disposition in the ED. The guidelines do not provide specific guidance on the identification and management of possible associated cervical spine injuries. Other exclusions are noted in the full text.

CONCLUSIONS

Recommendations to guide physicians practice when assessing children presenting to the ED following blunt head trauma are reported in both summary and extensive format in the guideline document.

Bronchoscopy versus an endotracheal tube mounted camera for the peri-interventional visualization of percutaneous dilatational tracheostomy - a prospective, randomized trial (VivaPDT)

Background

Percutaneous dilatational tracheostomy (PDT) in critically ill patients often involves bronchoscopic optical guidance. However, this procedure is not without disadvantages. Therefore, we aimed to study a recently introduced endotracheal tube-mounted camera (VivaSight^TM-SL tube [VST]; ETView, Misgav, Israel) for guiding PDT.

Methods

This was a randomized controlled trial involving 46 critically ill patients who received PDT using optical guidance with a VST or with bronchoscopy. The primary outcome measure was visualization of the tracheal structures (i.e., identification and monitoring of the thyroid, cricoid, and tracheal cartilage and the posterior wall) rated on 4-point Likert scales. Secondary measures were the quality of ventilation (before puncture and during the tracheostomy procedure rated on 4-point Likert scales) and blood gases sampled at standardized time points.

Results

The mean ratings for visualization (lower values better; values given for per-protocol analysis) were 5.4 (95% CI 4.5–6.3) for the VST group and 4.0 (95% CI 4.0–4.0) for the bronchoscopy group (p < 0.001). Mean ventilation ratings were 2.5 (95% CI 2.1–2.9) for VST and 5.0 (95% CI 4.4–5.7) for bronchoscopy (p < 0.001). Arterial carbon dioxide increased to 5.9 (95% CI 5.4–6.5) kPa in the VST group vs. 8.3 (95% CI 7.2–9.5) kPa in the bronchoscopy group (p < 0.001), and pH decreased to 7.40 (95% CI 7.36–7.43) in the VST group vs. 7.26 (95% CI 7.22–7.30) in the bronchoscopy group (p < 0.001), at the end of the intervention.

Conclusions

Visualization of PDT with the VST is not noninferior to guidance by bronchoscopy. Ventilation is superior with less hypercarbia with the VST. Because visualization is not a prerequisite for PDT, patients requiring stable ventilation with normocarbia may benefit from PDT with the VST.

Trial registration

ClinicalTrials.gov, NCT02861001. Registered on 13 June 2016.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1901-0) contains supplementary material, which is available to authorized users.

Partial pressure of arterial carbon dioxide and survival to hospital discharge among patients requiring acute mechanical ventilation: A cohort study

PURPOSE

To describe the prevalence of hypocapnia and hypercapnia during the earliest period of mechanical ventilation, and determine the association between PaCO2 and mortality.

MATERIALS AND METHODS

A cohort study using an emergency department registry of mechanically ventilated patients. PaCO2 was categorized: hypocapnia (<35mmHg), normocapnia (35-45mmHg), and hypercapnia (>45mmHg). The primary outcome was survival to hospital discharge.

RESULTS

A total of 1,491 patients were included. Hypocapnia occurred in 375 (25%) patients and hypercapnia in 569 (38%). Hypercapnia (85%) had higher survival rate compared to normocapnia (74%) and hypocapnia (66%), P<0.001. PaCO2 was an independent predictor of survival to hospital discharge [hypocapnia (aOR 0.65 (95% confidence interval [CI] 0.48-0.89), normocapnia (reference category), hypercapnia (aOR 1.83 (95% CI 1.32-2.54)]. Over ascending ranges of PaCO2, there was a linear trend of increasing survival up to a PaCO2 range of 66-75mmHg, which had the strongest survival association, aOR 3.18 (95% CI 1.35-7.50).

CONCLUSIONS

Hypocapnia and hypercapnia occurred frequently after initiation of mechanical ventilation. Higher PaCO2 levels were associated with increased survival. These data provide rationale for a trial examining the optimal PaCO2 in the critically ill.

Carbon dioxide-dependent regulation of NF-κB family members RelB and p100 gives molecular insight into CO2-dependent immune regulation

CO₂ is a physiological gas normally produced in the body during aerobic respiration. Hypercapnia (elevated blood pCO₂ >≈50 mm Hg) is a feature of several lung pathologies, e.g. chronic obstructive pulmonary disease. Hypercapnia is associated with increased susceptibility to bacterial infections and suppression of inflammatory signaling. The NF-κB pathway has been implicated in these effects; however, the molecular mechanisms underpinning cellular sensitivity of the NF-κB pathway to CO₂ are not fully elucidated. Here, we identify several novel CO₂-dependent changes in the NF-κB pathway. NF-κB family members p100 and RelB translocate to the nucleus in response to CO₂ A cohort of RelB protein-protein interactions (e.g. with Raf-1 and IκBα) are altered by CO₂ exposure, although others are maintained (e.g. with p100). RelB is processed by CO₂ in a manner dependent on a key C-terminal domain located in its transactivation domain. Loss of the RelB transactivation domain alters NF-κB-dependent transcriptional activity, and loss of p100 alters sensitivity of RelB to CO₂ Thus, we provide molecular insight into the CO₂ sensitivity of the NF-κB pathway and implicate altered RelB/p100-dependent signaling in the CO₂-dependent regulation of inflammatory signaling.

Initial arterial carbon dioxide tension is associated with neurological outcome after resuscitation from cardiac arrest

STUDY OBJECTIVES

To determine the relationships between partial pressure of arterial carbon dioxide (PaCO₂), prescribed minute ventilation (MV), and neurologic outcome in patients resuscitated from cardiac arrest.

METHODS

This was a retrospective cohort study utilizing a multicenter database of adult patients with return of spontaneous circulation (ROSC) after cardiac arrest. The primary outcome was neurologic status at hospital discharge, defined by Cerebral Performance Category (CPC) score: CPC 1-2 was favorable, CPC 3-5 was poor. We compared rates of initial normocarbia (PaCO₂ 31-49mmHg) and mean sequential PaCO₂ measurements obtained over the first 24h. We also assessed the influence of MV on the PaCO₂ at initial, 6, 12, 18, and 24h after cardiac arrest using univariate linear regression.

RESULTS

One hundred and fourteen patients from 3 institutions met inclusion criteria. Overall, 46/114 (40.4%, 95% CI: 31.4-49.4%) patients survived to hospital discharge, and 33/114 (28.9%, 20.6-37.2%) had CPC 1-2 at the time of discharge. A total of 38.9% (95% CI: 29.9-47.9%) of patients had initial normocarbia; 43.2% (28.6-57.8%) of these patients were discharged with CPC 1-2, compared with 20.3% (10.8-29.8%) of dyscarbic patients. By 6h, neurologic outcomes were not significantly associated with PaCO₂. Prescribed MV was not associated with PaCO₂ at any time point with the exception of a weak correlation at hour 18.

CONCLUSION

Initial normocarbia was associated with favorable neurological outcome in patients resuscitated from cardiac arrest. This relationship was not seen at subsequent time points. There was no significant association between prescribed MV and PaCO₂ or neurologic outcome.

Airway management and mechanical ventilation in acute brain injury

Patients with acute neurologic disease often develop respiratory failure, the management of which profoundly affects brain physiology and long-term functional outcomes. This chapter reviews airway management and mechanical ventilation of patients with acute brain injury, offering practical strategies to optimize treatment of respiratory failure and minimize secondary brain injury. Specific concerns that are addressed include physiologic changes during intubation and ventilation such as the effects on intracranial pressure and brain perfusion; cervical spine management during endotracheal intubation; the role of tracheostomy; and how ventilation and oxygenation are utilized to minimize ischemia-reperfusion injury and cerebral metabolic distress.

Changes in cardiac arrest patients' temperature management after the 2013 "TTM" trial: results from an international survey

BACKGROUND

Therapeutic hypothermia (TH between 32 and 34 °C) was recommended until recently in unconscious successfully resuscitated cardiac arrest (CA) patients, especially after initial shockable rhythm. A randomized controlled trial published in 2013 observed similar outcome between a 36 °C-targeted temperature management (TTM) and a 33 °C-TTM. The main aim of our study was to assess the impact of this publication on physicians regarding their TTM practical changes.

METHODS

A declarative survey was performed using the webmail database of the French Intensive Care Society including 3229 physicians (from May 2014 to January 2015).

RESULTS

Five hundred and eighteen respondents from 264 ICUs in 11 countries fulfilled the survey (16 %). A specific attention was generally paid by 94 % of respondents to TTM (hyperthermia avoidance, normothermia, or TH implementation) in CA patients, whereas 6 % did not. TH between 32 and 34 °C was declared as generally maintained during 12-24 h by 78 % of respondents or during 24-48 h by 19 %. Since the TTM trial publication, 56 % of respondents declared no modification of their TTM practice, whereas 37 % declared a practical target temperature change. The new temperature targets were 35-36 °C for 23 % of respondents, and 36 °C for 14 %. The duration of overall TTM (including TH and/or normothermia) was declared as applied between 12 and 24 h in 40 %, and between 24 and 48 h in 36 %. In univariate analysis, the physicians' TTM modification seemed related to hospital category (university versus non-university hospitals, P = 0.045), to TTM-specific attention paid in CA patients (P = 0.008), to TH durations (<12 versus 24-48 h, P = 0.01), and to new targets temperature (32-34 versus 35-36 °C, P < 0.0001).

CONCLUSIONS

The TTM trial publication has induced a modification of current practices in one-third of respondents, whereas the 32-34 °C target temperature remained unchanged for 56 %. Educational actions are needed to promote knowledge translations of trial results into clinical practice. New international guidelines may contribute to this effort.

The impact of extracerebral organ failure on outcome of patients after cardiac arrest: an observational study from the ICON database

Background

We used data from a large international database to assess the incidence and impact of extracerebral organ dysfunction on prognosis of patients admitted after cardiac arrest (CA).

Methods

This was a sub-analysis of the Intensive Care Over Nations (ICON) database, which contains data from all adult patients admitted to one of 730 participating intensive care units (ICUs) in 84 countries from 8–18 May 2012, except admissions for routine postoperative surveillance. For this analysis, patients admitted after CA (defined as those with “post-anoxic coma” or “cardiac arrest” as the reason for ICU admission) were included. Data were collected daily in the ICU for a maximum of 28 days; patients were followed up for outcome data until death, hospital discharge, or a maximum of 60 days in-hospital. Favorable neurological outcome was defined as alive at hospital discharge with a last available neurological Sequential Organ Failure Assessment (SOFA) subscore of 0–2.

Results

Among the 469 patients admitted after CA, 250 (53 %) had had out-of-hospital CA; 210 (45 %) patients died in the ICU and 357 (76 %) had an unfavorable neurological outcome. Non-survivors had a higher incidence of renal (43 vs. 16 %), cardiovascular (56 vs. 45 %), and respiratory (62 vs. 48 %) failure on admission and during the ICU stay than survivors (all p < 0.05). Similar results were found for patients with unfavorable vs. favorable neurological outcomes. In multivariable analysis, independent predictors of ICU mortality were renal failure on admission, high admission Simplified Acute Physiology Score (SAPS) II, high maximum serum lactate levels within the first 24 h after ICU admission, and development of sepsis. Independent predictors of unfavorable neurological outcome were mechanical ventilation on admission, high admission SAPS II score, and neurological dysfunction on admission.

Conclusions

In this multicenter cohort, extracerebral organ dysfunction was common in CA patients. Renal failure on admission was the only extracerebral organ dysfunction independently associated with higher ICU mortality.

Electronic supplementary material

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Making sense of clinical outcomes following cardiac arrest

PURPOSE OF REVIEW

To provide a summary of the recent literature on clinical outcomes in adults with cardiac arrest, focusing on the impact of patient-specific factors in combination with cardio-pulmonary resuscitation (CPR) related, and postresuscitative-related factors.

RECENT FINDINGS

Cardiac arrest is a major cause of morbidity and mortality worldwide. Despite the use of conventional cardiopulmonary resuscitation, rates of return of spontaneous circulation and survival with minimal neurologic impairment remain low. A number of recent studies have examined the impact of patient-specific factors (duration of cardiac arrest, initial rhythm, age, premorbid states), CPR-related (the use of mechanical CPR, the use of impedance threshold device, vasopressors, extra-corporeal membrane oxygenation, active compression-decompression, and impedance threshold device), and postresuscitative-related factors (hypothermia, coronary angiography, hyperoxia, hyper/hypocapnia, mean arterial blood pressure) on cardiac arrest outcomes.

SUMMARY

Further studies, namely randomized controlled trials, assessing the impact of advanced therapies are warranted to evaluate their impact on survival and neurologic function in adults with cardiac arrest.