A systematic review and meta-analysis of the association between arterial carbon dioxide tension and outcomes after cardiac arrest

Fifteen-minute consultation: A guide to paediatric post-resuscitation care following return of spontaneous circulation

Paediatric resuscitation is a key skill for anyone in medicine who is involved in the care of children. Basic and advance paediatric life support courses are crucial in teaching those skills nationwide in a way that is memorable, protocolised and standardised. These courses are vital in the dissemination and upkeep of both theoretical and practical knowledge of paediatric resuscitation, with their primary aim being the return of spontaneous circulation. While sustaining life is important, preserving a life with quality, one with good functional and neurological outcomes should be the gold standard of any resuscitative attempt. Good neurological outcomes are dependent, in large part, on how well the postresuscitation stage is managed. This stage does not start in the intensive care unit, it starts at the point at which spontaneous circulation has been reinstated. The aim of this paper is to provide a basic overview of the main strategies that should be followed in order to minimise secondary brain injury after successful resuscitation attempts.

Association of Arterial Carbon Dioxide Tension Following In-Hospital Cardiac Arrest With Survival and Favorable Neurologic Outcome

BACKGROUND

In-hospital cardiac arrest (IHCA) continues to be associated with high morbidity and mortality. The objective of this study was to study the association of arterial carbon dioxide tension (PaCO2) on survival to discharge and favorable neurologic outcomes in adults with IHCA.

METHODS

The study population included 353 adults who underwent resuscitation from 2011 to 2019 for IHCA at an academic tertiary care medical center with arterial blood gas testing done within 24 hours of arrest. Outcomes of interest included survival to discharge and favorable neurologic outcome, defined as Glasgow outcome score of 4-5.

RESULTS

Of the 353 patients studied, PaCO2 classification included: hypocapnia (PaCO2 <35 mm Hg, n = 89), normocapnia (PaCO2 35-45 mm Hg, n = 151), and hypercapnia (PaCO2 >45 mm Hg, n = 113). Hypercapnic patients were further divided into mild (45 mm Hg < PaCO2 ≤55 mm Hg, n = 62) and moderate/severe hypercapnia (PaCO2 > 55 mm Hg, n = 51). Patients with normocapnia had the highest rates of survival to hospital discharge (52.3% vs. 32.6% vs. 30.1%, P < 0.001) and favorable neurologic outcome (35.8% vs. 25.8% vs. 17.9%, P = 0.005) compared those with hypocapnia and hypercapnia respectively. In multivariable analysis, compared to normocapnia, hypocapnia [odds ratio (OR), 2.06; 95% confidence interval (CI), 1.15-3.70] and hypercapnia (OR, 2.67; 95% CI, 1.53-4.66) were both found to be independently associated with higher rates of in-hospital mortality. Compared to normocapnia, while mild hypercapnia (OR, 2.53; 95% CI, 1.29-4.97) and moderate/severe hypercapnia (OR, 2.86; 95% CI, 1.35-6.06) were both independently associated with higher in-hospital mortality compared to normocapnia, moderate/severe hypercapnia was also independently associated with lower rates of favorable neurologic outcome (OR, 0.28; 95% CI, 0.11-0.73), while mild hypercapnia was not.

CONCLUSIONS

In this prospective registry of adults with IHCA, hypercapnia noted within 24 hours after arrest was independently associated with lower rates of survival to discharge and favorable neurologic outcome.

Emergent Management of Hypoxic-Ischemic Brain Injury

OBJECTIVE

This article outlines interventions used to improve outcomes for patients with hypoxic-ischemic brain injury after cardiac arrest.

LATEST DEVELOPMENTS

Emergent management of patients after cardiac arrest requires prevention and treatment of primary and secondary brain injury. Primary brain injury is minimized by excellent initial resuscitative efforts. Secondary brain injury prevention requires the detection and correction of many pathophysiologic processes that may develop in the hours to days after the initial arrest. Key physiologic parameters important to secondary brain injury prevention include optimization of mean arterial pressure, cerebral perfusion, oxygenation and ventilation, intracranial pressure, temperature, and cortical hyperexcitability. This article outlines recent data regarding the treatment and prevention of secondary brain injury. Different patients likely benefit from different treatment strategies, so an individualized approach to treatment and prevention of secondary brain injury is advisable. Clinicians must use multimodal sources of data to prognosticate outcomes after cardiac arrest while recognizing that all prognostic tools have shortcomings.

ESSENTIAL POINTS

Neurologists should be involved in the postarrest care of patients with hypoxic-ischemic brain injury to improve their outcomes. Postarrest care requires nuanced and patient-centered approaches to the prevention and treatment of primary and secondary brain injury and neuroprognostication.

Association among blood pressure, end-tidal carbon dioxide, peripheral oxygen saturation and mortality in prehospital post-resuscitation care

Aim

Post-resuscitation care is described as the fourth link in a chain of survival in resuscitation guidelines. However, data on prehospital post-resuscitation care is scarce. We aimed to examine the association among systolic blood pressure (SBP), peripheral oxygen saturation (SpO2) and end-tidal carbon dioxide (EtCO2) after prehospital stabilisation and outcome among patients resuscitated from out-of-hospital cardiac arrest (OHCA).

Methods

In this retrospective study, we evaluated association of the last measured prehospital SBP, SpO2 and EtCO2 before patient handover with 30-day and one-year mortality in 2,611 patients receiving prehospital post-resuscitation care by helicopter emergency medical services in Finland. Statistical analyses were completed through locally estimated scatterplot smoothing (LOESS) and multivariable logistic regression. The regression analyses were adjusted by sex, age, initial rhythm, bystander CPR, and time interval from collapse to the return of spontaneous circulation (ROSC).

Results

Mortality related to SBP and EtCO2 values were U-shaped and lowest at 135 mmHg and 4.7 kPa, respectively, whereas higher SpO2 shifted towards lower mortality. In adjusted analyses, increased 30-day mortality and one year mortality was observed in patients with SBP < 100 mmHg (OR 1.9 [95% CI 1.4-2.4]) and SBP < 100 (OR 1.8 [1.2-2.6]) or EtCO2 < 4.0 kPa (OR 1.4 [1.1-1.5]), respectively. SpO2 was not significantly associated with either 30-day or one year mortality.

Conclusions

After prehospital post-resuscitation stabilization, SBP < 100 mmHg and EtCO2 < 4.0 kPa were observed to be independently associated with higher mortality. The optimal targets for prehospital post-resuscitation care need to be established in the prospective studies.

Post Cardiac Arrest Care in the Cardiac Intensive Care Unit

PURPOSE OF REVIEW

Cardiac arrests constitute a leading cause of mortality in the adult population and cardiologists are often tasked with the management of patients following cardiac arrest either as a consultant or primary provider in the cardiac intensive care unit. Familiarity with evidence-based practice for post-cardiac arrest care is a requisite for optimizing outcomes in this highly morbid group. This review will highlight important concepts necessary to managing these patients.

RECENT FINDINGS

Emerging evidence has further elucidated optimal care of post-arrest patients including timing for routine coronary angiography, utility of therapeutic hypothermia, permissive hypercapnia, and empiric aspiration pneumonia treatment. The complicated state of multi-organ failure following cardiac arrest needs to be carefully optimized by the clinician to prevent further neurologic injury and promote systemic recovery. Future studies should be aimed at understanding if these findings extend to specific patient populations, especially those at the highest risk for poor outcomes.

Prehospital Advanced Airway Management and Ventilation for Out-of-Hospital Cardiac Arrest with Prehospital Return of Spontaneous Circulation: A Prospective Observational Cohort Study in Japan

BACKGROUND

The relationship among advanced airway management (AAM), ventilation, and oxygenation in patients with out-of-hospital cardiac arrest (OHCA) who achieve prehospital return of spontaneous circulation (ROSC) has not been validated. This study was designed to evaluate ventilation and oxygenation for each AAM technique (supraglottic devices [SGA] or endotracheal intubation [ETI]) using arterial blood gas (ABG) results immediately after hospital arrival.

METHODS

This observational cohort study, using data from the Japanese Association for Acute Medicine OHCA Registry, included patients with OHCA with prehospital and hospital arrival ROSC between July 1, 2014, and December 31, 2019. The primary outcomes were the partial pressure of carbon dioxide in the arterial blood (PaCO2) and partial pressure of oxygen in the arterial blood (PaO2) in the initial ABG at the hospital for each AAM technique (SGA or ETI) performed by paramedics. The secondary outcome was favorable neurological outcome (cerebral performance category [CPC] 1 or 2) for specific PaCO2 levels, which were defined as good ventilation (PaCO2 ≤45 mmHg) and insufficient ventilation (PaCO2 >45 mmHg).

RESULTS

This study included 1,527 patients. Regarding AAM, 1,114 and 413 patients were ventilated using SGA and ETI, respectively. The median PaCO2 and PaO2 levels were 74.50 mmHg and 151.35 mmHg in the SGA group, while 66.30 mmHg and 173.50 mmHg in the ETI group. PaCO2 was significantly lower in the ETI group than in the SGA group (12.55 mmHg; 95% CI 15.27 to 8.20, P-value < 0.001), while no significant difference was found in PaO2 by multivariate linear regression analysis. After stabilizing inverse probability of weighting (IPW), the adjusted odds ratio for favorable neurological outcome at 1 month was significant in the good ventilation group compared to the insufficient ventilation cohort (adjusted odds ratio = 2.12, 95%CI: 1.40 to 3.19, P value < 0.001).

CONCLUSION

The study showed that in OHCA patients with prehospital ROSC, the PaCO2 levels in the initial ABG were lower in the group with AAM by ETI than in the SGA group. Furthermore, patients with prehospital ROSC and PaCO2 ≤45 mmHg on arrival had an increased odds of favorable neurological outcome after stabilized IPW adjustment.

General Critical Care, Temperature Control, and End-of-Life Decision Making in Patients Resuscitated from Cardiac Arrest

Cardiac arrest affects millions of people per year worldwide. Although advances in cardiopulmonary resuscitation and intensive care have improved outcomes over time, neurologic impairment and multiple organ dysfunction continue to be associated with a high mortality rate. The pathophysiologic mechanisms underlying the post-resuscitation disease are complex, and a coordinated, evidence-based approach to post-resuscitation care has significant potential to improve survival. Critical care management of patients resuscitated from cardiac arrest focuses on the identification and treatment of the underlying cause(s), hemodynamic and respiratory support, organ protection, and active temperature control. This review provides a state-of-the-art appraisal of critical care management of the post-cardiac arrest patient.

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.

Clinical Phenotyping of Out-of-Hospital Cardiac Arrest Patients With Shockable Rhythm - Machine Learning-Based Unsupervised Cluster Analysis

BACKGROUND

The hypothesis of this study is that latent class analysis could identify the subphenotypes of out-of-hospital cardiac arrest (OHCA) patients associated with the outcomes and allow us to explore heterogeneity in the effects of extracorporeal cardiopulmonary resuscitation (ECPR).

METHODS AND RESULTS

This study was a retrospective analysis of a multicenter prospective observational study (CRITICAL study) of OHCA patients. It included adult OHCA patients with initial shockable rhythm. Patients from 2012 to 2016 (development dataset) were included in the latent class analysis, and those from 2017 (validation dataset) were included for evaluation. The association between subphenotypes and outcomes was investigated. Further, the heterogeneity of the association between ECPR implementation and outcomes was explored. In the study results, a total of 920 patients were included for latent class analysis. Three subphenotypes (Groups 1, 2, and 3) were identified, mainly characterized by the distribution of partial pressure of O2(PO2), partial pressure of CO2(PCO2) value of blood gas assessment, cardiac rhythm on hospital arrival, and estimated glomerular filtration rate. The 30-day survival outcomes were varied across the groups: 15.7% in Group 1; 30.7% in Group 2; and 85.9% in Group 3. Further, the association between ECPR and 30-day survival outcomes by subphenotype groups in the development dataset was as varied. These results were validated using the validation dataset.

CONCLUSIONS

The latent class analysis identified 3 subphenotypes with different survival outcomes and potential heterogeneity in the effects of ECPR.

Post-Resuscitation Partial Pressure of Arterial Carbon Dioxide and Outcome in Patients with Out-of-Hospital Cardiac Arrest: A Multicenter Retrospective Cohort Study

We aimed to estimate the association between PaCO2 level in the patient after out-of-hospital cardiac arrest (OHCA) resuscitation with patient outcome based on a multicenter prospective cohort registry in Japan between June 2014 and December 2015. Based on the PaCO2 within 24 h after return of spontaneous circulation (ROSC), patients were divided into six groups as follows: severe hypocapnia (<25 mmHg), mild hypocapnia (25−35 mmHg,), normocapnia (35−45 mmHg), mild hypercapnia (45−55 mmHg), severe hypercapnia (>55 mmHg), or exposure to both hypocapnia and hypercapnia. Multivariate logistic regression analysis was conducted to calculate the adjusted odds ratios (aORs) and 95% confidence interval (CI) for the 1-month poor neurological outcome (Cerebral Performance Category ≥ 3). Among the 13,491 OHCA patients, 607 were included. Severe hypocapnia, mild hypocapnia, severe hypercapnia, and exposure to both hypocapnia and hypercapnia were associated with a higher rate of 1-month poor neurological outcome compared with mild hypercapnia (aORs 6.68 [95% CI 2.16−20.67], 2.56 [1.30−5.04], 2.62 [1.06−6.47], and 5.63 [2.21−14.34], respectively). There was no significant difference between the outcome of patients with normocapnia and mild hypercapnia. In conclusion, maintaining normocapnia and mild hypercapnia during the 24 h after ROSC was associated with better neurological outcomes than other PaCO2 abnormalities in this study.

Narrative Review of Neurologic Complications in Adults on ECMO: Prevalence, Risks, Outcomes, and Prevention Strategies

Extracorporeal membrane oxygenation (ECMO), a life-saving technique for patients with severe respiratory and cardiac diseases, is being increasingly utilized worldwide, particularly during the coronavirus disease 2019(COVID-19) pandemic, and there has been a sharp increase in the implementation of ECMO. However, due to the presence of various complications, the survival rate of patients undergoing ECMO remains low. Among the complications, the neurologic morbidity significantly associated with venoarterial and venovenous ECMO has received increasing attention. Generally, failure to recognize neurologic injury in time is reportedly associated with poor outcomes in patients on ECMO. Currently, multimodal monitoring is increasingly utilized in patients with devastating neurologic injuries and has been advocated as an important approach for early diagnosis. Here, we highlight the prevalence and outcomes, risk factors, current monitoring technologies, prevention, and treatment of neurologic complications in adult patients on ECMO. We believe that an improved understanding of neurologic complications presumably offers promising therapeutic solutions to prevent and treat neurologic morbidity.

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.

Neuromonitoring After Cardiac Arrest: Can Twenty-First Century Medicine Personalize Post Cardiac Arrest Care?

Cardiac arrest survivors comprise a heterogeneous population, in which the etiology of arrest, systemic and neurologic comorbidities, and sequelae of post-cardiac arrest syndrome influence the severity of secondary brain injury. The degree of secondary neurologic injury can be modifiable and is influenced by factors that alter cerebral physiology. Neuromonitoring techniques provide tools for evaluating the evolution of physiologic variables over time. This article reviews the pathophysiology of hypoxic-ischemic brain injury, provides an overview of the neuromonitoring tools available to identify risk profiles for secondary brain injury, and highlights the importance of an individualized approach to post cardiac arrest care.

Arterial carbon dioxide tension has a non-linear association with survival after out-of-hospital cardiac arrest: A multicentre observational study

PURPOSE

International guidelines recommend targeting normocapnia in mechanically ventilated out-of-hospital cardiac arrest (OHCA) survivors, but the optimal arterial carbon dioxide (PaCO₂) target remains controversial. We hypothesised that the relationship between PaCO₂ and survival is non-linear, and targeting an intermediate level of PaCO₂ compared to a low or high PaCO₂ in the first 24-h of ICU admission is associated with an improved survival to hospital discharge (STHD) and at 12-months.

METHODS

We conducted a retrospective multi-centre cohort study of adults with non-traumatic OHCA requiring admission to one of four tertiary hospital intensive care units for mechanical ventilation. A four-knot restricted cubic spline function was used to allow non-linearity between the mean PaCO₂ within the first 24 h of ICU admission after OHCA and survival, and optimal PaCO₂ cut-points were identified from the spline curve to generate corresponding odds ratios.

RESULTS

We analysed 3769 PaCO₂ results within the first 24-h of ICU admission, from 493 patients. PaCO₂ and survival had an inverted U-shape association; normocapnia was associated with significantly improved STHD compared to either hypocapnia (<35 mmHg) (adjusted odds ratio [aOR] 0.45, 95% confidence interval [CI] 0.24-0.83) or hypercapnia (>45 mmHg) (aOR 0.45, 95% CI 0.24-0.84). Of the twelve predictors assessed, PaCO₂ was the third most important predictor, and explained >11% of the variability in survival. The survival benefits of normocapnia extended to 12-months.

CONCLUSIONS

Normocapnia within the first 24-h of intensive care admission after OHCA was associated with an improved survival compared to patients with hypocapnia or hypercapnia.

The effect of mild hypercapnia on hospital mortality after cardiac arrest may be modified by chronic obstructive pulmonary disease

BACKGROUND

The main objective was to evaluate the effect of carbon dioxide on hospital mortality in chronic obstructive pulmonary disease (COPD) and non-COPD patients with out-of-hospital cardiac arrest (OHCA).

METHODS

We conducted a retrospective observational study in OHCA patients from the eICU database (eicu-crd.mit.edu). The main exposure was the partial pressure of arterial carbon dioxide (PaCO₂). The proportion of time spent (PTS) within four predefined PaCO₂ ranges (hypocapnia: <35 mmHg, normocapnia: 35-45 mmHg, mild hypercapnia: 46-55 mmHg, and severe hypercapnia: >55 mmHg) were calculated respectively. The primary outcome was hospital mortality. Multivariable logistic regression models were performed to assess the independent relationship between PTS within PaCO₂ range and hospital mortality, and the interaction between PTS within PaCO₂ range and COPD was explored.

RESULTS

A total of 1721 OHCA patients were included, of which 272 (15.8%) had COPD. After adjusted for the confounders, the PTS within mild hypercapnia was associated with lower odds ratio for hospital mortality in COPD patients (OR 0.923; 95% CI 0.857-0.992; P = 0.036); however, it was associated with higher odds ratio for hospital mortality in non-COPD patients (OR 1.053; 95% CI 1.012-1.097; P = 0.012; P_interaction = 0.008). The PTS within normocapnia was not associated with hospital mortality in COPD patients (OR 0.987; 95% CI 0.914-1.067; P = 0.739); however, it was associated with lower odds ratio for hospital mortality in non-COPD patients (OR 0.944; 95% CI 0.916-0.973; P < 0.001; P_interaction = 0.113).

CONCLUSIONS

The effect of carbon dioxide on hospital mortality differed between COPD and non-COPD patients. Mild hypercapnia was associated with increased hospital mortality for non-COPD patients but reduced hospital mortality for COPD patients. It would be reasonable to adjust PaCO₂ targets in OHCA patients with COPD.

Post-cardiac arrest care and targeted temperature management: A consensus of scientific statement from the Taiwan Society of Emergency & Critical Care Medicine, Taiwan Society of Critical Care Medicine and Taiwan Society of Emergency Medicine

BACKGROUND

Post-cardiac arrest care is critically important in bringing cardiac arrest patients to functional recovery after the detrimental event. More high quality studies are published and evidence is accumulated for the post-cardiac arrest care in the recent years. It is still a challenge for the clinicians to integrate these scientific data into the real clinical practice for such a complicated intensive care involving many different disciplines.

METHODS

With the cooperation of the experienced experts from all disciplines relevant to post-cardiac arrest care, the consensus of the scientific statement was generated and supported by three major scientific groups for emergency and critical care in post-cardiac arrest care.

RESULTS

High quality post-cardiac arrest care, including targeted temperature management, early evaluation of possible acute coronary event and intensive care for hemodynamic and respiratory care are inevitably needed to get full recovery for cardiac arrest. Management of these critical issues were reviewed and proposed in the consensus CONCLUSION: The goal of the statement is to provide help for the clinical physician to achieve better quality and evidence-based care in post-cardiac arrest period.

Outcome and status of postcardiac arrest care in Korea: results from the Korean Hypothermia Network prospective registry

Objective

High-quality intensive care, including targeted temperature management (TTM) for patients with postcardiac arrest syndrome, is a key element for improving outcomes after out-of-hospital cardiac arrest (OHCA). We aimed to assess the status of postcardiac arrest syndrome care, including TTM and 6-month survival with neurologically favorable outcomes, after adult OHCA patients were treated with TTM, using data from the Korean Hypothermia Network prospective registry.

Methods

We used the Korean Hypothermia Network prospective registry, a web-based multicenter registry that includes data from 22 participating hospitals throughout the Republic of Korea. Adult comatose OHCA survivors treated with TTM between October 2015 and December 2018 were included. The primary outcome was neurological outcome at 6 months.

Results

Of the 1,354 registered OHCA survivors treated with TTM, 550 (40.6%) survived 6 months, and 413 (30.5%) had good neurological outcomes. We identified 839 (62.0%) patients with preClinsumed cardiac etiology. A total of 937 (69.2%) collapses were witnessed, shockable rhythms were demonstrated in 482 (35.6%) patients, and 421 (31.1%) patients arrived at the emergency department with prehospital return of spontaneous circulation. The most common target temperature was 33°C, and the most common target duration was 24 hours.

Conclusion

The survival and good neurologic outcome rates of this prospective registry show great improvements compared with those of an earlier registry. While the optimal target temperature and duration are still unknown, the most common target temperature was 33°C, and the most common target duration was 24 hours.

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.

Postarrest Interventions that Save Lives

Patients resuscitated from cardiac arrest require complex management. An organized approach to early postarrest care can improve patient outcomes. Priorities include completing a focused diagnostic work-up to identify and reverse the inciting cause of arrest, stabilizing cardiorespiratory instability to prevent rearrest, minimizing secondary brain injury, evaluating the risk and benefits of transfer to a specialty care center, and avoiding early neurologic prognostication.

Impact of low and high partial pressure of carbon dioxide on neuron-specific enolase derived from serum and cerebrospinal fluid in patients who underwent targeted temperature management after out-of-hospital cardiac arrest: A retrospective study

AIM

In a previous study, low and high-normal arterial carbon dioxide tension (PaCO₂) were not associated with serum neuron-specific enolase (NSE) in cardiac arrest survivors. We assessed the effect of PaCO₂ on NSE in cerebrospinal fluid (CSF) and serum.

METHODS

This was a retrospective study. PaCO₂ for the first 24 h was analysed in four means, qualitative exposure state (qES), time-weighted average (TWA), median, and minimum-maximum (Min-Max). These subgroups were divided into low (LCO₂) and high PaCO₂ (HCO₂) groups defined as PaCO₂ ≤ 35.3 and PaCO₂ > 43.5 mmHg, respectively. NSE was measured at 24, 48, and 72 h (sNSE_24,48,72 and cNSE_24,48,72) from return of spontaneous circulation (ROSC). The primary outcome was the association between PaCO₂ and the NSE measured at 24 h after ROSC.

RESULTS

Forty-two subjects (male, 33; 78.6%) were included in total cohort. PaCO₂ in TWA subgroup was associated with cNSE_24,48,72, while PaCO₂ in the other subgroup were only associated with cNSE₂₄. PaCO₂ and cNSE in qES subgroup showed good correlation (r = -0.61; p < 0.01), and in TWA, median, and Min-Max subgroup showed moderate correlations (r = -0.57, r = -0.48, and r = -0.60; p < 0.01). Contrastively, sNSE was not associated and correlated with PaCO₂ in all analysis. Poor neurological outcome in LCO₂ was significantly higher than HCO₂ in qES, TWA, and median subgroups (p < 0.01, p < 0.01, and p = 0.02).

CONCLUSION

Association was found between NSE and PaCO₂ using CSF, despite including normocapnic ranges; TWA of PaCO₂ may be most strongly associated with CSF NSE levels. A prospective, multi-centre study is required to confirm our results.

Association between low pH and unfavorable neurological outcome among out-of-hospital cardiac arrest patients treated by extracorporeal CPR: a prospective observational cohort study in Japan

Background

We aimed to identify the association of pH value in blood gas assessment with neurological outcome among out-of-hospital cardiac arrest (OHCA) patients treated by extracorporeal cardiopulmonary resuscitation (ECPR).

Methods

We retrospectively analyzed the database of a multicenter prospective observational study on OHCA patients in Osaka prefecture, Japan (CRITICAL study), from July 1, 2012 to December 31, 2016. We included adult OHCA patients treated by ECPR. Patients with OHCA from external causes such as trauma were excluded. We conducted logistic regression analysis to identify the odds ratio (OR) and 95% confidence interval (CI) of the pH value for 1 month favorable neurological outcome adjusted for potential confounders including sex, age, witnessed by bystander, CPR by bystander, pre-hospital initial cardiac rhythm, and cardiac rhythm on hospital arrival.

Results

Among the 9822 patients in the database, 260 patients were finally included in the analysis. The three groups were Tertile 1: pH ≥ 7.030, Tertile 2: pH 6.875–7.029, and Tertile 3: pH < 6.875. The adjusted OR of Tertiles 2 and 3 compared with Tertile 1 for 1 month favorable neurological outcome were 0.26 (95% CI 0.10–0.63) and 0.24 (95% CI 0.09–0.61), respectively.

Conclusions

This multi-institutional observational study showed that low pH value (< 7.03) before the implementation of ECPR was associated with 1 month unfavorable neurological outcome among OHCA patients treated with ECPR. It may be helpful to consider the candidate for ECPR.

State-of-the-art considerations in post-arrest care

Cardiac arrest has a high rate of morbidity and mortality. Several advances in post-cardiac arrest management can improve outcome, but are time-dependent, placing the emergency physician in a critical role to both recognize the need for and initiate therapy. We present a novel perspective of both the workup and therapeutic interventions geared toward the emergency physician during the first few hours of care. We describe how the immediate care of a post-cardiac arrest patient is resource intensive and requires simultaneous evaluation for the underlying cause and intensive management to prevent further end organ damage, particularly of the central nervous system. The goal of the initial focused assessment is to rapidly determine if any reversible causes of cardiac arrest are present and to intervene when possible. Interventions performed in this acute period are aimed at preventing additional brain injury through optimizing hemodynamics, providing ventilatory support, and by using therapeutic hypothermia when indicated. After the initial phase of care, disposition is guided by available resources and the clinician's judgment. Transfer to a specialized cardiac arrest center is prudent in centers that do not have significant support or experience in the care of these patients.

Association between mild hypercapnia and hospital mortality in patients admitted to the intensive care unit after cardiac arrest: A retrospective study

BACKGROUND

Mild hypercapnia may increase cerebral oxygenation and attenuate cerebral injury in post-cardiac arrest patients. However, its association with hospital mortality has not been evaluated.

METHODS

We conducted a retrospective multi-center study of prospectively collected data of all cardiac arrest patients admitted to the ICU between 2014 and 2015. Different kinds of arterial carbon dioxide tension (PaCO₂), including time-weighted mean PaCO₂, mean PaCO₂, admission PaCO₂ and proportion of time spent in four PaCO₂ categories (hypocapnia, normocapnia, mild hypercapnia, and severe hypercapnia) were used to explore the association with outcomes. Restricted cubic splines models were built to evaluate the association between PaCO₂ and odds ratio for hospital mortality in overall population and subgroups of different pH levels (acidosis, normal pH and alkalosis).

RESULTS

2783 post-cardiac arrest patients in 150 ICUs were included. 933 (33.5%) were classified into the hypocapnia (PaCO₂ < 35 mmHg), 1088 (39.1%) into the normocapnia (35-45 mmHg), 472 (17%) into the mild hypercapnia (45-55 mmHg) and 390 (10.4%) into the severe hypercapnia (>55 mmHg) group. Compared with normocapnia, mild hypercapnia was not associated with higher hospital survival probability (OR 1.08 [95% CI 0.84-1.38, p = 0.558]). Time spent in the normocapnia was associated with good outcome (OR 0.98 [95% CI 0.97-0.99, p < 0.001], for every 5 percentage point increase in time), but mild hypercapnia was not (OR 1 [95% CI 0.98-1.01, p = 0.542]). Cox-proportional hazards models supported these findings. Associations between PaCO₂ and hospital mortality were not statistically significant in normal pH and alkalosis subgroups.

CONCLUSIONS

PaCO₂ has a U-shaped association with odds ratio for hospital mortality, with mild hypercapnia not having a higher hospital survival probability than normocapnia in post-cardiac arrest patients.

Targeted temperature management guided by the severity of hyperlactatemia for out-of-hospital cardiac arrest patients: a post hoc analysis of a nationwide, multicenter prospective registry

Background

The International Liaison Committee on Resuscitation guidelines recommend target temperature management (TTM) between 32 and 36 °C for patients after out-of-hospital cardiac arrest, but did not indicate patient-specific temperatures. The association of serum lactate concentration and neurological outcome in out-of-hospital cardiac arrest patient has been reported. The study aim was to investigate the benefit of 32–34 °C in patients with various degrees of hyperlactatemia compared to 35–36 °C.

Methods

This study was a post hoc analysis of the Japanese Association for Acute Medicine out-of-hospital cardiac arrest registry between June 2014 and December 2015. Patients with complete targeted temperature management and lactate data were eligible. Patients were stratified to mild (< 7 mmol/l), moderate (< 12 mmol/l), or severe (≥ 12 mmol/l) hyperlactatemia group based on lactate concentration after return of spontaneous circulation. They were subdivided into 32–34 °C or 35–36 °C groups. The primary endpoint was an adjusted predicted probability of 30-day favorable neurological outcome, defined as a cerebral performance category score of 1 or 2.

Result

Of 435 patients, 139 had mild, 182 had moderate, and 114 had severe hyperlactatemia. One hundred and eight (78%) with mild, 128 with moderate (70%), and 83 with severe hyperlactatemia (73%) received TTM at 32–34 °C. The adjusted predicted probability of a 30-day favorable neurological outcome following severe hyperlactatemia was significantly greater with 32–34 °C (27.4%, 95% confidence interval: 22.0–32.8%) than 35–36 °C (12.4%, 95% CI 3.5–21.2%; p = 0.005). The differences in outcomes in those with mild and moderate hyperlactatemia were not significant.

Conclusions

In OHCA patients with severe hyperlactatemia, the adjusted predicted probability of 30-day favorable neurological outcome was greater with TTM at 32–34 °C than with TTM at 35–36 °C. Further evaluation is needed to determine whether TTM at 32–34 °C can improve neurological outcomes in patients with severe hyperlactatemia after out-of-hospital cardiac arrest.

Optimizing the Early Resuscitation After Out-of-Hospital Cardiac Arrest

Resuscitation after out-of-hospital cardiac arrest can be one of the most challenging scenarios in acute-care medicine. The devastating effects of postcardiac arrest syndrome carry a substantial morbidity and mortality that persist long after return of spontaneous circulation. Management of these patients requires the clinician to simultaneously address multiple emergent priorities including the resuscitation of the patient and the efficient diagnosis and management of the underlying etiology. This review provides a concise evidence-based overview of the core concepts involved in the early postcardiac arrest resuscitation. It will highlight the components of an effective management strategy including addressing hemodynamic, oxygenation, and ventilation goals as well as carefully considering cardiac catheterization and targeted temperature management. An organized approach is paramount to providing effective care to patients in this vulnerable time period.

Targeted Temperature Management and Postcardiac arrest Care

Despite recent advances, care of the post-cardiac arrest patient remains a challenge. In this article, the authors discuss an approach to the initial care of post-cardiac arrest patients with particular focus on targeted temperature management (TTM). The article starts with history, physiologic rationale, and the major randomized controlled trials that have shaped guidelines for post-cardiac arrest care. It also reviews controversial topics, including TTM for nonshockable rhythms, TTM dose, and surface versus endovascular cooling. The article concludes with a brief review of other key aspects of post-arrest care: coronary angiography, hemodynamic optimization, ventilator management, and prognostication.

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.

Targeting two different levels of both arterial carbon dioxide and arterial oxygen after cardiac arrest and resuscitation: a randomised pilot trial

Purpose

We assessed the effects of targeting low-normal or high-normal arterial carbon dioxide tension (PaCO₂) and normoxia or moderate hyperoxia after out-of-hospital cardiac arrest (OHCA) on markers of cerebral and cardiac injury.

Methods

Using a 2³ factorial design, we randomly assigned 123 patients resuscitated from OHCA to low-normal (4.5–4.7 kPa) or high-normal (5.8–6.0 kPa) PaCO₂ and to normoxia (arterial oxygen tension [PaO₂] 10–15 kPa) or moderate hyperoxia (PaO₂ 20–25 kPa) and to low-normal or high-normal mean arterial pressure during the first 36 h in the intensive care unit. Here we report the results of the low-normal vs. high-normal PaCO₂ and normoxia vs. moderate hyperoxia comparisons. The primary endpoint was the serum concentration of neuron-specific enolase (NSE) 48 h after cardiac arrest. Secondary endpoints included S100B protein and cardiac troponin concentrations, continuous electroencephalography (EEG) and near-infrared spectroscopy (NIRS) results and neurologic outcome at 6 months.

Results

In total 120 patients were included in the analyses. There was a clear separation in PaCO₂ (p < 0.001) and PaO₂ (p < 0.001) between the groups. The median (interquartile range) NSE concentration at 48 h was 18.8 µg/l (13.9–28.3 µg/l) in the low-normal PaCO₂ group and 22.5 µg/l (14.2–34.9 µg/l) in the high-normal PaCO₂ group, p = 0.400; and 22.3 µg/l (14.8–27.8 µg/l) in the normoxia group and 20.6 µg/l (14.2–34.9 µg/l) in the moderate hyperoxia group, p = 0.594). High-normal PaCO₂ and moderate hyperoxia increased NIRS values. There were no differences in other secondary outcomes.

Conclusions

Both high-normal PaCO₂ and moderate hyperoxia increased NIRS values, but the NSE concentration was unaffected.

Registration

ClinicalTrials.gov, NCT02698917. Registered on January 26, 2016.

Electronic supplementary material

The online version of this article (10.1007/s00134-018-5453-9) contains supplementary material, which is available to authorized users.

Critical Care of the Post-Cardiac Arrest Patient

The post-cardiac arrest syndrome is a highly inflammatory state characterized by organ dysfunction, systemic ischemia and reperfusion injury, and persistent precipitating pathology. Early critical care should focus on identifying and treating arrest etiology and minimizing further injury to the brain and other organs by optimizing perfusion, oxygenation, ventilation, and temperature. Patients should be treated with targeted temperature management, although the exact temperature goal is not clear. No earlier than 72 hours after rewarming, prognostication using a multimodal approach should inform discussions with families regarding likely neurologic outcome.

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.

Ventilator Management and Respiratory Care After Cardiac Arrest: Oxygenation, Ventilation, Infection, and Injury

Return of spontaneous circulation after cardiac arrest results in a systemic inflammatory state called the post-cardiac arrest syndrome, which is characterized by oxidative stress, coagulopathy, neuronal injury, and organ dysfunction. Perturbations in oxygenation and ventilation may exacerbate secondary injury after cardiac arrest and have been shown to be associated with poor outcome. Further, patients who experience cardiac arrest are at risk for a number of other pulmonary complications. Up to 70% of patients experience early infection after cardiac arrest, and the respiratory tract is the most common source. Vigilance for early-onset pneumonia, as well as aggressive diagnosis and early antimicrobial agent administration are important components of critical care in this population. Patients who experience cardiac arrest are at risk for the development of ARDS. Risk factors include aspiration, pulmonary contusions (from chest compressions), systemic inflammation, and reperfusion injury. Early evidence suggests that they may benefit from ventilation with low tidal volumes. Meticulous attention to mechanical ventilation, early assessment and optimization of respiratory gas exchange, and therapies targeted at potential pulmonary complications may improve outcomes after cardiac arrest.

Effect of non-linearity of a predictor on the shape and magnitude of its receiver-operating-characteristic curve in predicting a binary outcome

Area under a receiver-operating-characteristic (AUROC) curve is widely used in medicine to summarize the ability of a continuous predictive marker to predict a binary outcome. This study illustrated how a U-shaped or inverted U-shaped continuous predictor would affect the shape and magnitude of its AUROC curve in predicting a binary outcome by comparing the ROC curves of the worst first 24-hour arterial pH values of 9549 consecutive critically ill patients in predicting hospital mortality before and after centering the predictor by its mean or median. A simulation dataset with an inverted U-shaped predictor was used to assess how this would affect the shape and magnitude of the AUROC curve. An asymmetrical U-shaped relationship between pH and hospital mortality, resulting in an inverse-sigmoidal ROC curve, was observed. The AUROC substantially increased after centering the predictor by its mean (0.611 vs 0.722, difference = 0.111, 95% confidence interval [CI] 0.087–0.135), and was further improved after centering by its median (0.611 vs 0.745, difference = 0.133, 95%CI 0.110–0.157). A sigmoidal-shaped ROC curve was observed for an inverted U-shaped predictor. In summary, a non-linear predictor can result in a biphasic-shaped ROC curve; and centering the predictor can reduce its bias towards null predictive ability.

Recent developments in the management of patients resuscitated from cardiac arrest

Cardiac arrest is the leading cause of death in Europe and the United States. Many patients who are initially resuscitated die in the hospital, and hospital survivors often have substantial neurologic dysfunction. Most cardiac arrests are caused by coronary artery disease; patients with coronary artery disease likely benefit from early coronary angiography and intervention. After resuscitation, cardiac arrest patients remain critically ill and frequently suffer cardiogenic shock and multiorgan failure. Early cardiopulmonary stabilization is important to prevent worsening organ injury. To achieve best patient outcomes, comprehensive critical care management is needed, with primary goals of stabilizing hemodynamics and preventing progressive brain injury. Targeted temperature management is frequently recommended for comatose survivors of cardiac arrest to mitigate the neurologic injury that drives outcomes. Accurate neurologic assessment is central to managing care of cardiac arrest survivors and should combine physical examination with objective neurologic testing, with the caveat that delaying neurologic prognosis is essential to avoid premature withdrawal of supportive care. A combination of clinical findings and diagnostic results should be used to estimate the likelihood of functional recovery. This review focuses on recent advances in care and specific cardiac intensive care strategies that may improve morbidity and mortality for patients after cardiac arrest.