Effect of moderate hyperventilation and induced hypertension on cerebral tissue oxygenation after cardiac arrest and therapeutic hypothermia

Cerebral Autoregulation: A Target for Improving Neurological Outcomes in Extracorporeal Life Support

Despite improvements in survival after illnesses requiring extracorporeal life support, cerebral injury continues to hinder successful outcomes. Cerebral autoregulation (CA) is an innate protective mechanism that maintains constant cerebral blood flow in the face of varying systemic blood pressure. However, it is impaired in certain disease states and, potentially, following initiation of extracorporeal circulatory support. In this review, we first discuss patient-related factors pertaining to venovenous and venoarterial extracorporeal membrane oxygenation (ECMO) and their potential role in CA impairment. Next, we examine factors intrinsic to ECMO that may affect CA, such as cannulation, changes in pulsatility, the inflammatory and adaptive immune response, intracranial hemorrhage, and ischemic stroke, in addition to ECMO management factors, such as oxygenation, ventilation, flow rates, and blood pressure management. We highlight potential mechanisms that lead to disruption of CA in both pediatric and adult populations, the challenges of measuring CA in these patients, and potential associations with neurological outcome. Altogether, we discuss individualized CA monitoring as a potential target for improving neurological outcomes in extracorporeal life support.

Critical Care Management of Patients After Cardiac Arrest: A Scientific Statement from the American Heart Association and Neurocritical Care Society

The critical care management of patients after cardiac arrest is burdened by a lack of high-quality clinical studies and the resultant lack of high-certainty evidence. This results in limited practice guideline recommendations, which may lead to uncertainty and variability in management. Critical care management is crucial in patients after cardiac arrest and affects outcome. Although guidelines address some relevant topics (including temperature control and neurological prognostication of comatose survivors, 2 topics for which there are more robust clinical studies), many important subject areas have limited or nonexistent clinical studies, leading to the absence of guidelines or low-certainty evidence. The American Heart Association Emergency Cardiovascular Care Committee and the Neurocritical Care Society collaborated to address this gap by organizing an expert consensus panel and conference. Twenty-four experienced practitioners (including physicians, nurses, pharmacists, and a respiratory therapist) from multiple medical specialties, levels, institutions, and countries made up the panel. Topics were identified and prioritized by the panel and arranged by organ system to facilitate discussion, debate, and consensus building. Statements related to postarrest management were generated, and 80% agreement was required to approve a statement. Voting was anonymous and web based. Topics addressed include neurological, cardiac, pulmonary, hematological, infectious, gastrointestinal, endocrine, and general critical care management. Areas of uncertainty, areas for which no consensus was reached, and future research directions are also included. Until high-quality studies that inform practice guidelines in these areas are available, the expert panel consensus statements that are provided can advise clinicians on the critical care management of patients after cardiac arrest.

Recovery and Survival of Patients After Out-of-Hospital Cardiac Arrest: A Literature Review Showcasing the Big Picture of Intensive Care Unit-Related Factors

As an important public health issue, out-of-hospital cardiac arrest (OHCA) requires several stages of high quality medical care, both on-field and after hospital admission. Post-cardiac arrest shock can lead to severe neurological injury, resulting in poor recovery outcome and increased risk of death. These characteristics make this condition one of the most important issues to deal with in post-OHCA patients hospitalized in intensive care units (ICUs). Also, the majority of initial post-resuscitation survivors have underlying coronary diseases making revascularization procedure another crucial step in early management of these patients. Besides keeping myocardial blood flow at a satisfactory level, other tissues must not be neglected as well, and maintaining mean arterial pressure within optimal range is also preferable. All these procedures can be simplified to a certain level along with using targeted temperature management methods in order to decrease metabolic demands in ICU-hospitalized post-OHCA patients. Additionally, withdrawal of life-sustaining therapy as a controversial ethical topic is under constant re-evaluation due to its possible influence on overall mortality rates in patients initially surviving OHCA. Focusing on all of these important points in process of managing ICU patients is an imperative towards better survival and complete recovery rates.

Critical Care Management of Patients After Cardiac Arrest: A Scientific Statement From the American Heart Association and Neurocritical Care Society

The critical care management of patients after cardiac arrest is burdened by a lack of high-quality clinical studies and the resultant lack of high-certainty evidence. This results in limited practice guideline recommendations, which may lead to uncertainty and variability in management. Critical care management is crucial in patients after cardiac arrest and affects outcome. Although guidelines address some relevant topics (including temperature control and neurological prognostication of comatose survivors, 2 topics for which there are more robust clinical studies), many important subject areas have limited or nonexistent clinical studies, leading to the absence of guidelines or low-certainty evidence. The American Heart Association Emergency Cardiovascular Care Committee and the Neurocritical Care Society collaborated to address this gap by organizing an expert consensus panel and conference. Twenty-four experienced practitioners (including physicians, nurses, pharmacists, and a respiratory therapist) from multiple medical specialties, levels, institutions, and countries made up the panel. Topics were identified and prioritized by the panel and arranged by organ system to facilitate discussion, debate, and consensus building. Statements related to postarrest management were generated, and 80% agreement was required to approve a statement. Voting was anonymous and web based. Topics addressed include neurological, cardiac, pulmonary, hematological, infectious, gastrointestinal, endocrine, and general critical care management. Areas of uncertainty, areas for which no consensus was reached, and future research directions are also included. Until high-quality studies that inform practice guidelines in these areas are available, the expert panel consensus statements that are provided can advise clinicians on the critical care management of patients after cardiac arrest.

High versus low mean arterial pressure targets after out-of-hospital cardiac arrest: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Targeting a specific mean arterial pressure (MAP) has been evaluated as a treatment strategy after out-of-hospital cardiac arrest (OHCA) resuscitation. However, the current evidence lacks clear guidelines regarding the optimal MAP target after OHCA.

METHODS

A systematic review and meta-analysis synthesizing randomized controlled trials (RCTs), retrieved by systematically searching: PubMed, EMBASE, WOS, SCOPUS, and Cochrane through January 18th, 2023. Our review protocol was prospectively published on PROSPERO with ID: CRD42023395333.

RESULTS

Four RCTs with a total of 1065 patients were included in our analysis. There was no difference between high MAP versus low MAP regarding the primary outcomes: all-cause mortality (RR: 1.07 with a 95% CI [0.91, 1.27], P = 0.4) and favorable neurological recovery (RR: 1.02 with a 95% CI [0.93, 1.13], P = 0.68). However, high MAP target was significantly associated with decreased ICU stay duration (MD: -0.78 with a 95 CI [-1.54, -0.02], P = 0.04) and mechanical ventilation duration (MD: -0.91 with a 95 CI of [-1.51, -0.31], P = 0.003).

CONCLUSION

A high MAP target may reduce ICU stay and mechanical ventilation duration but did not demonstrate improvements in either mortality or favorable neurological recovery. Therefore, the role of high MAP target remains uncertain and requires further RCTs.

Blood pressure targets and management during post-cardiac arrest care

Blood pressure is one modifiable physiological target in patients treated in the intensive care unit after cardiac arrest. Current Guidelines recommend targeting a mean arterial pressure (MAP) of higher than 65-70 mmHg using fluid resuscitation and the use of vasopressors. Management strategies will vary based in the setting, i.e. the pre-hospital compared to the in-hospital phase. Epidemiological data suggest that some degree of hypotension requiring vasopressors occur in almost 50% of patients. A higher MAP could theoretically increase coronary blood flow but on the other hand the use of vasopressor may result in an increase in cardiac oxygen demand and arrhythmia. An adequate MAP is paramount for maintaining cerebral blood flow. In some cardiac arrest patients the cerebral autoregulation may be disturbed resulting in the need for higher MAP in order to avoid decreasing cerebral blood flow. Thus far, four studies including little more than 1000 patients have compared a lower and higher MAP target in cardiac arrest patients. The achieved mean difference of MAP between groups has varied from 10-15 mmHg. Based on these studies a Bayesian meta-analysis suggests that the posterior probability that a future study would find treatment effects higher than a 5% difference between groups to be less than 50%. On the other hand, this analysis also suggests, that the likelihood of harm with a higher MAP target is also low. Noteworthy is that all studies to date have focused mainly on patients with a cardiac cause of the arrest with the majority of patients being resuscitated from a shockable initial rhythm. Future studies should aim to include also non-cardiac causes and aim to target a wider separation in MAP between groups.

Targeted Temperature Management in Cardiac Arrest: An Updated Narrative Review

The established benefits of cooling along with development of sophisticated methods to safely and precisely induce, maintain, monitor, and reverse hypothermia have led to the development of targeted temperature management (TTM). Early trials in human subjects showed that hypothermia conferred better neurological outcomes when compared to normothermia among survivors of cardiac arrest, leading to guidelines recommending targeted hypothermia in this patient population. Multiple studies have sought to explore and compare the benefit of hypothermia in various subgroups of patients, such as survivors of out-of-hospital cardiac arrest versus in-hospital cardiac arrest, and survivors of an initial shockable versus non-shockable rhythm. Larger and more recent trials have shown no statistically significant difference in neurological outcomes between patients with targeted hypothermia and targeted normothermia; further, aggressive cooling is associated with a higher incidence of multiple systemic complications. Based on this data, temporal trends have leaned towards using a lenient temperature target in more recent times. Current guidelines recommend selecting and maintaining a constant target temperature between 32 and 36 °C for those patients in whom TTM is used (strong recommendation, moderate-quality evidence), as soon as possible after return of spontaneous circulation is achieved and airway, breathing (including mechanical ventilation), and circulation are stabilized. The comparative benefit of lower (32-34 °C) versus higher (36 °C) temperatures remains unknown, and further research may help elucidate this. Any survivor of cardiac arrest who is comatose (defined as unarousable unresponsiveness to external stimuli) should be considered as a candidate for TTM regardless of the initial presenting rhythm, and the decision to opt for targeted hypothermia versus targeted normothermia should be made on a case-by-case basis.

The effect of fluid bolus administration on cerebral tissue oxygenation in post-cardiac arrest patients

PURPOSE

Fluid boluses (FB) are often used in post-cardiac arrest (CA) patients with haemodynamic instability. Although FB may improve cardiac output (CO) and mean arterial pressure (MAP), FB may also increase central venous pressure (CVP), reduce arterial PaO₂, dilute haemoglobin and cause interstitial oedema. The aim of the present study was to investigate the net effect of FB administration on cerebral tissue oxygenation saturation (SctO₂) in post-CA patients.

METHODS

Pre-planned sub-study of the Neuroprotect post-CA trial (NCT02541591). Patients with anticipated fluid responsiveness based on stroke volume variation (SVV) or passive leg raising test were administered a FB of 500 ml plasma-lyte A (Baxter Healthcare) and underwent pre- and post-FB assessments of stroke volume, CO, MAP, CVP, haemoglobin, PaO₂ and SctO₂.

RESULTS

52 patients (mean age 64 ± 12 years, 75% male) received a total of 115 FB. Although administration of a FB resulted in a significant increase of stroke volume (63 ± 22 vs 67 ± 23 mL, p = 0.001), CO (4,2 ± 1,6 vs 4,4 ± 1,7 L/min, p = 0.001) and MAP (74,8 ± 13,2 vs 79,2 ± 12,9 mmHg, p = 0.004), it did not improve SctO₂ (68.54 ± 6.99 vs 68.70 ± 6.80%, p = 0.49). Fluid bolus administration also resulted in a significant increase of CVP (10,0 ± 4,5 vs 10,7 ± 4,9 mmHg, p = 0.02), but did not affect PaO₂ (99 ± 31 vs 94 ± 31 mmHg, p = 0.15) or haemoglobin concentrations (12,9 ± 2,1 vs 12,8 ± 2,2 g/dL, p = 0.10). In a multivariate model, FB-induced changes in CO (beta 0,77; p = 0.004) and in CVP (beta -0,23; p = 0.02) but not in MAP (beta 0,02; p = 0.18) predicted post-FB ΔSctO₂.

CONCLUSIONS

Despite improvements in CO and MAP, FB administration did not improve SctO₂ in post-cardiac arrest patients.

Ventilation in Simulated Out-of-Hospital Cardiac Arrest Resuscitation Rarely Meets Guidelines

OBJECTIVE

The American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care recommend ventilation rates of eight to ten breaths per minute or two ventilations every 30 compressions, and tidal volumes between 500-600 ml. However, compliance with these guidelines is mainly unknown. The objective of this study is to estimate the proportion of simulated adult OHCA cases that meet guideline-based ventilation targets.

METHODS

We conducted a blinded prospective observational study of standardized simulated cases of EMS-witnessed adult OHCA. During scheduled training sessions, resuscitations were performed by high-quality CPR trained EMS teams composed of four on-duty, full-time EMT/Paramedics from a large urban fire-based EMS agency. A high-fidelity simulation center allowed complete audio and video monitoring from a control room. Rescuers were unaware of the study, or that ventilation practices were being observed. All interventions, including airway and ventilation strategies, were at the discretion of the clinical team. A calibrated Laerdal SimMan 3 G manikin and associated Laerdal Debrief Viewer software recorded ventilation rate, tidal volume, and minute ventilation. Simulations achieving median ventilation rate 7-10 breaths/min, tidal volume 500-600 ml, and minute ventilation 3.5-6 liters/min were considered meeting guideline-based targets.

RESULTS

A total of 106 EMS teams were included in the study. Only 3/106 [2.8% (95% CI: 0.6-8.0)] of the EMS teams demonstrated ventilation characteristics meeting all guideline-based targets. The median ventilation rate was 5.8 breaths/min (IQR 4.4-7.7 breaths/min) with 26/106 [24.5% (95% CI: 17.2-33.7)] between 7-10 breaths/min. The median tidal volume was 413.5 ml (IQR 280.5-555.4 ml), with 18/106 [17.0% (95% CI: 10.9-25.5)] between 500-600 ml. The median minute ventilation was 2.4 L/min (IQR 1.2-3.6 L/min) with 16/106 [15.1% (95% CI: 9.4-23.3)] between 3.5-6.0 L/min.

CONCLUSION

During simulated adult OHCA resuscitation attempts, ventilation practices rarely met guideline-based targets, despite being performed by well-trained EMS providers. Methods should be developed to monitor and ensure high-quality ventilation during actual OHCA resuscitation attempts.

Management of Comatose Survivors of Cardiac Arrest

PURPOSE OF REVIEW

Because the whole-body ischemia-reperfusion insult associated with cardiac arrest often results in brain injury, neurologists perform an important role in postresuscitation cardiac arrest care. This article provides guidance for the assessment and management of brain injury following cardiac arrest.

RECENT FINDINGS

Neurologists have many roles in postresuscitation cardiac arrest care: (1) early assessment of brain injury severity to help inform triage for invasive circulatory support or revascularization; (2) advocacy for the maintenance of a neuroprotective thermal, hemodynamic, biochemical, and metabolic milieu; (3) detection and management of seizures; (4) development of an accurate, multimodal, and conservative approach to prognostication; (5) application of shared decision-making paradigms around the likely outcomes of therapy and the goals of care; and (6) facilitation of the neurocognitive assessment of survivors. Therefore, optimal management requires early neurologist involvement in patient care, a detailed knowledge of postresuscitation syndrome and its complex interactions with prognosis, expertise in bringing difficult cases to their optimal conclusions, and a support system for survivors with cognitive deficits.

SUMMARY

Neurologists have a critical role in postresuscitation cardiac arrest care and are key participants in the treatment team from the time of first restoration of a perfusing heart rhythm through the establishment of rehabilitation services for survivors.

Monitorage cérébral après arrêt cardiaque : techniques et utilité clinique potentielle

L’arrêt cardiaque cause une hypoxie-ischémie globale, suivi de reperfusion, qui est susceptible d’engendrer des effets délétères sur la perfusion et l’oxygénation cérébrales, ainsi que le métabolisme cellulaire. Dans ce contexte, et en l’absence de thérapies spcéfiques de l’ischémie-reperfusion globale, le traitement est essentiellement de soutien, visant à optimiser la perfusion et l’oxygénation cérébrale, dans le but de prévenir ou atténuer les dégâts secondaires sur la fonction cérébrale. Dans ce contexte, le monitorage cérébral multimodal, notamment les techniques non-invasives, ont une utilité potentielle à la phase agiuë de l’arrêt cardiaque. Le but prinicpal de cette revue est de décrire les techniques actuellement dipsonibles, en nous focalisant surtout sur les outils noninvasifs (doppler transcranien, spectrospcope de proche infrarouge, électroencéphalographie, pupillométrie automatisée proche infrarouge), leur utilité clinique potentielle ainsi que leurs limitations, dans la prise en charge aiguë (optimisation de la perfusion et de l’oxygénation cérébrales) ainsi que pour la détermination du pronostic précoce après arrêt cardiaque.

Targeting low-normal or high-normal mean arterial pressure after cardiac arrest and resuscitation: a randomised pilot trial

PURPOSE

We aimed to determine the feasibility of targeting low-normal or high-normal mean arterial pressure (MAP) after out-of-hospital cardiac arrest (OHCA) and its effect on markers of neurological injury.

METHODS

In the Carbon dioxide, Oxygen and Mean arterial pressure After Cardiac Arrest and REsuscitation (COMACARE) trial, we used a 23 factorial design to randomly assign patients after OHCA and resuscitation to low-normal or high-normal levels of arterial carbon dioxide tension, to normoxia or moderate hyperoxia, and to low-normal or high-normal MAP. In this paper we report the results of the low-normal (65-75 mmHg) vs. high-normal (80-100 mmHg) MAP comparison. The primary outcome was the serum concentration of neuron-specific enolase (NSE) at 48 h after cardiac arrest. The feasibility outcome was the difference in MAP between the groups. Secondary outcomes included S100B protein and cardiac troponin (TnT) concentrations, electroencephalography (EEG) findings, cerebral oxygenation and neurological outcome at 6 months after cardiac arrest.

RESULTS

We recruited 123 patients and included 120 in the final analysis. We found a clear separation in MAP between the groups (p < 0.001). The median (interquartile range) NSE concentration at 48 h was 20.6 µg/L (15.2-34.9 µg/L) in the low-normal MAP group and 22.0 µg/L (13.6-30.9 µg/L) in the high-normal MAP group, p = 0.522. We found no differences in the secondary outcomes.

CONCLUSIONS

Targeting a specific range of MAP was feasible during post-resuscitation intensive care. However, the blood pressure level did not affect the NSE concentration at 48 h after cardiac arrest, nor any secondary outcomes.

Airway and ventilation management during cardiopulmonary resuscitation and after successful resuscitation

After cardiac arrest a combination of basic and advanced airway and ventilation techniques are used during cardiopulmonary resuscitation (CPR) and after a return of spontaneous circulation (ROSC). The optimal combination of airway techniques, oxygenation and ventilation is uncertain. Current guidelines are based predominantly on evidence from observational studies and expert consensus; recent and ongoing randomised controlled trials should provide further information. This narrative review describes the current evidence, including the relative roles of basic and advanced (supraglottic airways and tracheal intubation) airways, oxygenation and ventilation targets during CPR and after ROSC in adults. Current evidence supports a stepwise approach to airway management based on patient factors, rescuer skills and the stage of resuscitation. During CPR, rescuers should provide the maximum feasible inspired oxygen and use waveform capnography once an advanced airway is in place. After ROSC, rescuers should titrate inspired oxygen and ventilation to achieve normal oxygen and carbon dioxide targets.

Changes in cerebral oxygenation based on intraoperative ventilation strategy

Introduction

Cerebral oxygenation can be monitored clinically by cerebral oximetry (regional oxygen saturation, rSO₂) using near-infrared spectroscopy (NIRS). Changes in rSO₂ have been shown to precede changes in pulse oximetry, providing an early detection of clinical deterioration. Cerebral oximetry values may be affected by various factors, including changes in ventilation. The aim of this study was to evaluate the changes in rSO₂ during intraoperative changes in mechanical ventilation.

Patients and methods

Following the approval of the institutional review board (IRB), tissue and cerebral oxygenation were monitored intraoperatively using NIRS. Prior to anesthetic induction, the NIRS monitor was placed on the forehead and over the deltoid muscle to obtain baseline values. NIRS measurements were recorded each minute over a 5-min period during general anesthesia at four phases of ventilation: 1) normocarbia (35–40 mmHg) with a low fraction of inspired oxygen (FiO₂) of 0.3; 2) hypocarbia (25–30 mmHg) and low FiO₂ of 0.3; 3) hypocarbia and a high FiO₂ of 0.6; and 4) normocarbia and a high FiO₂. NIRS measurements during each phase were compared with sequential phases using paired t-tests.

Results

The study cohort included 30 adolescents. Baseline cerebral and tissue oxygenation were 81% ± 9% and 87% ± 5%, respectively. During phase 1, cerebral rSO₂ was 83% ± 8%, which decreased to 79% ± 8% in phase 2 (hypocarbia and low FiO₂). Cerebral oxygenation partially recovered during phase 3 (81% ± 9%) with the increase in FiO₂ and then returned to baseline during phase 4 (83% ± 8%). Each sequential change (e.g., phase 1 to phase 2) in cerebral oxygenation was statistically significant (p < 0.01). Tissue oxygenation remained at 87%–88% throughout the study.

Conclusion

Cerebral oxygenation declined slightly during general anesthesia with the transition from normocarbia to hypocarbic conditions. The rSO₂ decrease related to hypocarbia was easily reversed with a return to baseline values by the administration of supplemental oxygen (60% vs. 30%).

Effects of hyperventilation on cerebral oxygen saturation estimated using near-infrared spectroscopy: A randomised comparison between propofol and sevoflurane anaesthesia

BACKGROUND

Near-infrared spectroscopy estimates cerebral regional tissue oxygen saturation (rSO2), which may decrease under hyperventilation. Propofol and sevoflurane act differently on cerebral blood vessels. Consequently, cerebral blood flow during hyperventilation with propofol and sevoflurane anaesthesia may differ.

OBJECTIVES

The first aim of this study was to compare the changes in rSO2 between propofol and sevoflurane anaesthesia during hyperventilation. The second aim was to assess changes in rSO2 with ventilation changes.

DESIGN

A randomised, open-label study.

SETTING

University of Yamanashi Hospital, Yamanashi, Japan from January 2014 to September 2014.

PARTICIPANTS

Fifty American Society of Anesthesiologists physical status 1 or 2 adult patients who were scheduled for elective abdominal surgery were assigned randomly to receive either propofol or sevoflurane anaesthesia. Exclusion criterion was a known history of cerebral disease such as cerebral infarction, cerebral haemorrhage, transient ischaemic attack and subarachnoid haemorrhage.

INTERVENTIONS

After induction of anaesthesia but before the start of surgery, rSO2, arterial carbon dioxide partial pressure (PaCO2) and arterial oxygen saturation were measured. Measurements were repeated at 5-min intervals during 15 min of hyperventilation with a PaCO2 around 30 mmHg (4 kPa), and again after ventilation was normalised.

MAIN OUTCOME MEASURES

The primary outcome was the difference of changes in rSO2 between propofol anaesthesia and sevoflurane anaesthesia during and after hyperventilation. The second outcome was change in rSO2 after the initiation of hyperventilation and after the normalisation of ventilation.

RESULTS

Changes of rSO2 during hyperventilation were -10 ± 7% (left) and -11 ± 8% (right) in the propofol group, and -10 ± 8% (left) and -9 ± 7% (right) in the sevoflurane group. After normalisation of PaCO2, rSO2 returned to baseline values. Arterial oxygen saturation remained stable throughout the measurement period. The rSO2 values were similar in the propofol and the sevoflurane groups at each time point.

CONCLUSION

The effects of hyperventilation on estimated rSO2 were similar with propofol and sevoflurane anaesthesia. Changes in rSO2 correlated well with ventilation changes.

TRIAL REGISTRATION

Japan Primary Registries Network (JPRN); UMIN-CTR ID; UMIN000010640.

Hunt-Hess 5 subarachnoid haemorrhage presenting with cardiac arrest is associated with larger volume bleeds

AIMS

The mechanism, effects, and outcomes of cardiac arrest (CA) caused by subarachnoid haemorrhage (SAH) remain unclear. We compared SAH patients presenting with CA to other high-grade SAH patients presenting without CA in order to better understand (1) the cause of CA, (2) cerebral pathophysiology following CA, and (3) outcomes of CA in patients with SAH.

METHODS

We performed a retrospective analysis of a prospectively collected observational cohort. 31 Hunt-Hess 5 patients that presented with CA were compared to 146 Hunt-Hess 5 patients that presented without CA. Clinical and imaging findings were predefined and adjudicated. Cerebral physiology measures were available for a subset of patients, matched 1:1 by age.

RESULTS

Twenty-two (71%) CA patients had pulseless electrical activity/asystole compared to 2 (6%) with a shockable rhythm. The CA patients were younger (OR 0.96, 95% CI 0.93-0.99, p=0.009), had more SAH on CT (OR 1.07, 95% CI 1.01-1.13, p=0.02), and had higher in-hospital mortality (87% vs. 58%, OR 6.2 (2.1-26.6), p=0.004). There were no differences in aneurysm location, cerebral herniation, or ictal seizures. Despite similar cerebral perfusion pressure, CA patients had pathologically lower brain tissue oxygenation, lower glucose, and higher lactate to pyruvate ratios.

CONCLUSIONS

CA in SAH is associated with larger volume bleeds. Despite normal cerebral perfusion pressures, CA patients show compromised cerebral physiology.

A comparison of pediatric airway management techniques during out-of-hospital cardiac arrest using the CARES database

OBJECTIVE

To compare odds of survival to hospital discharge among pediatric out-of-hospital cardiac arrest (OHCA) patients receiving either bag-valve-mask ventilation (BVM), supraglottic airway (SGA) or endotracheal intubation (ETI), after adjusting for the propensity to receive a given airway intervention.

METHODS

Retrospective cohort study using the Cardiac Arrest Registry to Enhance Survival (CARES) database from January 1 201-December 31, 2015. The CARES registry includes data on cardiac arrests from 17 statewide registries and approximately 55 additional US cities. We included patients less than18 years of age who suffered a non-traumatic OHCA and received a resuscitation attempt by Emergency Medical Services (EMS). The key exposure was the airway management strategy (BVM, ETI, or SGA). The primary outcome was survival to hospital discharge.

RESULTS

Of the 3793 OHCA cases included from 405 EMS agencies, 1724 cases were analyzed after limiting the analysis to EMS agencies that used all 3 devices. Of the 1724, 781 (45.3%) were treated with BVM only, 727 (42.2%) ETI, and 215 (12.5%) SGA. Overall, 20.7% had ROSC and 10.9% survived to hospital discharge. After using a propensity score analysis, the odds ratio for survival to hospital discharge for ETI compared to BVM was 0.39 (95%CI 0.26-0.59) and for SGA compared to BVM was 0.32 (95% CI 0.12-0.84). These relationships were robust to the sensitivity analyses including complete case, EMS-agency matched, and age-stratified.

CONCLUSIONS

BVM was associated with higher survival to hospital discharge compared to ETI and SGA. A large randomized clinical trial is needed to confirm these findings.

Intensive care medicine research agenda on cardiac arrest

Over the last 15 years, treatment of comatose post-cardiac arrest patients has evolved to include therapeutic strategies such as urgent coronary angiography with percutaneous coronary intervention (PCI), targeted temperature management (TTM)-requiring mechanical ventilation and sedation-and more sophisticated and cautious prognostication. In 2015, collaboration between the European Resuscitation Council (ERC) and the European Society for Intensive Care Medicine (ESICM) resulted in the first European guidelines on post-resuscitation care. This review addresses the major recent advances in the treatment of cardiac arrest, recent trials that have challenged current practice and the remaining areas of uncertainty.

Cardiac arrest and therapeutic hypothermia

Therapeutic hypothermia for patients who remain comatose following resuscitation from a cardiac arrest improves both survival and neurologic outcomes. Although this therapy has been incorporated into the guidelines for routine post-resuscitation care and has been in clinical use for over a decade, significant questions and controversies remain. In this review, we discuss these questions in the context of the current evidence and provide a practical framework to help guide clinicians.

Myocardial Dysfunction and Shock after Cardiac Arrest

Postarrest myocardial dysfunction includes the development of low cardiac output or ventricular systolic or diastolic dysfunction after cardiac arrest. Impaired left ventricular systolic function is reported in nearly two-thirds of patients resuscitated after cardiac arrest. Hypotension and shock requiring vasopressor support are similarly common after cardiac arrest. Whereas shock requiring vasopressor support is consistently associated with an adverse outcome after cardiac arrest, the association between myocardial dysfunction and outcomes is less clear. Myocardial dysfunction and shock after cardiac arrest develop as the result of preexisting cardiac pathology with multiple superimposed insults from resuscitation. The pathophysiology involves cardiovascular ischemia/reperfusion injury and cardiovascular toxicity from excessive levels of inflammatory cytokine activation and catecholamines, among other contributing factors. Similar mechanisms occur in myocardial dysfunction after cardiopulmonary bypass, in sepsis, and in stress-induced cardiomyopathy. Hemodynamic stabilization after resuscitation from cardiac arrest involves restoration of preload, vasopressors to support arterial pressure, and inotropic support if needed to reverse the effects of myocardial dysfunction and improve systemic perfusion. Further research is needed to define the role of postarrest myocardial dysfunction on cardiac arrest outcomes and identify therapeutic strategies.

Are changes in cerebrovascular autoregulation following cardiac arrest associated with neurological outcome? Results of a pilot study

PURPOSE

To investigate the association between impaired cerebrovascular autoregulation (CVAR) and outcome in comatose survivors of cardiac arrest.

METHODS

The correlation in the time domain between cerebral tissue oxygenation (cStO2) using near infrared spectroscopy (NIRS) and mean arterial pressure was used to determine the tissue oxygenation index (TOx) as a reflection of normal (TOx<0) or impaired (TOx>0) CVAR. Daily measurements (>1h recording time) were performed in the first three days post cardiac arrest. Survival and neurological outcome was assessed at three months following cardiac arrest. A control group of healthy volunteers was also investigated.

RESULTS

23 patients and 28 volunteers were studied. All survivors (n=8) of cardiac arrest had a good neurological outcome. The TOx (median [interquartile range] for days 1-3) was higher (Mann Whitney test, p<0.001) in non-survivors (0.04 [-0.02 to -0.16]) compared to survivors (-0.11 [-0.19 to -0.02]) and healthy volunteers (-0.15 [-0.27 to -0.04]) on every day and for days 1-3 following cardiac arrest. The TOx was not significantly different between survivors and healthy volunteers. The cStO2 did not discriminate survivors (67 [62-72]%) from non-survivors (71 [65-75]%). Logistic regression analysis demonstrated TOx to be independently associated with survival at three months post cardiac arrest (odds ratio [95% confidence interval] 0.01 [0.01-0.50], p=0.04).

CONCLUSIONS

Early impairment of CVAR following cardiac arrest is independently associated with mortality at three months follow-up. Assessments of CVAR could add to the management and prognostication during post-resuscitation care and should be further investigated as a guide to optimise cerebral perfusion pressure.

Optimal blood pressure for favorable neurological outcome in adult patients following in-hospital cardiac arrest

BACKGROUND

Adequate cerebral blood flow maintained by optimal blood pressure is important in neurological recovery for patients sustaining transient brain ischemia. Few clinical studies have investigated the relationship between blood pressure and neurological outcomes of patients resuscitated following cardiac arrest.

METHODS

This was a retrospective observational study, from a single medical center, of adult patients between 2006 and 2012 who had in-hospital cardiac arrest and achieved sustained return of spontaneous circulation (ROSC). Multivariable logistic regression analysis was used to identify factors associated with a favorable neurological outcome at hospital discharge. Maximal mean arterial pressure (MAP) during the initial 24h after sustained ROSC was used for analysis.

RESULTS

Of the 319 study patients, 56 (17.6%) achieved a favorable neurologic outcome. The mean MAP was 95 mmHg. MAP above 85 mmHg was found to correlate with a favorable neurological outcome (odds ratio [OR] 4.12, 95% confidence interval [CI] 1.47-14.39, p = 0.01). For patients without arterial hypertension, the optimal MAP was between 85 and 115 mmHg (OR 8.80, 95% CI 3.13-28.55, p < 0.001); for patients with arterial hypertension, the threshold MAP for achieving a favorable neurological outcome was above 88 mmHg (OR 4.04, 95% CI 1.41-13.03, p = 0.01).

CONCLUSIONS

The blood pressure over the first 24h following resuscitation was correlated with neurological outcome. There may be a threshold blood pressure required to affect a favorable neurological outcome. The optimal blood pressure may be dependent on the presence or absence of arterial hypertension.

[Near-infrared spectroscopy during cardiopulmonary resuscitation and mechanical circulatory support: From the operating room to the intensive care unit]

BACKGROUND

Near infrared spectroscopy (NIRS) allows continuous measurement of cerebral regional oxygen saturation (rSO2). It is a weighted saturation value derived from approximately 70-75 % venous, 20-25 % arterial and 2.5-5 % capillary blood. In contrast to pulse oximetry, NIRS is independent of pulsatile flow. Therefore, it is also applicable during extracorporeal circulation, cardiopulmonary resuscitation (CPR), and hypothermia.

OBJECTIVES

The purpose of this work is to describe the application of cerebral and somatic NIRS in cardiology and cardiac surgery patients in the operation room, during and after CPR, and during the intensive care unit stay.

MATERIALS AND METHODS

This article is based on peer-reviewed literature from PubMed.

RESULTS

Interventions based on decline of cerebral NIRS values during on-pump cardiac surgery can reduce major organ morbidity and mortality; however, the appearance of a postoperative cognitive dysfunction is scarcely influenced. Persisting of low cerebral oximetry values during resuscitation is a marker for not achieving return of spontaneous circulation under normothermia. NIRS is an additional method for monitoring that can be used during extracorporeal circulation.

CONCLUSION

NIRS is a rapidly available, user-friendly, and noninvasive method for continuous measurement of rSO2. NIRS provides additional information about tissue oxygenation especially during resuscitation and extracorporeal circulatory assist support. Recommendations concerning the use of NIRS for standard monitoring during resuscitation and mechanical circulatory support are not currently available. Further studies are required to show if use of NIRS can reduce pulse control and hands-off times during resuscitation and if use of NIRS can improve outcome after CPR and mechanical circulatory support.

Can Therapeutic Hypothermia Be Guided by Advanced Neuromonitoring in Neurocritical Care Patients? A Review

The impact of therapeutic hypothermia (TH) on long-term neurological outcome is still controversial. Data on the effects of TH on brain homeostasis are mostly derived from experimental research. Invasive multimodal neuromonitoring techniques may provide additional insight into pathophysiological changes associated with primary or secondary brain injury in humans. In this study we describe the principles of multimodal neuromonitoring and its potential in the clinical setting of TH. We call for more research using multimodal neuromonitoring techniques in patients undergoing TH to optimize cooling and rewarming strategies.

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

OBJECTIVE

Partial pressure of arterial carbon dioxide (PaCO2) is a major regulator of cerebral blood flow (CBF). Derangements in PaCO2 have been thought to worsen clinical outcomes after many forms of cerebral injury by altering CBF. Our aim was to systematically analyze the biomedical literature to determine the effects of PaCO2 derangements on clinical outcomes after cerebral injury.

METHODS

We performed a search of Cochrane Library, PUBMED, CINHAL, conference proceedings, and other sources using a comprehensive strategy. Study inclusion criteria were (1) human subjects; (2) cerebral injury; (3) mechanical ventilation post-injury; (4) measurement of PaCO2; and (5) comparison of a clinical outcome measure (e.g. mortality) between different PaCO2 exposures. We performed a qualitative analysis to collate and summarize effects of PaCO2 derangements according to the recommended methodology from the Cochrane Handbook.

RESULTS

Seventeen studies involving different etiologies of cerebral injury (six traumatic brain injury, six post-cardiac arrest syndrome, two cerebral vascular accident, three neonatal ischemic encephalopathy) met all inclusion and no exclusion criteria. Three randomized control trials were identified and only one was considered a high quality study as per the Cochrane criteria for assessing risk of bias. In 13/17 (76%) studies examining hypocapnia, and 7/10 (70%) studies examining hypercapnia, the exposed group (hypercapnia or hypocapnia) was associated with poor clinical outcome.

CONCLUSION

The majority of studies in this report found exposure to hypocapnia and hypercapnia after cerebral injury to be associated with poor clinical outcome. However, the optimal PaCO2 range associated with good clinical outcome remains unclear.

An observational near-infrared spectroscopy study on cerebral autoregulation in post-cardiac arrest patients: time to drop 'one-size-fits-all' hemodynamic targets?

AIMS

A subgroup of patients with ROSC after cardiac arrest (CA) with disturbed cerebral autoregulation might benefit from higher mean arterial pressures (MAP). We aimed to (1) phenotype patients with disturbed autoregulation, (2) investigate whether these patients have a worse prognosis, (3) define an individual optimal MAP per patient and (4) investigate whether time under this individual optimal MAP is associated with outcome.

METHODS

Prospective observational study in 51 post-CA patients monitored with near infrared spectroscopy.

RESULTS

(1) 18/51 patients (35%) had disturbed autoregulation. Phenotypically, a higher proportion of patients with disturbed autoregulation had pre-CA hypertension (31±47 vs. 65±49%, p=0.02) suggesting that right shifting of autoregulation is caused by chronic adaptation of cerebral blood flow to higher blood pressures. (2) In multivariate analysis, patients with preserved autoregulation (n=33, 65%) had a significant higher 180-days survival rate (OR 4.62, 95% CI [1.06:20.06], p=0.04]. Based on an index of autoregulation (COX), the average COX-predicted optimal MAP was 85 mmHg in patients with preserved and 100 mmHg in patients with disturbed autoregulation. (3) An individual optimal MAP could be determined in 33/51 patients. (4) The time under the individual optimal MAP was negatively associated with survival (OR 0.97, 95% CI [0.96:0.99], p=0.02). The time under previously proposed fixed targets (65, 70, 75, 80 mmHg) was not associated with a differential survival rate.

CONCLUSION

Cerebral autoregulation showed to be disturbed in 35% of post-CA patients of which a majority had pre-CA hypertension. Disturbed cerebral autoregulation within the first 24h after CA is associated with a worse outcome. In contrast to uniform MAP goals, the time spent under a patient tailored optimal MAP, based on an index of autoregulation, was negatively associated with survival.