Autoregulation of cerebral blood flow in patients resuscitated from cardiac arrest

Prognostic Value of Early Intermittent Electroencephalography in Patients after Extracorporeal Cardiopulmonary Resuscitation

The aim of this study was to investigate whether early intermittent electroencephalography (EEG) could be used to predict neurological prognosis of patients who underwent extracorporeal cardiopulmonary resuscitation (ECPR). This was a retrospective and observational study of adult patients who were evaluated by EEG scan within 96 h after ECPR. The primary endpoint was neurological status upon discharge from the hospital assessed with a Cerebral Performance Categories (CPC) scale. Among 69 adult cardiac arrest patients who underwent ECPR, 17 (24.6%) patients had favorable neurological outcomes (CPC score of 1 or 2). Malignant EEG patterns were more common in patients with poor neurological outcomes (CPC score of 3, 4 or 5) than in patients with favorable neurological outcomes (73.1% vs. 5.9%, p < 0.001). All patients with highly malignant EEG patterns (43.5%) had poor neurological outcomes. In multivariable analysis, malignant EEG patterns and duration of cardiopulmonary resuscitation were significantly associated with poor neurological outcomes. In this study, malignant EEG patterns within 96 h after cardiac arrest were significantly associated with poor neurological outcomes. Therefore, an early intermittent EEG scan could be helpful for predicting neurological prognosis of post-cardiac arrest patients after ECPR.

Resuscitating the Globally Ischemic Brain: TTM and Beyond

Cardiac arrest (CA) afflicts ~ 550,000 people each year in the USA. A small fraction of CA sufferers survive with a majority of these survivors emerging in a comatose state. Many CA survivors suffer devastating global brain injury with some remaining indefinitely in a comatose state. The pathogenesis of global brain injury secondary to CA is complex. Mechanisms of CA-induced brain injury include ischemia, hypoxia, cytotoxicity, inflammation, and ultimately, irreversible neuronal damage. Due to this complexity, it is critical for clinicians to have access as early as possible to quantitative metrics for diagnosing injury severity, accurately predicting outcome, and informing patient care. Current recommendations involve using multiple modalities including clinical exam, electrophysiology, brain imaging, and molecular biomarkers. This multi-faceted approach is designed to improve prognostication to avoid "self-fulfilling" prophecy and early withdrawal of life-sustaining treatments. Incorporation of emerging dynamic monitoring tools such as diffuse optical technologies may provide improved diagnosis and early prognostication to better inform treatment. Currently, targeted temperature management (TTM) is the leading treatment, with the number of patients needed to treat being ~ 6 in order to improve outcome for one patient. Future avenues of treatment, which may potentially be combined with TTM, include pharmacotherapy, perfusion/oxygenation targets, and pre/postconditioning. In this review, we provide a bench to bedside approach to delineate the pathophysiology, prognostication methods, current targeted therapies, and future directions of research surrounding hypoxic-ischemic brain injury (HIBI) secondary to CA.

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.

Anoxic Brain Injury Detection with the Normalized Diffusion to ASL Perfusion Ratio: Implications for Blood-Brain Barrier Injury and Permeability

BACKGROUND AND PURPOSE

Anoxic brain injury is a result of prolonged hypoxia. We sought to describe the nonquantitative arterial spin-labeling perfusion imaging patterns of anoxic brain injury, characterize the relationship of arterial spin-labeling and DWI, and evaluate the normalized diffusion-to-perfusion ratio to differentiate patients with anoxic brain injury from healthy controls.

MATERIALS AND METHODS

We identified all patients diagnosed with anoxic brain injuries from 2002 to 2019. Twelve ROIs were drawn on arterial spin-labeling with coordinate-matched ROIs identified on DWI. Linear regression analysis was performed to examine the relationship between arterial spin-labeling perfusion and diffusion signal. Normalized diffusion-to-perfusion maps were generated using a custom-built algorithm.

RESULTS

Thirty-five patients with anoxic brain injuries and 34 healthy controls were identified. Linear regression analysis demonstrated a significant positive correlation between arterial spin-labeling and DWI signal. By means of a combinatory cutoff of slope of >0 and R² of > 0.78, linear regression using arterial spin-labeling and DWI showed a sensitivity of 0.86 (95% CI, 0.71-0.94) and specificity of 0.82 (95% CI, 0.66-0.92) for anoxic brain injuries. A normalized diffusion-to-perfusion color map demonstrated heterogeneous ratios throughout the brain in healthy controls and homogeneous ratios in patients with anoxic brain injuries.

CONCLUSIONS

In anoxic brain injuries, a homogeneously positive correlation between qualitative perfusion and DWI signal was identified so that areas of increased diffusion signal showed increased ASL signal. By exploiting this relationship, the normalized diffusion-to-perfusion ratio color map may be a valuable imaging biomarker for diagnosing anoxic brain injury and potentially assessing BBB integrity.

A randomised double-blind pilot trial comparing a mean arterial pressure target of 65 mm Hg versus 72 mm Hg after out-of-hospital cardiac arrest

BACKGROUND

After resuscitation from out-of-hospital cardiac arrest, mean arterial pressure below 65 mm Hg is avoided with vasopressors. A higher blood-pressure target could potentially improve outcome. The aim of this pilot trial was to investigate the effect of a higher mean arterial pressure target on biomarkers of organ injury.

METHODS

This was a single-centre, double-blind trial of 50 consecutive, comatose out-of-hospital cardiac arrest patients randomly assigned in a 1:1 ratio to a mean arterial pressure target of 65 mm Hg (MAP65) or 72 mm Hg (MAP72). Modified blood pressure modules with a -10% offset were used, enabling a double-blind study design. End-points were biomarkers of organ injury including markers of endothelial integrity (soluble trombomodulin) brain damage (neuron-specific enolase) and renal function (estimated glomerular filtration rate).

RESULTS

Mean arterial pressure was significantly higher in MAP72 with a mean difference of 5 mm Hg (p_group=0.03). After 48 h, soluble trombomodulin (median (interquartile range)) was 8.2 (6.7-12.9) ng/ml and 8.3 (6.0-10.8) ng/ml (p=0.29), neuron-specific enolase was 20 (13-31 μg/l) and 18 (13-44 μg/l) p=0.79) and estimated glomerular filtration rate (mean (±standard deviation)) was 61±19 ml/min/1.73m2 and 48±22 ml/min/1.73 m2 (p=0.08) for the MAP72 and MAP65 groups, respectively. Renal replacement therapy was needed in eight patients (31%) in MAP65 and three patients (13%) in MAP72 (p=0.14).

CONCLUSIONS

Double-blind allocation to different mean arterial pressure targets is feasible in comatose out-of-hospital cardiac arrest patients. A mean arterial pressure target of 72 mm Hg compared to 65 mm Hg did not result in improved biomarkers of organ injury. We observed a trend towards preserved renal function in the MAP72 group.

Dissociation of Cerebral Blood Flow and Femoral Artery Blood Pressure Pulsatility After Cardiac Arrest and Resuscitation in a Rodent Model: Implications for Neurological Recovery

Background

Impaired neurological function affects 85% to 90% of cardiac arrest (CA) survivors. Pulsatile blood flow may play an important role in neurological recovery after CA. Cerebral blood flow (CBF) pulsatility immediately, during, and after CA and resuscitation has not been investigated. We characterized the effects of asphyxial CA on short‐term (<2 hours after CA) CBF and femoral arterial blood pressure (ABP) pulsatility and studied their relationship to cerebrovascular resistance (CVR) and short‐term neuroelectrical recovery.

Methods and Results

Male rats underwent asphyxial CA followed by cardiopulmonary resuscitation. A multimodal platform combining laser speckle imaging, ABP, and electroencephalography to monitor CBF, peripheral blood pressure, and brain electrophysiology, respectively, was used. CBF and ABP pulsatility and CVR were assessed during baseline, CA, and multiple time points after resuscitation. Neuroelectrical recovery, a surrogate for neurological outcome, was assessed using quantitative electroencephalography 90 minutes after resuscitation. We found that CBF pulsatility differs significantly from baseline at all experimental time points with sustained deficits during the 2 hours of postresuscitation monitoring, whereas ABP pulsatility was relatively unaffected. Alterations in CBF pulsatility were inversely correlated with changes in CVR, but ABP pulsatility had no association to CVR. Interestingly, despite small changes in ABP pulsatility, higher ABP pulsatility was associated with worse neuroelectrical recovery, whereas CBF pulsatility had no association.

Conclusions

Our results reveal, for the first time, that CBF pulsatility and CVR are significantly altered in the short‐term postresuscitation period after CA. Nevertheless, higher ABP pulsatility appears to be inversely associated with neuroelectrical recovery, possibly caused by impaired cerebral autoregulation and/or more severe global cerebral ischemia.

Non-pulsatile blood flow is associated with enhanced cerebrovascular carbon dioxide reactivity and an attenuated relationship between cerebral blood flow and regional brain oxygenation

BACKGROUND

Systemic blood flow in patients on extracorporeal assist devices is frequently not or only minimally pulsatile. Loss of pulsatile brain perfusion, however, has been implicated in neurological complications. Furthermore, the adverse effects of absent pulsatility on the cerebral microcirculation are modulated similarly as CO₂ vasoreactivity in resistance vessels. During support with an extracorporeal assist device swings in arterial carbon dioxide partial pressures (PaCO₂) that determine cerebral oxygen delivery are not uncommon-especially when CO₂ is eliminated by the respirator as well as via the gas exchanger of an extracorporeal membrane oxygenation machine. We, therefore, investigated whether non-pulsatile flow affects cerebrovascular CO₂ reactivity (CVR) and regional brain oxygenation (rSO₂).

METHODS

In this prospective, single-centre case-control trial, we studied 32 patients undergoing elective cardiac surgery. Blood flow velocity in the middle cerebral artery (MCAv) as well as rSO₂ was determined during step changes of PaCO₂ between 30, 40, and 50 mmHg. Measurements were conducted on cardiopulmonary bypass during non-pulsatile and postoperatively under pulsatile blood flow at comparable test conditions. Corresponding changes of CVR and concomitant rSO₂ alterations were determined for each flow mode. Each patient served as her own control.

RESULTS

MCAv was generally lower during hypocapnia than during normocapnia and hypercapnia (p < 0.0001). However, the MCAv/PaCO₂ slope during non-pulsatile flow was 14.4 cm/s/mmHg [CI 11.8-16.9] and 10.4 cm/s/mmHg [CI 7.9-13.0] after return of pulsatility (p = 0.03). During hypocapnia, non-pulsatile CVR (4.3 ± 1.7%/mmHg) was higher than pulsatile CVR (3.1 ± 1.3%/mmHg, p = 0.01). Independent of the flow mode, we observed a decline in rSO2 during hypocapnia and a corresponding rise during hypercapnia (p < 0.0001). However, the relationship between ΔrSO₂ and ΔMCAv was less pronounced during non-pulsatile flow.

CONCLUSIONS

Non-pulsatile perfusion is associated with enhanced cerebrovascular CVR resulting in greater relative decreases of cerebral blood flow during hypocapnia. Heterogenic microvascular perfusion may account for the attenuated ΔrSO₂/ΔMCAv slope. Potential hazards related to this altered regulation of cerebral perfusion still need to be assessed.

TRIAL REGISTRATION

The study was retrospectively registered on October 30, 2018, with Clinical Trial.gov (NCT03732651).

Parameters Influencing Brain Oxygen Measurement by Regional Oxygen Saturation in Postcardiac Arrest Patients with Targeted Temperature Management

In several studies, regional cerebral oxygen saturation (rSO₂) has been measured in patients with postcardiac arrest syndrome (PCAS) to analyze the brain's metabolic status. However, the significance of rSO₂ in PCAS patients remains unclear. In the present study, we investigated the relationship between rSO₂ and physiological parameters. Comatose survivors of out-of-hospital PCAS with targeted temperature management (TTM) at 34°C for 24 hours were included. All patients were monitored for their rSO₂ and additional parameters (arterial oxygen saturation [SaO₂], hemoglobin [Hb], mean arterial pressure [MAP], arterial carbon dioxide pressure [PaCO₂], and body temperature]) measured at the start of monitoring and 24 and 48 hours after return of spontaneous circulation (ROSC). Patients were divided into favorable and unfavorable groups, and the correlation between rSO₂ and these physiological parameters was evaluated by multiple regression analysis. Forty-nine patients were included in the study, with 15 in the favorable group and 34 in the unfavorable group. There was no significant difference in the rSO₂ value between the two groups at any time point. The multiple regression analysis of the favorable group revealed a moderate correlation between rSO₂ and SaO₂, Hb, and PaCO₂ only at 24 hours (coefficients: 0.482, 0.422, and 0.531, respectively), whereas that of the unfavorable group revealed moderate correlations between rSO₂ and Hb values at all time points, PaCO₂ at 24 hours and MAP at 24 and 48 hours. rSO₂ was moderately correlated to MAP in unfavorable patients. To optimize brain oxygen metabolic balance for PCAS patients with TTM measuring rSO₂, we suggest total evaluation of each parameters of SaO₂, Hb, MAP, and PaCO₂.

Optimal Hemodynamic Parameter to Predict the Neurological Outcome in Out-of-Hospital Cardiac Arrest Survivors Treated with Target Temperature Management

Current guidelines suggest the maintenance of systolic blood pressure (SBP) at >90 mmHg and mean arterial pressure (MAP) at >65 mmHg in postcardiac arrest patients. There remains a lack of clarity regarding optimal values and timing of blood pressure parameters associated with the improvement of neurologic outcome. We investigated the association of time-weighted average (TWA) blood pressure parameters with favorable neurological outcome (FO) in postcardiac arrest patients. This was a registry-based observational study with consecutive adult out-of-hospital cardiac arrest (OHCA) survivors who were treated using targeted temperature management (TTM). During 72 hours of TTM period, we abstracted hemodynamic parameters such as SBP, diastolic blood pressure, pulse rate (PR), and MAP. Shock index (SI; PR/SBP) and modified shock index (MSI; PR/MAP) were calculated from each measured hemodynamics. Logistic regression was performed to assess the associations between TWA blood pressure parameters and FO, defined as cerebral performance category 1 or 2 at hospital discharge. Among the 173 patients (median age: 58 years; 64% male), 51 (29.3%) had FO in this study. MAP, SI, and MSI at 6 hours after return of spontaneous circulation (ROSC) showed considerable differences in patients with FO (MAP: 89.1 ± 14.7 vs. 83.6 ± 15.8 mmHg, p = 0.033, SI: 0.7 ± 0.2 vs. 0.9 ± 0.9, p = 0.002, MSI: 1.0 ± 0.3 vs. 1.2 ± 0.3, p ≤ 0.001). Among them, MSI, especially at 6 hours, had the highest area under the curve for prediction of FO (0.685; 95% confidence interval: 0.597-0.772, p < 0.001). Also, MSI <1.0 had a sensitivity of 64.7%, a specificity of 64.2% to predict FO. In comatose survivors of OHCA with TTM, MSI at 6 hours after ROSC had the highest prognostic value for neurologic outcome among blood pressure parameters.

Association Between Elevated Mean Arterial Blood Pressure and Neurologic Outcome After Resuscitation From Cardiac Arrest: Results From a Multicenter Prospective Cohort Study

OBJECTIVES

Laboratory studies suggest elevated blood pressure after resuscitation from cardiac arrest may be protective; however, clinical data are limited. We sought to test the hypothesis that elevated postresuscitation mean arterial blood pressure is associated with neurologic outcome.

DESIGN

Preplanned analysis of a prospective cohort study.

SETTING

Six academic hospitals in the United States.

PATIENTS

Adult, nontraumatic cardiac arrest patients treated with targeted temperature management after return of spontaneous circulation.

INTERVENTIONS

Mean arterial blood pressure was measured noninvasively after return of spontaneous circulation and every hour during the initial 6 hours after return of spontaneous circulation.

MEASURES AND MAIN RESULTS

We calculated the mean arterial blood pressure and a priori dichotomized subjects into two groups: mean arterial blood pressure 70-90 and greater than 90 mm Hg. The primary outcome was good neurologic function, defined as a modified Rankin Scale less than or equal to 3. The modified Rankin Scale was prospectively determined at hospital discharge. Of the 269 patients included, 159 (59%) had a mean arterial blood pressure greater than 90 mm Hg. Good neurologic function at hospital discharge occurred in 30% of patients in the entire cohort and was significantly higher in patients with a mean arterial blood pressure greater than 90 mm Hg (42%) as compared with mean arterial blood pressure 70-90 mm Hg (15%) (absolute risk difference, 27%; 95% CI, 17-37%). In a multivariable Poisson regression model adjusting for potential confounders, mean arterial blood pressure greater than 90 mm Hg was associated with good neurologic function (adjusted relative risk, 2.46; 95% CI; 2.09-2.88). Over ascending ranges of mean arterial blood pressure, there was a dose-response increase in probability of good neurologic outcome, with mean arterial blood pressure greater than 110 mm Hg having the strongest association (adjusted relative risk, 2.97; 95% CI, 1.86-4.76).

CONCLUSIONS

Elevated blood pressure during the initial 6 hours after resuscitation from cardiac arrest was independently associated with good neurologic function at hospital discharge. Further investigation is warranted to determine if targeting an elevated mean arterial blood pressure would improve neurologic outcome after cardiac arrest.

Cerebrovascular autoregulation following cardiac arrest: Protocol for a post hoc analysis of the randomised COMACARE pilot trial

BACKGROUND

Approximately two-thirds of the mortality following out of hospital cardiac arrest is related to devastating neurological injury. Previous small cohort studies have reported an impaired cerebrovascular autoregulation following cardiac arrest, but no studies have assessed the impact of differences in oxygen and carbon dioxide tensions in addition to mean arterial pressure management.

METHODS

This is a protocol and statistical analysis plan to assess the correlation between changes in cerebral tissue oxygenation and arterial pressure as measure of cerebrovascular autoregulation, the tissue oxygenation index, in patients following out of hospital cardiac arrest and in healthy volunteers. The COMACARE study included 120 comatose survivors of out of hospital cardiac arrest admitted to ICU and managed with low-normal or high-normal targets for mean arterial pressure, arterial oxygen and carbon dioxide partial pressures. In addition, 102 healthy volunteers have been investigated as a reference group for the tissue oxygenation index. In both cohorts, the cerebral tissue oxygenation was measured by near infrared spectroscopy.

CONCLUSIONS

Cerebrovascular autoregulation is critical to maintain homoeostatic brain perfusion. This study of changes in autoregulation following out of hospital cardiac arrest over the first 48 hours, as compared to data from healthy volunteers, will generate important physiological information that may guide the rationale and design of interventional studies.

Comparison of Quantitative Characteristics of Early Post-resuscitation EEG Between Asphyxial and Ventricular Fibrillation Cardiac Arrest in Rats

BACKGROUND

Quantitative electroencephalogram (EEG) analysis has shown promising results in studying brain injury and functional recovery after cardiac arrest (CA). However, whether the quantitative characteristics of EEG, as potential indicators of neurological prognosis, are influenced by CA causes is unknown. The purpose of this study was designed to compare the quantitative characteristics of early post-resuscitation EEG between asphyxial CA (ACA) and ventricular fibrillation CA (VFCA) in rats.

METHODS

Thirty-two Sprague-Dawley rats of both sexes were randomized into either ACA or VFCA group. Cardiopulmonary resuscitation was initiated after 5-min untreated CA. Characteristics of early post-resuscitation EEG were compared, and the relationships between quantitative EEG features and neurological outcomes were investigated.

RESULTS

Compared with VFCA, serum level of S100B, neurological deficit score and brain histopathologic damage score were dramatically higher in the ACA group. Quantitative measures of EEG, including onset time of EEG burst, time to normal trace, burst suppression ratio, and information quantity, were significantly lower for CA caused by asphyxia and correlated with the 96-h neurological outcome and survival.

CONCLUSIONS

Characteristics of earlier post-resuscitation EEG differed between cardiac and respiratory causes. Quantitative measures of EEG not only predicted neurological outcome and survival, but also have the potential to stratify CA with different causes.

Hemodynamic, Biochemical, and Ventilatory Parameters are Independently Associated with Outcome after Cardiac Arrest

BACKGROUND

Hypotension, hyperglycemia, dysoxia, and dyscarbia may contribute to reperfusion injury, and each is independently associated with poor outcome (PO) after cardiac arrest. We investigated whether the combined effects of these physiological derangements are associated with cardiac arrest outcomes.

METHODS

This institutional review board-approved retrospective cohort study included consecutive resuscitated cardiac arrest patients that received targeted temperature management at Maine Medical Center from 2013 to 2015. We abstracted demographics, intra-arrest factors, and physiological parameters. The primary outcome was dichotomized cerebral performance category (CPC 1-2 vs 3-5) at hospital discharge. After comparing demographics, clinical factors, and persistent post-arrest physiological derangements in patients with good and PO, we constructed a logistic regression model comprised of clinical and demographic factors separately associated with severity, and physiology variables, attempting to evaluate the independent effects of persistent physiological derangements on outcome.

RESULTS

Sixty-eight of 222 (31%) patients had CPC 1-2 (good outcome [GO]) at discharge. In bivariate analysis, factors associated with PO included increased time from collapse to resuscitation, non-shockable rhythm, and age-combined Charlson comorbidity index. In multivariate analysis, each persistent physiological derangement incrementally decreased the likelihood of GO [OR GO per derangement 0.71 (interquartile range [IQR] 0.51-0.99), p = 0.042, area under the curve (AUC) for final model 0.769].

CONCLUSIONS

Uncorrected physiological derangements in the first 24 h after cardiac arrest are independently associated with PO. Although causality cannot be established, these findings support preclinical models suggesting that aggressive normalization of physiology after resuscitation may be a reasonable strategy to decrease reperfusion injury.

Effect of Body Temperature on Cerebral Autoregulation in Acutely Comatose Neurocritically Ill Patients

OBJECTIVES

Impaired cerebral autoregulation following neurologic injury is a predictor of poor clinical outcome. We aimed to assess the relationship between body temperature and cerebral autoregulation in comatose patients.

DESIGN

Retrospective analysis of prospectively collected data.

SETTING

Neurocritical care unit of the Johns Hopkins Hospital.

PATIENTS

Eighty-five acutely comatose patients (Glasgow Coma Scale score of ≤ 8) admitted between 2013 and 2017.

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

Cerebral autoregulation was monitored using multimodal monitoring with near-infrared spectroscopy-derived cerebral oximetry index. Cerebral oximetry index was calculated as a Pearson correlation coefficient between low-frequency changes in regional cerebral oxygenation saturation and mean arterial pressure. Patients were initially analyzed together, then stratified by temperature pattern over the monitoring period: no change (< 1°C difference between highest and lowest temperatures; n = 11), increasing (≥ 1°C; n = 9), decreasing (≥ 1°C; n = 9), and fluctuating (≥ 1°C difference but no sustained direction of change; n = 56). Mixed random effects models with random intercept and multivariable logistic regression analysis were used to assess the association between hourly temperature and cerebral oximetry index, as well as between temperature and clinical outcomes. Cerebral oximetry index showed a positive linear relationship with temperature (β = 0.04 ± 0.10; p = 0.29). In patients where a continual increase or decrease in temperature was seen during the monitoring period, every 1°C change in temperature resulted in a cerebral oximetry index change in the same direction by 0.04 ± 0.01 (p < 0.001) and 0.02 ± 0.01 (p = 0.12), respectively, after adjusting for PaCO2, hemoglobin, mean arterial pressure, vasopressor and sedation use, and temperature probe location. There was no significant difference in mortality or poor outcome (modified Rankin Scale score of 4-6) between temperature pattern groups at discharge, 3, or 6 months.

CONCLUSIONS

In acute coma patients, increasing body temperature is associated with worsening cerebral autoregulation as measured by cerebral oximetry index. More studies are needed to clarify the impact of increasing temperature on cerebral autoregulation in patients with acute brain injury.

Validation and Clinical Evaluation of a Method for Double-Blinded Blood Pressure Target Investigation in Intensive Care Medicine

OBJECTIVES

No double-blinded clinical trials have investigated optimal mean arterial pressure targets in the ICU. The aim of this study was to develop and validate a method for blinded investigation of mean arterial pressure targets in patients monitored with arterial catheter in the ICU.

DESIGN

Prospective observational study (substudy A) and prospective, randomized, controlled clinical study (substudy B).

SETTING

ICU, Department of Cardiology, University Hospital of Copenhagen, Rigshospitalet, Copenhagen, Denmark.

PATIENTS

Adult patients resuscitated from out-of-hospital cardiac arrest.

INTERVENTIONS

Standard blood pressure measuring modules were offset to display 10% lower or higher blood pressure values. We then: 1) confirmed this modification in vivo by comparing offset to standard modules in 22 patients admitted to the ICU. Thereafter we 2) verified the method in two randomized, clinical trials, each including 50 out-of-hospital cardiac arrest patients, where the offset of the blood pressure module was blinded to the treating staff.

MEASUREMENTS AND MAIN RESULTS

Substudy A showed that the expected separation of blood pressure measurements was achieved with an excellent correlation of the offset and standard modules (R = 0.997). Bland-Altman plots showed no bias of modified modules over a clinically relevant range of mean arterial pressure. The primary endpoint of the clinical trials was between-group difference of norepinephrine dose needed to achieve target mean arterial pressure. Trial 1 aimed at a 10% difference between groups in mean arterial pressure (targets: 65 and 72 mm Hg, respectively) and demonstrated a separation of 5 ± 1 mm Hg (p < 0.001). The difference in norepinephrine dose was not significantly different (0.03 ± 0.03 µg/kg/min; p = 0.42). Trial 2 aimed at a 20% difference between groups in mean arterial pressure (targets: 63 and 77 mm Hg, respectively). Separation was 12 ± 1 mm Hg (p < 0.01) in mean arterial pressure and 0.07 ± 0.03 µg/kg/min (p < 0.01) in norepinephrine dose.

CONCLUSIONS

The present method is feasible and robust and provides a platform for double-blinded comparison of mean arterial pressure targets in critically ill patients.

Amplitude-Integrated Electroencephalography and Brain Oxygenation for Postcardiac Arrest Patients with Targeted Temperature Management

Brain injury is the most common cause of death postcardiac arrest. Amplitude-integrated electroencephalography (aEEG) is suggested to be useful in the prognostication in cases of postcardiac arrest brain injury. However, combined monitoring with aEEG and regional oxygen saturation (rSO₂) for postcardiac arrest syndrome (PCAS) patients to improve accuracy has not been reported. The purpose of this prospective observational study is to assess the usefulness of aEEG and rSO₂ for PCAS patients with targeted temperature management (TTM) to predict neurological outcome and possibly identify the pathophysiology of postcardiac arrest brain injury. PCAS patients with TTM at 34°C were monitored by aEEG and rSO₂ immediately after admission to the intensive care unit and evaluated at the start of monitoring, and 24 and 48 hours after return of spontaneous circulation (ROSC). Patients were divided into two groups according to electroencephalography (EEG) pattern: a continuous EEG (C) pattern group and a noncontinuous EEG (NC) pattern group. Patients with C pattern had a significantly more favorable neurologic outcome compared with patients with an NC pattern at each point in time. No significant difference in rSO₂ values was observed between the C pattern and the NC pattern at any time point. Variation coefficient at rSO₂ in the NC group was significantly greater than that in the C group from the start of the monitoring to 24 hours. aEEG is useful in predicting outcome for PCAS patients whereas rSO₂ is not.

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.

Arterial blood pressure during targeted temperature management after out-of-hospital cardiac arrest and association with brain injury and long-term cognitive function

OBJECTIVES

During targeted temperature management after out-of-hospital cardiac arrest infusion of vasoactive drugs is often needed to ensure cerebral perfusion pressure. This study investigated mean arterial pressure after out-of-hospital cardiac arrest and the association with brain injury and long-term cognitive function.

METHODS

Post-hoc analysis of patients surviving at least 48 hours in the biobank substudy of the targeted temperature management trial with available blood pressure data. Patients were stratified in three groups according to mean arterial pressure during targeted temperature management (4-28 hours after admission; <70 mmHg, 70-80 mmHg, >80 mmHg). A biomarker of brain injury, neuron-specific enolase, was measured and impaired cognitive function was defined as a mini-mental state examination score below 27 in 6-month survivors.

RESULTS

Of the 657 patients included in the present analysis, 154 (23%) had mean arterial pressure less than 70 mmHg, 288 (44%) had mean arterial pressure between 70 and 80 mmHg and 215 (33%) had mean arterial pressure greater than 80 mmHg. There were no statistically significant differences in survival (P=0.35) or neuron-specific enolase levels (P=0.12) between the groups. The level of target temperature did not statistically significantly interact with mean arterial pressure regarding neuron-specific enolase (P_{interaction_MAP*TTM}=0.58). In the subgroup of survivors with impaired cognitive function (n=132) (35%) mean arterial pressure during targeted temperature management was significantly higher (P_group=0.03).

CONCLUSIONS

In a large cohort of comatose out-of-hospital cardiac arrest patients, low mean arterial pressure during targeted temperature management was not associated with higher neuron-specific enolase regardless of the level of target temperature (33°C or 36°C for 24 hours). In survivors with impaired cognitive function, mean arterial pressure during targeted temperature management was significantly higher.

Metoprolol and Nebivolol Prevent the Decline of the Redox Status of Low-Molecular-Weight Aminothiols in Blood Plasma of Rats During Acute Cerebral Ischemia

Cerebral ischemia has previously been shown to cause a systemic decrease in levels of the reduced forms of low-molecular-weight aminothiols [cysteine (Cys), homocysteine (Hcy), and glutathione (GSH)] in blood plasma. In this study, we examined the effect of beta-adrenergic receptor (β-AR) antagonists metoprolol (Met) and nebivolol (Neb) on the redox status of these aminothiols during acute cerebral ischemia in rats. We used a model of global cerebral ischemia (bilateral occlusion of common carotid arteries with hypotension lasting for 10 minutes). The antagonists were injected 1 hour before surgery. Total and reduced Cys, Hcy, and GSH levels were measured 40 minutes after the start of reperfusion. Neb (0.4 and 4 mg/kg) and Met (8 and 40 mg/kg) treatment increased the levels of reduced aminothiols and the global methylation index in the hippocampus. The treatments also prevented any decrease in reduced aminothiol levels in blood plasma during ischemia. Although both of these drugs eliminated delayed postischemic hypoperfusion, only Neb reduced neuronal damage in the hippocampus. The results indicate an essential role of β1-AR blockage in the maintenance of redox homeostasis of aminothiols in the plasma and brain during acute cerebral ischemia.

Untreated Relative Hypotension Measured as Perfusion Pressure Deficit During Management of Shock and New-Onset Acute Kidney Injury-A Literature Review

Maintaining an optimal blood pressure (BP) during shock is a fundamental tenet of critical care. Optimal BP targets may be different for different patients. In current practice, too often, uniform BP targets are pursued which may result in inadvertently accepting a degree of untreated relative hypotension, i.e., the deficit between patients' usual premorbid basal BP and the achieved BP, during vasopressor support. Relative hypotension is a common but an under-recognized and an under-treated sign among patients with potential shock state. From a physiological perspective, any relative reduction in the net perfusion pressure across an organ (e.g., renal) vasculature has a potential to overwhelm autoregulatory mechanisms, which are already under stress during shock. Such perfusion pressure deficit may consequently impact organs' ability to function or recover from an injured state. This review discusses such pathophysiologic mechanisms in detail with a particular focus on the risk of new-onset acute kidney injury (AKI). To review current literature, databases of Medline, Embase, and Google scholar were searched to retrieve articles that either adjusted BP targets based on patients' premorbid BP levels or considered relative hypotension as an exposure endpoint and assessed its association with clinical outcomes among acutely ill patients. There were no randomized controlled trials. Only seven studies could be identified and these were reviewed in detail. These studies indicated a significant association between the degree of relative hypotension that was inadvertently accepted in real-world practice and new-onset organ dysfunction or subsequent AKI. However, this is not a high-quality evidence. Therefore, well-designed randomized controlled trials are needed to evaluate whether adoption of individualized BP targets, which are initially guided by patient's premorbid basal BP and then tailored according to clinical response, is superior to conventional BP targets for vasopressor therapy, particularly among patients with vasodilatory shock states.

Design paper of the "Blood pressure targets in post-resuscitation care and bedside monitoring of cerebral energy state: a randomized clinical trial"

BACKGROUND

Neurological injuries remain the leading cause of death in comatose patients resuscitated from out-of-hospital cardiac arrest (OHCA). Adequate blood pressure is of paramount importance to optimize cerebral perfusion and to minimize secondary brain injury. Markers measuring global cerebral ischemia caused by cardiac arrest and consecutive resuscitation and reflecting the metabolic variations after successful resuscitation are needed to assist a more individualized post-resuscitation care. Currently, no technique is available for bedside evaluation of global cerebral energy state, and until now blood pressure targets have been based on limited clinical evidence. Recent experimental and clinical studies indicate that it might be possible to evaluate cerebral oxidative metabolism from measuring the lactate-to-pyruvate (LP) ratio of the draining venous blood. In this study, jugular bulb microdialysis and immediate bedside biochemical analysis are introduced as new diagnostic tools to evaluate the effect of higher mean arterial blood pressure on global cerebral metabolism and the degree of cellular damage after OHCA.

METHODS/DESIGN

This is a single-center, randomized, double-blinded, superiority trial. Sixty unconscious patients with sustained return of spontaneous circulation after OHCA will be randomly assigned in a one-to-one fashion to low (63 mm Hg) or high (77 mm Hg) mean arterial blood pressure target. The primary end-point will be a difference in mean LP ratio within 48 h between blood pressure groups. Secondary end-points are (1) association between LP ratio and all-cause intensive care unit (ICU) mortality and (2) association between LP ratio and survival to hospital discharge with poor neurological function.

DISCUSSION

Markers measuring cerebral ischemia caused by cardiac arrest and consecutive resuscitation and reflecting the metabolic changes after successful resuscitation are urgently needed to enable a more personalized post-resuscitation care and prognostication. Jugular bulb microdialysis may provide a reliable global estimate of cerebral metabolic state and can be implemented as an entirely new and less invasive diagnostic tool for ICU patients after OHCA and has implications for early prognosis and treatment.

TRIAL REGISTRATION

ClinicalTrials.gov (ClinicalTrials.gov Identifier: NCT03095742 ). Registered March 30, 2017.

Effect of serum albumin level on hospital outcomes in out-of-hospital cardiac arrest

Background:

Background: Serum albumin has been known as a strong predictive value of mortality in various disease conditions, severe burns, major surgeries, stroke, myocardial infarction, etc. But little is known for the effect of serum albumin level on out-of-hospital cardiac arrest patients.

Objectives:

This study aimed to investigate the effect of serum albumin level on the outcome of out of hospital cardiac arrest.

Methods:

This study was a prospective hospital-based patient cohort study, conducted during January to December 2014 at 27 emergency departments in Cardiac Arrest Pursuit Trial with Unique Registration and Epidemiologic Surveillance project. The albumin was measured immediately after arrival to the emergency department during cardiopulmonary resuscitation, and albumin was categorized into two groups, group < 3.5 g/dL group and ⩾ 3.5 g/dL group. The primary outcome was a good neurological recovery at discharge (cerebral performance category scale 1 or 2). Multivariable logistic regression was used for adjusting for confounders.

Results:

During the study period, 1616 out-of-hospital cardiac arrest patients with presumed cardiac etiology were enrolled, and the total of 1013 patients were analyzed in this study. A total 452 (44.6%) patients had serum albumin level less than 3.5 g/dL. The serum albumin ⩾ 3.5 g/dL group showed better neurological outcomes than the serum albumin < 3.5 g/dL group: 18.5% versus 4.0%, and ⩾ 3.5 g/dL group had higher survival discharge rates than the < 3.5 g/dL group: 23.9% versus 9.1% (p < 0.01). After adjusting for potential covariates, patients with serum albumin ⩾ 3.5 g/dL had a higher odds of good neurological recovery (adjusted odds ratio: 2.94 (95% confidence interval: [1.57, 5.49])), and higher survival to discharge (adjusted odds ratio: 1.74 (95% confidence interval: [1.10, 2.76])).

Conclusion:

Low serum albumin levels are associated with a worse neurologic outcome in patients with out-of-hospital cardiac arrest.

Associations between partial pressure of oxygen and neurological outcome in out-of-hospital cardiac arrest patients: an explorative analysis of a randomized trial

Objective

Exposure to hyperoxemia and hypoxemia is common in out-of-hospital cardiac arrest (OHCA) patients following return of spontaneous circulation (ROSC), but its effects on neurological outcome are uncertain, and study results are inconsistent.

Methods

Exploratory post hoc substudy of the Target Temperature Management (TTM) trial, including 939 patients after OHCA with return of spontaneous circulation (ROSC). The association between serial arterial partial pressures of oxygen (PaO₂) during 37 h following ROSC and neurological outcome at 6 months, evaluated by Cerebral Performance Category (CPC), dichotomized to good (CPC 1–2) and poor (CPC 3–5), was investigated. In our analyses, we tested the association of hyperoxemia and hypoxemia, time-weighted mean PaO₂, maximum PaO₂ difference, and gradually increasing PaO₂ levels (13.3–53.3 kPa) with poor neurological outcome. A subsequent analysis investigated the association between PaO₂ and a biomarker of brain injury, peak serum Tau levels.

Results

Eight hundred sixty-nine patients were eligible for analysis. Three hundred patients (35%) were exposed to hyperoxemia or hypoxemia at some time point after ROSC. Our analyses did not reveal a significant association between hyperoxemia, hypoxemia, time-weighted mean PaO₂ exposure or maximum PaO₂ difference and poor neurological outcome at 6-month follow-up after correction for co-variates (all analyses p = 0.146–0.847). We were not able to define a PaO₂ level significantly associated with the onset of poor neurological outcome. Peak serum Tau levels at either 48 or 72 h after ROSC were not associated with PaO₂.

Conclusion

Hyperoxemia or hypoxemia exposure occurred in one third of the patients during the first 37 h of hospitalization and was not significantly associated with poor neurological outcome after 6 months or with the peak s-Tau levels at either 48 or 72 h after ROSC.

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2322-z) contains supplementary material, which is available to authorized users.

A comparison of non-invasive versus invasive measures of intracranial pressure in hypoxic ischaemic brain injury after cardiac arrest

AIM

Increased intracranial pressure (ICP) in hypoxic ischaemic brain injury (HIBI) can cause secondary ischaemic brain injury and culminate in brain death. Invasive ICP monitoring is limited by associated risks in HIBI patients. We sought to evaluate the agreement between invasive ICP measurements and non-invasive estimators of ICP (nICP) in HIBI patients.

METHODS

Eligible consecutive adult (age>18) cardiac arrest patients with HIBI were included as part of a single centre prospective interventional study. Invasive ICP monitoring and nICP measurements were undertaken using: a) transcranial Doppler ultrasonography (TCD), b) optic nerve sheet diameter ultrasound (ONSD) and c) jugular venous bulb pressure (JVP). Multiple measurements applied in linear mixed-effects models were considered to obtain the correlation coefficient between ICP and nICP as well as their predictive abilities to detect intracranial hypertension (ICP≥20mm Hg).

RESULTS

Eleven patients were included (median age of 47 [range 20-71], 8 males and 3 females). There was a linear relationship between ICP and nICP with ONSD (R=0.53 [p<0.0001]), JVP (R=0.38 [p<0.001]) and TCD (R=0.30 [p<0.01]). The ability to predict intracranial hypertension was highest for ONSD and TCD (area under the receiver operating curve (AUC)=0.96 [95% CI: 0.90-1.00] and AUC=0.91 [95% CI: 0.83-1.00], respectively). JVP presented the weakest prediction ability (AUC=0.75 [95% CI: 0.56-0.94]).

CONCLUSIONS

ONSD and TCD methods demonstrated agreement with invasively-monitored ICP, suggesting their potential roles in the detection of intracranial hypertension in HIBI after cardiac arrest.

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.

Mean arterial pressure during targeted temperature management and renal function after out-of-hospital cardiac arrest

PURPOSE

This study investigates the association between mean arterial pressure (MAP) and renal function after out-of-hospital cardiac arrest (OHCA).

MATERIALS AND METHODS

Post-hoc analysis of 851 comatose OHCA-patients surviving >48 h included in the targeted temperature management (TTM)-trial.

RESULTS

Patients were stratified by mean MAP during TTM in the following groups; <70 mmHg (22%), 70-80 mmHg (43%), and > 80 mmHg (35%). Median (interquartile range) eGFR (ml/min/1.73 m²) 48 h after OHCA was inversely associated with MAP-group (70 (47-102), 84 (56-113), 94 (61-124), p < .001, for the <70-group, 70-80-group and > 80-group respectively). After adjusting for potential confounders, in a mixed model including eGFR after 1, 2 and 3 days this association remained significant (p_{group_adjusted} = 0.0002). Higher mean MAP was independently associated with lower odds of renal replacement therapy (odds ratio_adjusted = 0.77 [95% confidence interval, 0.65-0.91] per 5 mmHg increase; p = .002]).

CONCLUSIONS

Low mean MAP during TTM was independently associated with decreased renal function and need of renal replacement therapy in a large cohort of comatose OHCA-patients. Increasing MAP above the recommended 65 mmHg could potentially be renal-protective. This hypothesis should be investigated in prospective trials.

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.

Renal Function and Outcome of Out-of-Hospital Cardiac Arrest - Multicenter Prospective Study (SOS-KANTO 2012 Study)

BACKGROUND

Renal dysfunction is associated with increased cardiovascular-related mortality, but its impact on outcome of out-of-hospital cardiac arrest (OHCA) remains unclear. We assessed whether post-OHCA outcome correlated with renal function early after OHCA. Methods and Results: Of the 16,452 registered patients in the SOS-KANTO 2012 Study, 5,112 cardiogenic OHCA adults with creatinine measurement (mean age, 72 years; male, 64%) were examined. First-obtained creatinine was used to assess eGFR. Associations between eGFR groups, ≥60 (n=997), 45-59 (n=1,311), 30-44 (n=1,441), and <30 mL/min/1.73 m²(n=1,363), and 3-month survival and neurological outcomes were examined. Favorable neurological outcome was defined as cerebral performance categories 1 or 2. Survival rate (15.1%, 9.7%, 3.9%, and 2.9%; P<0.001) and proportion of favorable neurological outcome (12.3%, 7.4%, 2.6%, and 2.2%; P<0.001) were determined for eGFR groups ≥60, 45-59, 30-44, and <30 mL/min/1.73 m², respectively. The survival rate decreased with eGFR (<60 mL/min/1.73 m²), and survival adjusted OR were 0.74 (95% CI: 0.54-1.03), 0.42 (95% CI: 0.28-0.62), and 0.43 (95% CI: 0.28-0.68) for eGFR 45-59, 30-44, and <30 mL/min/1.73 m², respectively. The adjusted OR for favorable neurological outcome also decreased with eGFR: 0.74 (95% CI: 0.52-1.06), 0.40 (95% CI: 0.25-0.64), and 0.48 (95% CI: 0.29-0.81), respectively.

CONCLUSIONS

An independent and graded association was observed between decreased eGFR and 3-month survival and proportion of favorable neurological outcome in cardiogenic OHCA patients.

A novel approach to assess cerebral and coronary perfusion after cardiac arrest

BACKGROUND

Several indices exist to assess cerebral perfusion after cardiac arrest (CA). We aimed to investigate a new approach allowing absolute flow and microvascular resistance measurement based on selective arterial continuous thermodilution before and after CA resuscitation in a porcine model.

METHODS

In anaesthetised pigs, intravascular absolute cerebral blood flow (CBF) and absolute coronary blood flow (ABF) with corresponding microvascular resistances were measured. CA was induced using overdrive pacing with 3 (group 1, n = 5) or 5 min (group 2, n = 8) of no flow. After resuscitation, CBF was performed at baseline, at 15 min (T15) and at 30 min (T30). Thereafter, CBF in the contralateral cerebral artery and ABF were measured.

RESULTS

The protocol could not be completed in three pigs from group 2 due to haemodynamic instability. In the entire cohort, CBF was significantly lower at T30 after CA (0.026 ± 0.02 L/min vs 0.040 ± 0.03 at baseline; p = 0.03) and cerebral microvascular resistances were significantly higher (3202 ± 1838 Woods units vs 2014 ± 1015 at baseline; p = 0.04). ABF and resistances remained stable at baseline, as compared to T30 (0.122 ± 0.05 vs. 0.143 ± 0.06 L/min; p = 0.15 and 563 ± 203 vs. 478 ± 181 Woods units; p = 0.36, respectively). At T30, no significant differences in cerebral flow dynamics were observed between groups.

CONCLUSIONS

ABF and CBF measurement after CA resuscitation is feasible with thermodilution technique, allowing accurate monitoring and measurements. This novel approach allows simultaneous measurements of flow and microvascular resistances. This animal model simplifies cerebral perfusion measurements and allows to test new therapies to reduce cerebral injury post cardiac arrest.

Effect of neuromonitor-guided titrated care on brain tissue hypoxia after opioid overdose cardiac arrest

INTRODUCTION

Brain tissue hypoxia may contribute to preventable secondary brain injury after cardiac arrest. We developed a porcine model of opioid overdose cardiac arrest and post-arrest care including invasive, multimodal neurological monitoring of regional brain physiology. We hypothesized brain tissue hypoxia is common with usual post-arrest care and can be prevented by modifying mean arterial pressure (MAP) and arterial oxygen concentration (PaO2).

METHODS

We induced opioid overdose and cardiac arrest in sixteen swine, attempted resuscitation after 9 min of apnea, and randomized resuscitated animals to three alternating 6-h blocks of standard or titrated care. We invasively monitored physiological parameters including brain tissue oxygen (PbtO2). During standard care blocks, we maintained MAP > 65 mmHg and oxygen saturation 94-98%. During titrated care, we targeted PbtO2 > 20 mmHg.

RESULTS

Overall, 10 animals (63%) achieved ROSC after a median of 12.4 min (range 10.8-21.5 min). PbtO2 was higher during titrated care than standard care blocks (unadjusted β = 0.60, 95% confidence interval (CI) 0.42-0.78, P < 0.001). In an adjusted model controlling for MAP, vasopressors, sedation, and block sequence, PbtO2 remained higher during titrated care (adjusted β = 0.75, 95%CI 0.43-1.06, P < 0.001). At three predetermined thresholds, brain tissue hypoxia was significantly less common during titrated care blocks (44 vs 2% of the block duration spent below 20 mmHg, P < 0.001; 21 vs 0% below 15 mmHg, P < 0.001; and, 7 vs 0% below 10 mmHg, P = .01).

CONCLUSIONS

In this model of opioid overdose cardiac arrest, brain tissue hypoxia is common and treatable. Further work will elucidate best strategies and impact of titrated care on functional outcomes.

The impact of diastolic blood pressure values on the neurological outcome of cardiac arrest patients

AIM

Which haemodynamic variable is the best predictor of neurological outcome remains unclear. We investigated the association of several haemodynamic variables with neurological outcome in CA patients.

METHODS

Retrospective analysis of adult comatose survivors of CA admitted to the intensive care unit (ICU) of a University Hospital. Exclusion criteria were early death due to withdrawal of care, missing haemodynamic data and use of intra-aortic balloon pump or extracorporeal membrane oxygenation. We retrieved CA characteristics; lactate concentration and cardiovascular sequential organ failure assessment (cSOFA) score on admission; systolic (SAP), diastolic (DAP), mean arterial pressure (MAP), and the use of vasopressors and inotropic agents during the first 6 h of ICU stay. Unfavourable neurological outcome (UO) was defined as a 3-month cerebral performance category score of 3-5.

RESULTS

Among the 170 patients (median age 63 years, 67% male, 60% out-of-hospital CA), 106 (63%) had UO. Admission lactate was higher in patients with UO than in those with favourable neurological outcome (4.0[2.4-7.3] vs. 2.5[1.4-6.0] mEq/L; p = 0.003) as was the cSOFA (3 [1-4] vs. 2[0-3]; p = 0.007). The lowest DAP during the first 6 h after ICU admission was significantly lower in patients with unfavourable neurological outcome, notably in patients with high cSOFA scores. In multivariable analysis, high adrenaline doses and the lowest value of DAP during the first 6 h after ICU admission was significantly associated with unfavourable neurological outcome.

CONCLUSIONS

In CA patients admitted to the ICU, low DAP during the first 6 h is an independent predictor of unfavourable neurological outcome at 3 months.

Emergency Neurological Life Support: Resuscitation Following Cardiac Arrest

Cardiac arrest is the most common cause of death in North America. An organized bundle of neurocritical care interventions can improve chances of survival and neurological recovery in patients who are successfully resuscitated from cardiac arrest. Therefore, resuscitation following cardiac arrest was chosen as an Emergency Neurological Life Support protocol. Key aspects of successful early post-arrest management include: prevention of secondary brain injury; identification of treatable causes of arrest in need of emergent intervention; and, delayed neurological prognostication. Secondary brain injury can be attenuated through targeted temperature management (TTM), avoidance of hypoxia and hypotension, avoidance of hyperoxia, hyperventilation or hypoventilation, and treatment of seizures. Most patients remaining comatose after resuscitation from cardiac arrest should undergo TTM. Treatable precipitants of arrest that require emergent intervention include, but are not limited to, acute coronary syndrome, intracranial hemorrhage, pulmonary embolism and major trauma. Accurate neurological prognostication is generally not appropriate for several days after cardiac arrest, so early aggressive care should never be limited based on perceived poor neurological prognosis.

Influence of Induced Blood Pressure Variability on the Assessment of Cerebral Autoregulation in Patients after Cardiac Arrest

Objective

To determine if increasing variability of blood pressure influences determination of cerebral autoregulation.

Methods

A prospective observational study was performed at the ICU of a university hospital in the Netherlands. 13 comatose patients after cardiac arrest underwent baseline and intervention (tilting of bed) measurements. Mean flow velocity (MFV) in the middle cerebral artery and mean arterial pressure (MAP) were measured. Coefficient of variation (CV) was used as a standardized measure of dispersion in the time domain. In the frequency domain, coherence, gain, and phase were calculated in the very low and low frequency bands.

Results

The CV of MAP was significantly higher during intervention compared to baseline. On individual level, coherence in the VLF band changed in 5 of 21 measurements from unreliable to reliable and in 6 of 21 measurements from reliable to unreliable. In the LF band 1 of 21 measurements changed from unreliable to reliable and 3 of 21 measurements from reliable to unreliable. Gain in the VLF and LF band was lower during intervention compared to baseline.

Conclusions

For the ICU setting, more attention should be paid to the exact experimental protocol, since changes in experimental settings strongly influence results of estimation of cerebral autoregulation.

Optic nerve sheath diameter measured using early unenhanced brain computed tomography shows no correlation with neurological outcomes in patients undergoing targeted temperature management after cardiac arrest

AIM

Previous studies indicated that the optic nerve sheath diameter (ONSD) measured using brain computed tomography (CT) is a prognostic factor for poor neurological outcome after cardiac arrest. However, these studies were retrospective or included a small sample size. We performed a prospective multi-centre observational study to investigate the correlation between the ONSD on early brain CT and neurological outcomes in patients undergoing targeted temperature management (TTM).

METHODS

This study used data from the Korean Hypothermia Network prospective registry between November 2015 and October 2016. Out-of-cardiac arrest patients who underwent brain CT within 2 h after return of spontaneous circulation (ROSC) were included. The primary endpoint was neurological outcomes at 6 months (cerebral performance category; CPC); the secondary outcome was hospital mortality. The ONSD was measured using unenhanced brain CT images.

RESULTS

In total, 374 patients were included from 18 hospitals, and 329 underwent CT within 2 h after ROSC. Six months after cardiac arrest, good (CPC 1-2) and poor (CPC 3-5) neurological outcomes were observed in 99 (30.09%) and 230 (69.91%) patients, respectively. There was no significant difference in the ONSD between groups (good outcome group: 5.61 ± 0.59 mm, poor outcome group: 5.69 ± 0.79 mm; p = 0.275), nor between discharged patients who survived and those with hospital mortality (5.63 ± 0.64 mm and 5.70 ± 0.67 mm, respectively, p = 0.399).

CONCLUSION

The ONSD on initial brain CT after ROSC was not correlated with neurological outcome at 6 months in patients who underwent TTM.

Cerebral Perfusion and Cerebral Autoregulation after Cardiac Arrest

Out of hospital cardiac arrest is the leading cause of death in industrialized countries. Recovery of hemodynamics does not necessarily lead to recovery of cerebral perfusion. The neurological injury induced by a circulatory arrest mainly determines the prognosis of patients after cardiac arrest and rates of survival with a favourable neurological outcome are low. This review focuses on the temporal course of cerebral perfusion and changes in cerebral autoregulation after out of hospital cardiac arrest. In the early phase after cardiac arrest, patients have a low cerebral blood flow that gradually restores towards normal values during the first 72 hours after cardiac arrest. Whether modification of the cerebral blood flow after return of spontaneous circulation impacts patient outcome remains to be determined.

Hemodynamic Resuscitation Characteristics Associated with Improved Survival and Shock Resolution After Cardiac Arrest

PURPOSE

To determine which strategy of early post-cardiac arrest hemodynamic resuscitation was associated with best clinical outcomes. We hypothesized that higher mean arterial pressure (MAP) achieved using IV fluids over vasopressors would yield better outcomes.

METHODS

Retrospective cohort study of post-cardiac arrest patients between March 2011 and June 2012. Patients successfully resuscitated from cardiac arrest, admitted to an intensive care unit and surviving at least 24 h, were included. Patients missing data for >2 h after return of spontaneous circulation were excluded. The institutional standard for post-resuscitation MAP was ≥65 mm Hg with no guidelines on how MAP was supported. We examined the association between early (6 h) average MAP, vasopressor use summarized as cumulative vasopressor index and fluid intake with outcomes including survival to discharge, favorable neurologic outcome based on Cerebral Performance Category 1 or 2, and the surrogate outcome measure of lactate clearance using Pearson correlation and multivariable regression.

RESULTS

Of 118 patients, 55 (46%) survived to hospital discharge, 21 (18%) with favorable neurologic outcome. Higher 6-h mean cumulative vasopressor index was independently associated with worsened survival (OR 0.67; 95% CI 0.53, 0.85; P = 0.001). Resuscitation subgroups receiving higher than median vasopressors had worsened survival to hospital discharge regardless of fluid intake. In addition, higher MAP-6h correlated with increased lactate clearance (r = 0.29; P = 0.011).

CONCLUSIONS

Early post-return of spontaneous circulation hemodynamic resuscitation achieving higher MAP using fluid preferentially over vasopressors is associated with improved survival to hospital discharge as well as better lactate clearance.