Improving Outcomes After Post-Cardiac Arrest Brain Injury: A Scientific Statement From the International Liaison Committee on Resuscitation.

This scientific statement presents a conceptual framework for the pathophysiology of post-cardiac arrest brain injury, explores reasons for previous failure to translate preclinical data to clinical practice, and outlines potential paths forward. Post-cardiac arrest brain injury is characterized by 4 distinct but overlapping phases: ischemic depolarization, reperfusion repolarization, dysregulation, and recovery and repair. Previous research has been challenging because of the limitations of laboratory models; heterogeneity in the patient populations enrolled; overoptimistic estimation of treatment effects leading to suboptimal sample sizes; timing and route of intervention delivery; limited or absent evidence that the intervention has engaged the mechanistic target; and heterogeneity in postresuscitation care, prognostication, and withdrawal of life-sustaining treatments. Future trials must tailor their interventions to the subset of patients most likely to benefit and deliver this intervention at the appropriate time, through the appropriate route, and at the appropriate dose. The complexity of post-cardiac arrest brain injury suggests that monotherapies are unlikely to be as successful as multimodal neuroprotective therapies. Biomarkers should be developed to identify patients with the targeted mechanism of injury, to quantify its severity, and to measure the response to therapy. Studies need to be adequately powered to detect effect sizes that are realistic and meaningful to patients, their families, and clinicians. Study designs should be optimized to accelerate the evaluation of the most promising interventions. Multidisciplinary and international collaboration will be essential to realize the goal of developing effective therapies for post-cardiac arrest brain injury.

Improving Outcomes After Post-Cardiac Arrest Brain Injury: A Scientific Statement From the International Liaison Committee on Resuscitation.

This scientific statement presents a conceptual framework for the pathophysiology of post-cardiac arrest brain injury, explores reasons for previous failure to translate preclinical data to clinical practice, and outlines potential paths forward. Post-cardiac arrest brain injury is characterized by 4 distinct but overlapping phases: ischemic depolarization, reperfusion repolarization, dysregulation, and recovery and repair. Previous research has been challenging because of the limitations of laboratory models; heterogeneity in the patient populations enrolled; overoptimistic estimation of treatment effects leading to suboptimal sample sizes; timing and route of intervention delivery; limited or absent evidence that the intervention has engaged the mechanistic target; and heterogeneity in postresuscitation care, prognostication, and withdrawal of life-sustaining treatments. Future trials must tailor their interventions to the subset of patients most likely to benefit and deliver this intervention at the appropriate time, through the appropriate route, and at the appropriate dose. The complexity of post-cardiac arrest brain injury suggests that monotherapies are unlikely to be as successful as multimodal neuroprotective therapies. Biomarkers should be developed to identify patients with the targeted mechanism of injury, to quantify its severity, and to measure the response to therapy. Studies need to be adequately powered to detect effect sizes that are realistic and meaningful to patients, their families, and clinicians. Study designs should be optimized to accelerate the evaluation of the most promising interventions. Multidisciplinary and international collaboration will be essential to realize the goal of developing effective therapies for post-cardiac arrest brain injury.

Accuracy of a Continuous Glucose Monitor in the Intensive Care Unit: A Proposed Accuracy Standard and Calibration Protocol for Inpatient Use.

Background and Aims: Guidelines now recommend inpatient continuous glucose monitor (CGM) use with confirmatory blood glucose measurements. However, the Food and Drug Administration has not yet officially approved CGM for inpatient use in large part because its accuracy has not been established in this setting. We tested the accuracy of the Dexcom G6 (G6) in 28 adults on an insulin infusion in a medical-surgical intensive care unit with 1064 matched CGM and arterial point-of-care pairs. Methods: The participants were on average 57.29 (SD 2.39) years, of whom 13 had a prior diagnosis of diabetes and 14 were admitted for a surgical diagnosis. The first 19 participants received the G6 without calibration and had a mean absolute relative difference (MARD) of 13.19% (IQR 5.11, 19.03) across 659 matched pairs, which just meets the critical care expert recommendation of MARD <14%. We then aimed to improve accuracy for the subsequent 9 participants using a calibration protocol. Results: The MARD for calibrated participants was 9.65% (3.03, 13.33), significantly lower than for uncalibrated participants (P < 0.001). Calibration also demonstrated excellent safety with 100% of values within the Clarke Error Grid zones A and B compared with 99.07% without calibration. Our protocol achieved the lowest MARD and safest CEG profile in the critical care setting and well exceeds the critical care expert recommendations. Our large sample of heterogenous critically ill patients also reached comparable accuracy to the MARD of 9% for G6 in outpatients. We believe our calibration protocol will allow G6 to be used with sufficient accuracy in inpatients.

Shining a light on cerebral autoregulation: Are we anywhere near the truth?

The near-infrared spectroscopy (NIRS)-derived cerebral oximetry index (COx) has become popularized for non-invasive neuromonitoring of cerebrovascular function in post-cardiac arrest patients with hypoxic-ischemic brain injury (HIBI). We provide commentary on the physiologic underpinnings and assumptions of NIRS and the COx, potential confounds in the context of HIBI, and the implications for the assessment of cerebral autoregulation.

Wolf Creek XVII Part 8: Neuroprotection.

Introduction: Post-cardiac arrest brain injury (PCABI) is the primary determinant of clinical outcomes for patients who achieve return of spontaneous circulation after cardiac arrest (CA). There are limited neuroprotective therapies available to mitigate the acute pathophysiology of PCABI. Methods: Neuroprotection was one of six focus topics for the Wolf Creek XVII Conference held on June 14-17, 2023 in Ann Arbor, Michigan, USA. Conference invitees included international thought leaders and scientists in the field of CA resuscitation from academia and industry. Participants submitted via online survey knowledge gaps, barriers to translation, and research priorities for each focus topic. Expert panels used the survey results and their own perspectives and insights to create and present a preliminary unranked list for each category that was debated, revised and ranked by all attendees to identify the top 5 for each category. Results: Top 5 knowledge gaps included developing therapies for neuroprotection; improving understanding of the pathophysiology, mechanisms, and natural history of PCABI; deploying precision medicine approaches; optimizing resuscitation and CPR quality; and determining optimal timing for and duration of interventions. Top 5 barriers to translation included patient heterogeneity; nihilism & lack of knowledge about cardiac arrest; challenges with the translational pipeline; absence of mechanistic biomarkers; and inaccurate neuro-triage and neuroprognostication. Top 5 research priorities focused on translational research and trial optimization; addressing patient heterogeneity and individualized interventions; improving understanding of pathophysiology and mechanisms; developing mechanistic and outcome biomarkers across post-CA time course; and improving implementation of science and technology. Conclusion: This overview can serve as a guide to transform the care and outcome of patients with PCABI. Addressing these topics has the potential to improve both research and clinical care in the field of neuroprotection for PCABI.

Impact of Skin Pigmentation on Cerebral Regional Saturation of Oxygen Using Near-Infrared Spectroscopy: A Systematic Review.

OBJECTIVES: Near-infrared spectroscopy (NIRS) is used in critical care settings to measure regional cerebral tissue oxygenation (rSo2). However, the accuracy of such measurements has been questioned in darker-skinned individuals due to the confounding effects of light absorption by melanin. In this systematic review, we aim to synthesize the available evidence on the effect of skin pigmentation on rSo2 readings. DATA SOURCES: We systematically searched MEDLINE, Cochrane Database of Systematic Reviews, Embase, and Google Scholar from inception to July 1, 2023. STUDY SELECTION: In compliance with our PROSPERO registration (CRD42022347548), we selected articles comparing rSo2 measurements in adults either between racial groups or at different levels of skin pigmentation. Two independent reviewers conducted full-text reviews of all potentially relevant articles. DATA EXTRACTION: We extracted data on self-reported race or level of skin pigmentation and mean rSo2 values. DATA SYNTHESIS: Of the 11,495 unique records screened, two studies (n = 7,549) met our inclusion criteria for systematic review. Sun et al (2015) yielded significantly lower rSo2 values for African Americans compared with Caucasians, whereas Stannard et al (2021) found little difference between self-reported racial groups. This discrepancy is likely because Stannard et al (2021) used a NIRS platform which specifically purports to control for the effects of melanin. Several other studies that did not meet our inclusion criteria corroborated the notion that skin pigmentation results in lower rSo2 readings. CONCLUSIONS: Skin pigmentation likely results in attenuated rSo2 readings. However, the magnitude of this effect may depend on the specific NIRS platform used.

Characterizing the Relationship Between Arterial Carbon Dioxide Trajectory and Serial Brain Biomarkers with Central Nervous System Injury During Veno-Venous Extracorporeal Membrane Oxygenation: A Prospective Cohort Study.

BACKGROUND: Central nervous system (CNS) injury following initiation of veno-venous extracorporeal membrane oxygenation (VV-ECMO) is common. An acute decrease in partial pressure of arterial carbon dioxide (PaCO2) following VV-ECMO initiation has been suggested as an etiological factor, but the challenges of diagnosing CNS injuries has made discerning a relationship between PaCO2 and CNS injury difficult. METHODS: We conducted a prospective cohort study of adult patients undergoing VV-ECMO for acute respiratory failure. Arterial blood gas measurements were obtained prior to initiation of VV-ECMO, and at every 2-4 h for the first 24 h. Neuroimaging was conducted within the first 7-14 days in patients who were suspected of having neurological injury or unable to be examined because of sedation. We collected blood biospecimens to measure brain biomarkers [neurofilament light (NF-L); glial fibrillary acidic protein (GFAP); and phosphorylated-tau 181] in the first 7 days following initiation of VV-ECMO. We assessed the relationship between both PaCO2 over the first 24 h and brain biomarkers with CNS injury using mixed methods linear regression. Finally, we explored the effects of absolute change of PaCO2 on serum levels of neurological biomarkers by separate mixed methods linear regression for each biomarker using three PaCO2 exposures hypothesized to result in CNS injury. RESULTS: In our cohort, 12 of 59 (20%) patients had overt CNS injury identified on head computed tomography. The PaCO2 decrease with VV-ECMO initiation was steeper in patients who developed a CNS injury (- 0.32%, 95% confidence interval - 0.25 to - 0.39) compared with those without (- 0.18%, 95% confidence interval - 0.14 to - 0.21, P interaction < 0.001). The mean concentration of NF-L increased over time and was higher in those with a CNS injury (464 [739]) compared with those without (127 [257]; P = 0.001). GFAP was higher in those with a CNS injury (4278 [11,653] pg/ml) compared with those without (116 [108] pg/ml; P < 0.001). The mean NF-L, GFAP, and tau over time in patients stratified by the three thresholds of absolute change of PaCO2 showed no differences and had no significant interaction for time. CONCLUSIONS: Although rapid decreases in PaCO2 following initiation of VV-ECMO were slightly greater in patients who had CNS injuries versus those without, data overlap and absence of relationships between PaCO2 and brain biomarkers suggests other pathophysiologic variables are likely at play.

Monitoring of Brain Tissue Oxygen Tension in Cardiac Arrest: a Translational Systematic Review from Experimental to Clinical Evidence.

BACKGROUND: Cardiac arrest (CA) is a sudden event that is often characterized by hypoxic-ischemic brain injury (HIBI), leading to significant mortality and long-term disability. Brain tissue oxygenation (PbtO2) is an invasive tool for monitoring brain oxygen tension, but it is not routinely used in patients with CA because of the invasiveness and the absence of high-quality data on its effect on outcome. We conducted a systematic review of experimental and clinical evidence to understand the role of PbtO2 in monitoring brain oxygenation in HIBI after CA and the effect of targeted PbtO2 therapy on outcomes. METHODS: The search was conducted using four search engines (PubMed, Scopus, Embase, and Cochrane), using the Boolean operator to combine mesh terms such as PbtO2, CA, and HIBI. RESULTS: Among 1,077 records, 22 studies were included (16 experimental studies and six clinical studies). In experimental studies, PbtO2 was mainly adopted to assess the impact of gas exchanges, drugs, or systemic maneuvers on brain oxygenation. In human studies, PbtO2 was rarely used to monitor the brain oxygen tension in patients with CA and HIBI. PbtO2 values had no clear association with patients' outcomes, but in the experimental studies, brain tissue hypoxia was associated with increased inflammation and neuronal damage. CONCLUSIONS: Further studies are needed to validate the effect and the threshold of PbtO2 associated with outcome in patients with CA, as well as to understand the physiological mechanisms influencing PbtO2 induced by gas exchanges, drug administration, and changes in body positioning after CA.

Association of admission serum sodium and outcomes following out-of-hospital cardiac arrest.

BACKGROUND: The prognostic association between dysnatremia and outcomes in out-of-hospital cardiac arrest (OHCA) is not well understood. Given hypernatremia is associated with poor outcomes in critical illness and hyponatremia may exacerbate cerebral edema, we hypothesized that dysnatremia on OHCA hospital admission would be associated with worse neurological outcomes. METHODS: We studied adults (≥19 years) with non-traumatic OHCA between 2009 and 2016 who were enrolled in the British Columbia Cardiac Arrest Registry and survived to hospital admission at 2 quaternary urban hospitals. We stratified cases by admission serum sodium into hyponatremic (<135 mmol/L), normonatremic (135-145 mmol/L), and hypernatremic (>145 mmol/L) groups. We used logistic regression models, adjusted for age, sex, shockable rhythm, admission serum lactate, and witnessed arrest, to estimate the association between admission sodium and favorable neurological outcome (cerebral performance category 1-2 or modified Rankin scale 0-3). RESULTS: Of 414 included patients, 63 were hyponatremic, 330 normonatremic, and 21 hypernatremic. In each respective group, 21 (33.3%), 159 (48.2%), and 3 (14.3%) experienced good neurological outcomes. In univariable models, hyponatremia (OR 0.53, 95% CI 0.30-0.93) and hypernatremia (OR 0.19, 95% CI 0.05-0.65) were associated with lower odds of good neurological outcomes compared to the normonatremia group. After adjustment, only hypernatremia was associated with lower odds of good neurological outcomes (OR 0.22, 95% CI 0.05-0.98). CONCLUSIONS: Hypernatremia at admission was independently associated with decreased probability of good neurological outcomes at discharge post-OHCA. Future studies should focus on elucidating the pathophysiology of dysnatremia following OHCA.

Intracranial Pressure-Derived Cerebrovascular Reactivity Indices and Their Critical Thresholds: A Canadian High Resolution-Traumatic Brain Injury Validation Study.

Current neurointensive care guidelines recommend intracranial pressure (ICP) and cerebral perfusion pressure (CPP) centered management for moderate-severe traumatic brain injury (TBI) because of their demonstrated associations with patient outcome. Cerebrovascular reactivity metrics, such as the pressure reactivity index (PRx), pulse amplitude index (PAx), and RAC index, have also demonstrated significant prognostic capabilities with regard to outcome. However, critical thresholds for cerebrovascular reactivity indices have only been identified in two studies conducted at the same center. In this study, we aim to determine the critical thresholds of these metrics by leveraging a unique multi-center database. The study included a total of 354 patients from the CAnadian High-Resolution TBI (CAHR-TBI) Research Collaborative. Based on 6-month Glasgow Outcome Scores, patients were dichotomized into alive versus dead and favorable versus unfavorable. Chi-square values were then computed for incrementally increasing values of each physiological parameter of interest against outcome. The values that generated the greatest chi-squares for each parameter were considered to be the thresholds with the greatest outcome discriminatory capacity. To confirm that the identified thresholds provide prognostic utility, univariate and multivariable logistical regression analyses were performed adjusting for the International Mission for Prognosis and Analysis of Clinical Trials (IMPACT) variables. Through the chi-square analysis, a lower limit CPP threshold of 60 mm Hg and ICP thresholds of 18 mm Hg and 22 mm Hg were identified for both survival and favorable outcome predictions. For the cerebrovascular reactivity metrics, different thresholds were identified for the two outcome dichotomizations. For survival prediction, thresholds of 0.35, 0.25, and 0 were identified for PRx, PAx, and RAC, respectively. For favorable outcome prediction, thresholds of 0.325, 0.20, and 0.05 were found. Univariate logistical regression analysis demonstrated that the time spent above/below thresholds were associated with outcome. Further, multivariable logistical regression analysis found that percent time above/below the identified thresholds added additional variance to the IMPACT core model for predicting both survival and favorable outcome. In this study, we were able to validate the results of the previous two works as well as to reaffirm the ICP and CPP guidelines from the Brain Trauma Foundation (BTF) and the Seattle International Severe Traumatic Brain Injury Consensus Conference (SIBICC).

Cerebral uptake of microvesicles occurs in normocapnic but not hypocapnic passive hyperthermia in young healthy male adults.

Passive hyperthermia causes cerebral hypoperfusion primarily from heat-induced respiratory alkalosis. However, despite the cerebral hypoperfusion, it is possible that the mild alkalosis might help to attenuate cerebral inflammation. In this study, the cerebral exchange of extracellular vesicles (microvesicles), which are known to elicit pro-inflammatory responses when released in conditions of stress, were examined in hyperthermia with and without respiratory alkalosis. Ten healthy male adults were heated passively, using a warm water-perfused suit, up to core temperature + 2°C. Blood samples were taken from the radial artery and internal jugular bulb. Microvesicle concentrations were determined in platelet-poor plasma via cells expressing CD62E (activated endothelial cells), CD31+ /CD42b- (apoptotic endothelial cells), CD14 (monocytes) and CD45 (pan-leucocytes). Cerebral blood flow was measured via duplex ultrasound of the internal carotid and vertebral arteries to determine cerebral exchange kinetics. From baseline to poikilocapnic (alkalotic) hyperthermia, there was no change in microvesicle concentration from any cell origin measured (P-values all >0.05). However, when blood CO2 tension was normalized to baseline levels in hyperthermia, there was a marked increase in cerebral uptake of microvesicles expressing CD62E (P = 0.028), CD31+ /CD42b- (P = 0.003) and CD14 (P = 0.031) compared with baseline, corresponding to large increases in arterial but not jugular venous concentrations. In a subset of seven participants who underwent hypercapnia and hypocapnia in the absence of heating, there was no change in microvesicle concentrations or cerebral exchange, suggesting that hyperthermia potentiated the CO2 /pH-mediated cerebral uptake of microvesicles. These data provide insight into a potential beneficial role of respiratory alkalosis in heat stress. KEY POINTS: The hyperthermia-induced hyperventilatory response is observed in most humans, despite causing potentially harmful reductions in cerebral blood flow. We tested the hypothesis that the respiratory-induced alkalosis is associated with lower circulating microvesicle concentrations, specifically in the brain, despite the reductions in blood flow. At core temperature + 2°C with respiratory alkalosis, microvesicles derived from endothelial cells, monocytes and leucocytes were at concentrations similar to baseline in the arterial and cerebral venous circulation, with no changes in cross-brain microvesicle kinetics. However, when core temperature was increased by 2°C with CO2 /pH normalized to resting levels, there was a marked cerebral uptake of microvesicles derived from endothelial cells and monocytes. The CO2 /pH-mediated alteration in cerebral microvesicle uptake occurred only in hyperthermia. These new findings suggest that the heat-induced hyperventilatory response might serve a beneficial role by preventing potentially inflammatory microvesicle uptake in the brain.

Cerebral hemodynamics after cardiac arrest: implications for clinical management.

Following resuscitation from cardiac arrest, hypoxic ischemic brain injury (HIBI) ensues, which is the primary determinant of adverse outcome. The pathophysiology of HIBI can be compartmentalized into primary and secondary injury, resulting from cerebral ischemia during cardiac arrest and reperfusion following successful resuscitation, respectively. During the secondary injury phase, increased attention has been directed towards the optimization of cerebral oxygen delivery to prevent additive injury to the brain. During this phase, cerebral hemodynamics are characterized by early hyperemia following resuscitation and then a protracted phase of cerebral hypoperfusion termed "no-reflow" during which additional hypoxic-ischemic injury can occur. As such, identification of therapeutic strategies to optimize cerebral delivery of oxygen is at the forefront of HIBI research. Unfortunately, randomized control trials investigating the manipulation of arterial carbon dioxide tension and mean arterial pressure augmentation as methods to potentially improve cerebral oxygen delivery have shown no impact on clinical outcomes. Emerging literature suggests differential patient-specific phenotypes may exist in patients with HIBI. The potential to personalize therapeutic strategies in the critical care setting based upon patient-specific pathophysiology presents an attractive strategy to improve HIBI outcomes. Herein, we review the cerebral hemodynamic pathophysiology of HIBI, discuss patient phenotypes as it pertains to personalizing care, as well as suggest future directions.

Neuroinflammation and the immune system in hypoxic ischaemic brain injury pathophysiology after cardiac arrest.

Hypoxic ischaemic brain injury after resuscitation from cardiac arrest is associated with dismal clinical outcomes. To date, most clinical interventions have been geared towards the restoration of cerebral oxygen delivery after resuscitation; however, outcomes in clinical trials are disappointing. Therefore, alternative disease mechanism(s) are likely to be at play, of which the response of the innate immune system to sterile injured tissue in vivo after reperfusion has garnered significant interest. The innate immune system is composed of three pillars: (i) cytokines and signalling molecules; (ii) leucocyte migration and activation; and (iii) the complement cascade. In animal models of hypoxic ischaemic brain injury, pro-inflammatory cytokines are central to propagation of the response of the innate immune system to cerebral ischaemia-reperfusion. In particular, interleukin-1 beta and downstream signalling can result in direct neural injury that culminates in cell death, termed pyroptosis. Leucocyte chemotaxis and activation are central to the in vivo response to cerebral ischaemia-reperfusion. Both parenchymal microglial activation and possible infiltration of peripherally circulating monocytes might account for exacerbation of an immunopathological response in humans. Finally, activation of the complement cascade intersects with multiple aspects of the innate immune response by facilitating leucocyte activation, further cytokine release and endothelial activation. To date, large studies of immunomodulatory therapies have not been conducted; however, lessons learned from historical studies using therapeutic hypothermia in humans suggest that quelling an immunopathological response might be efficacious. Future work should delineate the precise pathways involved in vivo in humans to target specific signalling molecules.

Clinical targeting of the cerebral oxygen cascade to improve brain oxygenation in patients with hypoxic-ischaemic brain injury after cardiac arrest.

The cerebral oxygen cascade includes three key stages: (a) convective oxygen delivery representing the bulk flow of oxygen to the cerebral vascular bed; (b) diffusion of oxygen from the blood into brain tissue; and (c) cellular utilisation of oxygen for aerobic metabolism. All three stages may become dysfunctional after resuscitation from cardiac arrest and contribute to hypoxic-ischaemic brain injury (HIBI). Improving convective cerebral oxygen delivery by optimising cerebral blood flow has been widely investigated as a strategy to mitigate HIBI. However, clinical trials aimed at optimising convective oxygen delivery have yielded neutral results. Advances in the understanding of HIBI pathophysiology suggest that impairments in the stages of the oxygen cascade pertaining to oxygen diffusion and cellular utilisation of oxygen should also be considered in identifying therapeutic strategies for the clinical management of HIBI patients. Culprit mechanisms for these impairments may include a widening of the diffusion barrier due to peri-vascular oedema and mitochondrial dysfunction. An integrated approach encompassing both intra-parenchymal and non-invasive neuromonitoring techniques may aid in detecting pathophysiologic changes in the oxygen cascade and enable patient-specific management aimed at reducing the severity of HIBI.

High-normal versus low-normal mean arterial pressure thresholds in critically ill patients: a systematic review and meta-analysis of randomized trials.

PURPOSE: Targeted blood pressure thresholds remain unclear in critically ill patients. Two prior systematic reviews have not shown differences in mortality with a high mean arterial pressure (MAP) threshold, but there have been new studies published since. Thus, we conducted an updated systematic review and meta-analysis of randomized controlled trials (RCTs) that compared the effect of a high-normal vs low-normal MAP on mortality, favourable neurologic outcome, need for renal replacement therapy, and adverse vasopressor-induced events in critically ill patients. SOURCE: We searched six databases from inception until 1 October 2022 for RCTs of critically ill patients targeted to either a high-normal vs a low-normal MAP threshold for at least 24 hr. We assessed study quality using the revised Cochrane risk-of-bias 2 tool and the risk ratio (RR) was used as the summary measure of association. We used the Grading of Recommendations Assessment, Development, and Evaluation framework to assess the certainty of evidence. PRINCIPAL FINDINGS: We included eight RCTs with 4,561 patients. Four trials were conducted in patients following out-of-hospital cardiac arrest, two in patients with distributive shock requiring vasopressors, one in patients with septic shock, and one in patients with hepatorenal syndrome. The pooled RRs for mortality (eight RCTs; 4,439 patients) and favourable neurologic outcome (four RCTs; 1,065 patients) were 1.06 (95% confidence interval [CI], 0.99 to 1.14; moderate certainty) and 0.99 (95% CI, 0.90 to 1.08; moderate certainty), respectively. The RR for the need for renal replacement therapy (four RCTs; 4,071 patients) was 0.97 (95% CI, 0.87 to 1.08; moderate certainty). There was no statistical between-study heterogeneity across all outcomes. CONCLUSION: This updated systematic review and meta-analysis of RCTs found no differences in mortality, favourable neurologic outcome, or the need for renal replacement therapy between critically ill patients assigned to a high-normal vs low-normal MAP target. STUDY REGISTRATION: PROSPERO (CRD42022307601); registered 28 February 2022.

RéSUMé: OBJECTIF: Les seuils de pression artérielle ciblés demeurent incertains chez les patient·es gravement malades. Deux revues systématiques antérieures n'ont pas montré de différences dans la mortalité avec un seuil élevé de pression artérielle moyenne (PAM), mais de nouvelles études ont été publiées depuis. Pour cette raison, nous avons réalisé une revue systématique mise à jour et une méta-analyse d'études randomisées contrôlées (ERC) comparant l'effet d'une PAM normale élevée vs normale faible sur la mortalité, les devenirs neurologiques favorables, la nécessité d'un traitement substitutif de l'insuffisance rénale et les événements indésirables induits par les vasopresseurs chez les patient·es gravement malades. SOURCES: Nous avons effectué des recherches dans six bases de données depuis leur création jusqu'au 1er octobre 2022 pour trouver des ERC portant sur des patient·es gravement malades chez lesquel·les un seuil de PAM normale élevée ou normale faible a été ciblé pendant au moins 24 heures. Nous avons évalué la qualité des études à l'aide de l'outil de risque de biais 2 révisé de Cochrane, et le risque relatif (RR) a été utilisé comme mesure sommaire de l'association. Nous avons utilisé le système de notation GRADE (Grading of Recommendations Assessment, Development, and Evaluation) pour évaluer la certitude des données probantes. CONSTATATIONS PRINCIPALES: Nous avons inclus huit ERC portant sur 4561 personnes traitées. Quatre études ont été menées chez des patient·es à la suite d'un arrêt cardiaque hors de l'hôpital, deux chez des patient·es présentant un choc distributif nécessitant des vasopresseurs, une chez des patient·es présentant un choc septique et une chez des patient·es atteint·es d'un syndrome hépato-rénal. Les RR combinés pour la mortalité (huit ERC; 4439 personnes) et les devenirs neurologiques favorables (quatre ERC; 1065 personnes) étaient respectivement de 1,06 (intervalle de confiance [IC] à 95 %, 0,99 à 1,14; certitude modérée) et de 0,99 (IC 95 %, 0,90 à 1,08; certitude modérée). Le RR pour le besoin de traitement substitutif de l'insuffisance rénale (quatre ERC; 4071 patient·es) était de 0,97 (IC 95 %, 0,87 à 1,08; certitude modérée). Il n'y avait pas d'hétérogénéité statistique entre les études pour tous les critères d'évaluation. CONCLUSION: Ces revue systématique et méta-analyse mises à jour des ERC n'ont révélé aucune différence dans la mortalité, les devenirs neurologiques favorables ou la nécessité d'un traitement substitutif de l'insuffisance rénale entre les patient·es gravement malades assigné·es à une cible de PAM normale élevée vs normale faible. ENREGISTREMENT DE L'éTUDE: PROSPERO (CRD42022307601); enregistrée le 28 février 2022.

A brain-based definition of death and criteria for its determination after arrest of circulation or neurologic function in Canada: a 2023 clinical practice guideline.

This 2023 Clinical Practice Guideline provides the biomedical definition of death based on permanent cessation of brain function that applies to all persons, as well as recommendations for death determination by circulatory criteria for potential organ donors and death determination by neurologic criteria for all mechanically ventilated patients regardless of organ donation potential. This Guideline is endorsed by the Canadian Critical Care Society, the Canadian Medical Association, the Canadian Association of Critical Care Nurses, Canadian Anesthesiologists' Society, the Canadian Neurological Sciences Federation (representing the Canadian Neurological Society, Canadian Neurosurgical Society, Canadian Society of Clinical Neurophysiologists, Canadian Association of Child Neurology, Canadian Society of Neuroradiology, and Canadian Stroke Consortium), Canadian Blood Services, the Canadian Donation and Transplantation Research Program, the Canadian Association of Emergency Physicians, the Nurse Practitioners Association of Canada, and the Canadian Cardiovascular Critical Care Society.

RéSUMé: Ces Lignes directrices de pratique clinique 2023 Lignes directrices de pratique clinique dicale du décès basée sur l'arrêt permanent de la fonction cérébrale qui s'applique à toute personne, ainsi que des recommandations pour la détermination du décès par des critères circulatoires pour des donneurs d'organes potentiels et des recommandations pour la détermination du décès par des critères neurologiques pour tous les patients sous ventilation mécanique, indépendamment de leur potentiel de donneur d'organes. Les présentes Lignes directrices sont approuvées par la Société canadienne de soins intensifs, l'Association médicale canadienne, l'Association canadienne des infirmiers/infirmières en soins intensifs, la Société canadienne des anesthésiologistes, la Fédération des sciences neurologiques du Canada (représentant la Société canadienne de neurologie, la Société canadienne de neurochirurgie, la Société canadienne de neurophysiologie clinique, l'Association canadienne de neurologie pédiatrique, la Société canadienne de neuroradiologie et le Consortium neurovasculaire canadien), la Société canadienne du sang, le Programme de recherche en don et transplantation du Canada, l'Association canadienne des médecins d'urgence, l'Association des infirmières et infirmiers praticiens du Canada, et la Société canadienne de soins intensifs cardiovasculaires (CANCARE) et la Société canadienne de pédiatrie.