Ketone Bodies after Cardiac Arrest: A Narrative Review and the Rationale for Use

Cardiac arrest survivors suffer the repercussions of anoxic brain injury, a critical factor influencing long-term prognosis. This injury is characterised by profound and enduring metabolic impairment. Ketone bodies, an alternative energetic resource in physiological states such as exercise, fasting, and extended starvation, are avidly taken up and used by the brain. Both the ketogenic diet and exogenous ketone supplementation have been associated with neuroprotective effects across a spectrum of conditions. These include refractory epilepsy, neurodegenerative disorders, cognitive impairment, focal cerebral ischemia, and traumatic brain injuries. Beyond this, ketone bodies possess a plethora of attributes that appear to be particularly favourable after cardiac arrest. These encompass anti-inflammatory effects, the attenuation of oxidative stress, the improvement of mitochondrial function, a glucose-sparing effect, and the enhancement of cardiac function. The aim of this manuscript is to appraise pertinent scientific literature on the topic through a narrative review. We aim to encapsulate the existing evidence and underscore the potential therapeutic value of ketone bodies in the context of cardiac arrest to provide a rationale for their use in forthcoming translational research efforts.

Delayed Deterioration of Electroencephalogram in Patients with Cardiac Arrest: A Cohort Study

BACKGROUND

The aim of this study was to assess the prevalence of delayed deterioration of electroencephalogram (EEG) in patients with cardiac arrest (CA) without early highly malignant patterns and to determine their associations with clinical findings.

METHODS

This was a retrospective study of adult patients with CA admitted to the intensive care unit (ICU) of a university hospital. We included all patients with CA who had a normal voltage EEG, no more than 10% discontinuity, and absence of sporadic epileptic discharges, periodic discharges, or electrographic seizures. Delayed deterioration was classified as the following: (1) epileptic deterioration, defined as the appearance, at least 24 h after CA, of sporadic epileptic discharges, periodic discharges, and status epilepticus; or (2) background deterioration, defined as increasing discontinuity or progressive attenuation of the background at least 24 h after CA. The end points were the incidence of EEG deteriorations and their association with clinical features and ICU mortality.

RESULTS

We enrolled 188 patients in the analysis. The ICU mortality was 46%. Overall, 30 (16%) patients presented with epileptic deterioration and 9 (5%) patients presented with background deterioration; of those, two patients presented both deteriorations. Patients with epileptic deterioration more frequently had an out-of-hospital CA, and higher time to return of spontaneous circulation and less frequently had bystander resuscitation than others. Patients with background deterioration showed a predominantly noncardiac cause, more frequently developed shock, and had multiple organ failure compared with others. Patients with epileptic deterioration presented with a higher ICU mortality (77% vs. 41%; p < 0.01) than others, whereas all patients with background deterioration died in the ICU.

CONCLUSIONS

Delayed EEG deterioration was associated with high mortality rate. Epileptic deterioration was associated with worse characteristics of CA, whereas background deterioration was associated with shock and multiple organ failure.

Brain Oxygenation Response to Hypercapnia in Patients with Acute Brain Injury

BACKGROUND

Cerebral hypoxia is a frequent cause of secondary brain damage in patients with acute brain injury. Although hypercapnia can increase intracranial pressure, it may have beneficial effects on tissue oxygenation. We aimed to assess the effects of hypercapnia on brain tissue oxygenation (PbtO2).

METHODS

This single-center retrospective study (November 2014 to June 2022) included all patients admitted to the intensive care unit after acute brain injury who required multimodal monitoring, including PbtO2 monitoring, and who underwent induced moderate hypoventilation and hypercapnia according to the decision of the treating physician. Patients with imminent brain death were excluded. Responders to hypercapnia were defined as those with an increase of at least 20% in PbtO2 values when compared to their baseline levels.

RESULTS

On a total of 163 eligible patients, we identified 23 (14%) patients who underwent moderate hypoventilation (arterial partial pressure of carbon dioxide [PaCO2] from 44 [42-45] to 50 [49-53] mm Hg; p < 0.001) during the study period at a median of 6 (4-10) days following intensive care unit admission; six patients had traumatic brain injury, and 17 had subarachnoid hemorrhage. A significant overall increase in median PbtO2 values from baseline (21 [19-26] to 24 [22-26] mm Hg; p = 0.02) was observed. Eight (35%) patients were considered as responders, with a median increase of 7 (from 4 to 11) mm Hg of PbtO2, whereas nonresponders showed no changes (from - 1 to 2 mm Hg of PbtO2). Because of the small sample size, no variable independently associated with PbtO2 response was identified. No correlation between changes in PaCO2 and in PbtO2 was observed.

CONCLUSIONS

In this study, a heterogeneous response of PbtO2 to induced hypercapnia was observed but without any deleterious elevations of intracranial pressure.

The impact of perfusion computed tomography on the diagnosis and outcome of delayed cerebral ischemia after subarachnoid hemorrhage

BACKGROUND

Delayed cerebral ischemia (DCI) is a preventable cause of poor neurological outcome in aneurysmal subarachnoid hemorrhage (aSAH). Advances in radiological methods, such as cerebral perfusion computed tomography (CTP), could help diagnose DCI earlier and potentially improve outcomes in aSAH. The objective of this study was to assess whether the use of CTP to diagnose DCI early could reduce the risk of infarction related to DCI.

METHODS

Retrospective cohort study of patients in the intensive care unit of Erasme Hospital (Brussels, Belgium) between 2004 and 2021 with aSAH who developed DCI. Patients were classified as: "group 1" - DCI diagnosed based on clinical deterioration or "group 2" - DCI diagnosed using CTP. The primary outcome was the development of infarction unrelated to the initial bleeding or surgery.

RESULTS

211 aSAH patients were diagnosed with DCI during the study period: 139 (66%) in group 1 and 72 (34%) in group 2. In group 1, 109 (78%) patients developed a cerebral infarction, compared to 45 (63%) in group 2 (p = 0.02). The adjusted cumulative incidence of DCI over time was lower in group 2 than in group 1 [hazard ratio 0.65 (95% CI 0.48-0.94); p = 0.02]. The use of CTP to diagnose DCI was not independently associated with mortality or neurological outcome.

CONCLUSIONS

The use of CTP to diagnose DCI might help reduce the risk of developing cerebral infarction after aSAH, although the impact of such an approach on patient outcomes needs to be further demonstrated.

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.

The Impact of Inotropes and Vasopressors on Cerebral Oxygenation in Patients with Traumatic Brain Injury and Subarachnoid Hemorrhage: A Narrative Review

Traumatic brain injury (TBI) and subarachnoid hemorrhage (SAH) are critical neurological conditions that necessitate specialized care in the Intensive Care Unit (ICU). Managing cerebral perfusion pressure (CPP) and mean arterial pressure (MAP) is of primary importance in these patients. To maintain targeted MAP and CPP, vasopressors and/or inotropes are commonly used. However, their effects on cerebral oxygenation are not fully understood. The aim of this review is to provide an up-to date review regarding the current uses and pathophysiological issues related to the use of vasopressors and inotropes in TBI and SAH patients. According to our findings, despite achieving similar hemodynamic parameters and CPP, the effects of various vasopressors and inotropes on cerebral oxygenation, local CBF and metabolism are heterogeneous. Therefore, a more accurate understanding of the cerebral activity of these medications is crucial for optimizing patient management in the ICU setting.

The Effects of Acetazolamide on Cerebral Hemodynamics in Adult Patients with an Acute Brain Injury: A Systematic Review

BACKGROUND

Acetazolamide is a non-competitive inhibitor of carbonic anhydrase, an enzyme expressed in different cells of the central nervous system (CNS) and involved in the regulation of cerebral blood flow (CBF). The aim of this review was to understand the effects of acetazolamide on CBF, intracranial pressure (ICP) and brain tissue oxygenation (PbtO2) after an acute brain injury (ABI).

METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement (PRISMA), we performed a comprehensive, computer-based, literature research on the PubMed platform to identify studies that have reported the effects on CBF, ICP, or PbtO2 of acetazolamide administered either for therapeutic or diagnostic purposes in patients with subarachnoid hemorrhage, intracerebral hemorrhage, traumatic brain injury, and hypoxic-ischemic encephalopathy.

RESULTS

From the initial search, 3430 records were identified and, through data selection, 11 of them were included for the qualitative analysis. No data on the effect of acetazolamide on ICP or PbtO2 were found. Cerebral vasomotor reactivity (VMR-i.e., the changing in vascular tone due to a vasoactive substance) to acetazolamide tends to change during the evolution of ABI, with the nadir occurring during the subacute stage. Moreover, VMR reduction was correlated with clinical outcome.

CONCLUSIONS

This systematic review showed that the available studies on the effects of acetazolamide on brain hemodynamics in patients with ABI are scarce. Further research is required to better understand the potential role of this drug in ABI patients.

Cerebrospinal fluid analysis of metabolites is not correlated to microdialysis measurements in acute brain injured patients

BACKGROUND

Cerebral microdialysis (CMD) has become an established bedside monitoring modality but its implementation remains complex and costly and is therefore performed only in a few well-trained academic centers. This study investigated the relationship between cerebrospinal fluid (CSF) and CMD glucose and lactate concentrations.

METHODS

Two centers retrospective study of prospectively collected data. Consecutive adult (>18 years) acutely brain injured patients admitted to the Intensive Care Unit between 2010 and 2021 were eligible if CSF and CMD glucose and lactate concentrations were concomitantly measured at least once.

RESULTS

Of 113 patients being monitored with an external ventricular drainage and CMD, 49 patients (25 from Innsbruck and 24 from Brussels) were eligible for the final analysis, including a total of 96 measurements. Median CMD glucose and lactate concentrations were 1.15 (0.51-1.57) mmol/L and 3.44 (2.24-5.37) mmol/L, respectively; median CSF glucose and lactate concentrations were 4.67 (4.03-5.34) mmol/L and 3.40 (2.85-4.10) mmol/L, respectively. For the first measurements, no correlation between CSF and CMD glucose concentrations (R2 <0.01; p = 0.95) and CSF and CMD lactate concentrations (R2 =0.16; p = 0.09) was found. Considering all measurements, the repeated measure correlation analysis also showed no correlation for glucose (rrm = -0.01; 95% Confidence Intervals -0.306 to 0.281; p = 0.93) and lactate (rrm = -0.11; 95% Confidence Intervals -0.424 to 0.236; p = 0.55).

CONCLUSIONS

In this study including acute brain injured patients, no correlation between CSF and brain tissue measurements of glucose and lactate was observed. As such, CSF measurements of such metabolites cannot replace CMD findings.

The effect of increased positive end expiratory pressure on brain tissue oxygenation and intracranial pressure in acute brain injury patients

Cerebral hypoxia is an important cause of secondary brain injury. Improving systemic oxygenation may increase brain tissue oxygenation (PbtO2). The effects of increased positive end-expiratory pressure (PEEP) on PbtO2 and intracranial pressure (ICP) needs to be further elucidated. This is a single center retrospective cohort study (2016-2021) conducted in a 34-bed Department of Intensive Care unit. All patients with acute brain injury under mechanical ventilation who were monitored with intracranial pressure and brain tissue oxygenation (PbtO2) catheters and underwent at least one PEEP increment were included in the study. Primary outcome was the rate of PbtO2 responders (increase in PbtO2 > 20% of baseline) after PEEP increase. ΔPEEP was defined as the difference between PEEP at 1 h and PEEP at baseline; similarly ΔPbtO2 was defined as the difference between PbtO2 at 1 h after PEEP incrementation and PbtO2 at baseline. We included 112 patients who underwent 295 episodes of PEEP increase. Overall, the median PEEP increased form 6 (IQR 5-8) to 10 (IQR 8-12) cmH2O (p = 0.001), the median PbtO2 increased from 21 (IQR 16-29) mmHg to 23 (IQR 18-30) mmHg (p = 0.001), while ICP remained unchanged [from 12 (7-18) mmHg to 12 (7-17) mmHg; p = 0.42]. Of 163 episode of PEEP increments with concomitant PbtO2 monitoring, 34 (21%) were PbtO2 responders. A lower baseline PbtO2 (OR 0.83 [0.73-0.96)]) was associated with the probability of being responder. ICP increased in 142/295 episodes of PEEP increments (58%); no baseline variable was able to identify this response. In PbtO2 responders there was a moderate positive correlation between ΔPbtO2 and ΔPEEP (r = 0.459 [95% CI 0.133-0.696]. The response in PbtO2 and ICP to PEEP elevations in brain injury patients is highly variable. Lower PbtO2 values at baseline could predict a significant increase in brain oxygenation after PEEP increase.

The Role of Brain Tissue Oxygenation Monitoring in the Management of Subarachnoid Hemorrhage: A Scoping Review

Monitoring of brain tissue oxygenation (PbtO2) is an important component of multimodal monitoring in traumatic brain injury. Over recent years, use of PbtO2 monitoring has also increased in patients with poor-grade subarachnoid hemorrhage (SAH), particularly in those with delayed cerebral ischemia. The aim of this scoping review was to summarize the current state of the art regarding the use of this invasive neuromonitoring tool in patients with SAH. Our results showed that PbtO2 monitoring is a safe and reliable method to assess regional cerebral tissue oxygenation and that PbtO2 represents the oxygen available in the brain interstitial space for aerobic energy production (i.e., the product of cerebral blood flow and the arterio-venous oxygen tension difference). The PbtO2 probe should be placed in the area at risk of ischemia (i.e., in the vascular territory in which cerebral vasospasm is expected to occur). The most widely used PbtO2 threshold to define brain tissue hypoxia and initiate specific treatment is between 15 and 20 mm Hg. PbtO2 values can help identify the need for or the effects of various therapies, such as hyperventilation, hyperoxia, induced hypothermia, induced hypertension, red blood cell transfusion, osmotic therapy, and decompressive craniectomy. Finally, a low PbtO2 value is associated with a worse prognosis, and an increase of the PbtO2 value in response to treatment is a marker of good outcome.

Cervical Ganglion Sympathectomy to Treat Cerebral Vasospasm in Subarachnoid Hemorrhage

Delayed cerebral ischemia (DCI) is still a significant cause of death and disability after aneurysmal subarachnoid hemorrhage. Cerebral vasospasm represents one of the most reported mechanisms associated with DCI. The management of DCI-related vasospasm remains a significant challenge for clinicians; induced hypertension, intraarterial vasodilators, and/or intracranial vessel angioplasty-particularly in refractory or recurrent cases-are the most used therapies. Because an essential role in the pathophysiology of cerebral vasospasm has been attributed to the adrenergic sympathetic nerves, a "sympatholytic" intervention, consisting of a temporary interruption of the sympathetic pathways using local anesthetics, has been advocated to minimize the vascular narrowing and reverse the consequences of cerebral vasospasm on tissue perfusion. In this review, we have analyzed the existing literature on the block of the cervical ganglions, particularly the stellate ganglion, in managing refractory cerebral vasospasm in patients with aneurysmal subarachnoid hemorrhage. These findings could help clinicians to understand the potential role of such intervention and to develop future interventional trials in this setting.

Hypertonic sodium lactate infusion reduces vasopressor requirements and biomarkers of brain and cardiac injury after experimental cardiac arrest

INTRODUCTION

Prognosis after resuscitation from cardiac arrest (CA) remains poor, with high morbidity and mortality as a result of extensive cardiac and brain injury and lack of effective treatments. Hypertonic sodium lactate (HSL) may be beneficial after CA by buffering severe metabolic acidosis, increasing brain perfusion and cardiac performance, reducing cerebral swelling, and serving as an alternative energetic cellular substrate. The aim of this study was to test the effects of HSL infusion on brain and cardiac injury in an experimental model of CA.

METHODS

After a 10-min electrically induced CA followed by 5 min of cardiopulmonary resuscitation maneuvers, adult swine (n = 35) were randomly assigned to receive either balanced crystalloid (controls, n = 11) or HSL infusion started during cardiopulmonary resuscitation (CPR, Intra-arrest, n = 12) or after return of spontaneous circulation (Post-ROSC, n = 11) for the subsequent 12 h. In all animals, extensive multimodal neurological and cardiovascular monitoring was implemented. All animals were treated with targeted temperature management at 34 °C.

RESULTS

Thirty-four of the 35 (97.1%) animals achieved ROSC; one animal in the Intra-arrest group died before completing the observation period. Arterial pH, lactate and sodium concentrations, and plasma osmolarity were higher in HSL-treated animals than in controls (p < 0.001), whereas potassium concentrations were lower (p = 0.004). Intra-arrest and Post-ROSC HSL infusion improved hemodynamic status compared to controls, as shown by reduced vasopressor requirements to maintain a mean arterial pressure target > 65 mmHg (p = 0.005 for interaction; p = 0.01 for groups). Moreover, plasma troponin I and glial fibrillary acid protein (GFAP) concentrations were lower in HSL-treated groups at several time-points than in controls.

CONCLUSIONS

In this experimental CA model, HSL infusion was associated with reduced vasopressor requirements and decreased plasma concentrations of measured biomarkers of cardiac and cerebral injury.

Evaluation of nociception in unconscious critically ill patients using a multimodal approach

This prospective observational study included 80 adults (>18 years) patients admitted to the intensive care unit who were unconscious (Glasgow Coma Scale [GCS] score <9 with a motor response <5) and receiving mechanical ventilation. A tetanic stimulation was used to assess nociception; automated pupillometry (Algiscan, ID-MED, France) was used to compute the pupillary pain index score (PPI), with a PPI > 4 considered as nociception. Concomitantly, the number of skin conductance fluctuations (NSCF) per second, measured using a Skin Conductance Algesimeter (SCA, MEDSTORM Innovation AS, Norway; > 0.27 fluctuations/sec indicating nociception), and the instantaneous Analgesia Nociception Index (iANI, MDoloris Medical Systems, France; <50 indicating nociception) were collected. Tetanic stimulation resulted in a median pupillary dilation of 16 [6-25]% and a PPI of 5 [2-7]. According to the PPI assessment, 44 patients (55%) had nociception, whereas 23 (29%) and 18 (23%) showed nociception according to the algesimeter and iANI assessment, respectively. No significant changes in measured physiologic variables were observed after the tetanic stimulation. There were no correlations between PPI, post-stimulation iANI, and SCA-derived variables. There were no differences in PPI, iANI, and SCA variables in patients with low and normal baseline EEG power at baseline. PERSPECTIVES: Detection of nociception varies across different devices in unconscious critically ill patients. Further studies are required to understand which method to implement for analgesic administration in this patient population.

Automated Pupillometry for Prediction of Electroencephalographic Reactivity in Critically Ill Patients: A Prospective Cohort Study

Background

Electroencephalography (EEG) is widely used to monitor critically ill patients. However, EEG interpretation requires the presence of an experienced neurophysiologist and is time-consuming. Aim of this study was to evaluate whether parameters derived from an automated pupillometer (AP) might help to assess the degree of cerebral dysfunction in critically ill patients.

Methods

Prospective study conducted in the Department of Intensive Care of Erasme University Hospital in Brussels, Belgium. Pupillary assessments were performed using the AP in three subgroups of patients, concomitantly monitored with continuous EEG: "anoxic brain injury", "Non-anoxic brain injury" and "other diseases". An independent neurologist blinded to patient's history and AP results scored the degree of encephalopathy and reactivity on EEG using a standardized scale. The mean value of Neurologic Pupil Index (NPi), pupillary size, constriction rate, constriction and dilation velocity (CV and DV) and latency for both eyes, obtained using the NPi®-200 (Neuroptics, Laguna Hills, CA, USA), were reported.

Results

We included 214 patients (mean age 60 years, 55% male). EEG tracings were categorized as: mild (n = 111, 52%), moderate (n = 65, 30%) or severe (n = 16, 8%) encephalopathy; burst-suppression (n = 19, 9%) or suppression background (n = 3, 1%); a total of 38 (18%) EEG were classified as "unreactive". We found a significant difference in all pupillometry variables among different EEG categories. Moreover, an unreactive EEG was associated with lower NPi, pupil size, pupillary reactivity, CV and DV and a higher latency than reactive recordings. Low DV (Odds ratio 0.020 [95% confidence intervals 0.002-0.163]; p < 0.01) was independently associated with an unreactive EEG, together with the use of analgesic/sedative drugs and high lactate concentrations. In particular, DV values had an area under the curve (AUC) of 0.86 [0.79-0.92; p < 0.01] to predict the presence of unreactive EEG. In subgroups analyses, AUC of DV to predict unreactive EEG was lower (0.72 [0.56-0.87]; p < 0.01) in anoxic brain injury than Non-anoxic brain injury (0.92 [0.85-1.00]; p < 0.01) and other diseases (0.96 [0.90-1.00]; p < 0.01).

Conclusions

This study suggests that low DV measured by the AP might effectively identify an unreactive EEG background, in particular in critically ill patients without anoxic brain injury.

Fever management in acute brain injury

PURPOSE OF REVIEW

Fever is common after acute brain injury and is associated with poor prognosis in this setting.

RECENT FINDINGS

Achieving normothermia is feasible in patients with ischemic or hemorrhagic stroke, subarachnoid hemorrhage and traumatic brain injury. Pharmacological strategies (i.e. paracetamol or nonsteroidal anti-inflammatory drugs) are frequently ineffective and physical (i.e. cooling devices) therapies are often required. There are no good quality data supporting any benefit from therapeutic strategies aiming at normothermia in all brain injured patients when compared with standard of care, where mild-to-moderate fever is tolerated. However, recent guidelines recommended fever control in this setting.

SUMMARY

As fever is considered a clinically relevant secondary brain damage, we have provided an individualized therapeutic approach to treat it in brain injured patients, which deserved further validation in the clinical setting.

Prognostic role of automatic pupillometry in sepsis: a retrospective study

BACKGROUND

Sepsis-associated brain dysfunction is a frequent disorder in septic patients and has a multifactorial pathophysiology. Cholinergic pathways and brainstem dysfunction may result in pupillary alterations. The aim of this study was to evaluate whether early assessment of the Neurological Pupil Index (NPiTM) derived from an automated pupillometry could predict mortality in critically ill septic patients.

METHODS

Retrospective cohort study of adult critically ill septic patients admitted to the intensive care unit of an University Hospital; patients with acute or known brain damage were excluded. The severity of the patients was assessed by the daily Sequential Organ Failure Assessment score and the SOFAmax (i.e. highest SOFA score during the first 5 days) was computed. The worst NPi (i.e. lowest value from one eye) was collected daily and then computed over the first 5 days of assessment. Mortality was assessed at hospital discharge.

RESULTS

A total of 75 patients were included over the study period (median age 67 [53-75] years and median SOFA score at admission 10 [8-12]); 64 (85%) presented septic shock; 48 (64%) died at hospital discharge. The worst NPi during the first 5 days of sepsis was significantly lower in non-survivors compared to survivors (4.4 [3.6-4.6] vs. 4.5 [4.2-4.7]; p=0.042). The worst NPi was also significantly lower in high severity group (i.e. SOFAmax≥12) when compared to others (4.4 [3.2- 4.5] vs 4.5 [4.0-4.7] p=0.01). However, in the multivariate analyses, the NPi value was not independently associated with in-hospital mortality or high SOFAmax.

CONCLUSIONS

In this study, no independent prognostic role of NPi was observed in septic patients. Further larger prospective studies are needed to better evaluate the role of automated pupillometry in this setting.

The effect of the volemic and cardiac status on brain oxygenation in patients with subarachnoid hemorrhage: a bi-center cohort study

Background

Fluid management in patients after subarachnoid hemorrhage (SAH) aims at the optimization of cerebral blood flow and brain oxygenation. In this study, we investigated the effects of hemodynamic management on brain oxygenation by integrating advanced hemodynamic and invasive neuromonitoring.

Methods

This observational cohort bi-center study included data of consecutive poor-grade SAH patients who underwent pulse contour cardiac output (PiCCO) monitoring and invasive neuromonitoring. Fluid management was guided by the transpulmonary thermodilution system and aimed at euvolemia (cardiac index, CI ≥ 3.0 L/min/m²; global end-diastolic index, GEDI 680–800 mL/m²; stroke volume variation, SVV < 10%). Patients were managed using a brain tissue oxygenation (P_btO₂) targeted protocol to prevent brain tissue hypoxia (BTH, P_btO₂ < 20 mmHg). To assess the association between CI and P_btO₂ and the effect of fluid challenges on CI and P_btO₂, we used generalized estimating equations to account for repeated measurements.

Results

Among a total of 60 included patients (median age 56 [IQRs 47–65] years), BTH occurred in 23% of  the monitoring time during the first 10 days since admission. Overall, mean CI was within normal ranges (ranging from 3.1 ± 1.3 on day 0 to 4.1 ± 1.1 L/min/m² on day 4). Higher CI levels were associated with higher P_btO₂ levels (Wald = 14.2; p < 0.001). Neither daily fluid input nor fluid balance was associated with absolute P_btO₂ levels (p = 0.94 and p = 0.85, respectively) or the occurrence of BTH (p = 0.68 and p = 0.71, respectively). P_btO₂ levels were not significantly different in preload dependent patients compared to episodes of euvolemia. P_btO₂ increased as a response to fluid boluses only if BTH was present at baseline (from 13 ± 6 to 16 ± 11 mmHg, OR = 13.3 [95% CI 2.6–67.4], p = 0.002), but not when all boluses were considered (p = 0.154).

Conclusions

In this study a moderate association between increased cardiac output and brain oxygenation was observed. Fluid challenges may improve P_btO₂ only in the presence of baseline BTH. Individualized hemodynamic management requires advanced cardiac and brain monitoring in critically ill SAH patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00960-z.

Brain tissue oxygenation guided therapy and outcome in non-traumatic subarachnoid hemorrhage

Brain hypoxia can occur after non-traumatic subarachnoid hemorrhage (SAH), even when levels of intracranial pressure (ICP) remain normal. Brain tissue oxygenation (PbtO₂) can be measured as a part of a neurological multimodal neuromonitoring. Low PbtO₂ has been associated with poor neurologic recovery. There is scarce data on the impact of PbtO₂ guided-therapy on patients’ outcome. This single-center cohort study (June 2014–March 2020) included all patients admitted to the ICU after SAH who required multimodal monitoring. Patients with imminent brain death were excluded. Our primary goal was to assess the impact of PbtO₂-guided therapy on neurological outcome. Secondary outcome included the association of brain hypoxia with outcome. Of the 163 patients that underwent ICP monitoring, 62 were monitored with PbtO₂ and 54 (87%) had at least one episode of brain hypoxia. In patients that required treatment based on neuromonitoring strategies, PbtO₂-guided therapy (OR 0.33 [CI 95% 0.12–0.89]) compared to ICP-guided therapy had a protective effect on neurological outcome at 6 months. In this cohort of SAH patients, PbtO₂-guided therapy might be associated with improved long-term neurological outcome, only when compared to ICP-guided therapy.

Fever management in critically ill COVID-19 patients: a retrospective analysis

BACKGROUND

Fever has been reported as a common symptom in COVID-19 patients. The aim of the study was to describe the characteristics of COVID-19 critically ill patients with fever and to assess if fever management had an impact on some physiologic variables.

METHODS

This is a retrospective monocentric cohort analysis of critically ill COVID-19 patients admitted to the Department of Intensive Care Unit (ICU) of Erasme Hospital, Brussels, Belgium, between March 2020 and May 2020. Fever was defined as body temperature ≥ 38° C during the ICU stay. We assessed the independent predictors of fever during ICU stay. We reported the clinical and physiological variables before and after the first treated episode of fever during the ICU stay.

RESULTS

A total of 72 critically ill COVID-19 patients were admitted to the ICU over the study period and were all eligible for the final analysis; 53 (74%) of them developed fever, after a median of 4 [0-13] hours since ICU admission. In the multivariable analysis, male gender (OR 5.41 [C.I. 95% 1.34-21.92]; p=0.02) and low PaO2/FiO2 ratio (OR 0.99 [C.I. 95% 0.99-1.00]; p=0.04) were independently associated with fever. After the treatment of the first febrile episode, heart rate and respiratory rate significantly decreased together with an increase in PaO2 and SaO2.

CONCLUSIONS

In our study, male gender and severe impairment of oxygenation were independently associated with fever in critically ill COVID-19 patients. Fever treatment reduced heart rate and respiratory rate and improved systemic oxygenation.

Hyperventilation in Adult TBI Patients: How to Approach It?

Hyperventilation is a commonly used therapy to treat intracranial hypertension (ICTH) in traumatic brain injury patients (TBI). Hyperventilation promotes hypocapnia, which causes vasoconstriction in the cerebral arterioles and thus reduces cerebral blood flow and, to a lesser extent, cerebral blood volume effectively, decreasing temporarily intracranial pressure. However, hyperventilation can have serious systemic and cerebral deleterious effects, such as ventilator-induced lung injury or cerebral ischemia. The routine use of this therapy is therefore not recommended. Conversely, in specific conditions, such as refractory ICHT and imminent brain herniation, it can be an effective life-saving rescue therapy. The aim of this review is to describe the impact of hyperventilation on extra-cerebral organs and cerebral hemodynamics or metabolism, as well as to discuss the side effects and how to implement it to manage TBI patients.

The Prognostic Role of Lactate Concentrations after Aneurysmal Subarachnoid Hemorrhage

Blood lactate concentrations are often used to assess global tissue perfusion in critically ill patients; however, there are scarce data on lactate concentrations after subarachnoid hemorrhage (SAH). We aimed to assess the prognostic role of serial blood lactate measurements on hospital mortality and neurological outcomes at 3 months after SAH. We reviewed all SAH patients admitted to the intensive care unit from 2007 to 2019 and recorded the highest daily arterial lactate concentration for the first 6 days. Patients with no lactate concentration were excluded. Hyperlactatemia was defined as a blood lactate concentration >2.0 mmol/L. A total of 456 patients were included: 158 (35%) patients died in hospital and 209 (46%) had an unfavorable outcome (UO) at 3 months. The median highest lactate concentration was 2.7 (1.8–3.9) mmol/L. Non-survivors and patients with UO had significantly higher lactate concentrations compared to other patients. Hyperlactatemia increased the chance of dying (OR 4.19 (95% CI 2.38–7.39)) and of having UO in 3 months (OR 4.16 (95% CI 2.52–6.88)) after adjusting for confounding factors. Therefore, initial blood lactate concentrations have prognostic implications in patients with SAH; their role in conjunction with other prognostic indicators should be evaluated in prospective studies.

Acute Distress Respiratory Syndrome After Subarachnoid Hemorrhage: Incidence and Impact on the Outcome in a Large Multicenter, Retrospective Cohort

Background

Respiratory complications are frequently reported after aneurismal subarachnoid hemorrhage (aSAH), even if their association with outcome remains controversial. Acute respiratory distress syndrome (ARDS) is one of the most severe pulmonary complications after aSAH, with a reported incidence ranging from 11 to 50%. This study aims to assess in a large cohort of aSAH patients, during the first week after an intensive care unit (ICU) admission, the incidence of ARDS defined according to the Berlin criteria and its effect on outcome.

Methods

This is a multicentric, retrospective cohort study in 3 European intensive care units. We collected data between January 2009 and December 2017. We included adult patients (≥ 18 years) with a diagnosis of aSAH admitted to the ICU.

Results

A total of 855 patients fulfilled the inclusion criteria. ARDS was assessable in 851 patients. The cumulative incidence of ARDS was 2.2% on the first day since ICU admission, 3.2% on day three, and 3.6% on day seven. At the univariate analysis, ARDS was associated with a poor outcome (p = 0.005) at ICU discharge, and at the multivariable analysis, patients with ARDS showed a worse neurological outcome (Odds ratio = 3.00, 95% confidence interval 1.16–7.72; p = 0.023).

Conclusions

ARDS has a low incidence in the first 7 days of ICU stay after aSAH, but it is associated with worse outcome.

Electronic supplementary material

The online version of this article (10.1007/s12028-020-01115-x) contains supplementary material, which is available to authorized users.