Arterial-Sided Oxygenator Clot and Transcranial Doppler Ultrasound Emboli in Venoarterial Extracorporeal Membrane Oxygenation

Neurological Monitoring and Management for Adult Extracorporeal Membrane Oxygenation Patients: Extracorporeal Life Support Organization Consensus Guidelines

BACKGROUND

Critical care of patients on extracorporeal membrane oxygenation (ECMO) with acute brain injury (ABI) is notable for a lack of high-quality clinical evidence. Here, we offer guidelines for neurological care (neurological monitoring and management) of adults during and after ECMO support.

METHODS

These guidelines are based on clinical practice consensus recommendations and scientific statements. We convened an international multidisciplinary consensus panel including 30 clinician-scientists with expertise in ECMO from all chapters of the Extracorporeal Life Support Organization (ELSO). We used a modified Delphi process with three rounds of voting and asked panelists to assess the recommendation levels.

RESULTS

We identified five key clinical areas needing guidance: (1) neurological monitoring, (2) post-cannulation early physiological targets and ABI, (3) neurological therapy including medical and surgical intervention, (4) neurological prognostication, and (5) neurological follow-up and outcomes. The consensus produced 30 statements and recommendations regarding key clinical areas. We identified several knowledge gaps to shape future research efforts.

CONCLUSIONS

The impact of ABI on morbidity and mortality in ECMO patients is significant. Particularly, early detection and timely intervention are crucial for improving outcomes. These consensus recommendations and scientific statements serve to guide the neurological monitoring and prevention of ABI, and management strategy of ECMO-associated ABI.

Neurological monitoring and management for adult extracorporeal membrane oxygenation patients: Extracorporeal Life Support Organization consensus guidelines

BACKGROUND

Critical care of patients on extracorporeal membrane oxygenation (ECMO) with acute brain injury (ABI) is notable for a lack of high-quality clinical evidence. Here, we offer guidelines for neurological care (neurological monitoring and management) of adults during and after ECMO support.

METHODS

These guidelines are based on clinical practice consensus recommendations and scientific statements. We convened an international multidisciplinary consensus panel including 30 clinician-scientists with expertise in ECMO from all chapters of the Extracorporeal Life Support Organization (ELSO). We used a modified Delphi process with three rounds of voting and asked panelists to assess the recommendation levels.

RESULTS

We identified five key clinical areas needing guidance: (1) neurological monitoring, (2) post-cannulation early physiological targets and ABI, (3) neurological therapy including medical and surgical intervention, (4) neurological prognostication, and (5) neurological follow-up and outcomes. The consensus produced 30 statements and recommendations regarding key clinical areas. We identified several knowledge gaps to shape future research efforts.

CONCLUSIONS

The impact of ABI on morbidity and mortality in ECMO patients is significant. Particularly, early detection and timely intervention are crucial for improving outcomes. These consensus recommendations and scientific statements serve to guide the neurological monitoring and prevention of ABI, and management strategy of ECMO-associated ABI.

Short-Term Neurologic Complications in Patients Undergoing Extracorporeal Membrane Oxygenation Support: A Review on Pathophysiology, Incidence, Risk Factors, and Outcomes

Regardless of the type, extracorporeal membrane oxygenation (ECMO) requires the use of large intravascular cannulas and results in multiple abnormalities including non-physiologic blood flow, hemodynamic perturbation, rapid changes in blood oxygen and carbon dioxide levels, coagulation abnormalities, and a significant systemic inflammatory response. Among other sequelae, neurologic complications are an important source of mortality and long-term morbidity. The frequency of neurologic complications varies and is likely underreported due to the high mortality rate. Neurologic complications in patients supported by ECMO include ischemic and hemorrhagic stroke, hypoxic brain injury, intracranial hemorrhage, and brain death. In addition to the disease process that necessitates ECMO, cannulation strategies and physiologic disturbances influence neurologic outcomes in this high-risk population. For example, the overall documented rate of neurologic complications in the venovenous ECMO population is lower, but a higher rate of intracranial hemorrhage exists. Meanwhile, in the venoarterial ECMO population, ischemia and global hypoperfusion seem to compose a higher percentage of neurologic complications. In what follows, the literature is reviewed to discuss the pathophysiology, incidence, risk factors, and outcomes related to short-term neurologic complications in patients supported by ECMO.

Hypoxic-Ischemic Brain Injury in ECMO: Pathophysiology, Neuromonitoring, and Therapeutic Opportunities

Extracorporeal membrane oxygenation (ECMO), in conjunction with its life-saving benefits, carries a significant risk of acute brain injury (ABI). Hypoxic-ischemic brain injury (HIBI) is one of the most common types of ABI in ECMO patients. Various risk factors, such as history of hypertension, high day 1 lactate level, low pH, cannulation technique, large peri-cannulation PaCO2 drop (∆PaCO2), and early low pulse pressure, have been associated with the development of HIBI in ECMO patients. The pathogenic mechanisms of HIBI in ECMO are complex and multifactorial, attributing to the underlying pathology requiring initiation of ECMO and the risk of HIBI associated with ECMO itself. HIBI is likely to occur in the peri-cannulation or peri-decannulation time secondary to underlying refractory cardiopulmonary failure before or after ECMO. Current therapeutics target pathological mechanisms, cerebral hypoxia and ischemia, by employing targeted temperature management in the case of extracorporeal cardiopulmonary resuscitation (eCPR), and optimizing cerebral O2 saturations and cerebral perfusion. This review describes the pathophysiology, neuromonitoring, and therapeutic techniques to improve neurological outcomes in ECMO patients in order to prevent and minimize the morbidity of HIBI. Further studies aimed at standardizing the most relevant neuromonitoring techniques, optimizing cerebral perfusion, and minimizing the severity of HIBI once it occurs will improve long-term neurological outcomes in ECMO patients.

Brain injury in extracorporeal cardiopulmonary resuscitation: translational to clinical research

The addition of extracorporeal membrane oxygenation (ECMO) to conventional cardiopulmonary resuscitation (CPR), termed extracorporeal cardiopulmonary resuscitation (ECPR), has significantly improved survival in selected patient populations. Despite this advancement, significant neurological impairment persists in approximately half of survivors. ECPR represents a potential advancement for patients who experience refractory cardiac arrest (CA) due to a reversible etiology and do not regain spontaneous circulation. Important risk factors for acute brain injury (ABI) in ECPR include lack of perfusion, reperfusion, and altered cerebral autoregulation. The initial hypoxic-ischemic injury caused by no-flow and low-flow states after CA and during CPR is compounded by reperfusion, hyperoxia during ECMO support, and nonpulsatile blood flow. Additionally, ECPR patients are at risk for Harlequin syndrome with peripheral cannulation, which can lead to preferential perfusion of cerebral vessels with deoxygenated blood. Lastly, the oxygenator membrane is prothrombotic and requires systemic anticoagulation. The two competing phenomena result in thrombus formation, hemolysis, and thrombocytopenia, increasing the risk of ischemic and hemorrhagic ABI. In addition to clinical studies, we assessed available ECPR animal models to identify the mechanisms underlying ABI at the cellular level. Standardized multimodal neurological monitoring may facilitate early detection of and intervention for ABI. With the increasing use of ECPR, it is critical to understand the pathophysiology of ABI, its prevention, and the management strategies for improving the outcomes of ECPR. Translational and clinical research focusing on acute ABI immediately after ECMO cannulation and its short- and long-term neurological outcomes are warranted.

Brain Injury Is More Common in Venoarterial Extracorporeal Membrane Oxygenation Than Venovenous Extracorporeal Membrane Oxygenation: A Systematic Review and Meta-Analysis

OBJECTIVES

Despite the common occurrence of brain injury in patients undergoing extracorporeal membrane oxygenation, it is unclear which cannulation method carries a higher risk of brain injury. We compared the prevalence of brain injury between patients undergoing venoarterial and venovenous extracorporeal membrane oxygenation.

DATA SOURCES

PubMed and six other databases from inception to April 2020.

STUDY SELECTION

Observational studies and randomized clinical trials in adult patients undergoing venoarterial extracorporeal membrane oxygenation or venovenous extracorporeal membrane oxygenation reporting brain injury.

DATA EXTRACTION

Two independent reviewers extracted the data from the studies. Random-effects meta-analyses were used to pool data.

DATA SYNTHESIS

Seventy-three studies (n = 16,063) met inclusion criteria encompassing 8,211 patients (51.2%) undergoing venoarterial extracorporeal membrane oxygenation and 7,842 (48.8%) undergoing venovenous extracorporeal membrane oxygenation. Venoarterial extracorporeal membrane oxygenation patients had more overall brain injury compared with venovenous extracorporeal membrane oxygenation (19% vs 10%; p = 0.002). Venoarterial extracorporeal membrane oxygenation patients had more ischemic stroke (10% vs 1%; p < 0.001), hypoxic-ischemic brain injury (13% vs 1%; p < 0.001), and brain death (11% vs 1%; p = 0.001). In contrast, rates of intracerebral hemorrhage (6% vs 8%; p = 0.35) did not differ. Survival was lower in venoarterial extracorporeal membrane oxygenation (48%) than venovenous extracorporeal membrane oxygenation (64%) (p < 0.001). After excluding studies that included extracorporeal cardiopulmonary resuscitation, no significant difference was seen in the rate of overall acute brain injury between venoarterial extracorporeal membrane oxygenation and venovenous extracorporeal membrane oxygenation (13% vs 10%; p = 0.4). However, ischemic stroke (10% vs 1%; p < 0.001), hypoxic-ischemic brain injury (7% vs 1%; p = 0.02), and brain death (9% vs 1%; p = 0.005) remained more frequent in nonextracorporeal cardiopulmonary resuscitation venoarterial extracorporeal membrane oxygenation compared with venovenous extracorporeal membrane oxygenation.

CONCLUSIONS

Brain injury was more common in venoarterial extracorporeal membrane oxygenation compared with venovenous extracorporeal membrane oxygenation. While ischemic brain injury was more common in venoarterial extracorporeal membrane oxygenation patients, the rates of intracranial hemorrhage were similar between venoarterial extracorporeal membrane oxygenation and venovenous extracorporeal membrane oxygenation. Further research on mechanism, timing, and effective monitoring of acute brain injury and its management is necessary.

Modifiable Risk Factors and Mortality From Ischemic and Hemorrhagic Strokes in Patients Receiving Venoarterial Extracorporeal Membrane Oxygenation: Results From the Extracorporeal Life Support Organization Registry

OBJECTIVES

Although acute brain injury is common in patients receiving extracorporeal membrane oxygenation, little is known regarding the mechanism and predictors of ischemic and hemorrhagic stroke. We aimed to determine the risk factors and outcomes of each ischemic and hemorrhagic stroke in patients with venoarterial extracorporeal membrane oxygenation support.

DESIGN

Retrospective analysis.

SETTING

Data reported to the Extracorporeal Life Support Organization by 310 extracorporeal membrane oxygenation centers from 2013 to 2017.

PATIENTS

Patients more than 18 years old supported with a single run of venoarterial extracorporeal membrane oxygenation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 10,342 venoarterial extracorporeal membrane oxygenation patients, 401 (3.9%) experienced ischemic stroke and 229 (2.2%) experienced hemorrhagic stroke. Reported acute brain injury during venoarterial extracorporeal membrane oxygenation decreased from 10% to 6% in 5 years. Overall in-hospital mortality was 56%, but rates were higher when ischemic stroke and hemorrhagic stroke were present (76% and 86%, respectively). In multivariable analysis, lower pre-extracorporeal membrane oxygenation pH (adjusted odds ratio, 0.21; 95% CI, 0.09-0.49; p < 0.001), higher PO2 on first day of extracorporeal membrane oxygenation (adjusted odds ratio, 1.01; 95% CI, 1.00-1.02; p = 0.009), higher rates of extracorporeal membrane oxygenation circuit mechanical failure (adjusted odds ratio, 1.33; 95% CI, 1.02-1.74; p = 0.03), and renal replacement therapy (adjusted odds ratio, 1.49; 95% CI, 1.14-1.94; p = 0.004) were independently associated with ischemic stroke. Female sex (adjusted odds ratio, 1.61; 95% CI, 1.16-2.22; p = 0.004), extracorporeal membrane oxygenation duration (adjusted odds ratio, 1.01; 95% CI, 1.00-1.03; p = 0.02), renal replacement therapy (adjusted odds ratio, 1.81; 95% CI, 1.30-2.52; p < 0.001), and hemolysis (adjusted odds ratio, 1.87; 95% CI, 1.11-3.16; p = 0.02) were independently associated with hemorrhagic stroke.

CONCLUSIONS

Despite a decrease in the prevalence of acute brain injury in recent years, mortality rates remain high when ischemic and hemorrhagic strokes are present. Future research is necessary on understanding the timing of associated risk factors to promote prevention and management strategy.

Brain Injury in Extracorporeal Membrane Oxygenation: A Multidisciplinary Approach

Extracorporeal membrane oxygenation (ECMO) represents an established technique to provide temporary cardiac and/or pulmonary support. ECMO, in veno-venous, veno-arterial or in extracorporeal carbon dioxide removal modality, is associated with a high rate of brain injuries. These complications have been reported in 7 to 15% of adults and 20% of neonates, and are associated with poor survival. Thromboembolic events, loss of cerebral autoregulation, alteration of the blood-brain barrier, and hemorrhage related to anticoagulation represent the main causes of severe brain injury during ECMO. The most frequent forms of acute neurological injuries in ECMO patients are intracranial hemorrhage (2-21%), ischemic stroke (2-10%), seizures (2-6%), and hypoxic-ischemic brain injury; brain death may also occur in this population. Other frequent complications are infarction (1-8%) and cerebral edema (2-10%), as well as neuropsychological and psychiatric sequelae, including posttraumatic stress disorder.

Cerebral Emboli Monitoring Using Transcranial Doppler Ultrasonography in Adults and Children: A Review of the Current Technology and Clinical Applications in the Perioperative and Intensive Care Setting

Transcranial Doppler (TCD) ultrasonography is the only noninvasive bedside technology for the detection and monitoring of cerebral embolism. TCD may identify patients at risk of acute and chronic neurologic injury from gaseous or solid emboli. Importantly, a window of opportunity for intervention-to eliminate the source of the emboli and thereby prevent subsequent development of a clinical or subclinical stroke-may be identified using TCD. In this review, we discuss the application of TCD sonography in the perioperative and intensive care setting in adults and children known to be at increased risk of cerebral embolism. The major challenge for evaluation of emboli, especially in children, is the need to establish the ground truth and define true emboli identified by TCD. This requires the development and validation of a predictive TCD emboli monitoring technique so that appropriately designed clinical studies intended to identify specific modifiable factors and develop potential strategies to reduce pathologic cerebral embolic burden can be performed.

Neurocritical Care of Mechanical Circulatory Support Devices

PURPOSE OF REVIEW

Mechanical circulatory support (MCS) devices have demonstrated improved survival outcomes in otherwise refractory cardiopulmonary failure but are associated with significant neurologic morbidity and mortality. This review aims to characterize MCS-associated brain injury and discuss the neurocritical care of this population.

RECENT FINDINGS

We found no practice guidelines or specific management strategies for the neurocritical care of patients with MCS devices. Acute brain injury was commonly observed in short-term and durable MCS devices. There is emerging evidence that a standardized neurological monitoring and management algorithm for MCS device-associated brain injury is feasible and potentially improves neurological outcomes. While MCS devices are associated with significant neurologic morbidity and mortality, there is scant evidence regarding optimal neuromonitoring and neurocritical care. With the increase in use of MCS devices for both short-term and durable applications, improved outcomes will depend on early identification and intervention of neurologic complications and further research into their pathophysiology.

Risk Factors of Ischemic and Hemorrhagic Strokes During Venovenous Extracorporeal Membrane Oxygenation: Analysis of Data From the Extracorporeal Life Support Organization Registry

OBJECTIVES

Stroke is commonly reported in patients receiving venovenous extracorporeal membrane oxygenation, but risk factors are not well described. We sought to determine preextracorporeal membrane oxygenation and on-extracorporeal membrane oxygenation risk factors for both ischemic and hemorrhagic strokes in patients with venovenous extracorporeal membrane oxygenation support.

DESIGN

Retrospective analysis.

SETTING

Data reported to the Extracorporeal Life Support Organization by 366 extracorporeal membrane oxygenation centers from 2013 to 2019.

PATIENTS

Patients older than 18 years supported with a single run of venovenous extracorporeal membrane oxygenation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of 15,872 venovenous extracorporeal membrane oxygenation patients, 812 (5.1%) had at least one type of acute brain injury, defined as ischemic stroke, hemorrhagic stroke, or brain death. Overall, 215 (1.4%) experienced ischemic stroke and 484 (3.1%) experienced hemorrhagic stroke. Overall inhospital mortality was 36%, but rates were higher in those with ischemic or hemorrhagic stroke (68% and 73%, respectively). In multivariable analysis, preextracorporeal membrane oxygenation pH (adjusted odds ratio = 0.10; 95% CI, 0.03-0.35; p < 0.001), hemolysis (adjusted odds ratio = 2.27; 95% CI, 1.22-4.24; p = 0.010), gastrointestinal hemorrhage (adjusted odds ratio = 2.01; 95% CI 1.12-3.59; p = 0.019), and disseminated intravascular coagulation (adjusted odds ratio = 3.61; 95% CI, 1.51-8.66; p = 0.004) were independently associated with ischemic stroke. Pre-extracorporeal membrane oxygenation pH (adjusted odds ratio = 0.28; 95% CI, 0.12-0.65; p = 0.003), preextracorporeal membrane oxygenation Po2 (adjusted odds ratio = 0.96; 95% CI, 0.93-0.99; p = 0.021), gastrointestinal hemorrhage (adjusted odds ratio = 1.70; 95% CI, 1.15-2.51; p = 0.008), and renal replacement therapy (adjusted odds ratio=1.57; 95% CI, 1.22-2.02; p < 0.001) were independently associated with hemorrhagic stroke.

CONCLUSIONS

Among venovenous extracorporeal membrane oxygenation patients in the Extracorporeal Life Support Organization registry, approximately 5% had acute brain injury. Mortality rates increased two-fold when ischemic or hemorrhagic strokes occurred. Risk factors such as lower pH and hypoxemia during the pericannulation period and markers of coagulation disturbances were associated with acute brain injury. Further research on understanding preextracorporeal membrane oxygenation and on-extracorporeal membrane oxygenation risk factors and the timing of acute brain injury is necessary to develop appropriate prevention and management strategies.

Brain magnetic resonance imaging in adult survivors of extracorporeal membrane oxygenation

Despite the common occurrence of neurologic complications in patients with extracorporeal membrane oxygenation (ECMO), data on magnetic resonance imaging (MRI) findings in adult ECMO are limited. We aimed to describe the MRI findings of patients after ECMO cannulation. Records of patients who underwent ECMO from September 2017 to June 2019 were reviewed. MRI studies were performed using multiplanar sequences consisting of T1-, T2-weighted, fluid attenuated inversion recovery (FLAIR), diffusion-weighted imaging (DWI), and susceptibility weighted images (SWI). Of the 78 adult patients who underwent ECMO, 26 (33%) survived. Of 26, eight patients (31%) had MRI studies, with a median age of 47 years (interquartile range [IQR]: 25-57). The median ECMO support time was 8 days (IQR: 4-25) and the median time from decannulation to MRI was 12 days (IQR: 1-34). Five (63%) of eight patients had ischemic infarcts; 4 (50%) had cerebral microhemorrhage; 2 (25%) had intracranial hemorrhage; and 1 (13%) had thoracic cord ischemic infarct. There were no patients with normal MRI. All patients underwent transcranial Doppler (TCD). Four of 8 (50%) showed presence of microemboli with TCD; 3 of 4 (75%) had ischemic infarcts; and 1 of 4 (25%) had presence of multiple cerebral microhemorrhages on MRI. All ischemic infarcts had diffuse pattern of punctate to small lesions for ECMO survivors. The location of cerebral microhemorrhages included lobar (n = 4, 100%), deep (n = 2, 50%), and both (n = 2, 50%). Of the MRI studies, cerebrovascular related lesions were the most frequent, with punctate ischemic infarct being the most common type that may be associated with TCD microemboli. The results of the study suggest that subclinical cerebral lesions are commonly found in patients with ECMO support. Further research is needed to understand long-term effect of these cerebral lesions.

The Use of Cerebral NIRS Monitoring to Identify Acute Brain Injury in Patients With VA-ECMO

Acute brain injury (ABI) increases morbidity and mortality in patients with veno-arterial extracorporeal membrane oxygenation (VA-ECMO). Optimal neurologic monitoring methods have not been well-explicated. We studied the use of Near-infrared Spectroscopy (NIRS) to monitor cerebral regional oxygenation tissue saturation (rSO2) and its relation to ABI in VA-ECMO. In this prospective, observational cohort study of 39 consecutive patients, we analyzed the ability of rSO2 values from continuous bedside NIRS monitoring to predict ABI during VA-ECMO support. ABI occurred in 24 (61.5%) patients. Those with ABI had a lower pre-ECMO Glasgow Coma Scale, more blood product transfusions of pRBCs and FFP, and higher APACHEII score. Baseline rSO2 values were not significantly different between cohorts (54.25 vs 58.50, p = 0.260), while the minimum rSO2 value was lower for patients who experienced an ABI than those who did not (39.75 vs 44.50, p = 0.039). In patients with ABI, 21 (87.5%) had a drop in rSO2 of 25% from baseline, compared to only 7 (46.7%) patients without ABI (p = 0.017). By ROC analysis, we found that desaturations with >25% drop from the baseline rSO2 on VA-ECMO exhibited 86% sensitivity and 55% specificity to predict ABI, with an area under the curve of 0.68. Patients with ABI were more likely to have withdrawal of life sustaining therapy (17 vs 5, p = 0.049), while neurologic outcome and mortality were not statistically different between patients with or without ABI. Our results support that cerebral NIRS is a useful, real-time bedside neuromonitoring tool to detect ABI in VA-ECMO patients. A >25% drop from the baseline was sensitive in predicting ABI occurrence. Further research is needed to assess how to implement this knowledge to utilize NIRS in developing appropriate intervention strategy in VA-ECMO patients.