Early Low Pulse Pressure in VA-ECMO Is Associated with Acute Brain Injury

The physiology of venoarterial extracorporeal membrane oxygenation - A comprehensive clinical perspective

Venoarterial extracorporeal membrane oxygenation (VA ECMO) has become a standard of care for severe cardiogenic shock, refractory cardiac arrest and related impending multiorgan failure. The widespread clinical use of this complex temporary circulatory support modality is still contrasted by a lack of formal scientific evidence in the current literature. This might at least in part be attributable to VA ECMO related complications, which may significantly impact on clinical outcome. In order to limit adverse effects of VA ECMO as much as possible an indepth understanding of the complex physiology during extracorporeally supported cardiogenic shock states is critically important. This review covers all relevant physiological aspects of VA ECMO interacting with the human body in detail. This, to provide a solid basis for health care professionals involved in the daily management of patients supported with VA ECMO and suffering from cardiogenic shock or cardiac arrest and impending multiorgan failure for the best possible care.

Albumin Infusion Reduces Fluid Loading for Postresuscitation Syndrome in a Pig Model of Refractory Cardiac Arrest Resuscitated With Venoarterial Extra Corporeal Membrane Oxygenation

Hemodynamic instability in postresuscitation syndrome worsens survival and neurological outcomes. Venoarterial extracorporeal membrane oxygenation (VA ECMO) for refractory cardiac arrest might improve outcomes. Hemodynamical support under VA ECMO relies on norepinephrine and crystalloids. The present work aims to assess the effects of albumin (ALB) infusion in a swine model of ischemic refractory cardiac arrest implanted by VA ECMO. Cardiac arrest was performed in 18 pigs and VA ECMO was initiated after 30 minutes cardiopulmonary resuscitation (CPR). Pigs were randomly assigned to standard care (norepinephrine + crystalloids) versus ALB group (ALB + standard care). Hemodynamical assessments were performed over 6 hours. Severe hypoalbuminemia was observed in the control group and could be reversed with ALB infusion. Total crystalloid load was significantly reduced with ALB infusion (1,000 [1,000-2,278] ml vs. 17,000 [10,000-19,000] ml, ALB versus control group, respectively, p < 0.001). There was no significant impact with regard to lactate clearance (29.16% [12.5-39.32] and 10.09% [6.78-29.36] for control versus ALB groups, respectively, p = 0.185), sublingual capillary microvascular parameters, or cerebral near-infrared spectrometer (NIRS) values. Compared to standard care, ALB infusion was highly effective in reducing fluid loading in a porcine model of postresuscitation syndrome after refractory cardiac arrest treated with VA ECMO.

After ECMO Decannulation, Are Patients Thriving or Just Surviving?

The use of extracorporeal membrane oxygenation (ECMO) to support patients with cardiac arrest, cardiogenic shock, and acute respiratory distress syndrome is rising worldwide.1 While ECMO may save the lives of some of our sickest patients, the outlook of ECMO survivorship remains uncertain. Defining longer-term functional and neuropsychiatric outcomes in ECMO survivors is important for 3 reasons. First, critically ill patients are at high risk of experiencing postintensive care syndrome (PICS), defined as new physical, cognitive, or psychological impairments that present in survivors of critical illness after hospital discharge.2 PICS is associated with more severe illness and longer intensive care unit length of stay.3 Because ECMO is reserved for patients with refractory shock or hypoxia, patients treated with ECMO represent a severely ill patient population with prolonged length of stay, putting them at particularly high risk of developing PICS. Second, ECMO is associated with direct neurologic injury, including both macrohemorrhages and microhemorrhages, infarcts, and diffuse hypoxic-ischemic brain injury that likely contribute to long-term outcomes.4 Finally, ECMO is very expensive. A recent study determined that the average cost per admission for patients with COVID-19 placed on ECMO was nearly $850,000 more than those who received only mechanical ventilation.5 Understanding patient-centered outcomes will be an integral part of future cost-effectiveness analyses.

Stroke and Mechanical Circulatory Support in Adults

PURPOSE OF THE REVIEW

Short-term and durable mechanical circulatory support (MCS) devices represent life-saving interventions for patients with cardiogenic shock and end-stage heart failure. This review will cover the epidemiology, risk factors, and treatment of stroke in this patient population.

RECENT FINDINGS

Short-term devices such as intra-aortic balloon pump, Impella, TandemHeart, and Venoatrial Extracorporal Membrane Oxygenation, as well as durable continuous-flow left ventricular assist devices (LVADs), improve cardiac output and blood flow to the vital organs. However, MCS use is associated with high rates of complications, including ischemic and hemorrhagic strokes which carry a high risk for death and disability. Improvements in MCS technology have reduced but not eliminated the risk of stroke. Mitigation strategies focus on careful management of anti-thrombotic therapies. While data on therapeutic options for stroke are limited, several case series reported favorable outcomes with thrombectomy for ischemic stroke patients with large vessel occlusions, as well as with reversal of anticoagulation for those with hemorrhagic stroke. Stroke in patients treated with MCS is associated with high morbidity and mortality. Preventive strategies are targeted based on the specific form of MCS. Improvements in the design of the newest generation device have reduced the risk of ischemic stroke, though hemorrhagic stroke remains a serious complication.

Subtypes and Mechanistic Advances of Extracorporeal Membrane Oxygenation-Related Acute Brain Injury

Extracorporeal membrane oxygenation (ECMO) is a frequently used mechanical cardiopulmonary support for rescuing critically ill patients for whom conventional medical therapies have failed. However, ECMO is associated with several complications, such as acute kidney injury, hemorrhage, thromboembolism, and acute brain injury (ABI). Among these, ABI, particularly intracranial hemorrhage (ICH) and infarction, is recognized as the primary cause of mortality during ECMO support. Furthermore, survivors often suffer significant long-term morbidities, including neurocognitive impairments, motor disturbances, and behavioral problems. This review provides a comprehensive overview of the different subtypes of ECMO-related ABI and the updated advance mechanisms, which could be helpful for the early diagnosis and potential neuromonitoring of ECMO-related ABI.

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.

Characterization of Cerebral Hemodynamics with TCD in Patients Undergoing VA-ECMO and VV-ECMO: a Prospective Observational Study

BACKGROUND

Extracorporeal membrane oxygenation has a high risk of acute brain injury and resultant mortality. Transcranial Doppler characterizes cerebral hemodynamics in real time, but limited data exist on its interpretation in ECMO. Here, we report TCD mean flow velocity and pulsatility index in a large ECMO population.

METHODS

This was a prospective cohort study at a tertiary care center. The patients were adults on venoarterial ECMO or venovenous ECMO undergoing TCD studies.

RESULTS

A total of 135 patients underwent a total of 237 TCD studies while on VA-ECMO (n = 95, 70.3%) or VV-ECMO (n = 40, 29.6%). MFVs were captured reliably (approximately 90%) and were similar to a published healthy cohort in all vessels except the internal carotid artery. Presence of a recordable PI was strongly associated with ECMO mode (57% in VA vs. 95% in VV, p < 0.001). Absence of TCD pulsatility was associated with intraparenchymal hemorrhage (14.7 vs. 1.6%, p = 0.03) in VA-ECMO patients.

CONCLUSIONS

Transcranial Doppler analysis in a single-center cohort of VA-ECMO and VV-ECMO patients demonstrates similar MFVs and PIs. Absence of PIs was associated with a higher frequency of intraparenchymal hemorrhage and a composite bleeding event. However, cautious interpretation and external validation is necessary for these findings with a multicenter study with a larger sample size.