Oxygenation During Venoarterial Extracorporeal Membrane Oxygenation: Physiology, Current Evidence, and a Pragmatic Approach to Oxygen Titration

Abstract

OBJECTIVES: This review aims to: 1) identify the key circuit and patient factors affecting systemic oxygenation, 2) summarize the literature reporting the association between hyperoxia and patient outcomes, and 3) provide a pragmatic approach to oxygen titration, in patients undergoing peripheral venoarterial extracorporeal membrane oxygenation (ECMO). DATA SOURCES: Searches were performed using PubMed, SCOPUS, Medline, and Google Scholar. STUDY SELECTION: All observational and interventional studies investigating the association between hyperoxia, and clinical outcomes were included, as well as guidelines from the Extracorporeal Life Support Organization. DATA EXTRACTION: Data from relevant literature was extracted, summarized, and integrated into a concise narrative review. For ease of reference a summary of relevant studies was also produced. DATA SYNTHESIS: The extracorporeal circuit and the native cardiorespiratory circuit both contribute to systemic oxygenation during venoarterial ECMO. The ECMO circuit’s contribution to systemic oxygenation is, in practice, largely determined by the ECMO blood flow, whereas the native component of systemic oxygenation derives from native cardiac output and residual respiratory function. Interactions between ECMO outflow and native cardiac output (as in differential hypoxia), the presence of respiratory support, and physiologic parameters affecting blood oxygen carriage also modulate overall oxygen exposure during venoarterial ECMO. Physiologically those requiring venoarterial ECMO are prone to hyperoxia. Hyperoxia has a variety of definitions, most commonly Pao 2 greater than 150 mm Hg. Severe hypoxia (Pao 2 > 300 mm Hg) is common, seen in 20%. Early severe hyperoxia, as well as cumulative hyperoxia exposure was associated with in-hospital mortality, even after adjustment for disease severity in both venoarterial ECMO and extracorporeal cardiopulmonary resuscitation. A pragmatic approach to oxygenation during peripheral venoarterial ECMO involves targeting a right radial oxygen saturation target of 94–98%, and in selected patients, titration of the fraction of oxygen in the mixture via the air-oxygen blender to target postoxygenator Pao 2 of 150–300 mm Hg. CONCLUSIONS: Hyperoxia results from a range of ECMO circuit and patient-related factors. It is common during peripheral venoarterial ECMO, and its presence is associated with poor outcome. A pragmatic approach that avoids hyperoxia, while also preventing hypoxia has been described for patients receiving peripheral venoarterial ECMO.

Mechanical ventilation during extracorporeal membrane oxygenation support – New trends and continuing challenges

“…68,69 The occurrence of hyperoxemia (PaO 2 > 300 mmHg) and hypocarbia (PaCO 2 < 30 mmHg) in V-A ECMO support is common. 68,70,71 These entities carry even greater burden given the risk of differential hypoxemia, 69 which occurs when the upper body is perfused with low saturated blood from the heart and the lower body with ECMO oxygenated blood. 69 This state that may also develop where the upper body is deprived of oxygen due to failing native lung function 72 and/or improved native cardiac output.…”

“…68,73 A pragmatic approach during V-A ECMO involves measuring a right arterial radial oxygen saturation, echocardiography monitoring cardiac function and in selected patients, titration of the fraction of oxygen in the mixture via the air-oxygen blender to target postoxygenator PaO 2 of 150-300 mm Hg. 68 Planned RCTs will contribute valuable insights into the optimized mechanical ventilation during V-A ECMO support. Blend to Limit OxygEN in ECMO: A RanDomised ControllEd Registry (BLENDER) Trial is going to compare a conservative oxygenation strategy (target arterial saturations 92%-96%) with a liberal oxygenation strategy (target 97%-100%) in patients supported by V-A ECMO for cardiogenic shock or cardiac arrest.…”

“…Further, V-A femoro-femoral configuration changes the physiological flow in oxygen delivery and understanding of this pathophysiology is a key for appropriate patients’ management. 68,69…”

“…68,73 A pragmatic approach during V-A ECMO involves measuring a right arterial radial oxygen saturation, echocardiography monitoring cardiac function and in selected patients, titration of the fraction of oxygen in the mixture via the air-oxygen blender to target postoxygenator PaO 2 of 150–300 mm Hg. 68…”

“…Further, V-A femorofemoral configuration changes the physiological flow in oxygen delivery and understanding of this pathophysiology is a key for appropriate patients' management. 68,69 The occurrence of hyperoxemia (PaO 2 > 300 mmHg) and hypocarbia (PaCO 2 < 30 mmHg) in V-A ECMO support is common. 68,70,71 These entities carry even greater burden given the risk of differential hypoxemia, 69 which occurs when the upper body is perfused with low saturated blood from the heart and the lower body with ECMO oxygenated blood.…”