CC BY-NC-ND 4.0 · J Card Crit Care 2017; 1(02): 57-59
DOI: 10.1055/s-0038-1626681
Thieme Medical and Scientific Publishers Private Ltd. 2017

Hypoxia during VV ECMO

Pranay Oza
1  Riddhivinayak Critical Care and Cardiac Centre, Mumbai, Maharashtra, India
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Publication Date:
07 March 2018 (online)


Venovenous extracorporeal membrane oxygenation (VV ECMO) is the preferred mode for any kind of acute respiratory failure. The desired PO2 is > 50 and SPO2 > 88% but the acceptable values can be PO2 > 45 and SPO2 > 80%. In case if we are accepting lower PO2, we have to keep a higher hematocrit and meticulously monitor neurological status, lactates, and urine output to maintain oxygen delivery. Saturation during ECMO run depends on ECMO circulation, native circulation, and ratio of ECMO flow to cardiac output ([Table 1]). Whenever the effective ECMO circulation decreases, saturation decreases. So, decrease in ECMO flow, ECMO FiO2, failing membrane oxygenator, and increase in recirculation will lead to hypoxia. Similarly, anything that decreases the contribution from native circulation will also lead to hypoxia. So, decrease in ventilator settings and worsening lung status lead to hypoxia. Anything that increases metabolism, such as fever and restlessness, will also cause hypoxia due to increased consumption.

Table 1

Causes of hypoxia during ECMO

Abbreviation: ECMO, extracorporeal membrane oxygenation.

Technical problem

Ventilator related

Ventilator malfunctioning

ET tube blockage

ECMO related

Decreased ECMO flow or


Oxygenator failure

Increase recirculation

Lung condition worsening

Parenchymal worsening


Increased ratio of ECMO flow/cardiac output

Increased cardiac output

Recirculation is defined as the flow of oxygenated blood from the returning cannula to the draining cannula without entering systemic circulation. It decreases the efficacy of VV support. Around 30% of recirculation is average.[1] The factors on which the recirculation depends are pump flow ([Fig. 1]), catheter position, cardiac output, and RA size or intravascular volume. The recirculation can be calculated with the help of following equation:[2]

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Fig. 1 Recirculation: defining the curve.

Management of hypoxia will depend on treating the underlying cause ([Fig. 2]). The usual strategy is to increase oxygen transfer by increasing ECMO flow, ECMO FiO2, or by increasing hematocrit and thereby improving oxygen delivery. Many a times hypoxia is secondary to increased metabolic rate and just controlling that (controlling fever, giving sedation) will improve saturation. Recirculation can be managed by adjusting the flow; sometimes a higher flow is the cause of recirculation and just by decreasing flow we can get better saturation.[3] Too close placement of tip of drainage and return cannula may lead to recirculation and just repositioning of cannula can improve saturation.[4] If the recirculation persists, the last solution is to put additional cannula for drainage and switch to VVV ECMO.

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Fig. 2 Approach to hypoxia during VV ECMO. VV ECMO, venovenous extracorporeal membrane oxygenation.

In spite of all the above measures if the patient remains hypoxic and lactates are rising, then the last resource is to induce hypothermia and ultimately switch to VA or VAV ECMO ([Table 2]).

Table 2

Management of hypoxia during VV ECMO

Abbreviations: ECMO, extracorporeal membrane oxygenation; IVC, inferior vena cava; SVC, superior vena cava; VAV, veno-arterial-venous, VV, venovenous.

Maximizing gas transfer

Increase blood flow through the ECMO

Increasing FiO2 of ECMO

Increasing hematocrit

Minimizing oxygen utilization

Decreasing metabolic rate: control fever, sedation, etc


Decreasing recirculation in VV ECMO

Define the curve

Cannula reposition

Add cannula: for drainage, cannula can be added in IVC, SVC, and preferred cephalad cannula

Conversion to VA or VAV ECMO

  • References

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  • 2 Goyal V, Oza P. ECMO Volume I, Practical Manual. Vol. 1
  • 3 Heard M, Davis J, Fortenberry J. Principle and practice of venovenous and venoarterial ECMO. ECMO Specialist training manual. Billie Lou Short, Lisa Williams MHA, BSN, RNC-NIC; 2010:59–76
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  • 5 Goyal V, Oza P. Algorithm. ECMO Theoretical Mannual 2012; 2 (01) 248-250