ECMO or Extracorporeal Membrane Oxygenation
WHAT IS ECMO?
ECMO or Extracorporeal Membrane Oxygenation is a modality derived from the heart & lung machines now used in selected advanced ICU’s in a much miniaturized and user friendly format. It can be used as a ventilator /oxygenation support (Veno -Venous; V-V ECMO) or as a mechanical (Cardiac; Veno -Arterial; V-A ECMO) support.
One needs to remember that ECMO is a support modality which maintains the cardiac and/or respiratory functions of the body allowing the lungs and the heart to rest and therapies to act without causing adverse effects of conventional ventilation on the lungs and high dose vasopressors/ inotropes on the heart and other organs
There are two basic types which are described by the site of drainage & where the blood returns
WHEN IS ECMO INDICATED?
ECMO is not usually the first line therapy. It needs to be considered when first line modalities start failing or start causing unwanted effects. A patient deteriorating even after best of mechanical ventilatory efforts for the lungs OR after highest possible doses of inotropes/vasopressors, needs to be considered for ECMO provided the organ failure has a reversible cause.
The choice for the type of ECMO is determined by the predominant failure: V-A ECMO if cardiac and V-V ECMO if respiratory.
INDICATIONS OF V-V ECMO
Lung disease that is:Acute, Life threatening, Reversible, Unresponsive to conventional /alternative therapy for Example:
Severe COPD exacerbations
Auto immune diseases
WHEN DOES A RESPIRATORY FAILURE BECOMES AN ECMO CANDIDATE?
If 2 or more of the following criteria exist even after four-six hours of maximal conventional ventilation in a reversible disease.
Pa02/Fi02 ratio < 100 with Fi02 1.0
Murray score > 3
Respiratory acidosis pH < 7.2 or PaCO2 > 100
A-a gradient > 600mm Hg
Lung compliance < 0.5 ml/cm of H20/Kg
INDICATIONS OF V-A ECMO
Failure to wean from bypass
Myocarditis: toxic (aluminium phosphide, beta blockers, CCB) or viral
Cardiogenic Shock: Acute MI and its complications
Sepsis with profound cardiac depression
WHEN DOES A CARDIAC FAILURE BECOMES AN ECMO CANDIDATE?
If 2 or more of the following criteria exist even after four-six hours of maximal conventional support in a reversible disease
Cardiogenic shock on high vasopressors (>=0.2mcg/kg/min of noradrenaline or equivalent vasopressors)
Lactate> 5 mmol/L
ScV02 < 65%
Low cardiac output with Organ failure: AKI, Hepatic, pulmonary edema)
Life threatening arrhythmias unresponsive to medical therapy
HOW IS ECMO HELPFUL?
The body is primarily dependent on oxygen from the lungs and its transport to various organs by the pumping of the heart. Moreover, lungs also remove carbon dioxide. If any of these functions fail because of a disease process, external support is required: conventional ventilation for the lungs and vasopressors/inotropes for the heart. Mostly these modalities are helpful, but in some cases high pressure of ventilation and high levels of oxygen delivery to the lungs can cause more harm than good. Likewise, high doses of vasopressors/inotropes can damage the heart and end organs like kidney, peripheries, gut etc.
Putting such patients on ECMO support allows us to turn down the high degree of support thus preventing their side effects while allowing the heart/lungs to rest and heal without hampering the body physiology.