***ECMO does not “treat” any disease!!! It provides heart and lung bypass while you treat the underlying disease process***

***ECMO therefore serves as a “bridge” for 1) recovery 2) organ transplant 3) cardiac ventricular support devise or 4) decision***

Overview

Two Types: 

1) Veno-Arterial (VA) ECMO -- cardiac and pulmonary support 

2) Veno-Venous (VV) ECMO - pulmonary support 

A overview of EMCO from ICU One Pager below. 

Some of these elements are broken down into more detail on this page

General Terms

• Drainage (Access) Cannula- Where the patient's blood is drained from the body and heads to the circuit. This is negative pressure

• Return Cannula- Where the patient's blood is returned to the body, externally oxygenated

• Flow- the flow of blood through the circuit and can be thought of as "cardiac output" in VA ECMO. This is a function of volume status, the diameter and length of the cannulas (Poiseuilles Equation, see "Cardiac" tab for more of this)

  • • • Generally, full ECMO support is considered 100-150 ml/kg/min for infants, ~ 90-100 ml/kg/min for pediatric patients, and ~ 70 ml/kg/min for adults 

• Sweep/Gas flow- The rate of oxygen flowing through the oxygenator measured in L/min

  • • • The higher your sweep, the more CO2 you will remove (see image below)

• Pump

  • • • Centrifugal (see image below) - nonocclusive pump that moves blood forward by producing a constrained vortex within a polycarbonate structure

        • • • • Has either "cones" or "impellers" in the inner workings of the pump to cause rotations and produced higher RPMs as compared to roller head pumps

              • Advantages - will not pump against resistance, less likely for tube rupture, preload dependent, less hemolysis

              • Disadvantages - increased prime volume, thrombus formation more likely, magnetic decoupling, allows for retrograde flow

      • Roller head (see image below) - historically used more in pediatrics, though now many programs transititoning to centrifugal pumps 

        • • • • Advantages- lower prime volume, constant flow rate, no retrograde flow

              • Disadvantages - hemolysis, because constant flow, can increase pressure and cause tubing rupture, an be occulsive, preload dependent, lower overall flow rates when compared to centrifugal pumps

              • Bladder - a reservoir at the lowest point of the ECMO circult that can trap air and has an access port. Also a nice way to gauge the volume status/pressure status of the circuit.When volume is low or negative pressure is too high, the bladder will collapse on itself. 

• Heater- maintains temperature of the blood outside the body --> will have temp stability for patient and difficult to determine if patient has an organic fever

• Oxygenator - also known as the membrane lung; contains hollow fibers with countercurrent exchanges of water and oxygen in one direction and the patient's blood in another

• SvO2 - measure of the venous blood saturation of oxygen PRIOR to circulating through the oxygenation

  • • • • Normal ~ 70%; if higher, can indicate recirculation of deoxy and oxy blood in ecmo circuit or poor patient oxygen extraction; if lower, suggests higher patient oxygen demand/extraction and suggest patient needs more ECMO support

• Pre-membrane pressure- positive pressure in the blood from the pump BEFORE the oxygenator

• Post-membrane pressure - positive pressure in the blood after the oxygenator but BEFORE the patient

A nice overview of ECMO is here - from ELSO (Extracorporeal Life Support Organization)

ECMO Pump

Anticoagulation

• ELSO Anticoagulation Guidelines (2022)

• Need to prevent blood clotting while outside the body and in the circuit

• Systemic anticoagulation for patient - risk for bleeding

• Two main drugs

1. Heparin

• Bolus and then continuous infusion

• Measure heparin level/ACT

2. Bivalirudin

• Continuous infusion 

• Measure INR

Important to monitor Hb, Plt, Coags, Fibrinogen levels and replace with blood products per desired goals in ECMO protocol

See "Heme/Onc" section for more information, especially relating to Thromboelastography (TEG)

Anticoagulation on ECMO is an evolving topic and in need of more research!

Complications/Troubleshooting

• Summary form ICU One pager below

• Common issues:

  • • Patient Agitation

    • Hypovolemia

    • Anticoagulation vs Bleeding

    • Air Embolism 

    • Circuit Thrombosis 

    • Cannula Displacement

    • Cerebral Infarction 

    • Recirculation - read more about this!

Weaning off ECMO

As with all things in the PICU, once started on ECMO the goal is to start to plan how to come off!

1. VV ECMO - turn down FiO2 and sweep on ECMO circuit, and increase ventilator support. Monitor patient's blood gases, respiratory effort, plateau pressures, tidal volumes

2. VA ECMO - do this with "clamp trails" aka stopping ECMO flow by clamping cannuals and seeing patient's innate hemodynamics. 

• Need to ensure medications, oxygen, heparin/bival are transferred from ECMO circuit to the patient during trails or else will not receive these medications 

• May start with 1 clamp tria a day and increase in frequency OR may do one and determine patients cardiac function has improved and proceed with decannulation from ECMO