Overview
ECMO initiation comprises the process of establishing the patient on ECMO support. Additional specific emergency instructions for ECPR can be found under ECPR initiation.
Patient eligibility
ECMO console set up (see below)
- Patient positioning and explanations
- Bedside US sizing of vessels
- Gathering of equipment and set up at the bedside
- Allocation of roles
- Formulation of a cannulation plan, configuration, cannula sizes
The initiation of ECMO may be performed outside the ICU by accredited ICU medical staff (alternatively by the surgeon in the operating room). A more detailed nursing routine is provided under daily care once the patient arrives at the ICU cubicle.
Rotaflow Console and Circuit
Console and circuit set up
For circuit priming see here.
Collect the console with a pre-primed circuit from the ECMO equipment area. Unplug & wheel to the bedside.
Rotaflow power connections
Even in an ECPR, it is advisable to check the power supply at the initiation. The AC power indicator must be lit. This confirms AC power connection.
Battery support: note the battery light as well as the battery charging level at 25.0 in the display.
Plugged in, battery charging: the green light indicates the connection to the power source. The battery charging symbol will only be on until fully charged.
The AC Power Isolation Switch at the rear of the console must be “on”. If the Power Isolation Switch is accidentally switched to off, the AC power indicator will not light up after more than 15 seconds of AC power connection and the console will remain on battery-operated power.
Emergency drive unit
An emergency drive unit (“hand crank”) must be sited on the trolley in a position whereby the centrifugal pump can be transferred immediately in the case of either console or pump head failure.
The emergency hand crank must be freely accessible in the proximity of the pump head.
Pump head orientation and Oxygenator position
The pump head should be sited slightly higher than the oxygenator with the pump outlet pointing downwards. The pump head inlet should be positioned at approximately 30˚ to the vertical.
The pump head is tilted to 30˚ and placed higher than the oxygenator, also take note that the pre- and post-oxygenator pressure monitoring is leveled to the patient bed, not the oxygenator.
Oxygen connection
On ECMO initiation the gas connection is always made via the green oxygen tubing directly from the oxygen tank on the console to the oxygenator inlet. Ensure the white cap is removed. Air and oxygen “wall” connections are established after the initiation of the patient, regardless of the mode or urgency of the ECMO support in order to have a uniform approach. The gas outlet at the bottom of the oxygenator must not be occluded in any way.
Running primed PLS
The primed circuit needs to be run prior to patient connection to ensure
- A functioning ECMO console
- Air-free circuit
- Correct flow reading
- Warming of primed circuit to body temperature (unless urgent or ECPR)
The PLS system blood flow signal is obtained prior to patient connection via generous application of ultrasonic paste to flow sensor at the pump head
- Turn console on, confirm clamp and silence alarm
- Turn RPM knob up and down to zero
- If no flow signal or numerics appears and the display has three ‘dashes’ return RPM to zero and apply more ultrasonic paste
- If time allows remove the pump head and check for air bubbles
- Unscrew yellow cap from oxygenator
- Release all clamps and run at 2000 RPM (look for light agitation in priming reservoir bag) and confirm final de-airing of the circuit and oxygenator
- Re-apply yellow cap
- Place a ECMO clamp on the ECMO circuit (immediately post oxygenator), return RPM knob to zero and silence alarms. This is the final clamp to be removed after patient connection and ECMO pump initiation
- Clamp both blue and red tubing from the reservoir bag with blue clamps to hand over. This prevents circuit prime spilling from the reservoir during patient connection.
- Await handing over circuit for connection
Heating the circuit
Warming the circuit to body temperature before connection is mandatory in VV ECMO cannulation and desirable in VA ECMO if time permits (The risk of cardiac arrhythmias caused by infusing large amounts of cold saline rapidly is greatest in VV ECMO). In ECPR, pre-heating of the circuit may cause distraction or delay ECMO commencement and should be established after the support is established. Also, set the temperature not higher than 36°C until the core temperature is known to avoid overshooting the target temperature.
Flow Signal
The flow signal from the circuit needs to be re-zeroed once ECMO has been established to improve the accuracy of the flow readings. If there is no flow signal or ‘—’ is displayed more application of the ultrasonic contact cream is required. Commonly a generous application is required.
Zeroing Rotaflow
Circuit is clamped post oxygenator and the speed setting (RPM) is returned rapidly to zero.
Zeroing is performed by holding down the zero indicator button (3 beeps) and confirmed when the flow reading indicates zero flow. RPM is then increased and the clamp removed.
Quick guide to troubleshooting PLS
Cardiohelp Console and Circuit
Console and circuit set up
HLS circuit priming can be found here.
Cardiohelp power connection
Insert image
Ensure the Console is connected to AC power.
Emergency drive unit
An emergency drive unit (“hand crank”) must be sited on the trolley in a position whereby the centrifugal pump can be transferred immediately in the case of either console or pump head failure.
The emergency hand crank is freely accessible in proximity to the console, the heater connection may need to be disconned or can be pulled through.
Oxygen connection
On ECMO initiation the gas connection is always made via the green oxygen tubing directly from the oxygen tank on the console to the oxygenator inlet. Ensure the white cap on the membrane oxygenator inlet is removed. Air and oxygen “wall” connections are established after the initiation of the patient, regardless of the mode or urgency of the ECMO support in order to have a uniform approach. The gas outlet at the bottom of the oxygenator must not be occluded.
Running primed HLS circuit
Running the circuit prior to patient connection to ensure
- A functioning ECMO console
- Air-free circuit
- Correct pressure and flow monitoring
- Warming of primed circuit to body temperature (preferable)
The HLS system blood flow signal is obtained via the ultrasonic flow sensor that is clamped securely over the return (post oxygenator) line with flow indicator arrow facing in the direction of circuit blood flow (away from the oxygenator).
- Turn console on, remove clamp
- Turn RPM up to 3000 RPM
- Unscrew yellow cap from oxygenator
- Run at 4000 RPM for 1 min (look for light agitation in priming bag)
- Re-apply yellow cap
- Clamp circuit with ECMO clamp post oxygenator (also clamp both blue and red tubing at junction to reservoir bag with pre-attached white clamps)
- Await handing over circuit for connection – open lid of sterile tray if immediately anticipated
Heating the circuit
Warming the circuit to body temperature before connection is mandatory in VV ECMO cannulation and desirable in VA ECMO if time permits (The risk of cardiac arrhythmias caused by infusing a large amount of cold saline rapidly is greatest in VV ECMO). In ECPR, pre-heating of the circuit may cause distraction or delay of ECMO commencement and should be established after the ECMO support is established. Also, set the temperature not higher than 36°C until the core temperature is known to avoid overshooting the target temperature.
Zeroing HLS circuit
Principally, the HLS circuit pressures are only zeroed at the time of circuit priming before the tubing is filled with fluid. There is no need to routinely re-zero at the time of use or thereafter.
Circumstances where a primed HLS should be re-zeroed
- The zeroing step was missed during the priming procedure
- The primed circuit has been placed on a different console (with implausible readings)
- There is considerable concern that the pressure readings are erroneous on a current patient
Note: when the circuit is prepared for use the pressure readings reflect the hydrostatic pressures from the priming bag and should NOT trigger re-zeroing (e.g. with a typical elevation of the priming bag to about 80cm above the sensor the pressure reading will be around 60mmHg).
Zeroing pressures on a primed HLS circuit
There are two scenarios
The circuit is not connected to a patient
The priming bag has to be lowered to the level of the console to eliminate any hydrostatic pressure. No flow in the circuit, turn revs to 0. Then proceed to zero the pressures.
The circuit is running on a patient
Discuss with the clinician in charge regarding the need to zero.
- The patient needs to be at the same level as the console
- Apply a clamp on the return limp (to eliminate the systemic blood pressure)
- Turn RPM to zero
- Clamp the access limb, then proceed to zero the pressure
The clamp on the access side is somewhat optional since you will still zero to the patient’s venous pressure. This small error is acceptable though in a situation where there was considerable doubt about the correctness of the pressure readings beforehand and more importantly the delta pressure will be correct.
Note: Re-zero refers to all 3 pressures (pre/ inter/ post). In the process of zeroing there is a checkbox to confirm that the tubing is not filled with fluid. This can be confirmed, the difference between fluid-filled is small (approx 10mmhg) as described as long as there is no hydrostatic pressure applied to the sensor.
Flow Signal Zeroing Cardiohelp/HLS platform may be performed if required
- Clamp circuit below and upstream of flow sensor on return line (ensure the direction of flow sensor arrow is correct)
- Turn RPM to zero
- Select the flow monitoring screen on the touch screen panel and then press the zero indicator button once until zero flow is confirmed on the flow panel
- Pump speed is set to approximately 1500 RPM and the clamps are released over approximately 3-5 seconds whilst gradually increasing RPM until the desired flow is reached
Console initial settings
As a guide, the initial oxygen flow in L/min should match the blood flow in L/min. The aims at initiation are to prevent worsening of the acid-base of the patient while avoiding rapid, large changes in arterial CO2 gas tension.
Matching the blood flow ensures sufficient oxygen delivery and generally carbon dioxide removal. Patients in extremis, hypermetabolic or on VV ECMO with significantly increased minute ventilation beforehand will require substantially more oxygen flow and should be started at higher flow rates e.g. 6 L/min.
Blood flow delivery of the access cannula may be explored to establish the blood flow it can deliver without access insufficiency occurring up to 4000 RPM. Generally, the blood flow will then be set to the desired blood flow support in VA ECMO and to achieve sufficient oxygenation in VV ECMO.
Circuit Connection
The flushed access and return cannulae are connected to the access and return limbs of the primed circuit. The procedure is slightly different in PLS and HLS circuits.
PLS circuit – sterilise the end portion of the circuit with Betadine soaked gauze (this can be done by a third scrubbed assistant if available), apply clamp and cut one hand-width above. Bring the two ends into the sterile field.
HLS circuit – reach into the sterile tray, clamp circuit with provided blue clamps at marked ends. Disconnect and remove the circuit.
Be certain about matching the access cannula to access tubing (entering pump first, blue mark on tubing) and the return cannula to return tubing (coming from oxygenator, red mark on tubing).
FINAL CHECKS
Mandatory checks by cannulator before connection – assistant to remind them
- Check for obvious air – tubing, oxygenator, pumphead
- Clamp on the circuit
- Oxygen connected and turned on
Perform underwater seal connection
- Check connection for air bubbles
- Cannulators: CLAMPS OFF
- Set 1500 RPM and Console operator: CLAMP OFF
- Steadily increase ECMO support (3000-4000 RPM) to achieve desired blood flow
Confirmation
- Visualise direction of blood flow from the access cannula to pump head
- Colour change across the oxygenator confirms gas delivery and function
Notes and explanation of the process
After patient connection, all other clamps are removed by the proceduralist to handover to the console operator with only one clamp applied post oxygenator. Pump speed is set to approximately 1500 RPM and the post oxygenator clamp is released over approximately 3 seconds as RPM is gradually increased and the correct direction of blood flow confirmed. Setting the RPM to 1500 is commonly required in VA ECMO to overcome the pressure in the arterial system.