The purpose of this guideline is to provide a framework to support the extra corporeal life support (ECLS) team to provide ECLS using an open bridge technique.
An open bridge is a connection between the venous and arterial circuit limbs which allows isolation of the circuit from the patient in both VV and VA circuits.
The use of an 'open bridge' technique is to allow a constant blood flow through the bridge, thereby preventing the need to 'flush' the bridge every 15 minutes to prevent clot formation. There is also the reduced risk of hypotension and changes in cerebral blood flow in the child whilst the bridge is being flushed.
Background
The multiprofessional team involved in the care of the ECLS patient should have an understanding of the physiology of ECLS, familiarity with the ECLS circuit and have reached a recognised level of competence in managing the ECLS patient and prepared to deal with any trouble shooting that may be required.
Note: While this guideline refers to the ‘child’ throughout, all activities are applicable to young people.
This procedure is only undertaken once the child is established on ECLS, usually within one hour of commencing ECLS. Blood flow is measured across the bridge using the Transonic flow probe.
This procedure is performed by either the ECLS specialist nurse, the ECLS trainee or a perfusionist.
The ECLS specialist nurse will set up the Transonic flow probe. For this technique the bridge itself requires a gate clamp which fits the size of the circuit.
Procedure for open bridge technique
- Ensure the bridge is fully clamped with an ECLS metal clamp.
- Then place a gate clamp on the bridge and gate clamp must be tightly closed.
- Remove the ECLS clamp on the bridge and check the blood flow does not drop on the Spectrum Medical, ie the gate clamp is fully occlusive on the bridge.
- Gradually open the gate clamp until the spectrum Medical registers the blood flow drops by 100ml.
- Attach the Transonic flow probe and document the size of the blood shunt in the electronic patient record (PER).
- Increase the revolutions until the blood flow is back up to the original flow level as recorded on the Spectrum Medical monitor.
The bridge should be visibly checked four- to six-hourly. Document on ECLS pump checks on patient electronic record.
If platelets/clotting factors/clotting drugs cannot be administered via an intravenous line and need to be infused into the arterial limb of the extracorporeal membrane oxygenation (ECMO) circuit post oxygenator, remember to clamp the 'open bridge' during infusion to prevent fresh clotting products reaching the oxygenator. The bridge will need to be flushed every 15 minutes to prevent clot formation.
Check the shunt every four hours by briefly clamping the bridge with the ECLS clamp. If the shunt flow is less than 100ml, the bridge needs to be fully flushed and gate clamp re-sited. Document on ECLS pump checks.
Effect on venous blood gases and inline venous saturations
Venous blood taken after the bridge will include the arterial shunt across the bridge.
The venous saturations recorded on the Spectrum Medical monitor can be used to assess oxygen consumption as the Spectrum probe is above the bridge ie above the bridge shunt.
To obtain a true venous blood gas, take a blood sample from one of the child's venous lines or clamp the bridge, wait 15 minutes and take a blood sample from the venous pigtail.
Repeat procedure (above) to reset blood flow through the bridge using the open bridge technique.
The gate clamp should be moved along the bridge a minimum of once every 12 hours to check the shunt. If the bridge is becoming clotted or the blood flow sluggish, the gate clamp may need to be moved more frequently. Document observations in the ECLS pump checks on PER.
The minimum blood shunt across the bridge is 100ml, this can be increased up to 200ml if clot formation in the bridge is a problem.
When there is a higher risk of clot formation, eg when going 'heparin free', the bridge can be clamped with an ECLS clamp and flushed every 15 minutes. This allows more frequent assessment of the bridge and the circuit to reduce risk to the patient.
Document the blood flow into the patient (arterial and venous if applicable).
Document control information
Lead authorMaura O'Callaghan, ECMO Co-ordinator, ECMO
Additional authorLiz Smith, Lead Nurse ANP, ANP/ECMO
Document owner
Maura O'Callaghan, ECMO Co-ordinator, ECMO
Approved byClinical Practice Committee
First introduced: 28 May 2009
Date approved: 25 April 2012
Review schedule: Two years
Next review: 25 April 2014
Document version: 3.0
Replaces version: 2.0
