For most ECMO configurations, the ECMO circuit provides the optimal access for continuous renal replacement therapy (CRRT) and a separate vascular access catheter (vascath) is NOT required. ECMO configurations that may not support CRRT due to excessive circuit pressures are: dual lumen bi-caval (Avalon Elite) configuration in VV ECMO and any VA ECMO configuration with a small return cannulae (e.g. 15 Fr). In these settings, a vascath may be required. The process of connection of the CRRT (Prismaflex) circuit is described below. For more details regarding the medical use of CRRT in ECMO use the link.
ECMO trained bedside ICU nurses carry out the connection and disconnection of CRRT from the ECMO circuit. CRRT connection must always be sited on the positive pressure (post-pump) part of the circuit. No ports exist for connection pre-pump (access) side of an Alfred Hospital ECMO circuit. The same applies to temporary RVAD configurations. Note temporary LVAD should NOT be used for CRRT.
The CRRT machine (Prismaflex) will access the highly pressurised return limb of the ECMO circuit. Current Prismaflex software will accept these positive pressure ranges after the standard startup.
Connection and disconnection for both PLS and HLS consoles and temporary VAD circuits
- The connection and disconnection need to be completed with a dressing regime using a dressing trolley, dressing pack, 2 x 10ml syringes, and red caps
- ONLY ASPIRATE the luer connections on commencement of CRRT
- NEVER flush the luer connectors
- Cap off with sterile red caps
CRRT BLOOD IS NOT RETURNED TO THE PATIENT THROUGH THE ECMO CIRCUIT.
PLS circuit connection for CRRT
The access and return lines for CRRT are connected to the two Luer lock connectors between the outlet of the pump head (post-pump) and the oxygenator. The access line for CRRT is attached to the “proximal” (closer to the pump head) connector and the return line for the CRRT circuit is connected to the “distal” (closer to the oxygenator) connector.
The CRRT connection in the PLS circuit is pre-oxygenator with the access (red marked tubing) first and the return second (blue marked-tubing), any micro-bubbles would be caught in the oxygenator.
HLS circuit connection for CRRT
Oxygenator inlet and outlet Luer taps with wide bore extensions are used for CRRT connection. The CRRT access line is connected to the post oxygenator port and the return line for CRRT is connected to the pre oxygenator port. The oxygenator thereby functioning as a potential bubble trap.
The red marked tubing represents the access for the CRRT and is connected post-oxygenator, the CRRT return (blue) connects pre-oxygenator.
Temporary RVAD circuit connection for CRRT
The set up is analogous to the PLS only that the perfusionist has to be asked specifically to splice the side ports into the circuit beforehand. The access and return lines for CRRT are connected to the two Luer lock connectors between the outlet of the pump head (post-pump) and the oxygenator. The access line for CRRT is attached to the “proximal” (closer to the pump head) connector and the return line for the CRRT circuit is connected to the “distal” (closer to the patient) connector (See PLS connections above).
There should be NO CRRT connections in a temporary LVAD circuit.