Use of CRRT

Frequently relative tight control over the fluid balance is a desirable goal in most ECMO patients, whether that is for respiratory failure or cardiac failure. Achieving a substantial negative fluid balance may be challenging in the setting of shock. Rapid fluid shifts with diuretic boluses sometimes are not well tolerated and manifest intermittently with access insufficiency. For those reasons, there should be a low threshold to use CRRT as a means to control fluid balance as well as to replace renal function. Advantageously the CRRT circuit can be attached to the ECMO circuit without any further procedure or risk to the patient.

CRRT (Prismaflex) pressure alarms

High ECMO circuit pressures can result in CRRT high return positive pressure alarms. This is not uncommon. High ECMO circuit return pressures are expected with higher ECMO blood flow rates. Further factors are smaller ECMO return cannulae (e.g. VA ECMO with 15Fr return cannula; or dual-lumen, bi-caval (Avalon Elite) VV ECMO) and to a lesser degree the systemic blood pressure.

The CRRT blood flow settings will also be expected to raise the pressure in the CRRT return circuit usually between 150 and 250ml/min.

Options to manage high CRRT pressure alarms on ECMO

  • Reduce CRRT blood flow (if possible) – decreased solute clearance
  • Reduce ECMO blood flow (if possible) – decreased solute clearance
  • Replace ST 100 set with ST 150 set (Contact ECLS Coordinator or equipment nurse)
  • PLS/HLS: change CRRT return port to post-oxygenator connection – small effect avoiding the transmembrane pressure component. (increased risk of air emboli)
  • Consider non-ECMO site for CRRT return (e.g. large bore peripheral cannula, note 18G is limited to 100ml/min so minimum 16G and still need to return the blood flow, also consider the site of return, ability to observe for extravasation given the high flow rates.)
  • Consider inserting a separate vascath

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