CRRT Connected to ECMO: Managing High Pressures

Abstract

Metabolic disorders and fluid overload are indications of continuous renal replacement therapy (CRRT) including continuous venovenous hemofiltration in patients on extracorporeal membrane oxygenation (ECMO). Direct connection of CRRT machine to the ECMO circuit provides many advantages. Nevertheless, because pressures in CRRT lines relate to ECMO blood flow, high ECMO blood flow may be associated with high pressures in CRRT lines. Thus, management of CRRT pressure lines becomes challenging. We evaluated a protocol for managing high CRRT pressures. Connections were performed according to a standardized protocol to maintain CRRT lines in the correct pressure ranges without modifying ECMO settings or inhibiting pressure alarms. To achieve this goal, the way of connecting of CRRT lines was adapted following a standardized protocol. Connection was first attempted between pump and oxygenator in the 12 patients. In five cases, high pressures in CRRT lines were successfully managed by changing the connection segment. Continuous renal replacement therapy parameters were within target levels and reduction of serum creatinine was 37%. In conclusion, management of high pressures in CRRT lines induced by ECMO could be achieved without modifying ECMO blood flow or inhibiting CRRT alarms. Iterative stops were avoided allowing efficient procedures.

Using additional pressure control lines when connecting a continuous renal replacement therapy device to an extracorporeal membrane oxygenation circuit

“…In addition, the filter pressure was confirmed to be within the safety range when connected to the ECMO circuit. Owing to the stability of the CRRT system, a longer lifespan of the CRRT circuit was achieved without complications, compared to those reported in previous studies [10, 17, 18].…”

“…Blood flow within the ECMO circuit causes excessive positive or negative pressure above the physiological range to the CRRT device, which eventually leads to an interruption of CRRT [6, 8, 9]. There are various suggestions for improvement, such as changing the connection site of the ECMO circuit, adjusting the alarm value of the CRRT software, and using a clamp to control the pressures [8–11], but all are associated with potentially unpredictable consequences [10].…”

Optimizing renal replacement therapy for patients who need extracorporeal membrane oxygenation: cross-talk between two organ support machines

“…After the pump, however, the intra-circuit pressure is positive to ensure adequate blood flow into the oxygenator and eventually into the patient. In comparison, CRRT devices are set up to be connected to venous pressure 0 to + 20 mmHg [9] (equivalent to central venous pressure) and have built-in pressure alarms. The ECMO pump is able to generate pressures as high as 600 mmHg, which is higher than the safety limit of the ECMO circuit (around 300 mmHg) [10] and significantly higher than that of CRRT devices.…”

“…Connecting the CRRT device to the ECMO circuit may result in high- or low-pressure alarms depending on where the CRRT connections are made in relationship with the ECMO pump. To avoid high access pressures in the CRRT inlet line, the options are to connect the access line to the ECMO circuit pre-pump or to decrease the CRRT blood flow rates [9]. Similarly, to avoid high pressures in the return line (CRRT outlet line), connecting the access line to the ECMO circuit pre-pump could be considered.…”

“…Similarly, to avoid high pressures in the return line (CRRT outlet line), connecting the access line to the ECMO circuit pre-pump could be considered. Other options are to apply adjustable clamps to the RRT circuit [9]. Using clamps and pressure control lines could potentially reduce the number of alarms and improve the health of the dialyzer, and, therefore, its lifespan, but results in potential changes in the blood flow and an increased risk of turbulences and hemolysis.…”