Evaluation of a preprimed microporous hollow-fiber membrane for rapid response neonatal extracorporeal membrane oxygenation

Abstract

Delays in initiating extracorporeal membrane oxygenation (ECMO) in the critically ill pediatric patient may lead to adverse outcomes. Maintaining a primed ECMO circuit can considerably reduce the initiation time. The predominant concerns precluding this practice are a decrease in oxygenator efficiency due to the saturation of microporous hollow fibers and compromised sterility when the oxygenator has been primed for 30 days. For institutions using a hollow-fiber oxygenator for ECMO, there are no data reporting pre-primed hollow-fiber oxygenator viability. This study reports the efficiency of oxygen transfer and the sterility of the Carmeda Minimax Plus (Medtronic, Inc, Minneapolis, MN) oxygenator after being crystalloid primed for 30 days. A total of 10 Minimax Plus oxygenators were tested for oxygen transfer in a laboratory setting utilizing fresh whole bovine blood. The control group (n =5) were tested immediately after priming. The test group (n =5) were oxygenators primed for 30 days with crystalloid solution and left stagnant until tested. Prior to testing, all oxygenators were circulated for 5 min and samples drawn to test for circuit sterility. Venous inlet saturations were manipulated to achieve three levels of testing: venous saturation (SvO2) of 55% for an oxygen challenge, SvO2 of 65% to comply with AAMI standards, and SvO2 of 75% to assess oxygen transfer rates and peak PaO2 achievement. Blood flow for all tests was maintained at 2 L/min with 1:1 blood to gas flow ratio and 100% FiO2. Samples were drawn pre- and postoxygenator at 1- and 6-hour time intervals to compute actual oxygen transfer values. All cultures from the test group priming solution produced no microbial growth after 30 days of stagnant prime. Average oxygen transfer values (ml/O2/min) for the control group after 1 hour of continuous use were 130.1+/-15.5 (@ 55% SvO2), 113.7+/-10.4 (@ 65% SvO2), 97.7+/-8.9 (@ 75% SvO2). After 6 hours, the average transfer values increased to 134.2+/-13.2 (@ 55% SvO2), 118.76+/-6.6 (@ 65% SvO2) and 98.9+/-8.3 (@ 75% SvO2). The average oxygen transfer values after 1 hour for oxygenators primed for 30 days were 114.9+/-10.0 (@ 55% SvO2), 112.4+/-8.2 (@ 65% SvO2) and 89.6+/-16.0 (@ 75% SvO2). After 6 hours of use, the average transfer values all decreased to 111.4+/-2.1 (@ 55% SvO2, p <0.05 versus control), 104.0+/-5.6 (@ 65% SvO2, p <0.05 versus control) and 88.4+/-3.2 (@ 75% SvO2, p <0.05 versus control). In conclusion, there was a decrease in the average oxygen transfer values for the test group after 6 hours versus the control. The modest loss of oxygen transfer ability observed can be considered acceptable due to the amount of surface area of the Minimax Plus oxygenator when used on a neonate, making it feasible to adopt the practice of prepriming the Minimax oxygenator for neonatal ECMO.

Outcomes Before and After Implementation of a Pediatric Rapid-Response Extracorporeal Membrane Oxygenation Program

“…These circuits were primed in a sterile fashion with Normosol R (Hospira, Inc,. Lake Forest, IL), de-aired, and covered for a maximum of 30 days [8]. If blood products are not immediately available, the circuits are prepared for asanguineous ECMO deployment by adding 25 mEq sodium bicarbonate, 200 units heparin and 300 mg calcium gluconate to the circuit.…”

Is it safe to leave an ECMO circuit primed?

“…They then added bovine whole blood to the circuit and showed efficient oxygen transfer for up to six hours, which was the end point of the study. 15 We have shown that it is a safe and sterile practice to keep a primed ECMO circuit ready for rapid response for at least four weeks (the end point of the study), with no growth in the system, making the primed ECMO circuit ready for rapid response while keeping the cost of a valuable therapy to a minimum by not disposing of a wet circuit after 24-96 hours.…”

Sterility and performance of open and closed extracorporeal circuits after long-term dry-wet setups

“…Questions also arise on how long pre-primed circuits can safely be maintained wet and used without the fear of increased susceptibility to infection as well as concern for membrane failure and function. [11][12][13][14] Using coated circuits are our preference in all cases. Since this is a clinical question and there are no manufacturer studies in this arena, situations arise where there is a need to have a circuit quickly setup, to be able to support critical patients, when even the briefest time delay could affect outcomes.…”