Preclinical Studies on Pulsatile Veno-Arterial Extracorporeal Membrane Oxygenation: A Systematic Review

Refractory cardiogenic shock is increasingly being treated with veno-arterial extracorporeal membrane oxygenation (V-A ECMO), without definitive proof of improved clinical outcomes. Recently, pulsatile V-A ECMO has been developed to address some of the shortcomings of contemporary continuous-flow devices. To describe current pulsatile V-A ECMO studies, we conducted a systematic review of all preclinical studies in this area. We adhered to PRISMA and Cochrane guidelines for conducting systematic reviews. The literature search was performed using Science Direct, Web of Science, Scopus, and PubMed databases. All preclinical experimental studies investigating pulsatile V-A ECMO and published before July 26, 2022 were included. We extracted data relating to the 1) ECMO circuits, 2) pulsatile blood flow conditions, 3) key study outcomes, and 4) other relevant experimental conditions. Forty-five manuscripts of pulsatile V-A ECMO were included in this review detailing 26 in vitro , two in silico , and 17 in vivo experiments. Hemodynamic energy production was the most investigated outcome (69%). A total of 53% of studies used a diagonal pump to achieve pulsatile flow. Most literature on pulsatile V-A ECMO focuses on hemodynamic energy production, whereas its potential clinical effects such as favorable heart and brain function, end-organ microcirculation, and decreased inflammation remain inconclusive and limited.

Feasibility of Venovenous Extracorporeal Membrane Oxygenation Without Systemic Anticoagulation

BACKGROUND

Venovenous extracorporeal membrane oxygenation (ECMO) is increasingly being used for acute respiratory distress syndrome and as a bridge to lung transplantation. After initiation of venovenous ECMO, systemic anticoagulation therapy is traditionally administered and can cause bleeding diathesis. Here, we investigated whether venovenous ECMO can be administered without continuous systemic anticoagulation administration for patients with acute respiratory distress syndrome.

METHODS

This is a retrospective review of an institutional ECMO database. We included consecutive patients from January 2015 through February 2019. Overall, 38 patients received low levels of continuous systemic anticoagulation (AC+) whereas the subsequent 36 patients received standard venous thromboprophylaxis (AC-). Published Extracorporeal Life Support Organization guidelines were used for the definition of outcomes and complications.

RESULTS

Overall, survival was not different between the two groups (P = .58). However, patients in the AC+ group had higher rates of gastrointestinal bleeding (28.9%, vs AC- group 5.6%; P < .001). The events per patient-day of gastrointestinal bleeding was 0.00025 in the AC- group and 0.00064 in the AC+ group (P < .001). In addition, oxygenator dysfunction was increased in the AC+ group (28.9% and 0.00067 events per patient-day, vs AC- 11.1% and 0.00062 events per patient-day; P = .02). Furthermore, the AC+ group received more transfusions: packed red blood cells, AC+ group 94.7% vs AC- group 55.5% (P < .001); fresh frozen plasma, AC+ 60.5% vs AC- 16.6% (P = .001); and platelets, AC+ 84.2% vs AC- 27.7% (P < .001). There was no circuit thrombosis in either groups throughout the duration of ECMO support.

CONCLUSIONS

Our results suggest that venovenous ECMO can be safely administered without continuous systemic anticoagulation therapy. This approach may be associated with reduced bleeding diathesis and need for blood transfusions.

In Vitro Evaluation of an Alternative Neonatal Extracorporeal Life Support Circuit on Hemodynamic Performance and Bubble Trap

The objective of this study was to evaluate an alternative neonatal extracorporeal life support (ECLS) circuit with a RotaFlow centrifugal pump and Better-Bladder (BB) for hemodynamic performance and gaseous microemboli (GME) capture in a simulated neonatal ECLS system. The circuit consisted of a Maquet RotaFlow centrifugal pump, a Quadrox-iD Pediatric diffusion membrane oxygenator, 8 Fr arterial cannula, and 10 Fr venous cannula. A "Y" connector was inserted into the venous line to allow for comparison between BB and no BB. The circuit and pseudopatient were primed with lactated Ringer's solution and packed human red blood cells (hematocrit 35%). All hemodynamic trials were conducted at flow rates ranging from 100 to 600 mL/min at 36°C. Real-time pressure and flow data were recorded using a data acquisition system. For GME testing, 0.5 cc of air was injected via syringe into the venous line. GME were detected and characterized with or without the BB using the Emboli Detection and Classification Quantifier (EDAC) System. Trials were conducted at flow rates ranging from 200 to 500 mL/min. The hemodynamic energy data showed that up to 75.2% of the total hemodynamic energy was lost from the circuit. The greatest pressure drops occurred across the arterial cannula and increased with increasing flow rate from 10.1 mm Hg at 100 mL/min to 114.3 mm Hg at 600 mL/min. The EDAC results showed that the BB trapped a significant amount of the GME in the circuit. When the bladder was removed, GME passed through the pump head and the oxygenator to the arterial line. This study showed that a RotaFlow centrifugal pump combined with a BB can help to significantly decrease the number of GME in a neonatal ECLS circuit. Even with this optimized alternative circuit, a large percentage of the total hemodynamic energy was lost. The arterial cannula was the main source of resistance in the circuit.

Impact of pulsatile flow on hemodynamic energy in a Medos Deltastream DP3 pediatric extracorporeal life support system

The Medos Deltastream DP3 system is made up of a novel diagonal pump and hollow-membrane oxygenator that provides nonpulsatile and pulsatile flows for extracorporeal life support (ECLS). The objectives of this study are to (i) evaluate the efficacy of the hemodynamic energy provided by Medos Deltastream DP3 system in nonpulsatile and pulsatile mode and (ii) to evaluate the pulsatile mode under different frequencies. The experimental ECLS circuit was used in this study, primed with Ringer's lactate and packed red blood cells (hematocrit 35%). All trials were conducted at flow rates of 500, 1000, 1500, and 2000 mL/min with modified pulsatile frequencies of 60, 70, 80, and 90 bpm at 36°C. Simultaneous blood flow and pressures at the pre/postoxygenator and pre/postcannula sites were recorded for quantification of the pulsatile perfusion-generated energy-equivalent pressure (EEP), surplus hemodynamic energy (SHE), and total hemodynamic energy (THE). The experiments showed that under pulsatile flow conditions, at all flow rates and frequencies, (i) the EEP, SHE, and THE were significantly higher when compared with the nonpulsatile group and (ii) the pressure drop was minimal at lower flow rates and lower pulsatile frequencies but was significant when either the flow rate or the pulsatile frequency was increased. The Medos Deltastream DP3 System can provide nonpulsatile flow and physiologic quality pulsatile flow for pediatric ECLS. When the Medos DP3 pediatric ECLS system is used with pulsatile flow, there is more surplus hemodynamic energy and total hemodynamic energy than nonpulsatile flow.

A pilot study comparing two polymethylpentene extracorporeal membrane oxygenators

OBJECTIVE

We compared two polymethylpentene oxygenators being used in our unit: the Maquet Quadrox-iD paediatric and the Medos Hilite 800LT.

STUDY DESIGN

A mono-centric, prospective pilot study was conducted on ten consecutive newborn patients who had been admitted to our hospital service for extracorporeal circulation (EC) treatment. We examined the rate of oxygen transfer, the CO2 removal capacity and the average sweep gas flow required to produce this result. We also assessed the disturbances of haemostasis, the need for labile blood products and the membrane oxygenator lifetime and cost of use.

CONCLUSIONS

According to our study, it seems to us that Medos Hilite 800LT membrane oxygenators demonstrate greater oxygen transfer and CO2 removal capacity than Maquet Quadrox-iD paediatric membrane oxygenators, at a similar cost. These results lead us to conclude that it is reasonable to continue using Medos Hilite 800LT membrane oxygenators. A broader comparison study would be necessary in order to support these initial results.