Computational fluid dynamics analysis and experimental hemolytic performance of three clinical centrifugal blood pumps: Revolution, Rotaflow and CentriMag

Centrifugal blood pumps have become popular for adult extracorporeal membrane oxygenation (ECMO) due to their superior blood handling and reduced thrombosis risk featured by their secondary flow paths that avoid stagnant areas. However, the high rotational speed within a centrifugal blood pump can introduce high shear stress, causing a significant shear-induced hemolysis rate. The Revolution pump, the Rotaflow pump, and the CentriMag pump are three of the leading centrifugal blood pumps on the market. Although many experimental and computational studies have focused on evaluating the hydraulic and hemolytic performances of the Rotaflow and CentriMag pumps, there are few on the Revolution pump. Furthermore, a thorough direct comparison of these three pumps' flow characteristics and hemolysis is not available. In this study, we conducted a computational and experimental analysis to compare the hemolytic performances of the Revolution, Rotaflow, and CentriMag pumps operating under a clinically relevant condition, i.e., the blood flow rate of 5 L/min and pump pressure head of 350 mmHg, for adult ECMO support. In silico simulations were used to characterize the shear stress distributions and predict the hemolysis index, while in vitro blood loop studies experimentally determined hemolysis performance. Comparative simulation results and experimental data demonstrated that the CentriMag pump caused the lowest hemolysis while the Revolution pump generated the highest hemolysis.

Ex vivo models for research in extracorporeal membrane oxygenation: a systematic review of the literature

With ongoing progress of components of extracorporeal membrane oxygenation including improvements of oxygenators, pumps, and coating materials, extracorporeal membrane oxygenation became increasingly accepted in the clinical practice. A suitable testing in an adequate setup is essential for the development of new technical aspects. Relevant tests can be conducted in ex vivo models specifically designed to test certain aspects. Different setups have been used in the past for specific research questions. We conducted a systematic literature review of ex vivo models of extracorporeal membrane oxygenation components. MEDLINE and Embase were searched between January 1996 and October 2017. The inclusion criteria were ex vivo models including features of extracorporeal membrane oxygenation technology. The exclusion criteria were clinical studies, abstracts, studies in which the model of extracorporeal membrane oxygenation has been reported previously, and studies not reporting on extracorporeal membrane oxygenation components. A total of 50 studies reporting on different ex vivo extracorporeal membrane oxygenation models have been identified from the literature search. Models have been grouped according to the specific research question they were designed to test for. The groups are focused on oxygenator performance, pump performance, hemostasis, and pharmacokinetics. Pre-clinical testing including use of ex vivo models is an important step in the development and improvement of extracorporeal membrane oxygenation components and materials. Furthermore, ex vivo models offer valuable insights for clinicians to better understand the consequences of choice of components, setup, and management of an extracorporeal membrane oxygenation circuit in any given condition. There is a need to standardize the reporting of pre-clinical studies in this area and to develop best practice in their design.

Impact of Pulsatile Flow Settings on Hemodynamic Energy Levels Using the Novel Diagonal Medos DP3 Pump in a Simulated Pediatric Extracorporeal Life Support System

Background:

The objective of this study was to evaluate the pump performance of the novel diagonal Medos Deltastream DP3 diagonal pump (MEDOS Medizintechnik AG, , Stolberg, Germany) under nonpulsatile to pulsatile mode with varying differential speed values in a simulated pediatric extracorporeal life support system.

Methods:

The experimental circuit consisted of a Medos Deltastream DP3 pump head and console, a Medos Hilite 2400 LT hollow fiber membrane oxygenator (MEDOS Medizintechnik AG), a 14F Medtronic DLP arterial cannula (Medtronic Inc, Minnesota), and a 20F Terumo TenderFlow Pediatric venous return cannula (Terumo Corporation, Michigan). Trials were conducted at flow rates ranging from 500 mL/min to 2,000 mL/min (500 mL/min increments) and pulsatile differential speed values ranging from 500 rpm to 2,500 rpm (500 rpm increments) using human blood (hematocrit 35%). The postcannula pressure was maintained constantly at 60 mm Hg. Real-time pressure and flow data were recorded using a custom-made data acquisition system and Labview software.

Results:

Under all experimental conditions, pulsatile flow (P) generated significantly greater energy equivalent pressure (EEP), surplus hemodynamic energy (SHE), and total hemodynamic energy (THE) than those of nonpulsatile flow (NP). Under NP, SHE was zero. Higher differential speed values generated greater EEP, SHE, and THE values. There was little variation in the oxygenator pressure drop and the cannula pressure drop in P, compared to NP.

Conclusions:

The novel Medos Deltastream DP3 diagonal pump is able to generate physiological quality of P, without backflow. With increased differential rpm, the pump generated greater EEP, SHE, and THE. Physiological quality of pulsatility may be associated with better microcirculation because of greater EEP, SHE, and THE.

Challenges at the Bedside With ECMO and VAD

Patients on circulatory support can be the source of multiple challenges including optimizing the circuit for specific congenital heart lesions, troubleshooting circuit failures, transporting patients on the circuit, anticoagulation and bleeding, transitioning to more mobile ventricular assist device, listing for thoracic organ transplantation, weaning from the circuit, and educating the patient and family about mechanical support. These challenges ideally require a specialized multidisciplinary team, which includes anesthesiologists, child life specialists, extracorporeal membrane oxygenation (ECMO) specialists, intensivists, nurses, nutritionists, perfusionists, pharmacists, respiratory therapists, social workers, and surgeons.