Pediatric cardiopulmonary bypass devices: trends in device use for cardiopulmonary bypass and postcardiotomy support

Low-Cost Innovations in Global Cardiac Surgery

Cardiovascular diseases are the leading cause of morbidity and mortality worldwide, costing the lives of 18 million people annually, with up to one-third being attributable to cardiac surgical conditions. Approximately 6 billion people do not have access to safe, timely, and affordable cardiac surgery, predominantly affecting populations living in low-middle income countries. Cardiac surgical care is costly, resulting in few centers in variable-resource contexts operating continuously or with the resources observed in higher-resource environments. As a result, innovations may be formally developed or informally adopted to bypass resource constraints and ensure care delivery. Innovations have been observed across the cardiac surgical care continuum and across settings, potentially benefiting both high-income countries, where growing health care costs are becoming unsustainable, and low- and middle-income countries, where competing health agendas may limit investments into cardiac surgery. This narrative review attempts to address the costs associated with cardiac surgery, placing an emphasis on frugal innovations in the perioperative and postoperative care spectrum.

Effect of pump type on outcomes in neonates with congenital diaphragmatic hernia requiring ECMO

PURPOSE

With the exception of neonatal respiratory failure, most centers are now using centrifugal over roller-type pumps for the delivery of extracorporeal membrane oxygenation (ECMO). Evidence supporting the use of centrifugal pumps specifically in infants with congenital diaphragmatic hernia (CDH) remains lacking. We hypothesized that the use of centrifugal pumps in infants with CDH would not affect mortality or rates of severe neurologic injury (SNI).

METHODS

Infants with CDH were identified within the ELSO registry (2000-2016). Patients were then divided into those undergoing ECMO with rollertype pumps or centrifugal pumps. Patients were matched based on propensity score (PS) for the ECMO pump type based on pre-ECMO covariates. This was done for all infants and separately for each ECMO mode, venovenous (VV) and venoarterial (VA) ECMO.

RESULTS

We identified 4,367 infants who were treated with either roller or centrifugal pumps from 2000-2016. There was no difference in mortality or SNI between the two pump types in any of the groups (all infants, VA-ECMO infants, VV-ECMO infants). However, there was at least a six-fold increase in the odds of hemolysis for centrifugal pumps in all groups: all infants (odds ratio [OR] 6.99, p<0.001), VA-ECMO infants (OR 8.11, p<0.001 and VV-ECMO infants (OR 9.66, p<0.001).

CONCLUSION

For neonates with CDH requiring ECMO, there is no survival advantage or difference in severe neurologic injury between those receiving roller or centrifugal pump ECMO. However, there is a significant increase in red blood cell hemolysis associated with centrifugal ECMO support.

Diminished adhesion and activation of platelets and neutrophils with CD47 functionalized blood contacting surfaces

CD47 is a ubiquitously expressed transmembrane protein that, through signaling mechanisms mediated by signal regulatory protein alpha (SIRPα1), functions as a biological marker of 'self-recognition'. We showed previously that inflammatory cell attachment to polymeric surfaces is inhibited by the attachment of biotinylated recombinant CD47 (CD47B). We test herein the hypothesis that CD47 modified blood conduits can reduce platelet and neutrophil activation under clinically relevant conditions. We appended a poly-lysine tag to the C-terminus of recombinant CD47 (CD47L) allowing for covalent linkage to the polymer. SIRPα1 expression was confirmed in isolated platelets. We then compared biocompatibility between CD47B and CD47L functionalized polyvinyl chloride (PVC) surfaces and unmodified control PVC surfaces. Quantitative and Qualitative analysis of blood cell attachment to CD47B and CD47L surfaces, via scanning electron microscopy, showed strikingly fewer platelets attached to CD47 modified surfaces compared to control. Flow cytometry analysis showed that activation markers for neutrophils (CD62L) and platelets (CD62P) exposed to CD47 modified PVC were equivalent to freshly acquired control blood, while significantly elevated in the unmodified PVC tubing. In addition, ethylene oxide gas sterilization did not inhibit the efficacy of the CD47 modification. In conclusion, CD47 modified PVC inhibits both the adhesion and activation of platelets and neutrophils.

Hemolysis during cardiac extracorporeal membrane oxygenation: a case-control comparison of roller pumps and centrifugal pumps in a pediatric population

Extracorporeal membrane oxygenation (ECMO) is a lifesaving therapy, which has been used for the support of children with a broad range of diseases. Two pumps of differing mechanisms have been used to generate the extracorporeal flow: roller-head pumps and centrifugal pumps. Seven patients supported during ECMO with Levitronix Centrimag (Centrimag group [CG]) were matched to 14 patients supported with Stockert-Shiley SIII (Stockert-Shiley group [SSG]) at a single institution from July 2007 to July 2009. We hypothesized that hemolysis as measured by plasma-free hemoglobin (PFH) is elevated in the SSG versus the CG during cardiac ECMO. Categorical data were analyzed using Fisher's exact test. Plasma-free hemoglobin differences between groups were analyzed using both Wilcoxon rank sum and beta regression. Overall, SSG patients had two times the odds of having a higher PFH than CG patients adjusting for repeated measures (odds ratio [OR] = 1.96, 95% confidence interval [CI]: [1.15-3.34], p < 0.014). Differences between circuit failure in the first 168 hours did not reach statistical significance (1/7 CG vs. 7/14 SSG; p = 0.174). In this population of cardiac patients requiring ECMO support, more hemolysis occurred in the SSG, a roller-head pump supported group, when compared with the CG, a centrifugal pump supported group. Differences in circuit life did not reach statistical significance. This pilot study contrasts with past studies, which have demonstrated more hemolysis occurring with centrifugal pumps when compared with roller-head pumps.

An investigational study of minimum rotational pump speed to avoid retrograde flow in three centrifugal blood pumps in a pediatric extracorporeal life support model

During extracorporeal life support with centrifugal blood pumps, retrograde pump flow may occur when the pump revolutions decrease below a critical value determined by the circuit resistance and the characteristics of the pump. We created a laboratory model to evaluate the occurrence of retrograde flow in each of three centrifugal blood pumps: the Rotaflow, the CentriMag, and the Bio-Medicus BP-50. At simulated patient pressures of 60, 80, and 100 mmHg, each pump was evaluated at speeds from 1000 to 2200 rpm and flow rates were measured. Retrograde flow occurred at low revolution speeds in all three centrifugal pumps. The Bio-Medicus pump was the least likely to demonstrate retrograde flow at low speeds, followed by the Rotaflow pump. The CentriMag pump showed the earliest transition to retrograde flow, as well as the highest degree of retrograde flow. At every pump speed evaluated, the Bio-Medicus pump delivered the highest antegrade flow and the CentriMag pump delivered the least.

A novel, low cost, disposable, pediatric pulsatile rotary ventricular pump for cardiac surgery that provides a physiological flow pattern

Research is underway to develop a novel, low cost, disposable pediatric pulsatile rotary ventricular pump (PRVP) for cardiac surgery that provides a physiological flow pattern. This is believed to offer reduced morbidity and risk exposure within this population. The PRVP will have a durable design suitable for use in short- to mid-length prolonged support after surgery without changing pumps. The design is based on proprietary MC3 technology which provides variable pumping volume per stroke, thereby allowing the pump to respond to hemodynamic status changes of the patient. The novel pump design also possesses safety advantages that prevent retrograde flow, and maintain safe circuit pressures upon occlusion of the inlet and outlet tubing. The design is ideal for simple, safe and natural flow support. Computational methods have been developed that predict output for pump chambers of varying geometry. A scaled chamber and pump head (diameter = 4 in) were prototyped to demonstrate target performance for pediatrics (2 L/min at 100 rpm). A novel means of creating a pulsatile flow and pressure output at constant RPM was developed and demonstrated to create significant surplus hydraulic energy (>10%) in a simplified mock patient circuit.

B-type natriuretic peptide levels predict outcomes for children on extracorporeal life support after cardiac surgery

OBJECTIVE

Extracorporeal life support is used in 3% to 8% of infants and children after cardiac surgery. B-type natriuretic peptide may have utility as a biomarker in these patients. The objective of this study was to investigate potential associations between changes in B-type natriuretic peptide during trials off extracorporeal life support and clinical outcome.

METHODS

Ten infants and children requiring extracorporeal life support after cardiac surgery were studied prospectively. Before separation from extracorporeal life support, a shunt was placed in the circuit, allowing for temporary trials off life support. Serum lactate, arterial-venous oxyhemoglobin saturation difference, and B-type natriuretic peptide levels were determined before each trial off life support and at the end of each trial off life support, and the ability to predict postoperative outcome from these data was evaluated.

RESULTS

During trials off extracorporeal life support, lactate, the arterial-venous oxyhemoglobin saturation difference, and B-type natriuretic peptide levels increased above pre-trial values (P < .05). Only the arterial-venous oxyhemoglobin saturation difference predicted successful separation from extracorporeal life support after a trial (P < .05). There were no associations between long-term outcome and alterations in lactate and the arterial-venous oxyhemoglobin saturation difference during the final trials off life support. However, an increase in B-type natruiretic peptide levels during the final trial off life support (trial/pre-trial ratio of >1) had a sensitivity of 80% and a specificity of 100% for predicting the need for an unplanned operation or death within 3 months (P < .05).

CONCLUSION

B-type natriuretic peptide determinations may be a useful tool for clinicians caring for infants and children requiring extracorporeal life support after cardiac surgery.