Bridge to Lung Transplantation With the Extracorporeal Membrane Ventilator Novalung in the Veno-Venous Mode: The Initial Hannover Experience : ASAIO Journal

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Bridge to Lung Transplantation With the Extracorporeal Membrane Ventilator Novalung in the Veno-Venous Mode: The Initial Hannover Experience

Fischer, Stefan*; Hoeper, Marius M.; Tomaszek, Sandra*; Simon, Andre*; Gottlieb, Jens; Welte, Tobias; Haverich, Axel*; Strueber, Martin*

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ASAIO Journal 53(2):p 168-170, March 2007. | DOI: 10.1097/MAT.0b013e31802deb46
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Abstract

Increasing numbers of patients listed for lung transplantation (LTx), but a steady number of donor organs lead to increasing waiting times, and, consequently, waiting list morbidity and mortality.1 As a consequence, more patients require advanced respiratory support as a bridge to LTx. Given the high risk of LTx under such circumstances, many programs may not consider these patients as transplant candidates. Previously reported approaches to bridge to LTx include mechanical ventilation and extracorporeal membrane oxygenation (ECMO). Ventilator support and ECMO have both been identified as risk factors of postLTx mortality when applied preLTx.1 We have previously reported the successful use of the pumpless Novalung as a bridge to LTx in patients with severe ventilator-refractory hypercapnia.2 In this pumpless mode, the device achieves sufficient CO2 removal but not oxygenation due to limited blood flow, which is approximately 20% of the cardiac output.2 Therefore, in the pumpless arterio-venous mode, this device is not suitable as a bridge to LTx in patients with predominant hypoxemia. Sufficient oxygenation in these patients can only be achieved with veno-venous or veno-arterial pump-driven support, such as ECMO. This, however, is associated with various life-threatening side effects.3 In 1978, Gattinoni and co-workers4 showed the dependency of extracorporeal CO2 removal and oxygenation on transmembrane blood flow. Whereas sufficient CO2 removal could be achieved with low blood flows (0.5–1 l/min), oxygenation required much higher flows (3–5 l/min).

Here we report the veno-venous pump-driven use of the Novalung, which was originally designed for extracorporeal pumpless CO2 removal, as a bridge to LTx in patients with severe ventilator-refractory hypoxemia.

Patients and Outcome

The Novalung was used for veno-venous lung support in two patients with ventilator-refractory hypoxemia while listed for LTx. Pre-Novalung implantation data are provided in Table 1. The length of veno-venous support was 17 days in patient 1 and 9 days in patient 2. Both were successfully bridged to LTx.

T1-10
Table 1:
Patient Characteristics Before Novalung Implantation

A bolus of 10,000 units heparin was administered before cannulation. Anticoagulation was monitored by ACT levels every 2 hours. Heparin was given intravenously to maintain ACTs of 180–200 seconds. For veno-venous cannulation, a 22F 5-stage Heartport cannula was inserted into a femoral vein for drainage and a 17F single-stage cannula (Novalung GmbH, Hechingen, Germany) was inserted into an internal jugular vein for blood return percutaneously, as shown in Figure 1A. Blood flow was provided by a centrifugal pump. Figure 1B depicts chest x-ray findings immediately after Novalung insertion in patient 2. No cannulation-related complications occurred. In both cases the Novalung was explanted in the OR after LTx. Table 2 summarizes the course of both patients during the first week after Novalung initiation.

F1-10
Figure 1.:
(A) The veno-venous Novalung in a patient with cystic fibrosis before lung transplantation. (B) Chest x-ray immediately after Novalung initiation in the same patient.
T2-10
Table 2:
Patient Characteristics After Novalung Implantation

Patient 1 is currently alive and lives a normal life more than 1 year after LTx. Patient 2 was also bridged successfully with the veno-venous Novalung and tolerated the transplant well. Unfortunately, severe delayed graft failure that required ECMO support developed, and the patient died of multiorgan failure 9 days after LTx.

Discussion

We describe our initial experience with the Novalung in the veno-venous mode as a bridge to LTx in two patients with severe ventilator-refractory hypoxemia. Hitherto, the only alternative approach in these patients is conventional extracorporeal gas exchange. The reported outcome after LTx off ECMO is poor, with an approximate 40% 1-year survival, and it is associated with life-threatening complications.3

There are multiple differences between the veno-venous Novalung and conventional ECMO. First, the Novalung was not designed as an ECMO oxygenator but for pumpless extracorporeal CO2 removal controlled by sweep gas flow. Second, it is expected that the Novalung provides improved biocompatibility over alternative oxygenators for numerous reasons. The Novalung surface is significantly smaller then that of other ECMO oxygenators (1.5 m2vs. 2.5 m2). By the nature of its geometry, the Novalung is a low-resistance device with a biocompatible heparin/crosslinker-coated surface. It has previously been demonstrated that circulating leukocytes respond to fluid shear stresses.5 Therefore, leukocyte activation can be reduced in such a low-resistance device. The low resistance also allows the blood pump (i.e., centrifugal or axial) to run in a more biocompatible fashion, inflicting less blood trauma. Furthermore, less energy is required to run the blood pump, which may lead to a longer durability in battery-driven systems (i.e., for transportation). As previously reported in greater detail, the Novalung is a polymethylpentene (PMP) fiber gas-exchange device.2 In a study by Toomasian and colleagues,6 PMP membranes showed better oxygenation and CO2 removal abilities compared to conventional silicone rubber lung membrane (SRML) devices. It is noteworthy that the pressure gradient across PMP devices was lower with <20 mm Hg compared with >150 mm Hg for the SRMLs.

None of the above-mentioned side-effects of ECMO were seen with the veno-venous Novalung in our patients. We acknowledge that this is a report on our initial experience using the Novalung in the veno-venous mode, and it does not provide the degree of evidence of a controlled study. However, in the reported patients, this approach has proven its feasibility. We were able to safely bridge two patients to LTx, in whom severe hypoxemia refractory to mechanical ventilation had developed. Given the rarity of these patients, we thought to report our initial experience. Without any doubt, these patients are extremely complex. Therefore, as a routine, our multidisciplinary LTx group reassesses the indication for LTx in these patients individually on a daily basis. The intriguing results of our previous study with this device for bridge to LTx in the pumpless mode encouraged our use of the Novalung in the veno-venous mode, because the outcome after LTx off ECMO was poor in our and other LTx programs.

After the initial success with the veno-venous Novalung, we are now performing a prospective trial at our program to study this device more specifically. Hopefully, this will ultimately help to develop safe and sufficient strategies for bridge to LTx in patients with ventilator-refractory lung failure.

References

1. Trulock EP, Edwards LB, Taylor DO, et al: Registry of the International Society for Heart and Lung Transplantation: Twenty- Second Official Adult Lung and Heart-Lung Transplant Report—2005. J Heart Lung Transplant 24: 956–967, 2005.
2. Fischer S, Simon AR, Welte T, et al: Bridge to lung transplantation with the novel pumpless interventional lung assist device NovaLung. J Thorac Cardiovasc Surg 131: 719–723, 2006.
3. Fischer S, Bohn D, Rycus P, et al: Extracorporeal membrane oxygenation (ECMO) for primary graft dysfunction (PGD) after lung transplantation: Analysis of the extracorporeal life support organization (ELSO) registry. J Heart Lung Transplant 25: 124 (Abstract # 231), 2006.
4. Gattinoni L, Kolobow T, Tomlinson T, et al: Control of intermittent positive pressure breathing (IPPB) by extracorporeal removal of carbon dioxide. Br J Anaesth 50: 753–758, 1978.
5. Simon SI, Goldsmith HL: Leukocyte adhesion dynamics in shear flow. Ann Biomed Eng 30: 315–332, 2002.
6. Toomasian JM, Schreiner RJ, Meyer DE, et al: A polymethylpentene fiber gas exchanger for long-term extracorporeal life support. ASAIO J 51: 390–397, 2005.
Copyright © 2007 by the American Society for Artificial Internal Organs