Liver Transplantation with Hemodynamic Control of Lung Recruitment

24th EDM+ RCT shows benefit in Liver Transplantation

Yet another Randomized Controlled Trial (RCT) demonstrates the value of Deltex Medical’s TrueVue Esophageal Doppler Monitoring (EDM+). Once more it’s in a complex surgical setting; this time liver transplantation. The new trial by Halwa et al appears in the journal Experimental and Clinical Transplantation. The study claims to be “one of the few to address the effects of intra-operative prophylactic lung recruitment among liver transplant recipients during transplant surgery.” 

Liver Transplant cases number in the tens of thousands worldwide (13,000 in USA alone). Liver transplant patients are vulnerable to atelectasis (collapsed lung segments or alveoli). This condition can be evident at presentation, caused by ascites (fluid in the abdomen) or pleural effusion (water on the lungs). Alternatively it can occur intra-operatively, caused by lengthy periods of physical lung retraction during surgery. 

Lung “recruitment” in effect refers to the re-opening of non-functioning alveoli. Importantly, liver transplant patients present a different challenge to that faced in similarly compromised SARS-type patients. This is because the standard combination of Alveolar Recruitment Maneuver (ARM) and raised positive end-expiratory pressure (PEEP), can adversely affect liver perfusion and hepatic outflow. Both are undesirable conditions and predictive of poorer outcomes. Consequently this may explain why it’s only as recently as 2006 that clinicians first demonstrated successful lung recruitment in liver transplant patients.

TrueVue EDM+ could become a vital “Enabling” technology in liver transplantation

One question asked in this new RCT is whether hemodynamic control can enable clinicians to perform lung tissue recruitment during liver transplantation. In other words, could the transplant team maintain optimal blood flow during careful, stepwise recruitment of the alveoli? The investigators compared ARM re-expansion of collapsed lung alveoli with a control group. The control group were given no hemodynamically driven lung recruitment protocol.

Crucially, in order to maintain visibility of patients’ hemodynamic status, the ARM group monitoring used a Flow Time corrected (FTc) algorithm (<350ms). Unique to TrueVue EDM+, FTc is a heart rate independent measurement of the duration of aortic blood flow. It is therefore a very sensitive biomarker of real time changes in preload and afterload conditions. Furthermore Doppler FTc readings are not affected by the high PEEP. This is unlike Central Venous Pressure (CVP)-derived readings, as confirmed by the study authors. It means only flow-based EDM-derived FTc gives the right answer.

“Only TrueVue EDM+ can provide the clinician with a unique and reliable picture of hemodynamic status to guide them through the alveolar recruitment process.” Andy Mears, Deltex Medical CEO

Interestingly, three of the ARM group were subjected to a temporary hold of ARM in order to improve the venous return. All three patients were in fluid deficit. Once rectified, clinicians could successfully re-recruited their lungs. Without the use of TrueVue EDM+ these patients would not have benefited from this degree of diagnosis and resultant care. This demonstrates the unique potential of the system to guide fluids and therefore the progression of the procedure.

Significant Reduction in Post-op Pulmonary Complications

This study clearly offers the potential for liver transplantation teams to achieve the desirable outcome of better lung function (therefore oxygenation). Of particular note, the results showed a significant reduction in post-operative pulmonary complications in the ARM group, for instance in reduced pleural effusions.

In conclusion the authors state that; “Stepwise alveolar recruitment identified the optimal positive end-expiratory pressure to improve lung mechanics and oxygenation with minimal hemodynamic changes, without liver graft congestion/dysfunction, and was associated with significant reduction in post-operative pulmonary complications.”

As a result of this clinical work Prof. Khaled Ahmed Yassen now recommends the use of advanced hemodynamic monitoring within his ARM protocol for all liver transplantation patients.

Deltex Medical CEO comments

Andy Mears states; “RCTs represent the gold standard in terms of evidence base and are essential to achieving a ‘standard of care’. For this reason we’re delighted to see our 24th RCT published on the EDM system. This represents significantly more evidence than all of the other competing hemodynamic monitoring technologies combined.

“What this study demonstrates is that only TrueVue EDM+ delivers the capability to guide intra-operative lung recruitment. The associated improved outcome is extremely promising for thousands of liver transplant patients.”