Predictive criteria for the need of extracorporeal circulation in single-lung transplantation

The role of intraoperative pulmonary arterial catheterization data in determining the need for extracorporeal membrane oxygenation in lung transplantation

Background

This study aims to investigate predictive factors of identification of the need of patients for extracorporeal membrane oxygenation support during lung transplantation.

Methods

A total of 63 patients (49 males, 14 females, mean age: 44.9±14.4 years; range, 14 to 64 years) who underwent lung transplantation in our institution between December 2016 and December 2019 were retrospectively analyzed. Demographic characteristics and perioperative clinical data of patients were recorded. After induction and pulmonary artery catheterization, cardiac output, mean pulmonary artery pressure, pulmonary capillary wedge pressure, cardiac index, pulmonary vascular resistance, systemic vascular resistance, and right atrial pressure were measured using the thermodilution technique.

Results

Thirty-three of the patients received extracorporeal membrane oxygenation support during surgery. The right atrial pressure (p<0.001), pulmonary capillary wedge pressure (p<0.002), mean pulmonary artery pressure (p<0.001), and pulmonary vascular resistance (p<0.001) were statistically significantly higher in the patients who required extracorporeal membrane oxygenation support intraoperatively. The systemic vascular resistance (p<0.032) was statistically significantly lower in the patients who required extracorporeal membrane oxygenation support intraoperatively. A mean pulmonary artery pressure of >39 mmHg (p<0.02) and a right atrial pressure of >12 mmHg (p<0.047) were independent risk factors for ECMO support intraoperatively during lung transplantation.

Conclusion

Predicting the need of intraoperative extracorporeal membrane oxygenation support is of utmost importance in timing the need for mechanical support, protecting the new graft from high mechanical ventilator pressures, and adequately maintaining hemodynamic stability.

Aspects of Anesthesia for Lung Transplantation

Anesthesia for lung transplantation is both a demand ing and rewarding experience. Success requires team- work, experience, knowledge of cardiorespiratory patho physiology and its anesthetic implications, appropriate use of noninvasive and invasive monitoring, and the ability to respond quickly and effectively to life- threatening perioperative events. Specific issues in clude management of a patient with end-stage lung and heart disease, lung isolation and one-lung ventilation, perioperative respiratory failure, pulmonary hyperten sion, and acute right ventricular failure. Recent ad vances include greater understanding of dynamic hyper inflation ("gas-trapping") during mechanical ventilation, perioperative use of inhaled nitric oxide and treatment of acute right ventricular failure. Successful anesthetic management leads to greater hemodynamic stability, improvement in gas exchange and a reduction in need for cardiopulmonary bypass, all of which should lead to improved patient outcome.

Predicted oxygenation efficacy of a thoracic artificial lung

A thoracic artificial lung (TAL) provides respiratory support for lung disease. How well a TAL improves blood oxygenation for a specific pathology depends on how the TAL is attached to the pulmonary circulation: in series with the natural lungs (NLs), in parallel, or in a hybrid series/parallel combination. A computational model, including hemodynamic and O(2) and CO(2) exchange components, predicts TAL effects on blood flow rates and gas transport in pulmonary disease states modeled by elevated pulmonary vascular resistance (PVR) or reduced oxygen diffusivity in the NLs. In most cases, parallel and series TAL attachment provide comparable, maximal oxygenation. Series, with passage of total cardiac output (CO) through the NLs, is preferred for its filtration of emboli. Hybrid TAL attachment is more complicated, requiring a third graft, yet oxygenates less well than parallel and series. With extreme elevations of PVR, as in primary pulmonary hypertension, parallel TAL attachment provides an oxygenating shunt around the high resistance of the NLs, thus unloading the right ventricle, normalizing CO, and maximizing oxygenation.

Hemodynamic Consequences of Thoracic Artificial Lung Attachment Configuration: A Computational Model

A thoracic artificial lung (TAL) is being developed to assist treatment of acute and chronic pulmonary dysfunction. The TAL is attached directly to the pulmonary circulation. Depending on pathophysiology, the TAL may be attached in series with the natural lungs (NLs), in parallel with the NLs, or in an intermediate, hybrid configuration. We developed a computational model to study hemodynamic consequences of TAL attachment configuration under pathologic conditions. The pulmonary and systemic circulations, heart, and TAL are modeled as interconnected compliances and conductances, some valved. Time-varying cardiac compliance drives the system and generates pressures and flow rates. The model includes blood pressure feedback from the sympathetic nervous system, renin-angiotensin system, and renal volume control mechanism. We used previously published results from porcine experiments to verify model accuracy. We modeled normal physiology and four disease states. A hybrid configuration with 100% cardiac output through the TAL and 40% through the NLs would deliver maximal blood flow, 3.6 to 4.6 l/min, to the TAL and be tolerated by the right ventricle. Additionally, the model suggests that reducing the large "minor loss" resistances at the graft anastomoses to the pulmonary artery would improve the hemodynamics of all TAL attachment configurations.

In vivo hemodynamic responses to thoracic artificial lung attachment

A thoracic artificial lung (TAL) was attached to the pulmonary circulation in a porcine model. Proximal main pulmonary artery (PA) blood flow, in part or whole, was diverted to the TAL, and TAL outlet blood flow was split between the distal main PA and left atrium (LA). The right ventricle (RV) drove blood flow through the combined TAL/natural lung (NL) pulmonary system. Selective banding placed the TAL in parallel with the NLs, in series with the NLs, or in an intermediary hybrid configuration. Parallel TAL attachment lowered pulmonary system impedance, raised cardiac output (CO), and provided the greatest TAL blood flow rate, but reduced the NL blood flow rate which is important for pulmonary embolic clearance and metabolic blood processing. Hybrid or series TAL attachment raised pulmonary system impedance, lowered CO, increased RV oxygen consumption, and reduced RV oxygen supply. Redesign of the PA anastomoses, TAL inlet graft, and TAL entrance and exit would significantly improve hemodynamics and RV function with TAL attachment. Mean LA pressure increased throughout the experiment, which may indicate damage caused by graft attachment to the LA. Pulmonary resistance-flow rate curves may enable clinical prediction of tolerable TAL attachment configurations.

Anesthetic Considerations for Lung Volume Reduction Surgery and Lung Transplantation

Anesthetic considerations for lung transplantation and LVRS have been reviewed, with an emphasis on critical intraoperative junctures and decision points. Cognizance of these issues promotes coordinated and optimal care and provides the potential to improve outcome in this particularly high-risk population.

Replacing cardiopulmonary bypass with extracorporeal membrane oxygenation in lung transplantation operations

Cardiopulmonary bypass (CPB) is required in some lung transplantation (LTx) operations. However, it increases risks of bleeding and early graft dysfunction. We report our experiences of replacing CPB with heparin-bound extracorporeal membrane oxygenation (ECMO) in LTx operations. If extracorporeal circulation was anticipated for the LTx operations, ECMO support was set up through the femoral venoarterial route after induction of anesthesia; then, LTx was done as usual. Five thousand units of heparin was injected intravenously during the femoral vessels cannulation, but no more was used during the first 24 h of ECMO support. If necessary, as in patients undergoing single LTx for end-stage pulmonary hypertension, the ECMO support was directly extended into the postoperative period until reperfusion edema of the graft lung subsided. Twelve single LTxs and 3 bilateral sequential single LTxs were done under ECMO support. The advantages of using femoral ECMO rather than conventional CPB in LTx operations were the operative field was not disturbed by the bypass cannula, stable cardiopulmonary function and normothermia were maintained throughout the operations, there were less blood loss and transfusion requirements, and the left LTx was as easily performed as the right LTx. Red blood cell transfusion requirements during the operation and the first postoperative day were 4.4 +/- 2.8 and 2.4 +/- 2.0 U, respectively, in 10 adult patients undergoing uncomplicated single LTx with ECMO support, and 4.3 +/- 1.3 and 1.5 +/- 1.5 U in 8 adult patients undergoing single LTx without any extracorporeal circulatory support. The difference was not significant between the 2 groups (p = 0.53 and 0.32 by Mann-Whitney U test). The ECMO did not increase blood transfusion requirements. In comparison, 13 U of red blood cell transfusion was required in 2 patients receiving single LTx under CPB support. The ECMO support made the postoperative critical care easier in recipients with graft lung edema. Except for 2 cases of primary graft failure, the ECMO could be weaned off and removed at bedside within a short period (27.9 +/- 24.6 h, n = 13) with no major complications. In conclusion, the heparin-bound femoral ECMO rather than CPB should be used for LTx operations unless concomitant cardiac repair is planned.

Anesthesia for heart or single or double lung transplantation in the adult patient

Providing an anesthetic for patients undergoing heart or a single or double lung transplantation may represent a challenge even to the most experienced anesthesiologist. Patients with end-stage cardiac dysfunction have an impaired response to beta-agonist due to receptor downregulation. These patient will have isolated left ventricular dysfunction secondary to ischemic heart disease or present with biventricular failure with or without significant pulmonary hypertension. Increasingly, more patients have undergone prior major cardiac procedures and are at risk for significant perioperative bleeding. Patients undergoing single or double lung are particularly challenging because most of these procedures are performed without the aid of cardiopulmonary bypass. The anesthesiologist must be proficient at the management of one-lung ventilation techniques and have a rational physiologic approach to the management of intraoperative hypoxemia and auto-PEEP.

Experience with lung transplantation

BACKGROUND

On the basis of a 5-year experience with heart transplantation and long-term animal experimentation, a lung transplantation program was instituted in 1987. After 10 years of experience, the entire patient population was reviewed.

METHODS

Hospital records were reviewed to evaluate the underlying diagnosis, year of transplantation, type of procedure, and long-term follow-up. The changing scope of indications, procedures performed, and donor criteria, as well as survival data for various subgroups of high-risk candidates, were also examined.

RESULTS

A total of 283 heart-lung (n = 46), single-lung (n = 94), and bilateral lung transplantation procedures (n = 143) were performed, with 22 patients undergoing 24 retransplantation procedures. The overall 5-year survival rate was 63%, with no difference between types of operations. Patients with cystic fibrosis, emphysema, pulmonary fibrosis, and secondary pulmonary hypertension showed similar survival rates; primary pulmonary hypertension was associated with a lower long-term survival. In all groups, the bronchiolitis obliterans syndrome occurred at a rate of approximately 15%/year.

CONCLUSIONS

Acceptable long-term results can be obtained with lung transplantation. Because of expanded indications, no survival benefit was gained in the overall population over a 10-year period. The major obstacle to true long-term survival remains the bronchiolitis obliterans syndrome.