Donor ventilation parameters as predictors for length of mechanical ventilation after lung transplantation: Results of a prospective multicenter study

Lung donor bronchoalveolar lavage positivity: Incidence, risk factors, and lung transplant recipients' outcome

BACKGROUND

Inconsistent data exists regarding the risk factors for bronchoalveolar lavage (BAL) positivity in lung donors, the incidence of donor-derived infections (DDI), and the effect of BAL positivity on lung transplant (LuTx) recipients' outcome.

METHODS

A retrospective analysis was conducted on consecutive LuTx at a single center from January 2016 to December 2022. Donors' data, including characteristics, graft function and BAL samples were collected pre-procurement. Recipients underwent BAL before LuTx and about the 3rd, 7th and 14th day after LuTx. A DDI was defined as BAL positivity (bacterial growth ≥104 colony forming units) for identical bacterial species between donor and recipient. Recipients' pre-operative characteristics, intra-operative management, and post-operative outcomes were assessed. Two recipient cohorts were identified based on lung colonization status before undergoing LuTx.

RESULTS

Out of 188 LuTx procedures performed, 169 were analyzed. Thirty-six percent of donors' BAL tested positive. Donors' characteristics and graft function at procurement were not associated with BAL positivity. Fourteen DDI were detected accounting for 23% of recipients receiving a graft with a positive BAL. Only among uncolonized recipients, receiving a graft with positive BAL is associated with higher likelihood of requiring invasive ventilation at 72 hours after LuTx on higher positive end-expiratory pressure levels having lower PaO2/FiO2, prolonged duration of mechanical ventilation and longer ICU stay. No difference in hospital length of stay was observed.

CONCLUSIONS

Receiving a graft with a positive BAL, which is poorly predicted by donors' characteristics, carries the risk of developing a DDI and is associated to a worse early graft function among uncolonized recipients.

Mechanical Power Density Predicts Prolonged Ventilation Following Double Lung Transplantation

Prolonged mechanical ventilation (PMV) after lung transplantation poses several risks, including higher tracheostomy rates and increased in-hospital mortality. Mechanical power (MP) of artificial ventilation unifies the ventilatory variables that determine gas exchange and may be related to allograft function following transplant, affecting ventilator weaning. We retrospectively analyzed consecutive double lung transplant recipients at a national transplant center, ventilated through endotracheal tubes upon ICU admission, excluding those receiving extracorporeal support. MP and derived indexes assessed up to 36 h after transplant were correlated with invasive ventilation duration using Spearman's coefficient, and we conducted receiver operating characteristic (ROC) curve analysis to evaluate the accuracy in predicting PMV (>72 h), expressed as area under the ROC curve (AUROC). PMV occurred in 82 (35%) out of 237 cases. MP was significantly correlated with invasive ventilation duration (Spearman's ρ = 0.252 [95% CI 0.129-0.369], p < 0.01), with power density (MP normalized to lung-thorax compliance) demonstrating the strongest correlation (ρ = 0.452 [0.345-0.548], p < 0.01) and enhancing PMV prediction (AUROC 0.78 [95% CI 0.72-0.83], p < 0.01) compared to MP (AUROC 0.66 [0.60-0.72], p < 0.01). Mechanical power density may help identify patients at risk for PMV after double lung transplantation.

Expanding Donor Options for Lung Transplant: Extended Criteria, Donation After Circulatory Death, ABO Incompatibility, and Evolution of Ex Vivo Lung Perfusion

Only using brain-dead donors with standard criteria, the existing donor shortage has never improved in lung transplantation. Currently, clinical efforts have sought the means to use cohorts of untapped donors, such as extended criteria donors, donation after circulatory death, and donors that are ABO blood group incompatible, and establish the evidence for their potential contribution to the lung transplant needs. Also, technical maturation for using those lungs may eliminate immediate concerns about the early posttransplant course, such as primary graft dysfunction or hyperacute rejection. In addition, recent clinical and preclinical advances in ex vivo lung perfusion techniques have allowed the safer use of lungs from high-risk donors and graft modification to match grafts to recipients and may improve posttransplant outcomes. This review summarizes recent trends and accomplishments and future applications for expanding the donor pool in lung transplantation.

Limitations of arterial partial pressure of oxygen to fraction of inspired oxygen ratio for the evaluation of donor lung function

BACKGROUND

Evaluation of donor lung function relies on the arterial oxygen partial pressure to inspired oxygen fraction ratio (PaO₂ /FiO₂ ) measurement. Hemodynamic, metabolic derangements, and therapeutic intervention occurring during brain dead observation may influence the evaluation of gas exchange.

METHODS

We performed a mathematical analysis to explore the influence of the extrapulmonary determinants on the interpretation of PaO₂ /FiO₂ in the brain-dead donor and during Ex-Vivo Lung Perfusion (EVLP).

RESULTS

High FiO₂ and increased mixed venous oxygen saturation, caused by increased delivery and reduced consumption of oxygen, raise the PaO₂ /FiO₂ despite substantial intrapulmonary shunt. Anemia does not modify the PaO₂ /FiO₂ -intrapulmonary shunt relationship. During EVLP, the reduced artero-venous difference in oxygen content increases the PaO₂ /FiO₂ without this corresponding to an optimal graft function, while the reduced perfusate oxygen-carrying capacity linearizes the PaO₂ /FiO₂ -intrapulmonary shunt relationship.

CONCLUSIONS

Adopting PaO₂ /FiO₂ to evaluate graft suitability for transplantation should account for extrapulmonary factors affecting its interpretation.

The role of mechanical ventilation in primary graft dysfunction in the postoperative lung transplant recipient: A single center study and literature review

Background

Primary graft dysfunction (PGD) is still a major complication in patients undergoing lung transplantation (LTx). Much is unknown about the effect of postoperative mechanical ventilation on outcomes, with debate on the best approach to ventilation.

Aim/Purpose

The goal of this study was to generate hypotheses on the association between postoperative mechanical ventilation settings and allograft size matching in PGD development.

Method

This is a retrospective study of LTx patients between September 2011 and September 2018 (n = 116). PGD was assessed according to the International Society of Heart and Lung Transplantation (ISHLT) criteria. Data were collected from medical records, including chest x‐ray assessments, blood gas analysis, mechanical ventilator parameters and spirometry.

Results

Positive end‐expiratory pressures (PEEP) of 5 cm H₂O were correlated with lower rates of grade 3 PGD. Graft size was important as tidal volumes calculated according to the recipient yielded greater rates of PGD when low volumes were used, a correlation that was lost when donor metrics were used.

Conclusion

Our results highlight a need for greater investigation of the role donor characteristics play in determining post‐operative ventilation of a lung transplant recipient. The mechanical ventilation settings on postoperative LTx recipients may have an implication for the development of acute graft dysfunction. Severe PGD was associated with the use of a PEEP higher than 5 and lower tidal volumes and oversized lungs were associated with lower long‐term mortality. Lack of association between ventilatory settings and survival may point to the importance of other variables than ventilation in the development of PGD.

Double Lung Transplantation Bridged With Direct Central Ambulatory Veno-Arterial Extracorporeal Membrane Oxygenation in a Pulmonary Hypertension Patient With Extreme Mediastinal Shift

Lung transplantation is increasingly being performed for end-stage lung disease in patients with bronchiectasis and pulmonary hypertension. Outcomes of bilateral lung transplantation (BLT) are better in patients with pulmonary hypertension, whereas single lung transplant remains a controversy in bronchiectasis with fear of infections from the residual diseased lung. However, in patients with adhesions and extreme structural changes due to severe disease, BLT may be considered technically challenging. We describe a case of successful management of a patient with bronchiectasis-induced lung disease causing extreme mediastinal shift with a BLT. The patient was successfully bridged to transplant with central veno-arterial extracorporeal membrane oxygenation (VA-ECMO) for acute decompensated pulmonary hypertension while awaiting transplantation.

Predicting donor lung acceptance for transplant during ex vivo lung perfusion: The EX vivo lung PerfusIon pREdiction (EXPIRE)

Ex vivo lung perfusion (EVLP) has being increasingly used for the pretransplant assessment of extended-criteria donor lungs. Mathematical models to predict lung acceptance during EVLP have not been reported so far. Thus, we hypothesized that predictors of lung acceptance could be identified and used to develop a mathematical model describing the clinical decision-making process used in our institution. Donor lungs characteristics and EVLP physiologic parameters included in our EVLP registry were examined (derivation cohort). Multivariable logistic regression analysis was performed to identify predictors independently associated with lung acceptance. A mathematical model (EX vivo lung PerfusIon pREdiction [EXPIRE] model) for each hour of EVLP was developed and validated using a new cohort (validation cohort). Two hundred eighty donor lungs were assessed with EVLP. Of these, 186 (66%) were accepted for transplantation. ΔPO₂ and static compliance/total lung capacity were identified as independent predictors of lung acceptance and their respective cut-off values were determined. The EXPIRE model showed a low discriminative power at the first hour of EVLP assessment (AUC: 0.69 [95% CI: 0.62-0.77]), which progressively improved up to the fourth hour (AUC: 0.87 [95% CI: 0.83-0.92]). In a validation cohort, the EXPIRE model demonstrated good discriminative power, peaking at the fourth hour (AUC: 0.85 [95% CI: 0.76-0.94]). The EXPIRE model may help to standardize lung assessment in centers using the Toronto EVLP technique and improve overall transplant rates.

The Year in Cardiothoracic Transplant Anesthesia: Selected Highlights From 2020 Part I - Lung Transplantation

This special article focuses on the highlights in cardiothoracic transplantation literature in the year 2020. Part I encompasses the recent literature on lung transplantation, including the advances in preoperative assessment and optimization, donor management, including the use of ex-vivo lung perfusion, recipient management, including those who have been infected with coronavirus disease 2019, updates on the perioperative management, including the use of extracorporeal membrane oxygenation, and long-term outcomes.