COVID19 in Lung Transplanted Patients: Chronicles from an Italian Epicenter

Purpose

Lombardy was one of the hardest hit regions in Italy during the COVID19 pandemic. We hereby report our experience with SARS-CoV2 infection in lung transplant recipients.

Methods

We retrospectively collected clinical data on all the consecutive cases of COVID19 in our centre, based in Milan, from March 2020 to August 2021. Diagnosis was always confirmed by a positive nucleic acid amplification test (RT-PCR) for SARS-CoV-2 on nasopharyngeal swab and/or tracheal aspirate.

Results

21 patients were diagnosed with COVID19. Figure 1 summarizes the clinical course of these individuals. We reduced immunosuppressive regimen in all these patients, typically holding the antiproliferative agent and augmenting steroids; when hospitalized, everybody received initial empiric antibiotic treatment with piperacillin/tazobactam and high-dose LMWH. Hydroxychloroquine was used only in the "first wave" (4 patients). One patient was compassionately administered anakinra and remdesivir as a “rescue therapy”. Lymphocitopenia was a common presenting sign (14 patients, 66%). Aspergillus co-infection occurred in 5 patients (24%). Mortality rate was 29%; 4 out of these 6 patients were affected by CLAD and 3 had chronic kidney disease. Of note, in March 2021, we tested all our patients for anti-SARS-CoV-2 nucleocapsid antibodies before starting vaccinations: we found three additional seropositive patients, who were not included in the present analysis, but had been presumably affected by an asymptomatic/mild form of the disease.

Conclusion

Apart from immunosuppression, the majority of our patients presented at least one risk factor for mortality in COVID-19 (diabetes, chronic kidney disease, arterial hypertension) and, for this reason, we felt that they should be hospitalized to enable close monitoring and prompt management of possible complications and deterioration. Clinical course seemed favorable in only two thirds of our patients but, for the time being, none of these individuals showed sign of new-onset CLAD after COVID19.

Effects of bilateral lung transplantation on cardiac autonomic modulation and cardiorespiratory coupling: a prospective study

Background

Although cardiac autonomic modulation has been studied in several respiratory diseases, the evidence is limited on lung transplantation, particularly on its acute and chronic effects. Thus, we aimed to evaluate cardiac autonomic modulation before and after bilateral lung transplantation (BLT) through a prospective study on patients enrolled while awaiting transplant.

Methods

Twenty-two patients on the waiting list for lung transplantation (11 women, age 33 [24–51] years) were enrolled in a prospective study at Ospedale Maggiore Policlinico Hospital in Milan, Italy. To evaluate cardiac autonomic modulation, ten minutes ECG and respiration were recorded at different time points before (T0) and 15 days (T1) and 6 months (T2) after bilateral lung transplantation. As to the analysis of cardiac autonomic modulation, heart rate variability (HRV) was assessed using spectral and symbolic analysis. Entropy-derived measures were used to evaluate complexity of cardiac autonomic modulation. Comparisons of autonomic indices at different time points were performed.

Results

BLT reduced HRV total power, HRV complexity and vagal modulation, while it increased sympathetic modulation in the acute phase (T1) compared to baseline (T0). The HRV alterations remained stable after 6 months (T2).

Conclusion

BLT reduced global variability and complexity of cardiac autonomic modulation in acute phases, and these alterations remain stable after 6 months from surgery. After BLT, a sympathetic predominance and a vagal withdrawal could be a characteristic autonomic pattern in this population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12931-021-01752-6.

Lung Transplantation for Acute Respiratory Distress Syndrome Related to COVID-19: The Lesson Learned from the First Two Cases

Purpose

The respiratory system, and namely the lung, is undoubtedly the preferential target of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The clinical pictures are extremely various, up to the intensive care unit (ICU) admission for acute respiratory distress syndrome (ARDS). Lung transplantation (LT) is a consolidate therapeutic option for end-stage chronic respiratory diseases. Its role in an acute setting is questionable, particularly due to lack of experiences, donor shortage, and the difficulty to fully evaluate the potential recipient. We report our preliminary experience with the first two cases of LT for SARS-CoV-2 related ARDS, trying to provide some food for thought.

Methods

We retrospectively analysed our first two cases of bilateral LT for ARDS after COVID-19. We recorded data on pre-transplantation clinical course, transplantation management and outcomes.

Results

The two patients had a similar clinical evolution of COVID-19. Transplantations were successful in both cases; the first patient is alive and in good condition 5 months after transplantation, while the second died 62 days after surgery. Table 1 shows clinical details and relevant time-points.

Conclusion

Our experience showed that LT for COVID-19 is feasible. Importantly, observing a dedicated protocol made the procedure safe for the healthcare staff involved. On the other hand, our second unsuccessful case poses relevant questions: first of all, lung transplantation should be reserved to highly selected patient, after careful clinical, infective as well as psychiatric evaluation. The ethical aspects should also be considered in this situation, with regard to the centre rate mortality on waiting list. Anyway, the potential role of LT in the acute and sub-acute/chronic settings suggests the need for maintaining LT centre active during pandemic. Finally, COVID-19, once more, imposes to share clinical experiences.

Lung Allograft Dysfunction in a COVID-19 Transplanted Patient is Associated with a Peculiar Immunopathological Phenotype

Purpose

Lung transplantation (LT) after severe SARS-CoV-2 infection is emerging as a life-saving medical procedure for selected patients who experience acute respiratory distress syndrome (ARDS). We present the first immunopathological evaluation of a lung allograft rejection in a patient who underwent LT because of irreversible ARDS related to COVID-19.

Methods

Two male patients with irreversible ARDS caused by COVID-19 underwent bilateral LT at our Institution. A surveillance transbronchial biopsy (TBB) was performed 2 months after LT in the first patient (Pt#1), while the second patient (Pt#2) died because of allograft rejection at day 62 post LT and explanted lungs were retrieved. CT imaging of the lungs was performed three days before death. Morphological examination was performed by H&E, whereas the immunophenotyping was performed by immunohistochemistry.

Results

Imaging and morphological examination of Pt#2 lungs indicated the presence of a graft dysfunction with features of a restrictive, widespread usual interstitial pneumonia-like syndrome (Fig. 1A, B). The immunophenotyping showed that B-lymphocytes (CD20-positive) were nearly absent, CD8-T-cells were not particularly expanded (mean positive cells within the lung stroma=13.8%; Fig. 1C), and the CD4/CD8 ratio was not decreased (Fig. 1D). The T-regs (Foxp3-positive) were 6% of the overall population (Fig. 1E). Analysis of the immune checkpoint molecules PD1, Tigit, CTLA4 and PDL1 showed that the expression of PD-L1 alone was highly increased in vases and in alveolar cells of rejected lungs, whereas it was nearly undetectable in the TBB from Pt#1 (Fig. 1F, G).

Conclusion

PDL1 expression in vases was previously documented as a sign of indirect ARDS. Together with our preliminary data, we can hypothesize that PDL1 may play a role in tissue effacement and graft failure, possibly indicating poor allograft prognosis.

Evidence of Air Trapping During Ex Vivo Lung Perfusion: A Swine Experimental Lung Imaging and Mechanics Study

Ex vivo lung perfusion (EVLP) allows the ventilation and perfusion of lungs to evaluate their viability for transplantation. The aim of this study is to compare the mechanical, morphologic and functional properties of lungs during EVLP with values obtained in vivo to guide a safe mechanical ventilation strategy. Lungs from 5 healthy pigs were studied in vivo and during 4 hours of EVLP. Lung compliance, airway resistance, gas exchange, and hemodynamic parameters were collected at positive end-expiratory pressure (PEEP) of 5 cm H₂O. Computed tomography was performed at PEEP 0, PEEP 5, and total lung capacity (TLC). Lung pressure-volume (PV) curves were performed from PEEP 0 to TLC. Lung compliance decreased during EVLP (53 ± 5 mL/cm H₂O vs 29 ± 7 mL/cm H₂O, P < .05), and the PV curve showed a lower inflection point. Gas content (528 ± 118 mL vs 892 ± 402 mL at PEEP 0) and airway resistance (25 ± 5 vs 44 ± 9 cmH₂O/L∗s^-1, P < .05) were higher during EVLP. Alveolar dead space (5% ± 2% vs 17% ± 6%, P < .05) and intrapulmonary shunt (9% ± 2% vs 28% ± 13%, P < .05) increased ex vivo compared to in vivo, while the partial pressure of oxygen to inspired oxygen fraction ratio (PO₂/FiO₂) did not differ (468 ± 52 mm Hg vs 536 ± 14 mm Hg). In conclusion, during EVLP lungs show signs of air trapping and bronchoconstriction, resulting in low compliance and increased alveolar dead space. Intrapulmonary shunt is high despite oxygenation levels acceptable for transplantation.

Epstein-Barr Virus-Related Post-Transplant Lymphoproliferative Disorders in Cystic Fibrosis Lung Transplant Recipients: A Case Series

BACKGROUND

Solid organ transplantation is associated with a higher risk of Epstein-Barr virus (EBV)-related lymphoproliferative disease due to immunosuppressive regimen. Little evidence is currently available on post-transplant lymphoproliferative disorders (PTLDs) in the lung transplant (LuTx) setting, particularly in cystic fibrosis (CF) recipients.

METHODS

We retrospectively analyzed all the cases of PTLDs that occurred in our LuTx center between January 2015 and December 2017. We reviewed clinical and radiologic data, donor and recipient EBV serostatus, immunosuppressive therapy, histologic data, and follow-up of these patients.

RESULTS

A total of 77 LuTxs were performed at our center in the study period; 39 (50.6%) patients had CF; 4 developed EBV-related PTLDs. They were all young (17-26 years) CF patients with high serum EBV DNA load. Disease onset was within the first 3 months after LuTx. In 3 cases presentation was associated with fever and infection-like symptoms, whereas in 1 case radiologic suspicion arose unexpectedly from a CT scan performed for different clinical reasons. Diagnosis was reached through lung biopsy in all cases. All patients received rituximab, cyclophosphamide, doxorubicin hydrochloride (hydroxydaunomycin), vincristine sulfate (Oncovin), and prednisone with variable response and complications.

CONCLUSION

In our experience, the early development of EBV-related PTLD was a highly aggressive, life-threatening condition, which exclusively affected young CF patients in the early post-transplant period. The rate of this complication was relatively high in our population. Diagnosis with lung biopsy is crucial in all suspected cases and regular monitoring of EBV DNA levels is of utmost importance given the high correlation with PTLDs in patients at increased risk.

Lung Transplant From Donor With Tracheal Bronchus: Case Report and Literature Review

Donor lung abnormalities are quite rare; one of them is the presence of bronchial anomalies, whose incidence range is from 0.1% to 0.5%. The upper right tracheal bronchus is one of the most frequent anatomic variations. We present a case of successful double lung transplant in a young female patient affected by cystic fibrosis from a donor with upper right tracheal bronchus, emerging 2 rings before the tracheal carina. During implantation of the left lung, we performed a double apical segmentectomy on back table; therefore, the right lung was implanted with the standard technique. Four cases of graft transplant characterized by the presence of tracheal bronchus are reported in the scientific literature; the authors report 4 different technical solutions to tackle the problem of anatomic anomaly. We report the first case of graft segmentectomy at back table suggesting a simple, safe, and time-sparing procedure. In conclusion, provided that the team has sufficient skill in reductive surgery at the back table and the anthropometric data are permissive, we stress the opportunity to downsize the graft in order to minimize anastomotic risks and save time.

Surveillance Transbronchial Biopsy Program to Evaluate Acute Rejection After Lung Transplantation: A Single Institution Experience

BACKGROUND

There is no unanimity in the literature regarding the value of transbronchial biopsies (TBBs) performed at a scheduled time after lung transplantation (surveillance TBBs [SBs]), compared to biopsies performed for suspected clinical acute rejection (clinically indicated TBBs [CIBs]). This study exposes an assessment of our experience over the last 4 years through a retrospective analysis of the data collected.

METHODS

In our center, SBs are performed at 3, 6, and 12 months after a transplant. Data from 110 patients who underwent a TBB were collected from January 2013 to November 2017. Clinical and functional data along with the histologic results and complications were collected.

RESULTS

Overall 251 procedures were performed: 223 for surveillance purposes and 28 for clinical indications. The SBs diagnostic rate was 84%. A grade 2 acute rejection (AR) was detected in 9 asymptomatic patients, all of whom were medically treated, with downgrading of AR documented in all cases. The rate of medical intervention in the SB group was 8%. The CIBs diagnostic rate was 96%. The rate of AR detected by CIBs was significantly higher than by SBs (36% versus 4%; P < .0001). Overall the major complication rate was 4%; no patients required transfusions and no mortality occurred in the patient cohort.

CONCLUSIONS

The surveillance protocol did not eliminate the necessity of CIBs, but in 8% of patients early rejection was histologically assessed. The correlation between histologic and clinical data allows a more careful approach to transplanted patients.

Acute induction of anxiety in humans by delta-9-tetrahydrocannabinol related to amygdalar cannabinoid-1 (CB1) receptors

Use of Cannabis, the most widely used illicit drug worldwide, is associated with acute anxiety, and anxiety disorders following regular use. The precise neural and receptor basis of these effects have not been tested in man. Employing a combination of functional MRI (fMRI) and positron emission tomography (PET), we investigated whether the effects of delta-9-tetrahydrocannabinol (delta-9-THC), the main psychoactive ingredient of cannabis, on anxiety and on amygdala response while processing fearful stimuli were related to local availability of its main central molecular target, cannabinoid-1 (CB1) receptors in man. Fourteen healthy males were studied with fMRI twice, one month apart, following an oral dose of either delta-9-THC (10 mg) or placebo, while they performed a fear-processing task. Baseline availability of the CB1 receptor was studied using PET with [11C]MePPEP, a CB1 inverse agonist radioligand. Relative to the placebo condition, delta-9-THC induced anxiety and modulated right amygdala activation while processing fear. Both these effects were positively correlated with CB1 receptor availability in the right amygdala. These results suggest that the acute effects of cannabis on anxiety in males are mediated by the modulation of amygdalar function by delta-9-THC and the extent of these effects are related to local availability of CB1 receptors.

Test-retest reproducibility of quantitative binding measures of [11C]Ro15-4513, a PET ligand for GABAA receptors containing alpha5 subunits

INTRODUCTION

Alteration of γ-aminobutyric acid "A" (GABA_A) receptor-mediated neurotransmission has been associated with various neurological and psychiatric disorders. [¹¹C]Ro15-4513 is a PET ligand with high affinity for α5-subunit-containing GABA_A receptors, which are highly expressed in limbic regions of the human brain (Sur et al., 1998). We quantified the test-retest reproducibility of measures of [¹¹C]Ro15-4513 binding derived from six different quantification methods (12 variants).

METHODS

Five healthy males (median age 40 years, range 38-49 years) had a 90-min PET scan on two occasions (median interval 12 days, range 11-30 days), after injection of a median dose of 441 MegaBequerels of [¹¹C]Ro15-4513. Metabolite-corrected arterial plasma input functions (parent plasma input functions, ppIFs) were generated for all scans. We quantified regional binding using six methods (12 variants), some of which were region-based (applied to the average time-activity curve within a region) and others were voxel-based: 1) Models requiring arterial ppIFs - regional reversible compartmental models with one and two tissue compartments (2kbv and 4kbv); 2) Regional and voxelwise Logan's graphical analyses (Logan et al., 1990), which required arterial ppIFs; 3) Model-free regional and voxelwise (exponential) spectral analyses (SA; (Cunningham and Jones, 1993)), which also required arterial ppIFs; 4) methods not requiring arterial ppIFs - voxelwise standardised uptake values (Kenney et al., 1941), and regional and voxelwise simplified reference tissue models (SRTM/SRTM2) using brainstem or alternatively cerebellum as pseudo-reference regions (Lammertsma and Hume, 1996; Gunn et al., 1997). To compare the variants, we sampled the mean values of the outcome parameters within six bilateral, non-reference grey matter regions-of-interest. Reliability was quantified in terms of median absolute percentage test-retest differences (MA-TDs; preferentially low) and between-subject coefficient of variation (BS-CV, preferentially high), both compounded by the intraclass correlation coefficient (ICC). These measures were compared between variants, with particular interest in the hippocampus.

RESULTS

Two of the six methods (5/12 variants) yielded reproducible data (i.e. MA-TD <10%): regional SRTMs and voxelwise SRTM2s, both using either the brainstem or the cerebellum; and voxelwise SA. However, the SRTMs using the brainstem yielded a lower median BS-CV (7% for regional, 7% voxelwise) than the other variants (8-11%), resulting in lower ICCs. The median ICCs across six regions were 0.89 (interquartile range 0.75-0.90) for voxelwise SA, 0.71 (0.64-0.84) for regional SRTM-cerebellum and 0.83 (0.70-0.86) for voxelwise SRTM-cerebellum. The ICCs for the hippocampus were 0.89 for voxelwise SA, 0.95 for regional SRTM-cerebellum and 0.93 for voxelwise SRTM-cerebellum.

CONCLUSION

Quantification of [¹¹C]Ro15-4513 binding shows very good to excellent reproducibility with SRTM and with voxelwise SA which, however, requires an arterial ppIF. Quantification in the α5 subunit-rich hippocampus is particularly reliable. The very low expression of the α5 in the cerebellum (Fritschy and Mohler, 1995; Veronese et al., 2016) and the substantial α1 subunit density in this region may hamper the application of reference tissue methods.

Lung Allocation Score: A Single-Center Simulation

BACKGROUND

The lung allocation score (LAS) was introduced in the United States in May 2005 with the main goal of reducing the waiting list mortality of patients with end-stage lung diseases, but also to enhance the lung transplant benefit and improve the management of urgent candidates. Several papers have reported that LAS resulted in a reduction of the waiting list mortality but no significant survival benefit was noted.

METHODS

We evaluate the usefulness of LAS as a predictor for lung transplantation outcome in 123 patients listed for lung transplantation in an Italian center. Primary endpoints were waiting list mortality and posttransplant mortality at 1 year; secondary endpoints included perioperative circulatory support, cardiopulmonary bypass, primary graft dysfunction, and long-term survival after transplantation.

RESULTS

We observed the absence of correlation between LAS and waiting list mortality. The LAS did not affect the long-term survival in our population.

CONCLUSIONS

High LAS was predictive of primary graft dysfunction of grade 3 in the first 72 hours after transplantation.

Using [(11)C]Ro15 4513 PET to characterise GABA-benzodiazepine receptors in opiate addiction: Similarities and differences with alcoholism

The importance of the GABA-benzodiazepine receptor complex and its subtypes are increasingly recognised in addiction. Using the α1/α5 benzodiazepine receptor PET radioligand [¹¹C]Ro15 4513, we previously showed reduced binding in the nucleus accumbens and hippocampus in abstinent alcohol dependence. We proposed that reduced [¹¹C]Ro15 4513 binding in the nucleus accumbens was a marker of addiction whilst the reduction in hippocampus and positive relationship with memory was a consequence of chronic alcohol abuse. To examine this further we assessed [¹¹C]Ro15 4513 binding in another addiction, opiate dependence, and used spectral analysis to estimate contributions of α1 and α5 subtypes to [¹¹C]Ro15 4513 binding in opiate and previously acquired alcohol-dependent groups. Opiate substitute maintained opiate-dependent men (n = 12) underwent an [¹¹C]Ro15 4513 PET scan and compared with matched healthy controls (n = 13). We found a significant reduction in [¹¹C]Ro15 4513 binding in the nucleus accumbens in the opiate-dependent compared with the healthy control group. There was no relationship between [¹¹C]Ro15 4513 binding in the hippocampus with memory. We found that reduced [¹¹C]Ro15 4513 binding was associated with reduced α5 but not α1 subtypes in the opiate-dependent group. This was also seen in an alcohol-dependent group where an association between memory performance and [¹¹C]Ro15 4513 binding was primarily driven by α5 and not α1 subtype. We suggest that reduced α5 levels in the nucleus accumbens are associated with addiction since we have now shown this in dependence to two pharmacologically different substances, alcohol and opiates.

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Lower [¹¹C]Ro15 4513 binding is evident in the nucleus accumbens of opiate addicts.

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This appears primarily due to lower levels of α5 subtype of the GABA-A receptor.

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Lower [¹¹C]Ro15 4513 binding is similarly found in alcoholism.

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Lower levels of α5 GABA-A receptor in nucleus accumbens may underpin addiction.

Graft downsizing during ex vivo lung perfusion: case report and technical notes

Among patients with respiratory insufficiency awaiting lung transplantation, small adult patients have a lower opportunity of receiving size-matched pulmonary grafts, because of the shortage of donors, particularly those of small size. Reducing the size of an oversized graft is one of the methods to increase the donor pool; similarly, ex vivo lung perfusion is an emerging technique aimed toward the same purpose. We describe how we combined the 2 techniques (lobar transplantation plus contralateral nonanatomic graft reduction during ex vivo lung perfusion) to overcome graft shortage in a clinical case. For the 1st time, this case report demonstrates that surgical manipulation during ex vivo lung perfusion does not affect the functional improvement in a lung previously judged to be not suitable for transplantation. The 6-month follow-up results are similar to those of standard bilateral lung transplantation.

Clinical risk factors for primary graft dysfunction in a low-volume lung transplantation center

Primary graft dysfunction (PGD) is a severe acute lung injury syndrome following lung transplantation. Previous studies of clinical risk factors, including a multicenter prospective cohort trial, have identified a number of recipient, donor, and operative variables related to Grade 3 PGD. The aim of this study was to validate these risk factors in a lung transplantation center with a low volume of procedures. We conducted a retrospective cohort study of 45 consecutive lung transplantations performed between January 2011 and September 2013. PGD was defined according to the International Society for Heart and Lung Transplantation grading scale. Risk factors were evaluated independently and the significant confounders entered into multivariable logistic regression models. The overall incidence of Grade 3 PGD was 35.5% at T24, 17.7% at T48, and 15.5% at T72. The following risk factors were associated with Grade 3 PGD at the indicated time points: recipient female gender at T24 (P=.034), mixed diagnoses at T72 (P=.047), ECMO bridge-to-lung transplantation at T24 (P=.0004) and at T48 (P=.038), donor causes of death different from stroke and trauma at T24 (P=.019) and T72 (P=.014), blood transfusions during surgery at T24 (P=.001), intraoperative venoarterial ECMO T24 (P<.0001). Multivariate analysis at T24 identified recipient female gender and intraoperative venoarterial ECMO as risk factors (P=.010 and P=.018, respectively). This study demonstrated that risk factors for severe PGD in a low-volume center were similar to international reports in prevalence and type. ECMO bridge-to-lung transplantation emerged as a risk factor previously underestimated.

Particulate matter phagocytosis induces tissue factor in differentiating macrophages

Airborne exposure to particulate matter with diameter < 10 mcM (PM10) has been linked to an increased risk of thromboembolic events, but the mechanisms are not completely understood. The aim of this study was to evaluate the effect of PM10 phagocytosis on the release of procoagulant molecules in human differentiating macrophages, and that of PM10 inhalation in an experimental model in rats. Human monocytes were separated from the peripheral blood by the lymphoprep method, differentiated in vitro and treated with standard PM10 or vehicle. Sprague-Dawley rats were instilled intratracheally with PM10 or vehicle alone. The outcome was expression of proinflammatory genes and of tissue factor (TF). In human differentiating macrophages, PM10 exposure upregulated inflammatory genes, but most consistently induced TF mRNA and protein levels, but not TF protein inhibitor, resulting in increased TF membrane expression and a procoagulant phenotype. Differentiation towards the anti-inflammatory M2 phenotype inhibited PM10 -mediated TF expression. TF induction required phagocytosis of PM10 , whereas phagocytosis of inert particles was less effective. PM10 phagocytosis was associated with a gene expression profile consistent with intracellular retention of iron, inducing oxidative stress. Both PM10 and iron activated the stress kinases ERK1/2 pathway, involved in the induction of TF expression. In rats, alveolar exposure to PM10 was associated with pulmonary recruitment of inflammatory cells and resulted in local, but not systemic, induction of TF expression, which was sufficient to increase circulating TF levels. In conclusion, TF induction by differentiating lung macrophages, activated following phagocytosis, contributes to the increased risk of thromboembolic complications associated with PM10 exposure.

Test-retest reproducibility of cannabinoid-receptor type 1 availability quantified with the PET ligand [¹¹C]MePPEP

Background

Endocannabinoids are involved in normal cognition, and dysfunction in cannabinoid-receptor-mediated neurotransmission has been suggested in a variety of neurological and psychiatric pathologies. The type 1 cannabinoid receptor (CB₁) is widely expressed in the human central nervous system. The objective of this study was to quantify the test–retest reproducibility of measures of the PET ligand [¹¹C]MePPEP in order to assess the stability of CB₁-receptor quantification in humans in vivo.

Methods

Fifteen healthy subjects (eight females; median age 32 years, range 25 to 65 years) had a 90-minute PET scan on two occasions after injection of a median dose of [¹¹C]MePPEP of 364 MBq. Metabolite-corrected arterial plasma input functions were obtained for all scans. Eight ROIs, reflecting different levels of receptor densities/concentrations, were defined automatically: hippocampus, anterior cingulate gyrus, inferior frontal gyrus, caudate nucleus, globus pallidus, nucleus accumbens, thalamus, and pons. We used seven quantification methods: reversible compartmental models with one and two tissue classes, two and four rate constants, and a variable blood volume term (2kbv; 4kbv); model-free (spectral) analyses with and without regularisation, including one with voxel-wise quantification; the simplified reference tissue model (SRTM) with pons as a pseudo-reference region; and modified standard uptake values (mSUVs) calculated for the period of ~ 30–60 min after injection. Percentage test–retest change and between-subject variability were both assessed, and test–retest reliability was quantified by the intraclass correlation coefficient (ICC). The ratio of binding estimates pallidum:pons served as an indicator of a method's ability to reflect binding heterogeneity.

Results

Neither the SRTM nor the 4kbv model produced reliable measures, with ICCs around zero. Very good (> 0.75) or excellent (> 0.80) ICCs were obtained with the other methods. The most reliable were spectral analysis parametric maps (average across regions ± standard deviation 0.83 ± 0.03), rank shaping regularised spectral analysis (0.82 ± 0.05), and the 2kbv model (0.82 ± 0.09), but mSUVs were also reliable for most regions (0.79 ± 0.13). Mean test–retest changes among the five well-performing methods ranged from 12 ± 10% for mSUVs to 16% for 2kbv. Intersubject variability was high, with mean between-subject coefficients of variation ranging from 32 ± 13% for mSUVs to 45% for 2kbv. The highest pallidum:pons ratios of binding estimates were achieved by mSUV (4.2), spectral analysis-derived parametric maps (3.6), and 2kbv (3.6).

Conclusion

Quantification of CB₁ receptor availability using [¹¹C]MePPEP shows good to excellent reproducibility with several kinetic models and model-free analyses, whether applied on a region-of-interest or voxelwise basis. Simple mSUV measures were also reliable for most regions, but do not allow fully quantitative interpretation. [¹¹C]MePPEP PET is well placed as a tool to investigate CB₁-receptor mediated neurotransmission in health and disease.

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[11C]MePPEP is a PET tracer for cannabinoid receptors (CB1R).

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Extensive evaluation of [11C]MePPEP data quantification strategies in large sample

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We highlight successful methods to quantify CB1R in regions of interest.

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Highly reliable parametric maps (ICC 0.83 ± 0.03) allow whole-brain surveys.

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Modified standard uptake values also reliable, without arterial input functions

Lung transplantation and posterior reversible encephalopathy syndrome: a case series

Posterior reversible encephalopathy syndrome is a neurological problem characterized by headache, altered mental status, focal neurological deficits, visual disorders, and seizures. The disorder is related to a number of diseases including calcineurin inhibitor therapy in solid organ transplantation. The incidence of posterior reversible encephalopathy syndrome in lung transplantation patients is unclear; probably the majority of the cases are unreported. The authors have described a case series constituted of four patients presenting posterior reversible encephalopathy syndrome after bilateral lung transplantation. The cases had in common complicated surgery and a posttransplant course characterized by hypertension, hypomagnesemia and acidosis. Invasive mechanical ventilation, calcineurin inhibitor discontinuation, aggressive antihypertensive therapy, and electrolyte regulation led to near complete recovery of symptoms.

Extracorporeal lung perfusion and ventilation to improve donor lung function and increase the number of organs available for transplantation

INTRODUCTION

Ex vivo lung perfusion (EVLP) has been validated as a valuable technique to increase the pool of organs available for lung transplantation.

MATERIAL AND METHODS

After a preclinical experience, we obtained permission from the Ethics Committee of our institution to transplant lungs after EVLP reconditioning. ABO compatibility, size match, and donor arterial oxygen pressure (PaO(2))/fraction of inspired oxygen (FiO(2)) ≤ 300 mm Hg were considered to be inclusion criteria, whereas the presence of chest trauma and lung contusion, evidence of gastric content aspiration, pneumonia, sepsis, or systemic disease were exclusion criteria. We only considered subjects on an extra corporeal membrane oxygenation (ECMO) bridge to transplantation with rapid functional deterioration. Using Steen solution with packed red blood cells oxygenated with 21% O(2), 5% to 7% CO(2) was delivered, targeted with a blood flow of approximately 40% predicted cardiac output. Once normothermic, the lungs were ventilated with a tidal volume of 7 mL/kg a PEEP of 5 cmH(2)O and a respiratory rate of 7 bpm. Lungs were considered to be suitable for transplantation if well oxygenated [P(v-a) O(2) > 350 mm Hg on FiO(2) 100%], in the absence of deterioration of pulmonary vascular resistance and lung mechanics over the perfusion time.

RESULTS

From March to September 2011, six lung transplantations were performed, including two with EVLP. The functional outcomes were similar between groups: at T72 posttransplantation, the median PaO(2)/FiO(2) were 306 mm Hg (range, 282 to 331 mm Hg) and 323 mm Hg (range, 270 to 396 mm Hg) (P = 1, EVLP versus conventional). Intensive care unit ICU and hospital length of stay were similar (P = .533 and P = .663, respectively) with no mortality at 60 days in both groups. EVLP donors were older (49 ± 6 y versus 21 ± 7 y, P < .05), less well oxygenated (184 ± 6 mm Hg versus 570 ± 30, P < .05), displaying higher Oto scores (9.5 ± 0.7 versus 1.7 ± 1.5, P < .05).

CONCLUSIONS

The first 6 months of the EVLP program allowed us to increase the number of organs available for transplantation with short-term outcomes comparable to conventional transplantations.