Evaluating and developing sealants for the prevention of pulmonary air leakage: A systematic review of animal models

Sealants may provide a solution for pulmonary air leakage (PAL), but their clinical application is debatable. For sealant comparison, standardized animal models are lacking. This systematic review aims to assess methodology and quality of animal models for PAL and sealant evaluation. All animal models investigating lung sealing devices (e.g., staplers, glues, energy devices) to prevent or treat PAL were retrieved systematically from Embase, Pubmed and Web of science. Methodological study characteristics, risk of bias, reporting quality and publication bias were assessed. A total of 71 studies were included (N  =  75 experiments, N  =  1659 animals). Six different species and 18 strains were described; 92% of experiments used healthy animals, disease models were used in only six studies. Lesions to produce PAL were heterogenous, and only 11 studies used a previously reported technique, encompassing N  =  5 unique lesions. Clinically relevant outcomes were used in the minority of studies (imaging 16%, air leak 10.7%, air leak duration 4%). Reporting quality was poor, but revealed an upward trend per decade. Overall, high risk of bias was present, and only 18.7% used a negative control group. All but one study without control groups claimed positive outcomes (95.8%), in contrast to 84.3% using positive or negative control groups, which also concluded equivocal, adverse or inconclusive outcomes. In conclusion, animal studies evaluating sealants for prevention of PAL are heterogenous and of poor reporting quality. Using negative control groups, disease models and quantifiable outcomes seem important to increase validity and relevance. Further research is needed to reach consensus for model development and standardization.

Intrinsic pulmonary sealing, its mechanisms and impact on validity and translational value of lung sealant studies: a pooled analysis of animal studies

Background

No validated and standardized animal models of pulmonary air leakage (PAL) exist for testing aerostatic efficacy of lung sealants. Lack of negative control groups in published studies and intrinsic sealing mechanisms of healthy animal lungs might contribute to a translational gap, leading to poor clinical results. This study aims to address the impact of intrinsic sealing mechanisms on the validity of PAL models, and investigate the conditions required for an ovine model of PAL for lung sealant testing.

Methods

An ovine acute aerostasis model was developed, consisting of a bilateral thoracotomy with lesion creation, chest tube insertion and monitoring of air leaks using digital drains (≥80 minutes), under spontaneous respiration. Healthy mixed-breed adult female sheep were used and all in vivo procedures were performed under terminal anesthesia. Superficial parenchymal lesions were tested post-mortem and in vivo, extended lesions including bronchioles (deep bowl-shaped and sequential lung amputation lesions) were tested in vivo. Experiment outcomes include air leakage (AL), minimal leaking pressure (MLP) and histology.

Results

Two post-mortem (N=4 superficial parenchymal lesions) and 10 in vivo experiments (N=5 superficial parenchymal and N=16 lesions involving bronchioles) were performed. In contrast to the post-mortem model, superficial parenchymal lesions in vivo showed less air leak [mean flow ± standard deviation (SD): 760±693 vs. 42±33 mL/min, P=0.055]. All superficial parenchymal lesions in vivo sealed intrinsically within a median time of 20 minutes [interquartile range (IQR), 10-75 minutes]. Histology of the intrinsic sealing layer revealed an extended area of alveolar collapse below the incision with intra-alveolar hemorrhage. Compared to superficial parenchymal lesions in vivo, lesions involving bronchioles induced significantly higher air leak post-operatively (normalized mean flow ± SD: 459±221 mL/min, P=0.003). At termination, 5/9 (55.6%) were still leaking (median drain time: 273 minutes, IQR, 207-435 minutes), and intrinsic sealing for the remaining lungs occurred within a median of 115 minutes (IQR, 52-245 minutes).

Conclusions

Lung parenchyma of healthy sheep shows a strong intrinsic sealing mechanism, explained pathologically by an extended area of alveolar collapse, which may contribute to a translational gap in lung sealant research. A meaningful ovine model has to consist of deep lesions involving bronchioles of >⌀1.5 mm. Further research is needed to develop a standardized PAL model, to improve clinical effectiveness of lung sealants.

Sealing effectiveness of a novel NHS-POx based patch: experiments in a dynamic ex vivo porcine lung

Background

Sealants are used to prevent prolonged pulmonary air leakage (PAL) after lung resections (incidence 5.6-30%). However, clinical evidence to support sealant use is insufficient, with an unmet need for a more effective product. We compared a novel gelatin patch impregnated with functionalized polyoxazolines (NHS-POx) (GATT-Patch) to commercially available sealant products.

Methods

GATT-Patch Single/Double layers were compared to Progel®, Coseal®, Hemopatch® and TachoSil® in an ex vivo porcine lung model (first experiment). Based on these results, a second head-to-head comparison between GATT-Patch Single and Hemopatch® was performed. Air leakage (AL) was assessed in three settings using increasing ventilatory pressures (max =70 cmH2O): (I) baseline, (II) with 25 mm × 25 mm superficial pleural defect, and (III) after sealant application. Lungs floating on saline (37 ℃) were video recorded for visual AL assessment. Pressure and tidal volumes were collected from the ventilator, and bursting pressure (BP), AL and AL-reduction were determined.

Results

Per sealant 10 measurements were performed (both experiments). In the first experiment, BP was superior for GATT-Patch Double (60±24 cmH2O) compared to TachoSil® (30±11 cmH2O, P<0.001), Hemopatch® (33±6 cmH2O, P=0.006), Coseal® (25±13 cmH2O, P=0.001) and Progel® (33±11 cmH2O, P=0.005). AL-reduction was superior for GATT-Patch Double (100%±1%) compared to Hemopatch® (46%±50%, P=0.010) and TachoSil® (31%±29%, P<0.001), and also for GATT-Patch Single (100%±14%, P=0.004) and Progel (89%±40%, P=0.027) compared to TachoSil®. In the second experiment, GATT-Patch Single was superior regarding BP (45±10 vs. 40±6 cmH2O, P=0.043) and AL-reduction (100%±11% vs. 68%±40%, P=0.043) when compared to Hemopatch®.

Conclusions

The novel NHS-POx patch shows promise as a lung sealant, demonstrating elevated BP, good adhesive strength and a superior AL-reduction.

Risk of systemic metastases in clinical stage I nonseminoma germ cell testis tumor managed by retroperitoneal lymph node dissection

PURPOSE

We assess the risk of systemic recurrence after retroperitoneal lymph node dissection for clinical stage I nonseminoma germ cell testis tumor based on predominance of embryonal carcinoma and/or vascular invasion in the orchiectomy specimen.

MATERIALS AND METHODS

A total of 292 cases of clinical stage I nonseminoma germ cell testis tumor treated with retroperitoneal lymph node dissection from 1990 to 1995 were identified from the Indiana University database. A minimum of 2 years of followup was required for study entry. Review of the written pathological reports classified tumors as embryonal carcinoma predominant, when it was present at a level greater than any other histology, nonpredominant, when it was present but not as the main histological subtype, and absent. Vascular invasion was categorized as present or absent.

RESULTS

Of the 292 cases 226 (77. 4%) were pathological stage I and relapse rate after retroperitoneal lymph node dissection was 10.2%. Vascular invasion and embryonal carcinoma predominance in the orchiectomy specimen were predictors of relapse in this group. None of the 35 pathological stage II cases treated with adjuvant chemotherapy had relapse, whereas relapse occurred in 7 of 31 pathological stage II cases (22.6%) not treated with adjuvant chemotherapy.

CONCLUSIONS

Pathological stage I cases with predominant embryonal carcinoma and/or vascular invasion in the orchiectomy specimen have a higher probability of systemic recurrence after retroperitoneal lymph node dissection. Dissection alone still has a major therapeutic impact (77%) in patients with clinical stage I, pathological stage II nonseminoma germ cell testis tumor.

Results and outcome of retroperitoneal lymph node dissection for clinical stage I embryonal carcinoma--predominant testis cancer

PURPOSE

To determine the incidence of metastatic disease and usage of chemotherapy (adjuvant or metastatic) after primary retroperitoneal lymph node dissection (RPLND) in patients with clinical stage (CS) I embryonal carcinoma (EC)-predominant testicular cancer. EC predominance was defined as the presence of EC at a level greater than that of any other histologic diagnosis.

PATIENTS AND METHODS

All CS I patients with nonseminomatous germ cell tumors who underwent RPLND at Indiana University from 1990 to 1995 were reviewed retrospectively.

RESULTS

Two-year follow-up was available for 292 of 320 patients. EC-predominant disease was found in 125 (42.8%) of 292. Eighty-five (68.0%) of 125 patients with EC-predominant disease had pathologic stage (PS) I, and 18 (21.2%) of this group of 85 relapsed. A significantly lower PS I relapse rate of 3% was found for patients who had non-EC-predominant disease (P <.0001). PS II disease was more frequent in patients with EC predominance, as 40 (32.0%) of 125 had retroperitoneal metastases, compared with 26 (15.6%) of 167 patients with a non-EC-predominant histologic diagnosis (P =.0024). Chemotherapy was administered to 48 (38.4%) of the 125 patients with CS I EC-predominant disease after RPLND. This included 25 CS I patients with PS II disease who received adjuvant chemotherapy in addition to 23 patients who subsequently required chemotherapy for relapse after RPLND. Ten (66. 6%) of 15 PS II EC-predominant patients were cured by surgery alone. Currently, all 125 EC-predominant patients are disease-free.

CONCLUSION

Patients with CS I EC-predominant disease are at a relatively high risk for metastatic disease.

Colorectal villous tumors accuracy of the preoperative biopsies

This study was undertaken to assess the reliability of the endoscopic biopsies in the evaluation of colorectal villous tumors (CRVT). In 163 consecutive patients referred for surgical treatment of CRVT, preoperative evaluation had been routinely done by colonoscopy and multiple biopsies. Tumors were classified in 3 groups: low grade tumors, high grade tumors and adenocarcinomas. Infiltration in depth was staged on the postoperative specimens according to the Dukes-Aster-Coller's classification. All the tumors were completely resected by surgery and definitive pathological diagnosis was established. An exact correlation between the pre- and postoperative staging was observed in 48% of the cases. Accuracy averaged 54% in the group-by-group comparison, with an overstaging rate of 6.7%, and an understaging rate of 39%. The incidence of adenocarcinomas was 22% in the group with clearly benign preoperative biopsies and 50% in the other cases. There were significantly more B2 and C tumors among the patients referred after 3 or more endoscopic attempts (33%) than after one or two sessions (10%) (p < 0.0003). We confirm that in spite of multiple endoscopic biopsies, only a complete resection permits an exact staging and an appropriate therapeutic choice.

Is retroperitoneal lymph node dissection necessary for adult paratesticular rhabdomyosarcoma?

PURPOSE

We assess the benefit of retroperitoneal lymph node dissection for adult paratesticular rhabdomyosarcoma.

MATERIALS AND METHODS

A total of 19 adults with paratesticular rhabdomyosarcoma who underwent retroperitoneal lymph node dissection between 1980 and 1997 comprise our study population. Postoperative chemotherapy was administered in all patients, including cyclophosphamide, doxorubicin and vincristine with or without consolidation with ifosfamide and etoposide in 17, and vincristine, actinomycin D and cyclophosphamide in 2. Radiation therapy also was administered in 2 patients. Patients were classified into pathological and clinical groups according to the Intergroup Rhabdomyosarcoma Studies. Mean followup was 6.4 years (range 0.5 to 17.6).

RESULTS

A total of 17 patients (89%) were disease-free and 2 (1 in pathological group I and 1 in pathological group II) died of disease that recurred outside of the retroperitoneum. Of 16 clinical group I patients 9 were in pathological group II. There were negative nodes in 2 of 3 clinical group II patients. Thus, abdominal computerized tomography correctly staged only 8 of 19 patients (42%).

CONCLUSIONS

Retroperitoneal lymph node dissection accurately stages paratesticular rhabdomyosarcoma and eliminates the need for abdominal radiotherapy in patients in pathological group II. Combined modality therapy with retroperitoneal lymph node dissection and postoperative chemotherapy achieves a high cure rate.

Is retroperitoneal lymph node dissection necessary for adult paratesticular rhabdomyosarcoma?

PURPOSE

We assess the benefit of retroperitoneal lymph node dissection for adult paratesticular rhabdomyosarcoma.

MATERIALS AND METHODS

A total of 19 adults with paratesticular rhabdomyosarcoma who underwent retroperitoneal lymph node dissection between 1980 and 1997 comprise our study population. Postoperative chemotherapy was administered in all patients, including cyclophosphamide, doxorubicin and vincristine with or without consolidation with ifosfamide and etoposide in 17, and vincristine, actinomycin D and cyclophosphamide in 2. Radiation therapy also was administered in 2 patients. Patients were classified into pathological and clinical groups according to the Intergroup Rhabdomyosarcoma Studies. Mean followup was 6.4 years (range 0.5 to 17.6).

RESULTS

A total of 17 patients (89%) were disease-free and 2 (1 in pathological group I and 1 in pathological group II) died of disease that recurred outside of the retroperitoneum. Of 16 clinical group I patients 9 were in pathological group II. There were negative nodes in 2 of 3 clinical group II patients. Thus, abdominal computerized tomography correctly staged only 8 of 19 patients (42%).

CONCLUSIONS

Retroperitoneal lymph node dissection accurately stages paratesticular rhabdomyosarcoma and eliminates the need for abdominal radiotherapy in patients in pathological group II. Combined modality therapy with retroperitoneal lymph node dissection and postoperative chemotherapy achieves a high cure rate.

Radical esophageal resection for adenocarcinoma arising in Barrett's esophagus

BACKGROUND

Esophagectomy with extensive lymph node dissection is the best way to give Barrett's patients with locally advanced adenocarcinoma a good chance of cure.

MATERIAL AND METHODS

Fifty-five patients underwent subtotal (n = 47) or distal (n = 8) esophagectomy for Barrett's adenocarcinoma (n = 43) or high-grade dysplasia (HGD) (n = 12). Thirteen patients (23.6%) never had had any reflux symptom before disclosure of the neoplastic lesion, and 20 patients (36.4%) had esophageal shortening. Ro resections (n = 50) included removal of the esophageal tube en bloc with the locoregional lymph nodes.

RESULTS

An invasive carcinoma was found in the resected specimen of 4 of the 12 patients operated on for HGD. Two of the 5 patients whose metaplasia was surveyed endoscopically were operated on for an advanced lesion (T2N1, T3N1) because they had not strictly complied with the proposed schedule. One of the 4 patients whose HGD was followed up endoscopically until disclosure of deeper mucosal invasion had positive lymph nodes at operation. The prevalence of early lesions (Tis, T1, T2, No) was 7.4% in patients with tumor-related symptoms versus 85.7% in those having unrelated symptoms (P = 0.0000), which resulted in a 5-year survival rate of 33.8% and 82.4%, respectively (P = 0.0012). Five-year survival rate after Ro resection made for invasive carcinoma was 59.3% (all cases), 73.1% (No), 61.5% (< or =5 positive lymph nodes), and 0% (>5 positive lymph nodes).

CONCLUSIONS

High-grade dysplasia is an indication for esophageal resection. Early detection of the neoplastic transformation of Barrett's metaplasia prior to the onset of obstructive symptoms gives the best chance of cure. Esophagectomy with radical lymph node clearance is capable of curing a large proportion of the patients having no or a limited number of metastatic lymph nodes.

Laparoscopic appendicectomy: pros & cons--literature review of 4190 cases

The aim of this literature review is to evaluate current data on laparoscopic and open appendicectomy in order to establish a new gold standard in surgery. The authors have reviewed 4190 appendicectomies, 3322 laparoscopic appendicectomies (LA) and 868 open appendicectomies (OA), from 22 studies published between February 1992 and June 1994. Four studies dealt exclusively with pediatric patients (n = 1558). The analysis compares surgical technique, operating time, pathological findings, major and minor complications, postoperative pain and costs. The strongest arguments against LA are the increased rate of major complications, the increase of overall cost and the negative effect of the learning curve. The argument in favour of LA are the significant reduction of minor complications, the shortening of the postoperative hospitalization and of the time to resume full activity. The benefit of LA regarding the amount of analgesia requirement and the time needed to resume normal feeding after surgery is still controversial. The authors have reached the conclusion that LA might emerge as the first choice for appendicectomy. More studies are necessary to confirm this trend.

Extensive lymph node clearance for cancer of the esophagus or cardia: merits and limits in reference to 5-year absolute survival

BACKGROUND/AIMS

The present study evaluates both merits and limits of extensive lymph node clearance in the mediastinum and upper abdomen on patients operated on more than 5 years ago.

MATERIALS AND METHODS

One hundred forty-four esophageal cancer patients underwent subtotal (n = 97) or distal (n = 47) esophageal resection more than 5 years ago. Twenty-six patients operated on in a curative attempt were given radiotherapy (n = 14) or radiochemotherapy (n = 12).

RESULTS

Esophagectomy with extensive lymph node clearance was feasible in 102 of the 144 patients (70.8%). In-hospital mortality was 1.4%. Thirty-six patients lived more than 5 years, ie. 25% of all the esophagectomized patients and 35.3% (36/102) of those who were operated on in a curative attempt. Five-year absolute survival was 38.4% after combined therapy v.s. 34.2% after surgery alone (p > 0.05). In the latter instance, it was 57.1% for those patients with normal lymph nodes v.s. 14.6% for those with metastatic lymph nodes, and it was 64% for those with non-transmural tumors v.s. 19.6% for those with transmural tumors. One half of those patients who were not given adjuvant therapy following esophagectomy with extensive lymph node clearance died of neoplastic spread, namely distant metastases (27.6%), cervical spread (3.9%), and local recurrence (10.5%).

CONCLUSIONS

Esophagectomy with extensive lymph node clearance is not feasible in 30% of the patients in whom it is attempted, and it does not prevent further neoplastic spread in one half of those in whom it is feasible. It is capable of curing 15 to 20% of those patients with locally advanced neoplasms and shelters 90% of the patients from local recurrence.