The time course of resolution of adhesions during fibrinolytic therapy in tetracycline-induced pleural injury in rabbits

Abstract

The time required for the effective clearance of pleural adhesions/organization after intrapleural fibrinolytic therapy (IPFT) is unknown. Chest ultrasonography and computed tomography (CT) were used to assess the efficacy of IPFT in a rabbit model of tetracycline-induced pleural injury, treated with single-chain (sc) urokinase plasminogen activators (scuPAs) or tissue PAs (sctPA). IPFT with sctPA (0.145 mg/kg; n ϭ 10) and scuPA (0.5 mg/kg; n ϭ 12) was monitored by serial ultrasonography alone (n ϭ 12) or alongside CT scanning (n ϭ 10). IPFT efficacy was assessed with gross lung injury scores (GLIS) and ultrasonography scores (USS). Pleural fluids withdrawn at 0 -240 min and 24 h after IPFT were assayed for PA and fibrinolytic activities, ␣-macroglobulin/ fibrinolysin complexes, and active PA inhibitor 1 (PAI-1). scuPA and sctPA generated comparable steady-state fibrinolytic activities by 20 min. PA activity in the scuPA group decreased slower than the sctPA group (k obs ϭ 0.016 and 0.042 min Ϫ1 ). Significant amounts of bioactive uPA/␣-macroglobulin (but not tPA; P Ͻ 0.05) complexes accumulated at 0 -40 min after IPFT. Despite the differences in intrapleural processing, IPFT with either fibrinolysin was effective (GLIS Յ 10) in animals imaged with ultrasonography only. USS correlated well with postmortem GLIS (r 2 ϭ 0.85) and confirmed relatively slow intrapleural fibrinolysis after IPFT, which coincided with effective clearance of adhesions/organization at 4 -8 h. CT scanning was associated with less effective (GLIS Ͼ 10) IPFT and higher levels of active PAI-1 at 24 h following therapy. We concluded that intrapleural fibrinolysis in tetracycline-induced pleural injury in rabbits is relatively slow (4 -8 h). In CT-scanned animals, elevated PAI-1 activity (possibly radiation induced) reduced the efficacy of IPFT, buttressing the major impact of active PAI-1 on IPFT outcomes. fibrinolytic therapy; fibrinolysis; plasminogen activator inhibitor 1; pleural injury; urokinase; tissue plasminogen activator INTRAPLEURAL FIBRINOLYTIC THERAPY (IPFT) activates the endogenous fibrinolytic system, resolving intrapleural adhesions and complex fibrinous deposits that sequester pockets of inflammation loculations, thus improving drainage and clinical outcome, in part by decreasing surgical interventions (10). There are multiple reports of successful (88 -100% efficacy) IPFT in adult (1,7,8,16,17,29,42,47,48,66,67,72) and in pediatric (2,3,6,11,20,40,41,58,59,61,63,67) patients with empyema although outcomes in adult patients are inconsistent in these trials. Thus IPFT represents a less invasive and costly alternative to video-assisted thoracic surgery or other surgical interventions, which demonstrate comparable efficacy (16,44,45,58,60,71) in pediatric practice. IPFT also represents a preferred choice in high-risk (1, 22) and otherwise inoperable patients (10,43,49,56,57,69) or those with empyema/ loculation who refuse surgery. The reasons for the inconsistent results of IPFT in adult patients remain unclear but likely reflect...

Dose dependency of outcomes of intrapleural fibrinolytic therapy in new rabbit empyema models

“…B-mode ultrasonography of the chest was performed as described elsewhere (24) using Logiq e system (GE Healthcare, Milwaukee, WI), equipped with R5.2.x software and a multifrequency transducer model 12L-RS (3-10.0 MHz) at a working frequency of 10 MHz, as we previously reported (25).…”

“…Gross loculation injury scores (GLIS) were calculated for each animal as described (23,25). IPFT was considered successful based on a GLIS Ͻ 10.…”

“…Rabbits with P. multocida (n ϭ 18) EMP were initially used in these experiments and were treated at 72 h with intrapleural administration of a single TCN MED dose of 0.5 mg/kg scuPA or 0.145 mg/kg tPA (n ϭ 9/group). The results of IPFT were evaluated at 96 h, as previously described (13,24,25) by GLIS scoring of the extent of pleural injury. Vehicle control animals (n ϭ 5) were treated with intrapleural PBS vehicle.…”

“…We have previously shown that the rabbit model is advantageous for analysis of the safety and effects of IPFT designed for human use, given the similarity of the interactions between rabbit and human fibrinolysins and inhibitors (21, 26). Because we previously used models of tetracycline and Pasteurella multocida induced with limited pleural organization in rabbits (13,18,20,(23)(24)(25), we inferred that development of a novel model of EMP that recapitulated the organizational progression and sequestration of pleural fluid was possible. We therefore sought to generate a model of Streptococcus pneumoniae-induced EMP in rabbits,…”

“…Because we previously used models of tetracycline and Pasteurella multocida induced with limited pleural organization in rabbits (13,18,20,(23)(24)(25), we inferred that development of a novel model of EMP that recapitulated the organizational progression and sequestration of pleural fluid was possible. We therefore sought to generate a model of Streptococcus pneumoniae-induced EMP in rabbits, as this is a common cause of the clinical disease, because the relatively large size of the animal facilitates the testing of IPFT and the rabbit model is tractable for trended imaging of the chest by ultrasonography (25). We also adapted the P. multocida EMP model so that pleural adhesions simulating loculae developed.…”