Effectiveness of sodium hydroxide as a pleural sclerosing agent in rabbits: influence of concomitant intrapleural lidocaine

Influence of parecoxib (cox-2 inhibitor) in experimental pleurodesis

BACKGROUND

The intrapleural instillation of a sclerosing agent produces an inflammatory process frequently followed by pain. The treatment can include the use of analgesics or anti-inflammatory drugs. Previously, it was demonstrated (experimental studies) that corticoids and nonsteroidal anti-inflammatory drugs (diclofenac) reduce the inflammation and fibrosis produced by talc but not by transforming growth factor-beta or silver nitrate. The objective of this study was to determine whether parecoxib (COX-2 inhibitor) affects pleurodesis induced by talc or silver nitrate.

METHODS

140 rabbits received intrapleural injection (2mL) of 400mg/kg of talc or 0.5% silver nitrate. A subgroup of 70 animals received additional daily intramuscular parecoxib (1mg/kg). They were sacrificed at 4, 24, 48, 72h or 7, 14, or 28 days after the procedure. The pleural fluid was quantified; biochemical examinations (glucose, lactic dehydrogenase, and proteins) and immunologic dosages (interleukin-8, vascular endothelial growth factor, and transforming growth factor-beta(1)) were analyzed in pleural fluid and blood. Finally, macro- and microscopic pleura and lung studies were performed.

RESULTS

Evaluation after 28 days demonstrated that parecoxib reduced pleural and pulmonary inflammation but not pleural adhesions. The changes were observed precociously (congruent with 72h) and were more evident after silver nitrate injection.

CONCLUSION

Systemic parecoxib injection does not interfere with talc or silver nitrate pleurodesis. These results suggest that use of COX-2 inhibitors can be considered and depending of the results of other studies, recommended in human pleurodesis.

Management of malignancy-associated pleural effusion: current and future treatment strategies

Management of recurrent malignant pleural effusion, a common complication of malignancy, poses a challenge to clinicians. Although almost one century has elapsed since the introduction of the pleurodesis procedure, the ideal approach and best agent are still to be defined. Optimally, pleurodesis should be done at the bedside with a minimally invasive procedure, and suitable agents to achieve pleural symphysis should be inexpensive, available worldwide and free of adverse effects. To date, no substance completely fulfills these requirements. Silver nitrate should be considered for pleurodesis because of its low cost and ease of handling. Although talc has been used most frequently to induce pleurodesis, reports of death due to acute respiratory failure have raised concerns about the safety of this agent. Tetracycline, an effective alternative used in the past, is no longer commercially available. This agent has been substituted with derivatives of tetracycline, such as minocycline and doxycycline with success rates similar to those with tetracycline. Several antineoplastic agents have been injected into the pleural space with the aim of producing pleural symphysis, the most representative of this group being bleomycin. Recent knowledge of the molecular mechanisms involved in pleural inflammation has brought into focus new substances, such as transforming growth factor beta and vascular endothelial growth factor, which may be used as pleurodesis agents in the future. Nevertheless, more studies are necessary to better define the potential of these substances in the induction of pleural symphysis.Ideally, a sclerosing agent should be cost-effective, available worldwide and easily administered. Talc will probably stand as the preferred agent to be used for pleurodesis in malignant pleural effusion because of its efficacy, easy manipulation and handling. However, further investigation is necessary to minimize adverse effects related to talc.

A new look at old agents for pleurodesis: nitrogen mustard, sodium hydroxide, and silver nitrate

In this review we analyze the evolution of pleurodesis. In spite of the fact that this procedure started in the beginning of the 20th century, the ideal sclerosing agent is not yet known. Emphasis is placed on the current tendency toward minimally invasive procedures in which insertion of catheters is favored over surgical procedures such as placement of chest tubes or thoracoscopy. Among the sclerosing agents, talc is preferred throughout the world. However, the possible development of acute respiratory distress syndrome, which is sometimes fatal, caused the awakening of interest in other drugs. Nitrogen mustard induces pleurodesis but causes important side effects. Sodium hydroxide and silver nitrate are effective and may be used in humans beings.

Effectiveness of silver nitrate compared to talc slurry as pleural sclerosing agent in rabbits. Influence of concomitant intrapleural lidocaine

The ideal agent for producing pleurodesis has not been identified. Talc, the most commonly used, poses several problems. Another possibility is silver nitrate, which was widely used in the past.

PURPOSE

To determine the influence of the intrapleural instillation of lidocaine in producing a pleurodesis with silver nitrate, to define the effect of lidocaine in the maturation of the collagen fibers, and to confirm that the pleurodesis after silver nitrate is stronger than after talc.

METHODS

We studied three groups of 8 rabbits. Two groups received 0.5% silver nitrate; in one we had previously injected 0.5 ml of 2% lidocaine. The third group received 400 mg/kg talc (2 ml). The animals were sacrificed 28 days after the injection, and the pleural spaces were assessed grossly for evidence of pleurodesis and microscopically for evidence of inflammation and fibrosis. The total amount of pleural collagen and the distribution of thick and thin collagen fibers were quantified. Collagen was identified using picrosirius red stain.

RESULTS

In the two groups that received silver nitrate (without lidocaine: 3.5 + 03 and with lidocaine: 3.2 + 0.3), the macroscopic pleurodesis (scale 0 - 4) was significantly (p = 0.001) better than that resulting from talc (1.6 + 0.2). The mean degree of pleural fibrosis induced by silver nitrate (3.5 + 0.2) was significantly (p = 0.004) higher than that induced by talc (1.9 + 0.1). The previous instillation of lidocaine resulted in a tendency for decreased amounts of fibrosis (3.1 + 0.4). The mean amount (10(3)mm2) of pleural collagen was significantly (p = 0.009) greater in the rabbits that received silver nitrate (116.9 + 22.7) than in those that received talc (10.7 + 3.4). The injection of lidocaine slightly reduced the collagen (80.1 + 30.3). The distribution of collagen fibers did not differ among the groups.

CONCLUSION

This rabbit model clearly confirms that intrapleural silver nitrate is more effective than talc for producing pleurodesis. The previous intrapleural instillation of lidocaine results in a decreasing trend in the amount of collagen, but does not change the effectiveness of the pleural fusion or modify the process of collagen maturation.