Pleural empyema carries high morbidity and mortality rates. Therapy focuses on the control of the infectious process in its initial phase when parenteral antibiotics and chest drainage are likely to be most effective. The ability of dextrans in preventing peritoneal adhesions leads one to test their potential effectiveness in reducing fibrinous proliferation in a rat model of pleural empyema. Twenty-four Wistar rats weighing 250-400 grams were anesthetized, submitted to a right thoracotomy and then randomized into 3 groups (n = 8 each). Animals in group I were given intrapleural dextran 40 (1 ml/kg) + 1 ml/kg of Staphylococcus aureus extract (1010 cells/ml) in heart-brain culture media obtained from oropharyngeal swabs of the animals. Animals in group II received saline solution (1 ml/kg) +1 ml/kg of Staphylococcus aureus extract (1010 cells/ml) in heart-brain culture media. Animals in group III (controls) were given the culture media without bacteria (1 ml/kg) in addition to saline (1 ml/kg). Upon completion, the chest was deaired, the thoracotomy wound was closed, the animals recovered, observed for 4 days, and sacrificed. Only the animals in groups I and II developed pleural effusion and empyema (average volume of 9.7 ml and 8.1 ml respectively, p > 0.05, NS). There was a significant weight loss in groups I and II compared to control animals (p = 0.004). There were no significant differences in blood work-up tests between groups. The pleural fluid of all animals in groups I and II had positive cultures for Staphylococcus aureus. The biochemical analysis of the pleural fluid in animals from groups I and II did not show any significant differences. The authors concluded that in this novel and reliable model of pleural empyema in rats, the intrapleural administration of dextran 40 at time of inoculation of bacteria did not result in any measurable reduction of the pleural reaction after 96 hours of observation.

Keywords: Empyema. Pleura. Rat. Dextrans. Staphylococcus.