CHEMICAL IMMOBILIZATION AND KILLING OF INTRA-AURAL ROACHES - AN IN-VITRO COMPARATIVE-STUDY

Study objective: The treatment of live insects in patients' ears is co ntroversial. To determine which chemical agent is most effective for i mmobilizing and killing intra-aural cockroaches, we carried out the fo llowing investigation. Design: An in vitro blinded comparative study. Interventions: A model was developed in which live cockroaches were su bmerged in microscope immersion oil, 2% lidocaine, 4% lidocaine, or 2% viscous lidocaine in a glass beaker. Responses of cockroaches were re corded with a video-cassette recorder and evaluated later by a blinded observer. Measured variables were time to death and time-integrated a ctivity before death. Analysis was by analysis of variance with Tukey' s procedure. Results: Four groups of 40 cockroaches each were exposed to each of the four agents. Microscope oil killed the insects most qui ckly (mean, 27.2 seconds; 95% confidence interval, 23.8 to 30.6). The other agents required more than 40 seconds and were inferior to oil (F = 15.5, P< .0001). Total activity was also least in the microscope oi l group (F = 25.7, P<.0001). Conclusion: Microscope immersion oil is t he most effective agent for immobilizing and killing intra-aural cockr oaches.