Chemical immobilization and killing of intra-aural roaches: an in vitro comparative study.

ABSTRACT

STUDY OBJECTIVE: The treatment of live insects in patients' ears is controversial. To determine which chemical agent is most effective for immobilizing and killing intra-aural cockroaches, we carried out the following investigation. DESIGN: An in vitro blinded comparative study. INTERVENTIONS: A model was developed in which live cockroaches were submerged in microscope immersion oil, 2% lidocaine, 4% lidocaine, or 2% viscous lidocaine in a glass beaker. Responses of cockroaches were recorded with a video-cassette recorder and evaluated later by a blinded observer. Measured variables were time to death and time-integrated activity 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 quickly (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 oil group (F = 25.7, P < .0001). CONCLUSION: Microscope immersion oil is the most effective agent for immobilizing and killing intra-aural cockroaches.