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

Abstract

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. An in vitro blinded comparative study. 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. 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). Microscope immersion oil is the most effective agent for immobilizing and killing intra-aural cockroaches.