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 videocassette 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= t5.5, 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.