Evaluation of Open-Drop Isoflurane Anesthesia in Madagascar Hissing Cockroaches (Gromphadorhina Portentosa)

There is limited information on anesthetizing Madagascar hissing cockroaches (Gromphadorhina portentosa). This study assessed the feasibility of isoflurane for brief anesthesia. Fifteen adult Madagascar hissing cockroaches (10 males, five females) had baseline heart rates recorded. These cockroaches were anesthetized in groups of two or three using 2 ml of isoflurane on a cotton ball in a 1-L container. Induction time was recorded when there was no response to external movement of the chamber. Cockroaches were removed from the chamber and exposed to noxious (mock hemolymph collection) and nonnoxious (cotton-tip applicator) stimuli. Heart rates and nonnoxious stimuli were assessed every 5 min until cockroaches were able to right themselves, defined as recovery time. Data were assessed using a nonparametric Mann–Whitney U test, P ≤ 0.05. The median (range) induction time was 16 (6–20) min and was not significantly affected by sex (P ≥ 0.99), length (P = 0.81), or weight (P = 0.94). Median recovery time was 20.5 (15–30) min and was significantly impacted by sex (P = 0.007) and weight (P = 0.018), but not length (P = 0.16). Heart rate decreased (P = 0.07) from median 66 (52–104) bpm for baseline cockroach values to median 60 (48–84) bpm during anesthesia. Heart rate was not impacted by sex (P = 0.07; P = 0.57), length (P = 0.98; P = 0.37), or weight (P = 0.84; P = 0.48). Madagascar hissing cockroaches were successfully anesthetized with isoflurane (2 ml on a cotton ball in a 1-L container), which should be considered for brief procedures. Although not statistically significant, the use of Doppler for heart rate monitoring proved useful for assessing depth, but warrants further investigation.