Exposure of research personnel to carbon dioxide during euthanasia procedures.

CO2 is one of the most commonly used euthanasia agents for laboratory animals. Considerable research has gone into the effect of the agent on animals, but little has been done to examine potential human exposure during these procedures. In this study, we examine the CO2 concentrations to which personnel are exposed while euthanizing rodents with CO2. To examine the environmental levels of CO2 generated during euthanasia, we examined several variables including flow rate, inclusion of a cage in the euthanasia chamber, inversion of the euthanasia chamber, chamber size, distance from the euthanasia chamber, and room size. Under all conditions, CO2 concentrations in the room temporarily increased significantly to 600 to 4000 ppm. The results of this study show that, under several testing scenarios, occupational levels of CO2 did not exceed governmentally mandated allowable exposure limits during routine rodent euthanasia procedures.

Evaluation of carbon dioxide dissipation within a euthanasia chamber.

CO2 euthanasia is used widely for small laboratory animals, such as rodents. A common necessity in many animal research facilities is to euthanize mice in sequential batches. We assessed the effects of several variables on the time it took for CO2 to dissipate within a chamber. Using standard euthanasia time, changes in flow rate were compared between a slow 15% fill rate for 7 min, and a slow 15% followed by a rapid 50% filling for a total of 5 min. Additional variables assessed included the effects of opening the lid after the completion of chamber filling, turning the chamber over after completion of filling, and the use and removal of a cage from within the chamber. For all trials, CO2 levels in the chambers peaked between 50% and 80%. After the gas was turned off, the concentration of CO2 dropped to below 10% COv within 2 min, except when the lid was left on the chamber, where concentration levels remained above 10% after 20 min. CO2 dissipation was significantly faster when the chamber was turned upside down after filling. Significant interaction effects occurred among the factors of cage presence within the chamber, flow rate, and chamber position. Only leaving the lid on the chamber had any practical implication for delaying CO2 dissipation. We recommend that users allow 2 min for CO2 to clear from the chamber before subsequent euthanasia procedures, unless the chamber is manipulated to increase the dissipation rate.

Incidence of dental lesions in musk shrews (Suncus murinus) and their association with sex, age, body weight and diet.

Both wild and laboratory strains of the musk shrew (Suncus murinus) have a high incidence of periodontitis. The authors completed necropsy examinations in 51 shrews to identify dental lesions including tooth loss, mobility and fractures. Dental lesions were identified in significantly more females than males, and older animals were more likely to have lesions present. Shrews with one or more dental lesions weighed significantly less than those without lesions present. Dietary supplementation with mealworms did not significantly affect the incidence of dental lesions or the body weight of male or female shrews. The authors recommend routine body weight measurement as a simple, noninvasive method of detecting shrews with an increased likelihood of having dental lesions.

Healing of iatrogenic skeletal muscle wounds is affected by incision device.

Orthopedic joint procedures frequently require extensive dissection of skeletal muscles resulting in tissue injury, formation of scar tissue, pain, and potentially, functional impairment. The authors hypothesized that using a low-temperature ultrasonic cutting and coagulating device (Harmonic Blade, Ethicon Endo-Surgery, Cincinnati, OH) would result in reduction in tissue trauma in terms of reducing acute and chronic inflammation during healing. Bilateral longitudinal incisions were made into the tibialis cranialis muscles of rabbits with either a Harmonic Blade or a standard monopolar electrosurgical scalpel. At 3, 7, and 21 days postoperatively, necropsy and histological evaluations indicated a significant attenuation of acute inflammation (P = .011) for the Harmonic incisions compared with electrosurgery. No significant differences were observed for chronic inflammation, necrosis, or fibrosis. Use of a Harmonic scalpel during dissection of skeletal muscle in orthopedic surgery may result in reduced influx of neutrophils, reducing acute inflammation, and potentially aid in reducing postoperative pain and functional impairment.