Effects of a Heated Anesthesia Breathing Circuit on Body Temperature in Anesthetized Rhesus Macaques (Macaca mulatta).

This study evaluated the effects of using a heated anesthesia breathing circuit in addition to forced-air warming on body temperature in anesthetized rhesus macaques as compared with forced-air warming alone. Hypothermia is a common perianesthetic and intraoperative complication that can increase the risk of negative outcomes. Body heat is lost through 4 mechanisms during anesthesia: radiation, conduction, convection, and evaporation. Typical warming methods such as forced-air warming devices, conductive heating pads, and heated surgical tables only influence radiative and conductive mechanisms of heat loss. A commercially available heated breathing circuit that delivers gas warmed to 104 °F can easily be integrated into an anesthesia machine. We hypothesized that heating the inspired anesthetic gas to address the evaporative mechanism of heat loss would result in higher body temperature during anesthesia in rhesus macaques. Body temperatures were measured at 5-min intervals in a group of 10 adult male rhesus macaques during 2 anesthetic events: one with a heated anesthesia breathing circuit in addition to forced-air warming, and one with forced-air warming alone. The addition of a heated breathing circuit had a significant positive effect on perianesthetic body temperature, with a faster return to baseline temperature, earlier nadir of initial drop in body temperature, and higher body temperatures during a 2-h anesthetic procedure. Use of a heated anesthesia breathing circuit should be considered as a significant refinement to thermal support during macaque anesthesia, especially for procedures lasting longer than one hour.

Mid-Tibiofibular Amputation as a Method of Terminal Blood Collection in Xenopus Laevis.

The African clawed frog, Xenopus laevis, is a widely used model for biomedical research. X. laevis could be more useful as a model with a better method for collection and analysis of its blood and serum. However, blood collection in X. laevis can be challenging due to their small size, lack of peripheral vascular access, and species-specific hematology variables. The goal of this study was to compare cardiocentesis, the current gold standard terminal blood collection method, with a leg amputation technique. Blood samples were collected from 24 laboratory-reared X. laevis, randomized to either the cardiocentesis or leg amputation method, with 6 males and 6 females in each group. Hematology and serum biochemistry were also conducted to identify any lymph contamination in the samples. The leg amputation method produced significantly higher blood volumes in shorter times and showed no significant differences in clinical pathology parameters as compared with cardiocentesis. These results indicate that blood collection by leg amputation may be a valuable approach for increasing the utility of an already valuable biomedical research model.

Effect of Home Cage Bedding in the Induction Chamber on Serum Cortisol and Corticosterone Levels in Response to Isoflurane-induced Anesthesia in C57BL/6J Mice.

Mice are routinely anesthetized with isoflurane in an induction chamber. The AVMA Guidelines for the Euthanasia of Animals states that distress should be minimized during euthanasia but does not address this point in regard to induction of anesthesia. Here we evaluated the potential for familiar surroundings to reduce the adrenocortical response of mice during anesthesia induction with isoflurane. However, adding bedding from the animals' home cage to the induction chamber failed to significantly reduce serum cortisol or corticosterone levels in male and female C57BL/6J mice. These results indicate that familiar surroundings do not appear sufficient to reduce the adrenocortical response of mice during anesthesia induction with isoflurane.